critterhunter

Here's the new thread.

The original thread can be found here.

http://www.rcuniverse.com/forum/m_3511182/tm.htm

However, much of what was covered there will go gone over in this thread and condensed as most of us were learning how to work with foam and scratch build for the first time. This was (and is) an excellent plane to cut your teeth on and get into foam scratch building. I'll be shortly posting info on how to make hot wire cutting tools, where and what types of foam you can get, electronics, and so on. More importantly, the process of building this great yet simple plane will be covered. Other builds are also welcome, be they anything made from any type of foam. Let the fun begin...

Here's the plans for the plane...

http://www.qnet.com/~skif/plane.html

Here's the link to FoamFlyer's excellent website where I first ran across the plans for this plane. It's looks quickly sucked me in and it seemed like a simple (& free ) foam build to get my feet wet. While you're on his website check out his project history pages. There are many similar builds to the "So" we are building with his plans, along with some other excellent ones. They should give you some ideas for future builds, and you can use the knowledge from building the original "So" to build them and others. Making this plane was such a great learning tool for me.

http://www.qnet.com/~skif/rcmain.html

He also has some great articles, including ones on how to build cheaply, which I love. I tend to buy the cheapest lipos, motors, speed controls and so on that I can find. With a little research you can find the good stuff and avoid the junk thats out there. No longer does flying RC have to be expensive, and when you build with foam it gets dirt cheap. Not to mention the extra satisfaction you get from knowing you are flying some thing you built with your own two hands and didn't buy off the store shelf.

The original plane design uses a brushed motor and nimh packs. If you stick with the original plans, mounting the motor and such as suggested, when using a brushless motor and lipo the plane will probably be tail heavy. It took me three builds to tweak a few things on the plan dimensions. This wasn't all due to the tail heavy conditon (mostly pilot error), but it did need some tweaking for me. I'll be posting this information with photos as I build #4, which I just cut the wing out for last night.

Mainly, you need to move the fuse forward to flush with the trailing edge of the wing, lengthen it's nose a bit, and move the booms to the leading edge. Keep your servos in the very heads of the booms and your electronics as far forward as possible and you should be good. More details as I post the progress.

critterhunter

First thing to post would I guess be the Clark-Y airfoil. You can find it on the web but here's a repost from Fisher in the original thread. When I grab an airfoil now I load it into paint and just change the attributes (sp?) of the horizontal/vertical. Just increase or decrease them both by the same percentage number with paint and then print it out. Measure the length of the airfoil and if it isn't what you want play with the numbers again. Probably other ways to do this but this one works for me.

Repost From Fisher...

I worked on an airfoil template for over an hour that would print as a JPG and when I posted it the site cut it down too small to use you could print it and enlarge it on a copier until it is 7" long on the horizontal base line. Remember to use the flat horizontal base line for the bottom of the wing. Not the one aligned with the numbers.

I will try to PM it to you. Maybe that will work.

I just clicked on the embeded image. maximized it on screen. Copied it and pasted it into a Word Document. Set the page to landscape and drug the lower right hand corner down further to the right until the template was 7" long. Print and your ready to go.

critterhunter

Another repost from Fisher with good info on the airfoil...

The leading edge is rounded to the bottom, so I had to extend the template beyond the edge of the base board to allow the hot wire to follow around template without getting caught. The intended bottom line of the airfoil template should be the solid horizontal line that begins under the leading edge curve and extends under the numbers. If you need me to I can have another go at making the template less ambiguous. Your observation regarding the wing thickness was right on. It should be about an inch think at the deepest point.

(end quote)

I ended up using the wrong baseline for my airfoil but it still works good. I'm missing the curve under the leading edge, but I just use my oribital sander to sand that into the wing. Quick and easy. Remember that the airfoil should be 7" wide. Measure what you print out. More info on building the jig and hot wire tools later.

ken 68

Hook me up i'll watch. Im in the process of checking out some new receivers. I have 2 new Corona RP4S1's that need to be checked out. They had some problems with the first ones not wanting to lock on to yout transmitter. They don't use crystals. I also bought a couple of $4.50 6 channel receivers but I need the big crystals for them. Wheres the best price for single big xtals ? I bought some from BP products but there all small ones.

OH While your on wings look up the Clark-Y modified and show what it looks like. I can't get it to come up on this slow dial up. Happy building.

Ken

calvino

neat, glad to see the thread in pt. 2, PS, THANKS FOR THE CLARK AIRFOIL, check your PM's (crit)

critterhunter

Nice to see you guys are game for the new thread. I'm hoping Fisher and Saucerguy will pop in and contribute, as well as the others from the past who did. With a little luck this thread should be more condensed and to the point, since most of us were learning scratch building, let alone this plane. I'll make an effort to try to be as short and to the point as possible, but no promises.

For any lurkers checking into this plane, I should mention that both beginners and experienced pilots should find it worth building. Even with a single aileron it'll challenge you. I've said this in the past, this plane flies like no other I've ever flown. It almost feels like it will stop and turn around in mid air if you have the center of gravity right and not too much weight. A little "up" on the elevator and then a quick left or right and it will nose around real quick. It also has real good low and high speed ability. It for sure will handle at lower speeds better than my Stryker, and the Stryker does a really good job at that so it's saying a lot. This "So" planes traits and characteristics are just a real joy to fly. Add the killer looks and cheap and easy building and you've got a real winner.

Calvino, couldn't understand what you were asking for in the PM? I made a mistake in the above info on adjusting the size of an airfoil. What I do is load it into paint and then use the "Stretch/Skew" function to increase or decrease the picture size. Then print it out and measure the length of the airfoil. If it isn't what you want (7" on the So plane), then go ahead and change the stretch/skew numbers again to adjust it and try again. I tend to keep both the vertical and horizontal numbers the same. IE: If you want it smaller, try 80% for both. However, you can adjust the vertical to get the airfoil less/more thick. This isn't real critical in my experience. My airfoil happens to be less thick than what Fisher suggested, as I went with the higher horizontal line. Still, it's plenty thick enough. Remember too that thicker airfoils tend to have higher lift than thinner ones, while thinner airfoils tend to have less drag and more speed. The Clark-Y is a very high lift airfoil, one of the best.

Ken, I'll throw that airfoil up to soon enough. I have a bunch of pictures and such to post first.

Somebody PM Fisher and tell him to get over here!

critterhunter

Another addition to adjusting airfoils in paint. I'll use the cut function to grab the airfoil alone off the page and then place it in the far upper left corner of the screen. Then use attributes to delete the rest of the screen fairly close to the airfoil. Now when you print it out the printer won't cut it in half or create two pages. Just guess with the numbers on attributes until you get a box fairly close to the airfoil. Then use stretch/skew as covered in the messages above. The screen size will automaticly adjust as you increase the size of the airfoil.

First step on this plane for newbies would be to build a hot wire bow. It's simple and easy and you probably already have most of the parts laying around in the garage. I used some garden tool wood handles for mine. Set the bow up so that it looks like an "I", with one end of the "I" being connected to the main beam via a bolt, nut, and washers so it can pivot up and down. Then attach a spring (look in the screen door section of hardware stores) to both ends of the bow. This will keep constant tension on your cutting wire by pivoting one end of the bow. The other end of the bow should be stationary by bolted or screwing to the main beam. It's easiest to attach the wire first and then your spring.

There are various types of wire and gauges to use on a cutting tool. What you need will depend on the length of the wire and the volts and amps being put out by your charger. I'm using .022 stainless steel fishing leader from a local tackle store. With my 40" bow and my car battery charger set on 12V 55 amp cold starting mode it gets the wire just right without the need for a dimmer. The charger self regulates so it isn't putting out the full 55 amps. This wire is cheap, like $3 for 25 feet. Pick up a few diameters if you are unsure what you might need with your charger and not using a dimmer.

I hitch the charger leads to the eye bolts at each end of the bow where the fishing leader is tied to. If you notice the wire is not getting hot enough then slide one of the charger leads onto the wire a few inches. The shorter the distance between the charger leads the hotter the wire will get. Remember too that hitching the charger leads up to the eye bolts may stop the wire from heating up at all.

How hot does the wire need to get? If it gets too hot and glows red for more than a few seconds it will snap, so always wear eye protection. Normaly the best cutting temperture is just below it glowing red, but it depends on type of foam, how thick, and how fast you like to cut. If the wire is dragging and skipping through the foam the heat is too low. If the cut is too wide the wire is too hot and melting foam around it that it isn't even touching. Variables are type of foam and how fast or slow you like to move the wire.

Below you'll find a picture of the cheapest charger I found with the features I wanted from Harbor Tool & Freight. Price is under $30. With the numerous amp settings as well as 6 or 12 volt you can almost find the right heat range for most tools you may build in the future. The starting mode versus the charging mode can also help in that respect. Charging mode often will turn on/off as it gets tricked by your tool and thinks a battery is charged. This normaly happens quickly over and over in a matter of seconds, so it can aid in regulating wire heat.

I mostly find myself using the starting mode at 55 amps, though, and then use a dimmer switch to control the heat that way. With this method you can be sure that you'll be able to find the right heat range for any tool. Just remember, if using a dimmer or various charger settings on a new tool, ALWAYS start with the lowest voltage and amps. Test the wire on some foam and slowly work your way up. If you start out too high then the wire will instantly glow red and snap. Once you know what works the red glow isn't a problem with a dimmer. I often bring the wire just up to glowing red and then back it off a bit for a good cutting heat. It's also a great way to clean the wire by burning off debri.

In determining the size of your bow, remember that if the wire gets too long it won't get hot enough with certain power sources. I find a 40" bow is about perfect. You need a few inches of clearance on both sides of the bow for the charger clips and to clear the wing jigs on a 3 foot wingspan when cutting. If you want to make longer wings that won't be a problem, just cut two out and glue them together. More on that later on.

You'll also see in one of the photos below me just finishing a gravity cut. A gravity cut is a quick and easy way to cut a straight line with a bow. It's great for lopping off a square chunk of foam that you plan to to further cut into a wing or such. Just weight one end of the foam on a table, then hang the bow on the foam where you want to do a straight cut. Make sure the bow is fairly balanced on the foam by sliding it one way or the other to correct. Then just plug it in and let the bow do the work. Be ready to catch the bow when it cuts through the foam but don't touch or bump it until it's done cutting. You can see the piece I just cut leaning against the side of the work table, and the piece it was cut from weight down on the bench.

More later on dimmers as well as another handy tool (not required but very useful) called a table hot wire cutter.

critterhunter

Here's some photos of the hot wire table cutter and some photos. Sorry about the quality of these pictures as I was using a web cam at the time. I'll try to dig up some better ones. But first, a re-post from the old thread from me...

Yesterday I took about an hour to build my bandsaw hot wire cutter . Stole a good bit of the design from other hot wire cutter links and modified them a bit to my liking and building skills. Posted are three photos of the unit minus the cutting wire. I hitched up a .022 diameter wire last night for a test run and forgot I still had the battery charger set at 12V 6 amps. This was obviously too much power as the cutting wire instantly turned red hot and then snapped. This charger has a .2 to 1.2 amp variable dial as well so I think I'll try that next, creeping it up until I see the wire start to glow and then back it down. If this is still too much power at 12V I'll flip the charger over to 6V and try that. All of this would be mute if I'd just wire up that dimmer switch to the AC side of the charger. Then I could leave it at 12V 6 amps and then just slowly crank up the dimmer until I see things glow and back it off.

Three photos that follow are of the board (22x21 inches and a close up of the spring mounting area. I used a brass bolt, nuts and washers at the top as I intended to mount one of the charger wires here. However, I decided it might not be a good thing to pass a current through the spring (?) and get it hot as well, so I'll just attach the charger lead directly to the cutting wire where it hitches up to the spring. On the other photo you can see the bottom of the bandsaw table and how I have that rigged. Again, I'm using a brass bolt, nuts, and washers here to both hold the cutting wire and to hold the other lead from the battery charger. The cool thing about this entire setup is I have this bolt and the one on the top end at 90 degree angles from each other. This means I can adjust two nuts on either bolt to position the cutting wire exactly where I want it to get a perfect straight up and down cutting wire in relation to the board surface. In the one picture you'll notice I have bent the white shelf bracket's tip upward so the bolt going through it's hole would be in a horizontal orientation. No test cuts yet but maybe tonight after work.

(End Quote)

Since that post and the below photos I've done a few things to the table cutter. I've shortened the spring so the .022 wire is longer and can do cuts on thicker foam. I've also hitched up a $5 dimmer switch to the charger to adjust the heat range. The charger being used with this table cutter is an old one that can support 12V at 6 amps. You simply plug the charger into the light dimmer switch and then the light dimmer into the wall. As you adjust the dimmer it will adjust the power from the wall going into the charger. This causes the charger to raise or lower the amount of power going to the cutting wire so you can get the right heat range. If I need to use the dimmer with my newer charger shown pictured above that I use with my bow and various other tools, I simply plug that charger into the dimmer. I could use the new charger to power this tool, but since I had the old one laying around I figured it could stay put for use with the table cutter most of the time.

Table cutters like this are great tools for doing smaller cuts or cuts that aren't straight, such as the nose of a fuse. They eliminate the need for wood body jigs that would normaly be used in order to guide the big bow for accuracy. Simply trace the outline of the cut you want onto the foam and then use your table cutter to cut it. It also works great with flat foam for things like tail feathers. If you trace the outline onto flat foam with a pen with enough pressure to crease the foam a bit, the hot wire will follow the cut and guide your hand. Just remember to use less heat with thinner foam than you would with a fuse and such.

The parts needed for the table cutter are quick and easy to get. I garbage picked the table and bought the shelf bracket, spring, and brass bolts/nuts/washers from a hardware store. I've also since made the components more portable. The charger now just clips it's leads onto two bolts on one of the legs of the cutting table. Two wires run from these bolts to the cutting wire. This way I can unclip the charger for other uses without removing the leads at the cutting wire ends. I've also thrown legs on the table and hung the dimmer from one of them. I'll try to dig those pictures up.

One final note. To get the cutting wire straight simply adjust the nuts on the two bolts and use something like a right angle ruler to check that the wire is straight up and down from two sides in relation to the table surface. While you can get by with just a bow, I'd say the table cutter is just as useful for building planes.

critterhunter

Here's some better pictures of the table cutter along with the new mods I did to it, but the shorter spring/longer cutting wire was done after the photos. You can also see a picture of a mini bow I made for doing small free hand cuts that would be difficult with the big bow, yet are in areas of a piece of foam that would be in the way of the table cutter. For instance, I like to use this mini bow to cut ailerons out of a wing. I simply put a right angle metal ruler onto the wing with weights so it doesn't move in the exact spot I want the aileron, then just slide the wire across the ruler for a perfectly straight cut.

Here's a re-post on the mini bow...

I used one of the fiberglass rods from a garbage picked patio umbrella I have laying around to function as both my load spring and bow. .022 gauge stainless steel fishing leader. Fiberglass tube already had eyelits on it's ends to tie my wire to. Attached power leads a bit after the eyelits to hopefuly avoid the tied wire ends from getting hot and melting the wire free from the bow.

Isolated the bow at the other end of the garage (I only have one good eye as it is) and played with the settings on one of my car battery charger. Found the proper heat level and let it run for about 20 minutes to make sure the tied ends aren't getting hot.

critterhunter

Now that the tools are covered will get to cutting out the wing. You only need the bow, but even without that you can make this plane by cutting the foam with a hacksaw or something. However, that will get messy and you'll also need to sand body parts more without a hot wire cuttere.

Below you'll see the wing jigs attached to a board. Notice the numbers on the jigs. These aren't needed but rather are a good way to keep track of where one wire is versus the other end. It also helps if two people are doing the cut, having one person call out the number he's on so the other can speed up or slow down. It doesn't have to be perfect, but you do want to keep both ends fairly close. It'll require less or no sanding to smooth out the wing. The wood extending out from the bottom of the jig was intended to hold weights on to keep the board from moving. I later found out that just putting weights on top of the foam was more than enough, so it isn't needed.

I used handyboard to make the wing jig but anything will do that won't burn easily. There is also a better way to hitch the jigs to the board by drilling through the bottom of the board and running a screw up into the bottom of both jigs. This makes it easy to change airfoil jigs when cutting out various wing styles for other planes. It also allows you to adjust one jig's position versus the other to do tappered wings and such. More on that down the road. I was afraid of trying to cut tapered wings before, but now I know it's real easy.

First thing to do is lop off a piece of foam from your slab that is 36" long by about 7 and 1/2 to 8" wide. The little extra width will help to avoid and dings in the foam at the edges that will get cut off by the bow, and also helps to guide the wire when positioning the wire to start. It also makes it less hassle to line the foam up with the trailing and leading edges if the cut was a perfect 7". All the excess will be cut off by the bow anyway. Do a gravity cut with your bow to get it. Don't worry how thick the foam is, as long as it is at least as thick as your airfoil or more. By the way, too thick of a piece is often easier to cut off your main slab. That way you can flip it over after making one wing and cut another out of it in the future.

Now load the foam into your wing jig. Throw some weights on top of the foam to hold it in place, and fire up your bow. I like to start the bow at the leading edge of the jig. Take your bow and try to get it to start onto the jig as perfectly as possible. This is the hardest part. Keep constant down pressure on the bow so the wire ends ride the jigs and doesn't lift. Keep your speed as constant as possible. Normaly I use slow but steady. Keep both ends of the the bow wire as close to the same spot on the airfoil jig as possible as they slide. Once you reach the end of the airfoil just keep moving with the bow until you get it out of the foam. Remove the weights and check your cut. If the wing is bumpy don't worry about it. A little sanding by hand or with an orbital sander will clean it right up. As said, I don't have the bottom curve at the front going under the wing, so I simply sand that into the wing as well. Your main enemy when cutting a wing is lifting the wire off the jig or getting one end of the bow way far ahead of the other. This will make the wing much thicker on one end than the other, but it can be sanded out.

As you can see, the wing I just cut for build #4 has a few minor ripples in it. I've seen and fixed worse.

critterhunter

Forgot to cover what types of foam to use. The EPS white box foam from Home Depot that FoamFlyer talks about works well. It's lighter than anything out there. Pink or blue foam they sell will also work and is stronger and sands smoother, but it is a bit heavier. I'm now using an really dense white EPS foam that a friend is getting for free from a construction worker. I hear they use this stuff to stick in between rafters under roofs. It's really dense and strong, I'd say four times or more than the white box foam FoamFlyer uses. It's also much heavier, but I prefer my planes heavier (handle winds better) and you'll also save some weight in less strength mods such as tape or gluing in carbon tubes. In fact, I don't think I'll need carbon tubes in the booms on this build. You don't need them with the home depot foam either, but I like to build my planes real strong.

Another handy tip when foam hunting is to check dumpsters behind places like furniture stores, or to drive around on garbage day in the neighborhood. Not that the Home Depot stuff is expensive at around $10 for a 4x8 foot sheet. Get the 2" size or larger. It makes for strong bodies and is easier to hide the battery. I'm planning on an even thicker fuse for build #4. You can build a lot of planes out of one $10 piece of foam.

critterhunter

Got the booms and fuse cut out last night for the bird. More pictures and my tweaked dimensions of the plane will be posted soon. I almost decided to go with an inverted "V" tail design to replace the horizontal & vertical stabs, using only the V tail for the controls. It would be rather large and of course connect both booms together. I think it would be a really cool looking design but I miss the last build of this plane so much that I want to build the same platform again, only with a few slight changes.

critterhunter

More progress. Cut the booms and fuse out. The fuse is 4" by 2" wide and 27 inches long. Foam Flyer's is only 20" long and some front will be cut off mine once the plane is completely done and I know where the battery has to sit to get center of gravity right. On the first two builds with the 20" fuse I ran out of nose to move the battery forward, requiring me to add nose weight. Build #3 was able to achieve COG with I think the 20" fuse with the mods I did (moving the rear of the fuse to flush with the trailing edge of the wing, moving the servos to the boom heads, keeping electronics as far forward as wire length would allow, keeping the wing carbon tubes towards the front of the wing, etc).

It's better to just leave the fuse extra long until everything is in the plane and you can see where the battery needs to sit. COG on this 7" wing is about 2.1 to 2.3 inches back from the leading edge of the wing. I've flown mine nose heavy at about 2" or less for the COG spot with no problems. However, they tend to land a little faster and waste energy by keeping the nose up via the elevator trim. Neutral trim is best for speed and efficiency, so I try to keep COG right on. It also makes the plane handle better in some ways, like being able to turn without dropping the nose.

Foam Flyer gives 3 to 4 inches for fuse height and 1.5 to 2" for boom height. Meaning, booms should be roughly half the size of whatever fuse height you go with. I went with 4" to keep things stronger and also to help the prop clear the ground. In fact, I may mount the BP21 with an 8x4" prop on top of the wing in back to give me the little extra length to clear it. It doesn't matter for landings but I'd like to be able to rise off grass with no landing gear. I believe he goes with 1.5" wide fuse and booms. I prefer 2", not only for more strength but also to help hide the battery a little better. I'm planning on installing the battery from the top of the fuse rather than the side like I've done in the past.

For boom length I went to 21" instead of his 20". This is because I'm moving the booms up further towards the leading edge of the wing to help COG. This way the boom length behind the fuse will still be around the 14" he uses. None of these measurements are critical as he says in his plans. I've built this plane with the booms shorter and further apart, also changing the horizontal stabiler width/length and the elevator. The 2" elevator has way more control that you need. Even with a 1.5" wide elevator I had to lower the rates a lot, so I've gone to a 1.5" wide one again. I used a Stryker elevon I had sitting around for that, cutting it's length down to be just under 12" so it won't beind with the booms which span 12" apart. I kept the horizontal stabiler at 4" wide and 12" long like in his plans, but again I've changed this in prior builds with no problems. It as well as the fins are made from meat tray foam. Got some free trays by asking the butcher at the local supermarket.

I'm going with two ailerons for the first time on this build. Not that I was happy with the single aileron. I was impressed at how well it rolled using a single one, but I did increase it's width to 3 and 1/2" versus his 3" and it's length as long as possible at around 10" (more like 9 6/8"), butting up against the boom. If you move the booms in some you can make it longer for even more surface area, but I found the size above worked real well. Since I'm going with two ailerons, I don't need them as big. I'm going with 2" by 9 6/8". The aileron servos will also be going into the wing rather than in the booms so I can mount this at mid aileron length for less slop. It's also easier to mount them and route control rods if they are in the wing rather in the boom heads. Same deal with the elevator. I used to mount it in the other boom head and run a Dubro Golden rod all the way back to the elevator. For this build it's going to be sunk in the boom right under the elevator. I'm also going with rudders for the first time, and that servo will be in the other boom's tail end as well. Both rudders will be linked to each other via a carbon tube. For the above reasons I'll need all the frontal area weight I can get, probably requiring a longer than 20" fuse.

These booms with this denser/strong foam are so strong that I opted not to put carbon tubes in them that connected with the wing rod(s) like I have done with build #3. Even with the Home Depot weaker foam Fisher has never used carbon, rather just tapping over the booms with Extreme strapping tape (found at Staples or Office Max in the shipping supplies).

The wing was very strong and also didn't need a carbon tube, but being that I tend to build them like tanks and with the added stress from the booms hanging from the wing, I opted for a carbon arrow Gorilla glued into it. I've used Gorilla glue for everything thus far. The only place I may use Epoxy is to join the horizontal stabilizer to the two booms. Reason being that the thin surface area where they join is tricky to do with Gorilla glue without having it foam out. Same with the vertical stabs when I glue them in, though I've used hot glue in the past for them and it works well. You don't have to worry about holding them straight for very long that way, but I am using toothpicks stuck into them (and the horizontal stabilizer) to both hold them in place straight and to add strength to them.

Fin height is about 4 1/2" and length is about 5 6/8". This size is plenty even without the added rudders I have on mine. Remember that there are two of them so the surface area is double. I found about 4" high fins at around almost 6" long made build #3 roll better and they could probably have been even smaller. With smaller v-stabs they aren't fighting the roll, which helps the single aileron.

It's easiest to cut your ailerons out of the wing before gluing it onto the fuse. Foam Flyer says to glue the booms on first. I find it easier to glue the fuse on, then use it as a guide to my ruler to get the booms evenly spaced apart on the wing and straight. To get the fuse straight, I simply measure from the wing tips to a marked center point on the front fuse area. After that's dried the booms are easy. Just measure from the fuse out to get the proper span you want at two points so it's straight. Remember to account for the fuse thickness when figuring out your span between the booms, 12" total in the original plans. Again, not critical. I made a much wider boom span on the prior build and it made the plane look shorter to the eye. Handled great, though.

After cutting out the fuse and booms I sanded them down with sanding block, checking by eye to make sure everything looked straight. The most critical part of this is to make sure the fuse top where the wing mounts is as flat as possible, as well as the boom tops where they mount to the wing. If they are off a bit it won't matter. Build #3 had a fuse that was a bit off angle in relation to the flat wing surface. Trim will take care of that. Same with the booms, but it does help to get them flat at the tail end as well. Then I just mount the horizontal stabilizer as flush with the top inside edge of the booms as possible and it ends up being straight in relation to the wing.

After the ailerons were cut out I used a sanding block to sand a "knife's edge" to the hinge side of them. Check Foam Flyer's website on how to do that for a good hinge point. I installed carbon tubes in both of them to stiffen them up and also to provide a good strong surface for the horns to attach to. Not needed but I like overkill when it comes to strength mods. Flat carbon would work better but I was out.

I've been using Tyvek tape (found in Home Depot or Lowes in the insulation section) for taping hinges and such. It's meant for foam and so sticks much better than clear tape. Clear tape works well and can be improved by spraying 3M spray glue onto it before taping to the foam but there is no need for that with Tyvek. It's expensive but well worth the price. I also use a tacky cloth (found in the auto body section of Walmart or a parts store) to brush off and dirt of foam dust before taping or painting foam. It's got a sticky material in it that sucks up debri well. Cheap and can be used over and over.

When you get around to painting this plane make sure you use one that is foam safe. H20 paint (Walmart & other stores) is foam safe and works great. More on that later. I'll also cover cheap but good electronics when I get to installing them.

Sorry about the length and order of the above message. In a hurry with no time to edit/sort/fix/cut. Some pictures follow. More details and photos as the build continues....

critterhunter

More photos. Easier for me to upload only 3 at a time...

You can see that I moved the fuse up to flush with the trailing edge of the wing, and that I also cut an angle into the fuse at the tail to aid wind flow as well as COG.

critterhunter

Still more...

calvino

wow, looking good there crit, new one or older one

critterhunter

More progress...

After the Gorilla Glue on the booms had dried I glued in the horizontal stabilizer. I used a few toothpicks to hold it in place and also to help strengthen the joining between the booms and it. Would have used bambo skewers but was afraid I'd muck up the thin foam. I opted for 5 minute epoxy instead of Gorilla Glue because it's hard to prevent Gorilla glue from foaming out of thin areas like this. The stabilizer is just glued flush with the top inside corners of the booms. Once it was stuck in with the toothpicks I just eyed it up in relation to the wing to make sure it looked flat. In the prior builds I always kept the horizontal stabilizer flat and had no problem. This time I decided to lower it just a hair at the trailing edge. This insures good wing loading in the air.

After that I stuck toothpicks in the vertical stabs and rudders and also glued them into the booms with epoxy. Just eyed them up using the LAR method (looks about right). I stuck the toothpicks at the intended horn locations to give them extra strength. The rudder linkage has a total of three horns, being controlled by one HXT900 servo via a carbon tube linkage. Glued 2-56 threaded rods into both ends of the carbon tube for the clevises to screw onto. The linkage horns need to be placed at the trailing edge of the rudders to prevent slop, while the one the servo control rod hooks up to is at the leading edge for most throw. Taped over the vertical stabs/rudders first with Tyvek tape before installing the horns. Again, for added strength and also to hinge the rudders.

Melted out the HXT900 aileron servo chambers in the wing using a hot piece of metal. I have to make another hot wire tool to do this for cleaner chambers. I'll probably just cut out a piece of metal in the shape of the servo and heat it with a torch for future builds. Still,l it gets hidden anyway. I have the servos situated so that the control horns on the ailerons will be exactly at mid length of the ailerons. This provides less slop than putting them at the ends like most people do. Reason why they do this is to avoid using servo wire extensions. I'd rather do a little soldering and keep it mid center on my builds. I also melted the servo chambers as close to the leading edge of the wing as possible to help with center of gravity. It helps to also put your carbon wing tube past COG as well. The servos will be wrapped in a little masking tape and then Gorilla Glued into position. The glue will foam up around them for a really snug chamber. If the servo needs fixed you simply slit the tape and yoke it out of it, putting a little tape back over the slit when done.

In the next photo you can see where the elevator and rudder servos are going under the horizontal stabilizer in the booms. I could have mounted them on top of the booms but wanted to hide them as much as possible. The rudder contriol rod goes up through the boom at an angle to the horn. I've have pictures of that later. On the stock build of the "So" the elevator and aileron servos normaly go into the boom heads (in the slanted part of the front of the boom to help with COG. Mounting the rudder and elevator servos in the tail avoids the need for control rods such as the Dubro Golden Rods being routed all the way back, but you pay a price in tail weight. Another reason why the fuse is too long at the moment until I figure out COG. I could have probably used an HXT500 for the rudder but the added stress of the linkage to the two rudders worried me.

For those who don't know, HXT900 servos are real cheap, like $4 a piece, and are somewhere between an HS55 and HS81 in torque. They are great servos and many people even like them better than Hitec HS55s. You can find them on United Hobbies website. Beware of Tower Pro SG90 (?) and HXT900s sold from other sources. They have cheaper parts in them.

Last photo for now is of motor cowl. I decided to mount the motor on top of the wing so the prop can clear the ground with no landing gear. I can also move it foward a bit more this way to help with COG. The cowl is hollow at the back end and has air vents coming in from the sides. The motor will hide under the cowl completely and the prop shaft will exit a hole at the back, bigger than needed to provide an exit vent. I'm not sure if I'll stick with this cowl or make a slightly different one with a better contour. I used the foam cut left from the wing being cut out as it's already got the wing airfoil cut into it to fit nicely over the wing. It will also aid to smooth airflow over the front of the wing where it meets the fuse. If you install the cowl with a little foam safe CA or 3M spray glue (just enough to hold it on) then you can remove it later without hurting the foam for motor service.

This plane, like my last 3 (and Fisher's) is getting a BP21 (2408-21). This motor is plenty fast enough with this platform and will also do unlimited vertical if you keep the weight shy of around 23 ounces or so. Fisher prefers a 7x4 APC E (I think) on it, while I like an APC 8x4 E for more power. I beleive this prop draws around 12 or 13 amps and produces around 21 to 23 ounces of thrust or so. If you want a real speed demon you might try an APC 7x6 SF (slow flyer) prop on the BP21. I used to fly that on the Stryker and the speed was insane. It will draw around 16 amps, I think. I may try that prop later to see how this plane can handle that much speed. It might also still do unlimited vertical on that. I was tempted to throw a 2409-12 on this plane. I currently have one on my Stryker which is faster and has more torque than the BP21. Swinging an 8x6E or 7x6SF prop it does very well, but draws 20 to 30 amps on those two props. A 9x4.5E would lower the amp draw and keep the speed tamer, while giving great torque. A bit overkill for this plane with a 3' wingspan, though. A 2409-18 would also be a great choice. It's a lower k/v motor than the 2409-12 and produced a ton of torque at a low amp draw of about 10 to 14. It's comfortable with props in the 8" to 10x5 size or so. I've only used the "T" version of these motors, but the "D" version looks and is built better. Specs are the same, just a better construction. These motors are cheap at south of $12, but if you decide to buy one then pick up the Tower Pro 30 amp ESC to power it for around $15 (United Hobbies). Always better to have more amps than you need in an ESC, and provides room for future uprgrades on planes.

critterhunter

When shopping for lipos I go for price rather than name. Most people don't realize that there are only a handful of cell makers, most of them over seas, and that you are often paying for the name somebody slaps on them in the states. United Hobbies HXT packs are about the cheapest you'll find, but they also now have Loong Max packs that can be close in price (or cheaper) and I've also heard good things about so far. I like 2200ma 3 cell 20C packs as they cover just about any park flyer's weight and amp requirements, providing long run times as well. I do have a Loong Max 15C 2250ma pack on the way, which should work find for any plane I fly. A 10C 2000ma or more 3 cell pack is plenty enough for the BP21 if you want to stay as cheap as possible, though the Loong Max pack is only $19 and the HXT 20C packs are around $29.

For receivers, I like the GWS ones because they are only $20 at my local hobby store and I've have no trouble with them. They are "short range" rated but I've flown them out to some pretty amazing distances and never had a glitch. I hear good things about the cheaper Coronas from United Hobbies as well.

A few more photos for now.

critterhunter

Checked to see when Fisher was last on and it's been a while, but then noticed that he finally got on RCUniverse last night. Come on, Fisher, throw up some photos and advice on your prior "So" builds. [:@]

Fisher

The problem with anything I have to say is that it all comes from building 4 of these planes with no problems with any of them. If you follow Foam Flyers directions you can hardly go wrong. I really like using hot glue as he suggests as it is so quick and easy. Takes all of 15 minutes to assemble a complete airframe once you have cut out the parts.

Flight characteristics of the plane are just as you say (using a BP-21 and a 2000 ma 3 cell LiPo). Every time I take this plane out I learn a new maneuver with it. The only two things I have had issues with are inverted flight and outside loops. A symmetrical air foil on the wing would take care of that though.

The next direction is to up or down size it. Critters larger version is a good start on up sizing. I really think with the tiny BL motors available at United Hobbies someone could down size it to half scale and have a smoking hot little ride.

calvino

er, and um, give the linkie to his sweeet SOOO VID, LOVED IT BUT LOST THE PM[:@]

critterhunter

Hey, Fisher lives! Great to hear from you. Nice job on the So in the picture. Is it build #5? One question about following Foam Flyer's directions. Didn't you say that you also had prior tail heavy problems with the build since you where using a brushless motor and lipo? I could have swore I remember you saying you needed a good bit of down trim to try to compensate for it?

Inverted flight isn't so much from not having a symmetrical airfoil. I think the problem is the high lift the Clark-Y produces. But, I was able to do some decent inverted with mine, provided the COG is near perfect and the motor thrust angle isn't off. To be honest, though, I can't remember exactly how well it did at that, but will report back when #4 is flown.

I don't remember if I said it but Big'N has been retired. It only had two short maidens and showed promise, but I decided to re-build it. Not only because I want to tweak a few things (like not needing as fat of a fuse since it won't be flying my camcorder as originaly intended...got an AP build I'm working on for that), and building it out of the stronger EPS foam I've got now will be an added bonus. I also agree that a smaller version would be cool, perhaps an indoor bird.

Nice to see you around and hope you'll throw some more pictures up and offer more advice as you've done in the past. If it wasn't for you and Saucerguy I would have had a much harder time breaking into building with EPS.

Fisher

The pic is of my very first build. My most recent build is over a year old and has been reconstructed after several crashes with hot glue and packing tape. All the crashes were my fault. Flying in high winds and getting too low on fly bys.

First build wasn't really tail heavy more of a thrust alignment issue. It flew fine after adding some down trim. Glide performance was always very good. I was assuming a symmetrical airfoil would eliminate the lift impact during inverted flight as I agree that the Clark-y foil provides plenty of lift in normal orientation.

I need to get a second party to video the plane in flight to show off its capabilities. My only videos so far are from an on board camera and only give a planes eye view of things.

calvino

heck, the plane view looked awesome, I liked it, wow, such a slow flier, yeah, kindof learnin on a SS, WANT TO GET A SOO BUILT (that is if i don't turn a foam jet into a 3d plane, lol)

critterhunter

Fisher, wasn't sure which build that was but still think it looks great. I've been working on the dual boomer here and there and it's nearly complete. Servos and linkages are installed, etc. I've been taking pictures and will post them soon. It would have been done several days ago but I've been busy with my new venture...

I know I've kicked the idea around for a year or two but I finally took the plunge and am going to heating and air conditioning school. It's only 8 to noon Mon-Fri and today was my completion of week one at the trade school. It's a bit hard getting used to going back to "school" again but I took electronics in high school (years ago) and have toyed with projects over the years enough to keep most of it fresh in my memory. In fact, I think I'm hurting myself because I'm trying to make things more complicated than they have to be.

For instance, the teacher said "All loads (motors, pumps, etc) are in parallel.' I raised my hand and said that isn't true, because loads can be in series or parallel. He corrected me by saying "All loads in HVAC are in parallel, only controls are sometimes in series." Just one small example of me over complicating things for myself as I'm prone to do, so I now just keep my mouth shut and keep it simple as possible. It's only hurting me. Good news is I was the only one to get 100% on the test today. I'm going slow in the lab, though. Over analyzing everything instead of just doing what the instructions say to wire the circuit up. [:@]