beenie

My Feedback: (9)

Found out that I was going to be off for the RAMS float-fly down here the last weekend of August and decided to design something diffrent to bring. Besides, my old HOB V35 is getting very rough around the edges. I also have only 5 or so weeks to design, build, test, and refine as necessary. So it has to be easy to build, different, able to ROW, and of course 1/2A. I settled on a plane based on the great Laddie Mikulasko's Arrow. The Dart is not a scaled down Arrow, they just share the same configuration. It is hard not to design a tailless delta wing seaplane with a high mounted engine and not have it look like the Arrow The plane will be pretty no frills due to the timeframe and the desire to keep the weight down. I settled on the following dimensions ; 27"ws, 260sq/in wing/fuse combined area, 24" long with a weight goal of 20-24ozs, yielding a wing loading of about 12 oz/sqin. Power will be a Norvel .074.
I also decided to incorporate some building tools and methods that I have picked up on RCU and other sources. I picked up a couple chipped pool table slates from the local billards dealer for free. They are dead flat and make a tremendous difference in a build. They are also great for laminating balsa and sheeting foam cores. It also makes a great surface for sanding wings and control surfaces. I wish I would have gotten one years ago. I picked up some Midwest modeling pins from the Hobby lobby craft store. They have large red heads and very thin finely tapered shafts. They are the best pins by far that I have ever tried. I used building tabs on the wing ribs for the first time and learned of putting triangle stock on the tabs to keep the ribs square and provide a better spot for pinning. I know some of this sounds basic and a few of the things I have known about for a while and never tried, but wow, what a difference. I have been building balsa models for 22 years (the vast majority of my life) and it is amazing how much there is to learn to improve your builds.
As for the plane, I managed to get it designed on my last trip and got a fair amount built this weekend. I chose to make the wing removable using carbon fiber tubes. This will be the first plane I have built where the wing halves come off. Still not too sure how to keep them attached. A few pics of the progress.
Ben

BMatthews

An interesting design. I'll be looking forward to the flight reports.

beenie

My Feedback: (9)

Also shown in the last post is a method for ensuring the wing spars fit perfectly. Instead of cutting the spar notches first, I built the wing and then used a spar with sandpaper to sand a notch at the proper angle. Something I'd known about but never tried. Neat trick and the spars fit perfectly. The fuse is just 1/16 sheet balsa with 1/8 sheet balsa formers. I chose to keep the formers solid to act as bulkheads to keep any water from sloshing around. I havn't figured out how to drain these compartments when the plane is finished, I am hoping to just keep the thing waterproof. The tail/nacelle seems to be strong enough to support the engine, testing will tell. That was one part I just had to guess on and hope I put enough wood back there without being too heavy. I put the plane together with most of the components in their places and tried to balance it. I thought that the servos would have to be in the foward compartment, but they ended up in the second compartment. I got the engine very close to the cg to try to minimize tail-heavyness and it looks like it worked. I have the cg so far at 14% based on people's experiences with the Arrow, although I am considering making a chuck glider to try it out. In one picture it shows most of the parts along with the engine, mount and tank on the scale. It shows 9.2 ozs. Add 3 mini servos and 1 micro, rx, battery, linkages, some more wood and covering and it looks like 20 ozs is attainable.

One thing that I am having problems with are the elevons. They are 13"long and taper from 1.5" to 1". I made some from 1/32 balsa laminated 90* in between two pieces of 1/16. They are fairly thin and way too flexable, certainly not acceptable. What do you delta guys use for elevons? I am considering using 2 layers of 1/32 layed 45* and 135* in between the 1/16 layers or even some fiberglass.
I will get some more building done when I get back this weekend, hopefully finishing the framework and getting it ready for covering. Until then I am open to suggestions, especially from the delta guys. There will be some reflex, either with the elevons or I may stop the elevons 3" or so from the tip and use reflex tabs. This is my first delta design and it looks so slick it will not be my last.
Ben

flyinrog

My Feedback: (1)

I saw a similar design in a .40 size,,it looks cool, but it also looks like a lot of surface area for that .074 to pull off the water with little to no propwash on the elevons.....hope it works ...keep the pics coming to...Rog

old git

I'm so glad to see someone trying out the chuck glider prototype. As a nipper I tried hundreds of shapes to see if they would fly. With some attention they all did other than one with a solid fuselage, I think even that might have flown if only I could have thrown it hard enough. I did find that butterflies did not improve flight patterns when I altered their planform. While talking about insects, I never managed to power a light H/L glider with a fly glued to the nose, it seemed a good idea at the time.

I have seen blue tape used in construction here on RCU, what for?



old git - - - - aka John L.

beenie

My Feedback: (9)

Rog, I never thought that the surface area would be too much for the engine, but I have given some thought to the lack of propwash over the elevons. I had designed a little fin that sits on the nacelle and would help the plane out. It could be stationary or mixed to the elevator channel. It would help it get up during takeoff and help the pitch coupling associated with an engine that high up. However, based on the Arrow, it will not be needed. The arrow has a 52" fuse that appears to be around 6" or so wide with 800sq/in of wing area pulled around with something as small as a .40.
The hull ended up a little deeper than I wanted it to be based on the requirement that it floats. When I first drew it it was a good bit shallower, but it would have had to sit with the wings on the water bearing about 8 oz of bouancy. So I deepened the hull and widened it a bit until the numbers worked out. I thought about the takeoff for a long time and decided that it sould be ok (maybe) because it will sit tail low at rest, with the wings either just touching or just over the water. On power application, the high thrust line should help it rotate to level and there should be enough speed after a moment for the elevons to be effective. The step is just foward of the CG so rotating for takeoff shouldn't take too much force. Or at least that is the plan. Getting up on plane will be helped greatly by the flat bottom and the fairly sharp rise aft of the step (I hope). I kept the nose broad as far foward as possible to help keep it from nosing down into the water on power application, I even did a drawing where the nose didn't taper at all in the top view. It looked too much like the stake.

As for the chuck glider, they are a really quick and handy way to try out stuff when you don't have a clue. Although I never thought of using a fly to power an airplane, guess it didn't work out too good Also. git, what blue tape are you refering to?
Not many more pics for now, I'm back out at work. I'll have some progress in a little less than a week.
Ben

old git

Hi Ben,

It's looking rather interesting, keep the info' coming please.

I tried a pylon mounted motor on a free flight duration job. The idea was to avoid downthrust and keep power on trim the same as power off. I was trying to avoid a needing a spiral climb using polyhedral wings.

The model had a super glide but destroyed itself totally in its first comp due to flying in too high a wind. Result, one big loop to ground and total destruction. I never revisited that concept. I probably needed to read a lot more or build more to resolve that situation.


I have seen BLUE TAPE used where I might have used normal buff coloured MASKING tape, I thought it may have some special properties.




old git - - - - aka John L.

flyinrog

My Feedback: (1)

Blue tape is painters tape,, it is just masking tape with less adhesive so that if pulls away with out much effort, wont tear up balsa or pull up paint with it.....

Beenie, I guess the flat bottom will help, not sure, the .074 is a great engine,,sure would love to see a video of the take off,,I remember Matchlessaero built a mudbug with a cox .010 it was too cool but the engine was over the wing, actually the rear mounting might help if you plane it up slowly,,,no water here, we have a swamp at our field(its an old land fill with low spots) and at my last flyin I had to walk right out into the middle of the thing to retrieve a HOB stick,,I got the best crash and splash award that day, plus theres a reason its called Copperhead field.....Rog

beenie

My Feedback: (9)

Well, I got some work done on the plane this weekend but nothing that makes an impressive picture. Not a whole lot left to do besides mount the fin/pylon and sheet the top of the fuse. Made a new set of elevons from 3 laminations of the hardest 1/16 balsa I could find and they were really no less flexable than the light ones. I have epoxied a carbon fiber tube for the leading edge of the elevon in an attempt to reduce the amount that they will twist. It helped, but not much. I am probably going to reduce their span so they end at the 2nd to last rib and just fix the outboard section to the wing. I am considering using that fixed outboard section as reflex tabs, having them angled up 5* or so.

Instead of spending shop time building the chuck glider, I bought a ruler, blade, square and some tape on the road to do it. Ended up with a overly nice little plane for a chuck glider but it was better then rotting in the hotel watching tv. My room is entirely too small for little airplane fliying so I am going to have to find a place to test it. Just messing around in the room shows that the 15% cg will work, but is fairly nose heavy and will need some reflex. I will have to work the cg back and see. Kind of a fun little plane. It makes me want to get some micro gear and run it in the pool! WS is 11" and it is about 10" long. There should be some visible progress on the bigger plane by next week. Less than one month to go!
Ben

old git

Yes it is looking great, the little one I mean. Makes me imagine tearing up one of the commercial toy aircraft and using the parts on your little one.

Keep the info coming, I am building it vicariously while I slump at the Confuser.



old git - - - - aka John L.

beenie

My Feedback: (9)

Git,
I was thinking that the little commercial stuff won't be strong enough for the plane, as I was thinking of running out and getting one here. I don't know the weight of the glider, although I suppose I could figure it out given the weight of the penny and the resulting cg change with that mass. But I don't care about the weight that much. It sure would be fun as the plane comes apart and easily fits into my suitcase.
I found one of those fields free flighters love for test glides. Foot tall soft grass and a nice downslope of about 15 feet followed by a flat area. Was able to glide to my hearts content up here (Rochester MN) in the nice late afternoon/early evening calm. Looks like 15% MAC was a good guess for the CG. It ended up having a fairly large range from about 12-18% where it the flight characteristics were basically unchanged. It also took very little reflex, just a couple of degrees. I tried to see how far back I could get it and ended up with a neat stall and flat spin. I didn't measure the cg for that but it was probably 25 or 30%. So it is set for the test flights, 15% MAC and 1/16 or 3/32" reflex on the elevons.
Ben

lildiesel

Nice ship.

Guaranteed to make me persona non grata at the nearest fishing pond.

beenie

My Feedback: (9)

Had a few days off and got a lot done on the plane. The aft end of the fuse was going to be difficult to sheet properly because of the pushrod exits. Well, turned out to be farily easy but it took 3 pieces of wood to do. Ended up with a nice looking watertight stern.

Lildiesel, thanks. Yeah, I don't think the fishermen would care too much for it buzzing about them while trying to fish.

beenie

My Feedback: (9)

I was hoping that I could still use the nice lightweight elevons that I had first made for this thing. They were light, 11grams for the pair, but they were so flexible that their weight was irrelevant because they were useless. Even though they were laminated from 2 layers of 1/16 with a 90* layer of 1/32 in the middle, they were tapered so much that they had no rigidity. I glued on the carbon rod LE and that had little to no effect. So I wrapped them in carbon fiber tow and then fiberglassed them with 3oz glass laid 45*. I also cut about 3" off the tip to help with the rigidity. Well, that really helped. With the new composite elevons, they are VERY rigid. It is amazing the difference, they used to twist almost 90* with very little force and now they only twist 5*. That came at a price, however, they now weigh 19 grams[X(] Very happy with how those came out. As an added bonus, the fiberglass surface is hard enough for the control arm to go on without a plywood mounting plate. And they are waterproof!

On the scale with most of the parts, 17.7ozs, looking like I might make the design weight. Only weight missing is wing and tail covering and fuse glass and paint.
Ben

beenie

My Feedback: (9)

I build all of my seaplanes and float sets with the intention of land operations as well. So for this thing I glassed the bottom from the step foward with 3oz fiberglass and the rest of the fuse got .5 oz glass. I forgot how thin and light that .5oz is. All told, the fuse glassing added about 12 grams. Filling the weave and the primer coat added another 10grams, some of which will be sanded off. So I think that I will be able to get away with waterproofing and finishing the fuse for about 1oz. It might have been lighter to just finish it in Ultracote, but I prefer having one continuous waterproof barrier that also seals the wood instead of strips of film stuck to the fuse with all of those seams waiting to open and leak. I also had to make a hatch of some sort. The Arrow has a nice canopy to allow access to the inside, but I just cut a hole in the top of the fuse. It isn't really waterproof, but I am considering some means of making it so. I don't plan to have a switch for the battery, so it will have to be easily removable. I just don't see a lot of water getting to the top of the fuse. Anybody with some experience on this?

Also, I was able to get the wings and most of the tail covered. Most all of my planes are scale, so choosing color schemes for them is fairly easy. Not so much with a sport plane so I had my wife go through the covering pile to pick some colors. She chose black and hot pink. We came to a compromise with the silver, purple and black. I was going to put bright yellow accents on the airframe for visibility, but down here anything purple and yellow is immediatly associated with LSU, and I didn't want anything to do with that! So I am a little concerned about visibility. Although I do think the shape lends itself pretty well to orientation in flight. One end is pointy and the other has wings and a big tail. The fuse will be black with the bottom a new Testors paint "Lime Ice" she just had to have at the hobby shop. It actually looks good with the other colors as they are all pearl.

Back on the scale now, the only thing not included is the fuse finish paint and a few bits of hardware. At 1# 3.2 ozs, it looks like I will be VERY close to making it in at the bottom of my weight range of 20ozs. I had this engine on a 17oz proflile and it would hover and accelerate vertically. So 20ozs should do quite nicely. Also the wing loading will be about 11 ozs/sq ft, I will be curious how slowly it will fly with that high angle of attack that the deltas can do. I am also considering the possibility of a grass takeoff. It took about 6oz of force to move the plane across my long grass at the house, it should take even less at the field. So I am thinking that if it is able, the first flight will be on land. It is easier to find the parts if things go badly.
Ben

beenie

My Feedback: (9)

Last thing I was able to do before going back out to work was check to see if it floats. Well, it does. The waterline is pretty much where I wanted it to be, even a little higher in the front due to the lighter weight. In the pics the elevons are just awash, but when they are reflexed they are on the surface. Although the additional 1.2 or so ozs of fuel might stick them back under. I don't think that it will matter because as soon at it starts moving they come out of the water. I was able to give it a little push and it seemed to ride just right. I was happy with how high the bow rides, should be able to take small lake waves without spearing them. Back to work for a week, but I should be able to get it flight ready and hopefully get a test flight this coming weekend.

Speaking of fuel weight, should I balance it with the tank empty or full? On a foward mounted tank it is done empty to give the aft most CG for the flight. Well, for this plane that condition occurs with a full tank. I am considering balancing it half full (or half empty) to split the difference.

Ben

Edit:Well, I just ran the numbers and it may be a moot point, the difference between a full and empty tank is 2% MAC. I think I will just balance it with an empty tank.

old git

Despite what you said I spent minutes trying to see what you had done, I was also listening to the news. Suddenly it was clear, the guide tubes were guide tubes and not pins.

It's amazing how perception is all, the images were quite clear but I still didn't see what suddenly became obvious. Explains the odd flight patterns of my models, better when free flight.


Looking good!


old git - - - - aka John L.

soarrich

My Feedback: (98)

When do you stop being a Craftsman and become an Artist? Beautiful plane!

beenie

My Feedback: (9)

Rich, thanks for the kind words. Congrats on your little John Deere's flight, what a neat little plane. That thing took off like a rocket on hand launch. My only diesel experience was the Davis head on a properly broken-in Norvel .061, only got it to run once, and then only for a short time. And it certainly wasn't for lack of trying.

General Lee Stupid

Beautiful plane, great design, hope it flies well!!

beenie

My Feedback: (9)

I was able to get the Dart finished and tested out. Final empty weight was 20.4 ozs, on the low end of the estimate. The battery ended up under the servos to balance it at 15%, so no ballast was needed. I think I would have done some serious component moving before adding ballast. Ended up using small magnets to hold the wing on, they seem to be very adiquate and no tools are needed for wing removal.
Out on the lake for taxi tests and it is fairly well behaved on the water. It sits just right and the rudder has plenty of authority. I found out that the elevons are very handy on the water, when in displacement mode full up elevon causes it to squat and the plane stops very quickly. Also, when the engine quits fairly close to shore, you can move the elevons back and forth from full up to full down and they cause the plane to move. Its not fast, but it gets the job done. The .074 has more than enough power for this airplane. I was able to get it to flying speed on grass before I took it to the lake, a sure sign that it would have no problems planing out.
On the water it rises on plane quickly and is fairly stable there. Because the hull is flat bottomed and the skeg is out of the water in a level planing attitude, tracking is a little weak, but that was expected. It does pretty well considering the hull shape. I'm sure a few more test runs will uncover some neat water maneuvers and tricks. The wings act as great sponsons and it is impossible to flip as long as it is on or very close to the surface. They don't dig in nearly as bad as regular sponsons do. One thing that I did not anticipate was the torque of that high mounted engine. You can see in the video that it really wants to bank to the left. I don't know if there is much that can be done, but I am thinking of switching to a smaller prop. It may reduce power but there is plenty of that. I am currently running the MAS 7X3 getting about 16.5K RPM out of it. I will be trying the APC 6X4 or 6X3 and see what happens. I think the 6X3 will be a beter prop as it has much larger blades than the 6X4. Here is a link to the video of some of the test running. http://www.youtube.com/watch?v=8IWhraoUBBM
As for flying, I was able to get a short flight in. I have the video but the quality is poor. I think that CG is pretty close and so was the reflex. It only needed a few clicks of up to fly level. The ailerons where a different story. I had set their throws for what looked about right and set the D/R at about 55% with 35% expo. Well, I'm glad I did that because it was almost uncontrollable in roll on low rates. I thought that I had lost it a few times. Also, it needed a good bit of right trim to counteract the torque of the engine. I have since brought the both the high and low rates way down and increased expo.
It was fast for the few seconds that I had the courage to open the throttle up. Power and speed only exaserbated the aileron issue so most of the flight was at half throttle or less. Something that I wasn't quite ready for was how little drag it has, descending for landing took a lot of room and speed didn't bleed off too quickly. On my first approach I let it get a little too low before initiating a go-around, and then forgot to add power slowly. The result was an immediate dive to the water, a quick skip and a half roll to an inverted landing. It happened very quickly and was kind of funny. The plane was not damaged from the impact, but the fin filled with water that ran into the fuse when I turned it over. That damaged the aft half of the fuse and loosened several glue joints back there, including the fin spar/fuse joint. I think the water came in to the fin through nacelle and then through the holes for the antenna and throttle servo wires as there are no other holes in the fin. I had to remove the bottom of the aft part of the fuse and repair some wood. The damage isn't too bad and I should be able to get it finished and get in a few more flights next week. The good news is that the "non-waterproof" hatch for the radio compartment is in fact waterproof. Also, the plane is going to be very hard to sink because the wings provide enough bouancy to float the entire plane.
I have included a few screenshots because there were no stills taken at the lake.
Ben

Strykaas

How cool is that , nice [8D]

Beautiful flying site ! I wonder why your neighbours don't come out, shooting at you with a double barrel shotgun just like they would do here.

beenie

My Feedback: (9)

This lake is not a regular flying site. It is very close to where I live and was convienient. However, because it has houses around it, I went during the middle of the day during the week when everybody was at work. I don't plan to do any flying there but it is so nice and so close I may get back into boats. Also saw a bunch fish in it, so I may be after them soon.
Ben

KidEpoxy

how tall is the "step" on the hull bottom?
It doesnt look like much on the little pic of the plans at the beginning of the thread

beenie

My Feedback: (9)

No, the step isn't terribly deep, only 3/16". With the part behind the step rising so steeply, I could have probably gotten away with less, possibly even 1/16".
Ben