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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/14/2006 4:31 PM   
Fisher



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Thanks for the info on the Common Sense batteries and the balancing chip. I will have to look into that next time I need a new LiPo.

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/15/2006 9:46 AM   
Espresso-Outfitters


 

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I found this plane posted in another forums, but immediately was thinking, this is the free foam flier using different materials big time:

http://static.rcgroups.com/forums/attachments/4/7/6/7/9/544292.thumb?

Pretty cool huh?

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/15/2006 8:03 PM   
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I get a error 403 on that link...

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/15/2006 10:43 PM   
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you gotta cut and paste it in your browser

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/15/2006 10:55 PM   
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that worked thanks

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/18/2006 10:28 PM   
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Keep your jaw from hitting the floor...Critterhunter has finaly made some progress! Today I played hookey from work and hit Home Depot to pick up a few odds and ends for this foamie build. I picked up the hardware to build Expresso's "I" bow hot wire cutter design and the stuff I needed to build the wing airfoil jig.

I was roaming the store and found what looked like some good wood to use for the airfoil jig. This stuff is called "MDF Handy Panel" and I bought a 2x4' 3/4th inch sheet of it for about $5. It's not partical board. Much smoother/harder surface to this stuff...made out of some kind of wood product. Anyway, blew up the airfoil template that Fisher gave me at the local copy store to where the width was 7". Then printed this out on some card stock so I'd have better luck cutting it out to trace around on the handy panel. Cut the two airfoil jigs out with a jigsaw close to the trace lines. I then locked them side by side in a vice and used an orbital sander to fine tune their contour, getting them to match the printed airfoil templates completely. This handy board sands easy and smooth and I'm hoping it won't melt/bind when the hot wire cutter runs over it?
Anyway, I then cut a 7x36" board out of this stuff and then screwed the templates to both ends.

One question for Fisher...Is the flat (wing bottom) on the template the dotted line above the numbers or the solid line below that? I would figure it's the flat dotted line above the numbers because if I used the lower solid below it then I'd have to curve the bottom leading edge of the wing as well and you said it's meant to be flat. That wing looks like it's going to be pretty skinny for this kind of foam so that's what made me wonder. I also blew the template up at the copy store to match 7" in length for this dotted line. The line I'm talking about meets the leading edge right before the leading edge begins it's curve under the wing. I figured this was the line you were talking about since you mentioned keeping the bottom flat. If, somehow, I've used the wrong line for the bottom wing surface I'll just unscrew these jigs and place them on top of a new, slightly longer board, instead of screwed to the sides. In other words, I've got the height in these present jigs if they are sitting on top of a board but I'll have to cut a slightly longer board to compensate for the width of the jigs (3/4th inch). Just so happens that the width of this board is the exact same height of the airfoil template from the very bottom line to the dotted flat line above the numbers I specified, so I cut out the entire jig as printed and then simply screwed it right into the sides of the 7x36" board. The wing and it's airfoil on the template jig are flush with the top surface.

Question for Expresso...Do you think this stuff will work for your hot wire cutter design? I know you used Plywood but this stuff seems even stronger so I figure I should have no problems. One 2x4' sheet of this stuff will make you the airfoil jigs, wing board they bolt to, hot wire "I" cutter you showed plans for in this thread, and even body part jigs to trace around with the hot wire cutter instead of trying to follow lines drawn on the foam.

Heading back into the garage to start building the hot wire cutter and will post pictures as I make more progress.

Oh, by the way, I'm planning to hold the wing board jig down onto a work table by using "L" brackets at both ends of the board screwed into the sides of the template and held down to holes drilled into the work table via bolts and wingnuts. That way I can remove the wing board jig from the work table when not in use, yet have it held firmly to it while cutting wings. Now, the way I understand it, to hold the foam to the wing board while cutting you want to use double sided tape between the foam and the wing board? Thanks to your help and answers to the above questions.


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/18/2006 10:48 PM   
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The mdf "medium density fiberboard" should work, just will not last as long as a bow since you are putting tension upon a small area, ie. the mounting screws. It may appear to be strong, but structurally it is not. Plywoods comes in different densities as well, osb for example is a Fir based plywood which is rather soft compared to the shop grade birch plywood which is much more dense and rigid, I have plenty of scrap to make stuff like that with. You'll find after you build the first one it's easy to reproduce it, so don't sweat it. It's reccomended to just do some free hand test cuts to get used to the bow regardless, so don't worry about destroying material, going in this manner you'll get a feel as to it's cutting properties.

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/19/2006 2:15 AM   
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Just finished the cutting "I" bow about an hour ago. Didn't take long at all. I even cut the aligator clips off the battery charger and hitched an AC outlet plug to them, then used a short extension cord on the hot wire cutter so I can just plug it into the charger much like you did. On the bow I just snugged the two wire leads under the nuts on my eye bolts that the fishing leader is knotted too. No soldering or aligator clips to worry about. Did a few test cuts at 12V 6 amps and the results were mixed. If I do a short cut through some foam the results are good with a nice smooth surface and little or no binding. However, If I attempt to do a long cut the wire is grabbing and skipping a bit on me. There are two potential problems that might be causing this...One, the spring is too limp and isn't keeping the wire taught enough. I suspect this may be a problem anyway and may have to try a stronger spring. Exactly how tight should the cutting wire be? Just taught or very tight? Say on a scale of 1 to 5 with 5 being VERY tight. If I push on the wire with my finger I'd say I can put a decent flex into it.

The other problem may be that the wire isn't getting hot enough and I suspect it should be hotter. The cutting effect isn't like a hot knife through butter. There is some resistance. The cutting surface, while smooth, could be smoother. This has me scratching my head as I thought I read that 12 volts at 6 amps would work on a 6 foot bow. My bow wire is right around 44 inches long. I wanted to make sure I had plenty of clearance on both sides when cutting the 36 inch wing. The gage wire I'm using is .022 diameter steel fishing leader (check back a page or two for the specific metal makeup of this fishing leader. Am I thinking right that I should try a thinner wire as this has less current carrying ability and thus will get the wire hotter? Beyond that I'm not sure what the problem could be. I didn't get excessive with my length of extension cord between the charger and the cutter as I know this has some effect on the current. Ideas welcome.

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/19/2006 3:04 AM   
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well, like I said, you'll be wasting materials trying to get used to it, be sure your jigs have latex paint, or something smooth to allow the wire to glide along, my first jigs were plywood and it kept binding up the wire causing divots. The next time I drag out the cutter, I'll be messing around getting it tighter as well as moving the literal power source onto the wire itself such as fishers one in order to help address those very issues. So, those would be my suggestions, the spring can be mounted further away from the actual bow, or just pulled tighter and mounted mid section of the spring instead of the end, I can say mine taught to a point similar to your car engine drive belts.

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/19/2006 1:09 PM   
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Expresso, I've got about 7 or 8 feet of cord between the charger and the hot wire on the bow. I think this might be one problem with the wire not getting hot enough. Longer cords equal more resistance and less current flowing through the cutting wire. I also had the charger hitched up to an extension cord to power it that was 20 to 30 feet long. That will also lower the input AC voltage to the charger. Still, even with that I would have figured this .022 diameter steel fishing leader would get plenty hot enough. The other problem might be this old charger isn't putting out the amps it once did. I think I'll first try using a thinner fisher leader a size or two smaller than .022 and see if that gets the wire hotter. Made one other major design blunder. The bow isn't deep enough to cut out a 7" deep cut so I can't cut my wing blank out of the foam. Will have to rough cut out a piece and then fine cut it with the bow. I plan on making another hand tool or two anyway. A small bow for compartments and a bandsaw type table cutter for doing straight cuts. Will also need to pick up a stronger spring as I know this wire has too much give. As for the jigs, this handy board is very smooth and some test slides over it with the bow showed no binding. I used an orbital sander to smooth down the surface of the jigs so they matched each other perfectly. The results are it's smooth as silk.

Where's Fisher? Doesn't he realize I have a never ending stream of questions?

Here's a picture of my bow...


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/19/2006 1:34 PM   
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critterhunter my screen name is e"s"presso-outfitters, ie. Espresso-Outfitters, not Expresso or Expresso-Outfitters, use Espresso for short if you want, or EO as others refer to me in a forum I created, own, moderate and have another screen name, espresso outfitters: http://espressoforums.com . I had to bring this up since obviously you and I have a dialog going on.

Good job on the bow, it's liberating to be able to slice through this material when before you were relying upon more conventional means. Actually, before you get ahead of yourself, the bow will do "all cuts" so don't consider yourself to being reliant upon coneventional tools and equipment, it's all jigs and revisions to the bow(s) at this point. Heed my advice and you are skipping many steps most others will have to take to come to this conclusion.

Your extension cord to the charger has minimal impact, the distance from the charger to the hot wire is not, shorten it to the absolute minimum, your's is too long. Don't feel bad about destroying stuff, I do plenty since the egg heads have zero teaching skills for the noob, I'm taking this education in stride knowing I'll be able to translate this in human terms, in a simple format to the laymen when asked entirely because I had to go through the paces in geek speak and raw intuition.

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/19/2006 4:18 PM   
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Critter, I can't really see in the photo of your bow, but is your power wire attached directly to your cutting wire, or to the bolt/hook that is holding the wire?

I ask because when I attached mine to the bolt instead of directly to the wire (both are metal didnt think it'd make a diff)
My cutting wire wasnt as hot.. putting a big chunk of metal (the bolt) in the way gives less resistance, so the wire is cooler, go right onto the cutting wire and it'll be a lot hotter

As for tension, mine is a similar tension to a guitar string and gives a healthy twang when plucked

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/19/2006 6:17 PM   
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EO, sorry for using the wrong name. Just kind'a fell into that name and didn't pay attention to if it was correct or not.

I just tried an .018 diameter steel fishing leader (going down from the .022 size) and figured the thinner wire would get hotter. Nope, the wire cuts but if I don't go very very slow it starts binding and grabs. Exactly how fast are you moving the bow through the wire? I'm not expecting lightening speed but I still feel it's too cold. I think you are right that the extension cord between the charger and bow wire is too long. I'll shorten it down and try again. Just rebuilt the bow with longer boards at the ends so It's got a good 10 inches of depth now for cutting deeper pieces. Tied the spring into two knots and this helped increase the tension on the wire. It now makes a good "twang" when I pluck it. I could go down to an even smaller diameter fishing wire but it only is rated at about 36 pounds and worry I'll get a broken hot wire in the eye if I try using it.

Jax, yes at this time I have the lead wires snugged under the nuts on my eye bolts that fasten them to the board. Perhaps your right and the bolt is causing things to stay cooler. I would have figured that the eye bolts would have almost no resistance and thus wouldn't make much difference in the current loading. If shortening the extension cord between the charger and cutter doesn't heat things up I'll attach them to the wire directly. Unless this antique battery charger is putting out a weak voltage/amp at it's 12V 6 amp setting I can't see why things are staying so cool.


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 10:41 AM   
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Here is a few pics of my cutter so you can see what I'm talking about Not the best one I'm sure, but it works for me ok.

The pics are:
My bow, full pic.
Bow, close up of the spring tension I use
Bow, Power supply I use
Bow, close up of how I connect cutting wire to the power source

Bow is just 1 length of PVC pipe, 40mm, about 1.2m long
2x arms, 25mm (approx)pine dowel, 50cm long.
2 bolts
cutting wire and tension wire (same wire used for both)
Spring (approx 15cm long)
2x eyehooks
2x aligator clips

PVC has a 25mm slit cut into it about an inch deep on both ends.
1 of the dowels is bolted hard against pvc, about halfway up dowel.
other dowel is bolted to PVC but given a bit of room so it can swing a little
eye hooks bolted on the tension side of the dowel, tie wire to one hook and measure it out and tie to the spring. The spring then hooks to the other eyehook. if you need more tension, just tie the wire a bit shorter on the spring

I just drilled a small hole through the other end of the dowel to loop the cutting wire around, makes it pretty easy to replace, then just leave an inch free and hook the power to it using the aligator clips.

Cutting: cutting smaller pieces is easy will cut about 1cm/second.
Large cuts, IE wing takes about 1cm/2.5 seconds, and I have found it cuts a little quicker if you move the wire side to side in a gentle sawing motion. If you have a variable power output you could just up the amps a bit. I think 3 amp output.
Basically find out what amp will make your wire start to glow and then back it off a bit. Its worked for me so far and I'm a newb at it so I'm sure you can figure something out


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 11:00 AM   
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Good Job all of you that have created their bow's, again have to reinterate, it's liberating to be able to cut out parts out of foam without cutting and sanding with traditional tools, I have to add, the cutter is not the final get all of tools for building out of foam, there is plenty to add and needs to be addressed in order to effectivly create your own. Next, I'm going for a pro set up, both with the bow and the power source when I opt to get back into cutting foam again
my job of which I'm the owner prevents me from free time to do this stuff at present", it seems like it's easier to build jigs, and ultimaltely arf's then to reinvent the wheel upon creating the foam cutter(s).

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 11:02 AM   
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Oh yeah, here is what I have so far.
I havnt installed the rudders yet, or any electrics. Rudder I am thinking of using balsa as I think the foam I have would be too fragile if its that thin.
The electrics I have to save up for as I dont have anything yet as this is my first propper r/c plane lol.

Oh yeah, in the pics above the dowel looks like it has a small curve in it. yeah it does, but its strong enough to handle it. Also the longer the tension side of the arms are the less tension the spring needs to have



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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 1:42 PM   
critterhunter



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Thanks again for the input. Wire is still not getting hot enough even with a much shorter cord between the charger and bow. This time I only used the charger's original wire leads and no aligator clips. I secured the wire leads under the eye bolt nuts again that hold them to the wood. I guess next I'll try to attach the leads directly to the cutting wire ends. Perhaps it is getting hot enough because if I move slow (like less than an inch a second) the cut is smooth and no binding. Still, as you said I have read that the proper cutting temperture can be found by allowing the wire to get red hot, then backing the power down to where it doesn't glow anymore. I also hear allowing it to get read hot will allow it to self clean any debri on the wire before cutting.

EO, what diameter wire (I'm currently using .018 diameter) are you using and what is the full description of it? My only other suspect might be the wire. This stuff is single strand steel fishing leader and has the words "chrome" and "nickel" in the description so I think it's nicklechrome wire. Does this stuff not get as hot as other types? Also, exactly how fast is your bow moving through the wing while cutting the airfoil in inches per second?

Another question I have is about cutting out various body parts. Should I make templates out of the handy board of all the body parts so I can just run the cutting around them to cut out the parts? If so, exactly how should I secure the template to the foam while doing the cut around it? I quickly figured out that it is impossible to do a straight and level cut through the foam with the bow. While I can follow a line easy enough the top and bottom of the cut tend to be unlevel. I'm thinking that if I use a handy board template on top of the foam this will keep the cut straight from top to bottom through the foam. This is one reason why a bandsaw table top type hot wire cutter would be a good option. With something like that I wouldn't even need a body part jig, just guide the foam through the cutter wire over the table top and things should be straight and flush.

So close yet so far. Have to get this wire hotter.


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 3:45 PM   
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I had trouble getting straight cuts too, so my solution was to get 2x 5mm pine boards and screwed them to the edge of my bench, just a tough shorter than my bow length.
Using a set square both boards are at right angles to my bench so all I have to do is secure the foam to my bench using double sided tape and make sure my cut line is between the 2 upright boards. Pass the bow down, pressing the cutting wire against the uprights, hey presto! a hot wire guilotine and very straight cuts.

I also made an edger but putting a cutting wire between a small wooden right angle, about 20cm long. Have 3 angled cuts through the angle and that gives me 3 different variations of edges. used it on the booms of the plans, nice smooth angled edges, looks better

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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 3:56 PM   
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Garbage picked a nice square piece of laminated wood today that will serve as a nice base for a bandsaw type table cutter. Should only take me about twenty minutes to build a nice table top cutter for straight cuts and such. Beyond that I'll be making a few hand tools for cutting out square compartments on the plane and so on. I'm guessing the .2 to 1.2 amp variable dial on my battery charger should handle small hand tools and maybe the tabletop bandsaw device with no problem. Getting the 44" bow hot enough to cut the wing airfoil out is still my main concern at the moment. Also will be cutting out some templates of the body parts to act as guides on the foam today. Where's Fisher?


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/20/2006 4:44 PM   
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Where am I? Heck, I don't see any activity on this thread for 3 days and all of a sudden you guys are posting reams of stuff.

1. Look at post #16 from page #1 of this thread is has a detailed photo of the airfoil profile. 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.

2. The hot wire foam cutter will not normally cut like a hot knife through butter. There is always some resistance unless you have it super hot. I hold the bow with my finger tips and apply very gentle pressure, feeling my way along more than pushing the wire through the foam. It should take more than a second to move and inch.

3. Your bow is quite a bit longer than mine (size matters). The longer the wire the more current you need to keep the wire hot. My bow is 38 inch long. Just long enough to cut a 36 inch wing with a little breathing room.

In some respects I think that it was easier for me to build my foam cutter and templates without asking for too much information. Once I screw something up really well I understand how to do it right. My 13 year old son is wanting to build a Floating Arm Trebuchet as a science class project. We are at the Just Do Itphase. We will see how it goes.

< Message edited by Fisher -- 4/20/2006 4:49 PM >


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RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/21/2006 12:19 AM   
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critterhunter, attached is a photo of the fishing leader I used, next to it is my plexiglass bender and a piece of plexi already bent and clamped in place to cool down, just showing that for kicks. The line is multi strand stainless steel, I kept breaking guitar strings on the original's. You'll see what I mean about soldering this stuff, it's hard to tie in knots as well. I measured it's width at 1/32". Don't dig through the garbage for laminated wood, I not only have plenty I regularly throw out, I can custom build you a platform for this stuff. Also, take note to the volume of that wire, as you can tell since I only have that one bow, I have plenty more on that spool, perhaps I'll use it for pull/pull wire controls on the free foam flyer Fisher promised to me by the end of last week, hehe, just kidding.

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< Message edited by Espresso-Outfitters -- 4/21/2006 1:32 PM >


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(in reply to Fisher)
       Post #: 196

RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/21/2006 2:56 PM   
critterhunter



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From: Brook Park, OH, USA
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Thanks to you both for yet more answers to my questions. Fisher, it appears then that I have used the wrong line as the base for my airfoil templates. I used the dotted flat line that meets the leading edge of the airfoil before the airfoil starts it's curve under the wing. This also means I blew the template up to a 7" size at this line from tip to tail of the airfoil. However, after looking at the picture again I believe this will still work. My wing might be slightly thinner but the top airfoil curve is still intact. Since I planned to add a carbon tube to the wing anyway I'll try this airfoil first before decided if I need to cut it to proper dimensions.

It would also appear that the cutting wire may be getting hot enough. I'm just expecting it to cut a bit faster than it is. Based on your description that is takes more than a second to move an inch that's about the speed I have to move at to keep the cut clean with no binding. I'd still like to have enough control over the bow to get it red hot and then back it down to a cutting temperture to be sure. Still, I can also simply shorten the cutting wire on the bow as the pivot spring will of course adjust to compensate. Perhaps I'll cut the wire down to where it just bearly clears the airfoil jigs like you did. That should loose a good 8 to 10" of extra wire and make things a bit toastier.

Dug through the junk box last night in the garage to find some parts for the bandsaw cutter and am glad I did. I was just going to go up to Home Depot for the hardware but found everything I need short of the metal shelf support to hold the top of the wire above the table. Amazing the kind of stuff you can find in a junk box. The tricky part is mounting the wire ends so that they can be adjusted to create a perfect straight up and down vertical angle to the horizontal board surface.

EO, thanks for the offer to build me a platform but I've got all I need laying around here. Half the fun for me is making the hardware and building the planes. It forces me to learn new skills, such as how to hit a nail with a hammer. If I ever get the point of being able to build these bodies fairly well then I'll ship you one or two if Fisher hasn't beat me to the punch.

PS- Was doing some web searching on foam cutting and found (think it was in this forum) a thread on foam cutting. Man, you should see some of the plane bodies these guys have built out of solid foam just by using hand tools with different cutting abilities. They look store bought.


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(in reply to Espresso-Outfitters)
       Post #: 197

RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/22/2006 2:26 PM   
critterhunter



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From: Brook Park, OH, USA
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Measured my bow last night and it's only like 40" long...just enough clearance on both ends to clear the wing airfoil jigs so I can't shorten the wire anymore. I still suspect the wire is not getting as hot as it should but need to make a few more *slower* test cuts to see if I'm just rushing the cut on it.

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") 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.


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(in reply to critterhunter)
       Post #: 198

RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/22/2006 2:28 PM   
critterhunter



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From: Brook Park, OH, USA
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Sorry, can only post one photo at a time for some reason....


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(in reply to critterhunter)
       Post #: 199

RE: Here's a Simple & FREE First Foam Build Plan! Cool ... - 4/22/2006 2:31 PM   
critterhunter



Posts: 2717
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From: Brook Park, OH, USA
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And here is the bottom mounting bracket...Hope this bandsaw type cutter will eliminate the need for wood jigs to cut out my body parts. Going to try just following traced lines on the foam free hand.



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(in reply to critterhunter)
       Post #: 200

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