Why Foam

[Motorman]

Is there some advantage to a foam wing in stunt or is it just another way to do the same thing? Is the foam readily available or is it a treasure hunt?

Thanks,
MM

[Howard Rush]

Yes, yes, yes, and yes, respectfully.  It's another way to do the same thing, but it's a way that's easier to finish.  Go to a place that sells insulation materials and ask for 1 lb./cubic foot virgin expanded polystyrene foam, also known as beadboard.  Home Depot and guys like that probably won't have the thicknesses you want.  Search here for lots of advice on cutting and finishing foam wings.

[Brett Buck]

Is there some advantage to a foam wing in stunt or is it just another way to do the same thing?

  I think there are significant advantages to foam wings, particularly, they tend to be stiffer for a given weight, and when they do flex, there is less tendency to warp at the same time.

    Brett

[Bob Hunt]

Hi Ty:

Thanks for the plug. Yes, John and I have been doing this for a long while, but I started in 1968. I think John started in the mid to late 1980s. Either way, we can offer anyone who is interested a variety of wing designs. I offer not only cores, but also fully sheeted wings with lots of options including landing gear systems installed prior to sheeting and sheeted foam flaps. I have the templates for hundreds of designs in stock.

I've been sidelined for a few weeks due to back issues, but I'm much better now and I'm fully back to work in the old "foam shop."

Later - Bob Hunt

[Steve Fitton]

Foam wings are just so easy to work with, and easy to have an accurate light wing every time.  I need to increase my stockpile of cores before Bob retires!

[proparc]

As someone who both,builds up wings and cuts my own foam wings, I can say they are about equal in terms of skill and difficulty. That said, I personally believe the foam wing to be virtually unbeatable for long term stability and section fidelity.

[Motorman]

What's it cost to get set up for foam because for the price of one finished wing I could buy 3 brodak kits.

MM

[Tim Wescott]

What's it cost to get set up for foam because for the price of one finished wing I could buy 3 brodak kits.

I've never seen a complete Bob Hunt wing, but I rather suspect that it's worth it.

His cores are pretty reasonable, and cost a lot less than a Brodak kit.  If you want to do the work yourself and save some pennies, that may be a good way to go.

I'm in the process of learning to cut foam, and it's not something where you can just get all the equipment and start whacking out foam cores that are pro quality.  Every time I cut foam I discover something else that I did not know before.

[Paul Walker]

And they stand the test of time better. I still have the 2nd Bad News , it is foam, and in amazing condition considering its age. It will be eligible for Nostalgia 30 next year. I plan on flying it at least once in N30 then.

[Howard Rush]

What's it cost to get set up for foam[?]

If you search as I suggested (I haven't), you should find that you can do it well with stuff you have around the house.

[FLOYD CARTER]

I use the blue foam (Home Depot) for molds to form balsa parts.  I don't yet have the courage to try a home-made foam wing!

Floyd

[Brett Buck]

I use the blue foam (Home Depot) for molds to form balsa parts.  I don't yet have the courage to try a home-made foam wing!

   There's some skills to learn but it's ultimately pretty darned easy.

     Brett

[Motorman]

Where do you get the foam? Went to home depot and all they had was 3/4" thick.

MM

[jfv]

Motorman:

Your a Jersey boy.  I get my 1 pound virgin foam from:

Foam Pack Industries
72 Fadden Road
Springfield, NJ
973-376-3700

Lots of info on the net on how to build you own system cheap.

[Bill Little]

I do not cut my own cores (I did 40 plus years ago with a buddy!) but I have sheeted quite a few.  I like them but found they are almost as much work as a "Lost Foam" wing.  Lost foam wings, I beams and Foam are the ones I like to build now.  I have jigs of several types and sometimes have to use them, but foam cores are really reasonable, just add the cost of the balsa to sheet them.  I usually have that already.  For durability you cannot beat foam wings!  You can drop something out of your shirt pocket (like a glow plug) and it just bounces off! LOL!!  Plus, Bob and John (plus a few others) are the professionals at cutting cores, and they charge ridiculous low prices for cores. (don't tell them I said that! LOL!!)  I have a set of laser cut ribs for an SV-11 wing and have built three SV wings from foam since I got them!

BIG Bear
RNMM/AMM

[Motorman]

Ok, so what is so hard about cutting foam? I talked to one guy who makes it seem akin to playing a musical instrument where you need years of practice. Another guy doesn't even try to do it by hand and has gone CNC with it. Makes me almost not want to try it.

MM

[Brett Buck]

Ok, so what is so hard about cutting foam? I talked to one guy who makes it seem akin to playing a musical instrument where you need years of practice. Another guy doesn't even try to do it by hand and has gone CNC with it. Makes me almost not want to try it.

    It takes some skill and some knowledge to do, but I got acceptable results on the second try.

     Brett

[Tim Wescott]

My own experience is acceptable results after a few tries, and it gets better from there.

[Brent Williams]

There are a multitude of ways to accomplish the feat of dragging a hot wire through foam to make wings.   It would be very interesting to see the bow and power supply setups that you all use.  My few attempts at cutting a wing have not yielded a usable product,  but I will keep at it.  My templates shifted during the process and I think that I need more tension on the wire.  There was a definite bow in the cutting wire as I pulled it through the foam. 

[Igor Burger]

http://www.rcmania.cz/viewtopic.php?f=123&t=49483   

[dale gleason]

Mike Greb posted his foam cutting technique on you tube many year ago, but, I can no longer find it. He made it look easy.

I assisted Kyle Tankersly in cutting some foam bucks for Rabe Bearcat leading edges, and it seems to go well with two people moving the hot wire in harmony. If there is discord, the results suffer somewhat.


The best and strongest wing I ever built is a Hunt "lost foam" Impact wing. It's a great system in that the wing is straight and the lost foam can usually be found back in the foam cradle, ready to be utilized again and again.

Hopes this helps,
dg

[Dave_Trible]

I'd like to see how it's done these days.  I cut the wing for my first Music in 83' from foam as well as earlier combat stuff.  I used a nichrome wire from Sig and an electric train transformer with a wood bow.  Also used some controlline cable with some good result but the nichrome was hotter.  It didn't occur at the time to use the scrap cradles to glue the skins on.  I felt I gave up some control over the shape of the product although they turned out fine.  I see the point about weight.  A lot of silk span to fill over open bays is a lot of dope.

Dave

[Brent Williams]

http://www.rcmania.cz/viewtopic.php?f=123&t=49483  

Igor, that is a nice way to build.  What are you using for a power source, and what size/material wire are you using?

[Tim Wescott]

There are a multitude of ways to accomplish the feat of dragging a hot wire through foam to make wings.   It would be very interesting to see the bow and power supply setups that you all use.  My few attempts at cutting a wing have not yielded a usable product,  but I will keep at it.  My templates shifted during the process and I think that I need more tension on the wire.  There was a definite bow in the cutting wire as I pulled it through the foam. 

Template shift: nail them down somehow!  I'm not one to talk about the best way to do it, but for my efforts I've just glued them on with foam-safe CA, then broke them off carefully when I was done.  I've seen articles where people did, literally, nail them down to the foam.

Bow: Wire, like just about everything else, expands when it gets hot.  So you need a bow that will allow for expansion while retaining tension.  I use a bow that, for a 30" long wire, has about 1 1/2" of spring in it when it's cold.  You can see it relaxing a bit as the wire gets hot, but there's still plenty of tension.

Power supply: I'd like to know of good cheap ones, too.  I use a 12V DC supply, which probably runs the wire a bit cooler than optimal.  I need to pull the wire through the foam very slowly, which is a trial for me because I'm an impatient sort of fellow -- my first LE buck had the center bowed in, which I compensated for by sanding the ends to match, but had I pulled the wire more slowly I think it would have been just fine.

[Brent Williams]

I am using a cutting bow strung with 7 strand .015" stainless flying line.  I have experimented with a solid .015 steel guitar string also.  Tension on the cutting wire is provided by the 2x .250" music wire rods drilled at an angle and connected by the shorter section of .015 cutting wire.  Power is provided by a Craftsman manual car 12V battery charger which has a switch to choose between 10 amp/ 2 amp.  I am using a router speed control from Harbor Freight to control the voltage.

Current path = Wall 120V AC ➡ Router Speed Control ➡ Car Battery Charger 10A/2A DC ➡ Cutting Bow

Any tips or observations are welcomed, as I would really like to master this skill.

[Brett Buck]

Bow: Wire, like just about everything else, expands when it gets hot.  So you need a bow that will allow for expansion while retaining tension.  I use a bow that, for a 30" long wire, has about 1 1/2" of spring in it when it's cold.  You can see it relaxing a bit as the wire gets hot, but there's still plenty of tension.

  I use an old Fox aluminum bellcrank with one arm cut off and the pushrod arm formed in a hook to permit the wire to be removed and passed through the hold to hollow it out. The bellcrank is spring-loaded, and as the wire expands, the bellcrank moves a fair bit.

   I use .013 music wire for the cutting wire, formed as you would  a flying line with eyelets and wire-wrap and a car battery charger with a Variac on the input side to control the temperature. A critical tip is to reduced the temperature so it just barely melts the foam - otherwise, if the speed varies as you pull it through, it undercuts the templates.

    Brett

[Chris Wilson]

I have seen blue board sheets used for flap cores - seems to offer a nice flat surface.

[Tim Wescott]

Power is provided by a Craftsman manual car 12V battery charger which has a switch to choose between 10 amp/ 2 amp.  I am using a router speed control from Harbor Freight to control the voltage.

Do you use the 10A setting or the 2A?

[Paul Smith]

There are only four foam pieces for the wing and wingtips.  It would have taken countless wood pieces that to fabricate this airplane the old way. 

I just needed to make a half-rib template for the root and tip.   The 2" foam came from a local lumber yard.  I used an electric train transformer and scrap .018" flying line as the cutting wire.

[Brent Williams]

Do you use the 10A setting or the 2A?

I have tried both amperage settings depending on the type of wire that is being used.    I like the isolation that this DC method provides.  The the router speed control allows control of the temp and it also provides a fuse.  

The method of plugging into a 20 amp 120v AC circuit and using a variac straight to the bow without some manner of isolation really scares me!  

[dave siegler]

yes, isolation from the main line is good thing.  But some people do not use it feeling the GFI will protect them.

I don't count on a GFI, isolation is not expensive and I can't get s shock from the bow even if I try.  I use a 1:1 isolation transformer and a variac. 

A variac alone does not provide isolation, it is and auto transformer.
A router speed control or light dimmer does not  provide isolation.
 


   

[Motorman]

Would this work?



MM

[John Cralley]

Who knows? You don't give any specs!

[Paul Smith]

Crude, maybe.  But effective.

You see, the center pivot is the focal point of the LE & TE taper.  The tip template is just there for redundancy.  I pull on the wire with an old E Z Just handle.  The temperature is adjusted by personal finesse.  The core in the pitcher was the victim of a bit too little power.  A sanding block fixed it.

Nobody that gets close to a high performance engine skert of 110 AC.  Are you?

[Motorman]

When I was a kid I made a hotdog cooker from a 1x4 with 2 nails in it. The nails were connected to lamp cord that was plugged into the wall. Stick the hotdog on the nails and plug her in. My dad called it the idiot killer. Got the plans from a magazine, it was a different time. So no, not scared of electric but at the same time don't want it to stop my heart.

MM

[Igor Burger]

Igor, that is a nice way to build.  What are you using for a power source, and what size/material wire are you using?

Thanks Brent, I use cutting wire from resistor wire available from Graupner for foam cutting, it has 0.3 mm diameter and need 14V /2A power supply. I cut alone, so I have it connected via switch on floor. But lately I tried also Icharger (charger for lipo batteries) which has program for feeding foam cutter, but I can imagine better working power supply :- ))

[Stephen Jeansonne]

Here the one I made.  I'll try and find a pic of my bow to post.
--Stephen

[Larry Renger]

I use the TEKOA Feather Cut machine. See it at TEKOA.com

[Jim Dincau]

When I was a kid I made a hotdog cooker from a 1x4 with 2 nails in it. The nails were connected to lamp cord that was plugged into the wall. Stick the hotdog on the nails and plug her in. My dad called it the idiot killer. Got the plans from a magazine, it was a different time.

Talk about different times, I made one as a project in my Jr. High electric shop class.

[bruce finley]

When I was a kid I made a hotdog cooker from a 1x4 with 2 nails in it. The nails were connected to lamp cord that was plugged into the wall. Stick the hotdog on the nails and plug her in. My dad called it the idiot killer. Got the plans from a magazine, it was a different time. So no, not scared of electric but at the same time don't want it to stop my heart.

MM

There was a commercial model made like that that would cook 4-6 hot dogs at a time, cooked them by electrocution.  LOL..  We had one in the sixties

[Motorman]

Unit above is a Procraft by Grobet Model 45.51OG rated 25 amps continuous duty. I'm going to hook up some .012" flying wire and see if I can get it to glow.

The trick to the hotdog thing was to bend the nails to go into the ends of the dog. Anything not between the nails wouldn't cook.

Edit: Just tried the Procraft, it works! I hooked up 3' of .016 solid and had to turn it up quite a bit but it cut some packaging foam like butter. I am jones'n bad for some foam blanks! So glad no one bought this thing when I had it in the classifieds.


MM

[Motorman]

Found some bead board at Home Depot but it's 3/4" thick. Can I glue two pieces together, what kind of glue do you use on foam? Z poxy right?


Thanks,
MM

[Brett Buck]

Found some bead board at Home Depot but it's 3/4" thick. Can I glue two pieces together, what kind of glue do you use on foam? Z poxy right?

  As long as you don't try to cut through it, maybe. I have *occasionally* worked on laminated pieces but to cut through it with a hot wire is a bad idea. If you absolutely must, then use foam-safe spray adhesive.

   Brett

[Brett Buck]

I use the TEKOA Feather Cut machine. See it at TEKOA.com

   I also *borrow* a TEKOA cutter. It's a touch fussy setting up but the results are more consistent than I ever managed. There is some skill involved in cutting by hand and if you only do it occasionally, the failure rate is pretty high.

   4 of us got together early in 2014 and did a foam-cutting session with the TEKOA system and I think we got about 4 airplanes worth of wings and stabs in pretty short order (a few hours). In my case I think I took about an hour to two complete wing sets and two complete stab sets.

   I also only cut with positive templates, and flip the blank over, to ensure symmetry. The TEKOA instructions are geared to cutting the top and bottom of the same panel with the same arm setup, but to do that you have to have a positive and negative template. If you have camber (like RC), then you have to do that anyway.  With just a positive template you have to do "top1" (flip the setup over), "top2" (leave setup alone), "bottom1" (flip setup over), bottom2. That ensures that the cradles will line up perfectly when you join the two panels, otherwise the kerf will cause them a bit of misalignment (that you have to shim out).

    Brett

[Motorman]

Went to the H Depot and every store in the area was out of EPS anyway. They had extruded polystyrene, looked heavy.

Just found this cool web site. http://hotwirefoamfactory.com/036_Foam2inConstruction.html  They have special foam glue you can cut through but, I don't need it now because they sell 2" thick blanks. 6 for $30 that's 9 slow rat wings.

MM

[Avaiojet]

A dream come true.

100 bucks and your in business.

http://www.ebay.com/itm/cnc-foam-hot-wire-cutter-model-airplane-wing-not-kit-control-line-or-RC-EPS-EPP-/301683642996?pt=LH_DefaultDomain_0&hash=item463dbf1274#ht_112wt_849

What is all that stuff?

I cut foam wings with a hot bow, rib templates and a buddy you could trust.

[Larry Renger]

I had set up a foam cutting system to do manually and was at the old Pasadena Model show. I saw the TEKOA machine and thought who needs that? Then I saw the wing cuts being demonstrated and immediately said I have to have one of those.  There is no way a casual foam cutting person can begin to match the accuracy that system can achieve! Bob Hunt, I am not!  You will only pry it out of my dead, cold, workroom! 

[Igor Burger]

A dream come true.

100 bucks and your in business.

I do not think ... what you see there is only frame and screws, nothing more, you will need 4 motors, connectors between motors and screws, lot of electronic, like motor drivers, power supplies, cabling, controlling software for PC, you must have source for data (G code) - so another CAM software, and clearly you need some CAD to draw what you want :- ))

[Avaiojet]

I do not think ... what you see there is only frame and screws, nothing more, you will need 4 motors, connectors between motors and screws, lot of electronic, like motor drivers, power supplies, cabling, controlling software for PC, you must have source for data (G code) - so another CAM software, and clearly you need some CAD to draw what you want :- ))

I forgot what I paid for my foam cutter, offered by some manifacturer. It was the 80's.

Came in a kit with all one needed. We made our templates and we ran the wire bow by hand counting out the marks on the template as we moved the wire over the rib template.

With the correct settings, you could get great cut wings.

Here's the proof. Actually cut with a simple hot wire bow. We made dozens this way.