Hand-crafted Giant Scale R/C warbirds & Golden Age Racer kits!  Racers : Gee Bee Z, sport scale model, GeeBee, R-2, Super Sportster, GeeBee Y, R2, R1, Z, Y, Foam building techniques & technology, sheeting techniques. 
Warbird models: F-4U Corsair, F4-U, P-51, Mustang, P51, P-47, RC, Thunderbolt, P47, F8F Bearcat, PT-19, Fairchild, kit, 
Focke-Wulf, FW-190A, Sea Fury, A6M3,  Zero, P-40 Warhawk, P40, B-25 Mitchell, radio control .
 

Foam Building Technology
      Using Jack Devine's Foam Bond Cement

An easy way to keep this building page is to print it out!  Just set your printer properties to 'Landscape', and then print a set of full-width color instructions to use at your building table!  

 

Foam Building Technology has come a long way.  Here we will show some building techniques used in applying sheeting and capping to the foam cores, which are the heart of each lightweight, super-strong Jack Devine model.  One of their building secrets is their Foam-Bond contact cement, which is the perfect glue for a flawless sheeting job! 

     

 

 

Starting out.  All of NW HobbyTech's kits include foam core fuselage structure and flight surface components.  The edges of the wings and control surfaces are capped using laminated strips of balsa and aliphatic resin.  We used Sig-Bond aliphatic resin here for that purpose.  First, lightly sand the foam to open the pores.  On straight parts, standard balsa stock will be used.  On bands and curves, three thin strips are laid together with the glue, and once wetted with the glue, they are taped securely to the edges using Lacquer Masking Tape.  After the laminated strips dry, the Lacquer Masking Tape doesn't stick and peels right off!



 


The edges are then sanded flat as an extension of the surface they are glued to.  The strips will become the outermost part that the sheeting is glued to.  A square edge is essential for good glue contact where the sheets meet the edges.  Remember to lightly sand all foam surfaces to open up the pores before applying any adhesives!  These glues are designed to grip the foam, but they must be able to penetrate the foam to do the job the way they are supposed to. 
During the cutting process, the cutting wire leaves a hard, thin crust on every surface of the foam.  Whenever wood, foam or anything is to be glued to foam, the foam must be sanded lightly to break that crust!  



 

 


Inspection.  At this point, it's usually good to have an FAA inspector check your project to see how it's going.  As you can see from the photo, we called inspector REN.      8^)  
One reason we have included this photo is to show the fuselage construction.  The fuse comes from the factory just as you see it here with Ren.  The edges of the ring sections (where you see adhesive lines) are made a little higher than the centers of the ring sections.  They are built this way on purpose.  Before sheeting, you will want to take a long, flat sanding block, and sand across those adhesive joining-lines, and meld the lines of the fuselage into one long, gradual line up to the bevel in front.  The bevel you see in the nose should be left as it is, so you can easily sheet that with a flat piece of balsa and simply trim off the edges afterward.


 

Inspector REN was tough but fair.  We were a few dog biscuits short after he left, but everybody was happy, and the inspector was well-satisfied that the job was progressing satisfactorily.    8^)

 

 

 

 


 

Sheeting!    We're putting together surfaces for a (racing) Gee Bee Z here, and you'll notice that the wing shown here has an optional spar slot.  (Optional = not stock / but at no extra charge)  We've installed a hardwood spar using the Sig-Bond, making sure it does not extend out past the foam surface level.  As it began to dry, we simply wiped away the excess glue with a damp cloth, leaving a smooth surface.   While the capped edges and the spar dried, we joined sheets of high-grade balsa provided in the kit using the Sig-bond and the Lacquer Tape, leaving us with large sheets of balsa that are somewhat larger than the surfaces we were to be covering.  The construction video does a really good job of showing how these sheets are joined.  NW HobbyTech also has a dedicated page here for Joining Balsa Sheets , which has a lot of information to help you with your sheeting job as well.  Once the large sheets have dried and the tape has been removed, then we lay the surfaces on the sheets, and cut around them with some room to spare, as shown below.


    
Applying Foam bond cement. Foam Bond is THE secret weapon for easily sheeting foam with balsa.  Lightly sand foam surfaces first!  Using an ordinary 3" knapped paint roller (NOT a foam type roller!), apply Foam Bond in one generous, even coat over the entire surface that you will be sheeting. NOTE:  Before you start to apply Foam Bond, make sure that whatever you have to do to the foam core underneath is completed.    Apply the coat as you would a fairly heavy coat of paint, but only apply one coat.  Apply a similar even coat to the entire inside of the sheeting where the surfaces will meet.  Wipe off any excess foam bond from any surfaces you are not attaching sheeting to, using a wet cloth.  Do this NOW, and do not allow excess Foam Bond to dry on any surface.  You'll see why soon!


Now, allow both surfaces to dry COMPLETELY until all of the Foam bond has gone clear and is no longer tacky to the touch.  Once dry, it will seem like nothing would stick to it now, but this is when you must be the most careful!  This is THE perfect time to sheet up.  Don't let the treated pieces sit a long time, like overnight.  That's a bad thing.  The foam bond will lose an excessive amount of its contact-cement properties if it dries too long.  Roll on the Foam Bond only when you are completely ready to sheet up, when the only thing you'll have to wait for is the glue to dry enough to go from white to clear, then you're ready.    DO NOT allow any two surfaces with dried Foam Bond on them to touch each other unless you are doing it purposely.  You will not get a second chance!!

         
Wetting down the wood.  This is another one of those big secrets that makes or breaks a sheeting job.  We used a 50/50 mixture of ordinary ammonia & water in a spray bottle with good spraying capacity.  MAKE SURE you open windows and doors for ventilation.  Ammonia smells BAD!  
Wet the wood thoroughly on the OUTSIDE, which means the side WITHOUT the glue on it!  We wet it until it fairly drips off the balsa.  Don't allow any of the wetting mixture to get on the side with the dried glue on it!

 

 

 

 


        
Sheeting!  Okay, this is the really fun and interesting part, but you have to be careful!  Lay the wetted side DOWN on a flat, smooth table top, glue side UP.  We're sheeting a wing here.  Take the leading edge of the wing (glue side DOWN), touch down the very inside tip of it to the very inside corner of the balsa, then carefully follow with the rest of the leading edge until the entire leading edge is laying squarely down across the farthest side of the sheet.  You are now committed.  The leading edge is now securely fastened to the sheeting, and you could not make it let go if you wanted to, so follow along CAREFULLY here!  




Keeping pressure on the front leading edge and downward as well, begin a slow, careful rolling of the wing backwards toward you.  Maintain the pressure as you go, and do not stop the rolling or the pressure until you have rolled the entire chord of the wing from front to back.  Even if your core has a warp to it for some reason, the flat tabletop will make it come out perfectly flat and straight!  



 

Follow this up by rolling the balsa firmly with a laminate roller to make sure the glue adhered firmly and evenly, as shown here.  We got our roller (and Lacquer Tape) at Home Depot.  It's a roller for applying formica to countertop surfaces.
    There!  You've just sheeted a whole wing panel on one side!  Trim the edges to the point where you will be able to sand them square with the caps.  Now,  on the flip side of the wing, roll on Foam Bond immediately to sheet that other side in exactly the same fashion. 
It's important that both sides are done as closely together on the same day as possible!  The drying of the balsa on both sides of the wing must occur simultaneously or nearly so to guarantee a straight wing.

                           

Sheeting the washout basin at the tip!    The first thing we did (before we applied Foam Bond) was to lightly sand the wing so that the rounded-out symmetric surface rounded nicely into the line of the washout basin.  The one thing that will probably look impossible to you will be trying to figure out how to sheet the washout section of the wing, which basically goes IN, while your sheet of balsa basically rounds OUT with the wing, as you can see in the photo.  But it's simple!  Make sure you use the 50/50 mixture to wet the sheeting down thoroughly.  

 

 

 


Now, after a minute or two to allow the mixture to work itself into the grain, we ran the roller straight down the middle with a LOT of pressure!  That attached the middle, but left big rolls to the left and right.  We then rolled off to the left and right, taking in parts of the rolls each time, and used the roller to compress the balsa!  The Ammonia and water mixture allowed the balsa to compress, and the Foam Bond held the compressed balsa securely, and we didn't get ONE wrinkle!   Foam Bond, 50/50 spray mixture, and a good roller.  That's what it takes!  After drying, the completed wing was so strong and light we almost couldn't believe it!


Important Note:
  The balsa sheeting is critical to the structural integrity of the built-up surface or fuselage.  Once it is dry, DO NOT sand it heavily.  If you desire smoothness, use some brush-on superlight sandable filling sealer (Sig Mfg.  sells a VERY nice product for this) to fill the grain, and lightly sand it, you'll love the baby-smooth results, and you won't remove substantial amounts of material.  By doing this you will still have the full thickness of balsa, and your plane will be incredibly strong, as advertised.  
At Jack Devine  Models we want to stress the importance of following these instructions!  Not following them can cost you a plane...or worse!  
These planes are essentially exoskeletal, like a big beetle.  The skin is the strongest part, but MAN, is it EVER strong......so take anymeasures you can to retain its full thickness!


Sheeting the fuselage inside.  We took the sheets of balsa and cut pieces that were close to the sizes of the sides inside the fuse, and trimmed them in until they fit fairly close to the edges, but not too closely.  We found that after the Foam Bond dried that if we reached in with the piece of sheeting and lifted it UP into place that we were able to avoid making accidental contact with the inside before we were ready to press them together!  This "Box"  you see here that is created through this sheeting is ultimately reinforced with tri-stock, and the resultant strength is incredible.  

 

 

 

 

The fuselage will not bend, CANNOT be bent.  And there is still the outside which will be covered with sheeting and / or runners.  This massive GeeBee 'Z'  fuselage when completely sheeted, with stringers,  weighed under 3 pounds.  It is without a doubt the TOUGHEST fuselage I have ever built in my life.  Every other
                   

This building page is here to help you gain an understanding of how advanced foam-core models really are.  Jack Devine is a wealth of information on this subject, and he's always more than happy to talk about it.  The instructional videos that come with every kit have a lot more information on this, we've only scratched the surface here!  Jack Devine Kits are a lot of fun to build, and they don't use toxic or irritating glues or compounds to build them. 

 
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Jack Devine Models
14906 114th Ave. N.E.
Kirkland, WA        98034 - 1031

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