Foamboard

[mikemech]

I'm about to make my first foray into foamboard. A BT-80 Gyroc. Does anyone know of a manual or tutorial for beginners?
Best glues, can edges be sanded round, should edges be sealed or papered, will CA melt foam, etc., etc., ad nauseam.
Yes, I did a search.
Also posted on YORF

 

[Ravenex]

Not sure on some of these but there is a specific "foam safe" CA

 

[Rex R]

Best glues; white glue works pretty well, provided the joint is foam to paper or some other porous material, for foam to foam epoxy does well.
can edges be sanded round; yes but you will need to do some filling afterward with a water based filler.
should edges be sealed or papered; basically yes, white glue will work.
will CA melt foam: YES, along with lacquer and other strong solvents. foam core et al basically Styrofoam so anything that works (and doesn't work) for Styrofoam applies, for fins skinning them with card stock is a good idea. note, if working with 'foamcore', you may be better off peeling the paper off and applying your own paper, the paper on mine peeled off fairly easily. HTH
Rex

 

[Winston]

I'm about to make my first foray into foamboard. A BT-80 Gyroc. Does anyone know of a manual or tutorial for beginners?
Best glues, can edges be sanded round, should edges be sealed or papered, will CA melt foam, etc., etc., ad nauseam.
Yes, I did a search.
Also posted on YORF

Foamboard is also widely used for scratchbuilt RC aircraft construction. Here's a huge tutorial thread on using it which should also apply to rocketry use in some respects:

https://www.rcgroups.com/forums/showthread.php?t=1587275

 

[Micromeister]

I've used Foamcore 1/8" and 1/4" foamboard on a number of projects. As Rex-R mentioned plain old white glue works just fine, Yellow Carpenters glue sets up quicker with a stronger bond but dries yellow (Not Pretty). I've also used 5-minute Devcon 2 part epoxy without melting the foam on structural parts.

 

[Gary Byrum]

That's a big Gyroc you're planning. I did an upscale to a BT 55, and my descent was, uh, rather quick? I anticipated this, so I reinforced the nose cone with an oak dowel in the tip. Just a precautionary measure. You might consider the rate of descent VS the impact regarding the nose cone AND the airframe. It'd be a bad day in the field if your Gyroc crunched.

Food for thought....Maybe giving more play in the fin flaps the help slow it down a bit?

 

[TheTellurian]

Check out 'burkefj' for foam skills such as: https://www.rocketryforum.com/showthread.php?121292-Foamy-Jupiter-C His home page has all sorts of foam board RC rocket gliders so have a look there also.


Richard

 

[mikemech]

Thanks. all. Just what I needed.

 

[RAHagen]

Epoxy works really well. It kinda soaks up into the foam and makes a really strong bond. Last time I broke a foam core fin that was glued on my epoxy I has to use a band saw to get it off.

Also if you want to airfoil the fins, you can cut a slit out of the front and back and the foam and glue the edges together. Kinda like it is in the attached photo. Depending on the amount you cut out and the depth, you can make the fins either more rounded or more pointed.

 

[mikemech]

I finally got around to getting the foamboard (Adams) to make the wings, flaps and rudders for my big Gyroc. After I got home I noticed that both sheets have a kind of wave in the foam. Is this normal? Does the foamboard need to be faced with balsa or light-ply? If so, that kills the reason for the foam; the weight of the huge wings.

 

[TheTellurian]

It's very common but sometimes smooth foam board can be found or one can try the higher priced variations. I often go through the whole lot running my hand across to feel the waves, some will be worse than others or if not in a hurry try different stores as lots will very. Elmers Craft board is better than Dollar Store Redi Board generally and there are others.

The paper on the 20x30 size Redi board weighs in at 61 grams and is not always well adhered. If you have a lighter or stronger substitute then by all means go for it. You will have to determine what strength is adequate for the size and power of the Gyroc being built and a little carbon goes a long way.


Richard

 

[AstronMike]

I finally got around to getting the foamboard (Adams) to make the wings, flaps and rudders for my big Gyroc. After I got home I noticed that both sheets have a kind of wave in the foam. Is this normal? Does the foamboard need to be faced with balsa or light-ply? If so, that kills the reason for the foam; the weight of the huge wings.

So, you've 'discovered' Adams Readiboard, which only seems to exist at Dollar Tree/Deal$ type places. It's cheap and very light compared to standard foamboards, but with one drawback which you've discovered - warpage!

I've used LOTS of this stuff in gliders, even some borderline HPR jobs, but anything with a large surface area tends to warp over time. Now, if you can select the warp-free sheets to start with, you tend to be better off in the long run. I'm guessing you just picked up the end sheets laying looser in the box. DO NOT DO THIS. Instead, *always* get the ones at the *farthest back* of the case, since those tend to be 'pressed up' better and have little or no warpage. Now, even those can warp over time, but if you get straight board first and make your BT80 Gyroc flats with it ( and that's not even that big, to me) it will tend to hold up over time.

Another thing is to two ply it. That has the effect of 'cancelling' out inherent warpage, but only if you glue them together with the warpy middles opposed, NOT together. As light as Readiboard is, you'd still be lighter than standard foamboard but now thicker.

Id say just go back to DT and get a fresh 'backsheet' and go with that. Also - while the lightness is awesome, bear in mind that large single ply 'wings' made with this stuff should not be boosted toooo fast.

 

[PhlAsh]

Were you planning to glass it? Even if you don't, set down enough wax paper to lay it on with more to lay over it. using a foam brush, spread West System (or your preferred epoxy) on one face, flip it onto your wax paper, spread on the exposed side, cover that with wax paper and lay something heavy (and warp-free) on it. Pretest to ensure that the epoxy doesn't attack the foam!