Landracing Forum
Tech Information => Technical Discussion => Topic started by: debgeo on October 16, 2010, 12:30:29 PM
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I am starting the body for my sidecar. Using foam to develop shape. What is best glue to glue foam sheets together. I am not having good luck and hope to get some recommendations THANK George :? :? :?
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I have used just plain old drywall mud for some of the projects I have made. If you are using EPS or Styrofoam most glues will attack the foam and melt it. Even if you get it to bond it will have a hard line where the joints are and makes it very hard to sand. The foam goes away much faster than the glue line and makes it hard to get a smooth surface. The dry wall mud does not attack the foam and it sands very easy making it easier to get the desired shape you want. There will still be a hard line at the joint but much easier to deal with. This may not be the best way but it has worked for me.
Jerry O
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Model train people build styrofoam worlds. The hot glue gun and glue sticks shown are what we use and they are available from the typical hobby shop or www.woodlandscenics.com
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I used "Liquid Nail" from Home Depot, chaulking gun size.
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I have not found anything ideal for the job, but the spray foam insulation that comes in the can works OK. I like that it fills gaps. Like the others said, it makes a harder joint than the foam so you have to take that into account when sanding. It takes about an hour to set and that is a problem too.
Don
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3M has a spray glue #77 it works well :cheers:
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if the join is precise you can use PVA, if not as Jerry O said dry wall mud or what we call cornice cement is the go....cheap, non reactive, easy to sand or shape
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When it comes to finishing the buck spend the time to get a good finish surface. Have used JB Weld to keep sharp edges or details you want.
It will save you time sanding inside the mold on a concave surface.
Build the mold in several thin layers to keep from distorting the piece and reinforce with matting or heavy boat cloth.
Avoid using wood or other stiffener material until your mold is very thick.
Last bit of advice, use Duratec to finish off the mold.
Don't try to rush a part out on Duratec primer only surface, have done it twice, yes, a slow learner.
John
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While it's more expensive and takes a while to cure, we like to paint a thin coat of epoxy on the face of the foam block that has the coordinates. When it cures, the other face and corners (the ones we're getting rid of) carve off easily and the resin "sheets" act as semi-hard templates for the long board. We usually place each sheet in the stack on the layout marks of the previous sheet, punch in some toothpicks or wood skewers to stabilize it (depends on whether we are working in 1", 2", or 4"), and wipe the excess resin off the fillet.
Don't use fast epoxy or micro. The foam is an insulator and the resin can produce enough heat to melt the inside of the stack.
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Hello George.....
Here are a couple of pics of a nose cone plug I did last year. I use a ref. book purchased from Amazon, "Fiberglass & Other Composite Materials", and it provided most of the answers to my questions. I had absolutely no experience in fiberglass fabrication. Most importantly it covered the "do's & don'ts" when contructing a foam buck. What ever time you budget for the project multiply X 10.....btw I numbered all the pieces,then glued with liquid nail, filled seams with aerosol insulation foam. I used a carpenters keyhole saw and an air file with #36 grit paper to shape the plug, sealed with a latex exterior paint, then bondo and sanded to final finish, painted with laquer paint....making the mold off of the plug was another chapter....Good luck.
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I second the #77 spray glue; don't get the nozzle too close or it will eat the pink foam. Kids at our HS use it all the time to build their wind tunnel models
Michael
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Gorilla Glue works very well and is close to the density of the foam so that is doesn't leave a dimple or protrusion when you sand.
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George,
You can also use good old "Bondo", just keep it away from the edges. Main advantage is that it sets up quick and goes a long way.
Like Jerry, I have used drywall mud. It's easy to spread and sand. Just use thin layers as thick layers dry slowly and shrink.
Tom
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I have to second that the book "fiberglass and other materials" book is definately worth the purchase it changed my thought process in a good way for building some parts and has a lot of do's and dont's to save you time and money!!! But i ordered mine from aircraft spruce when ordering some dzus fasteners.
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I purchased the book. Between it and all of great help I recd here I am working on my first mold. Thanks to all for help. I am planning on showing results at Salt Flats 2011
George
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I will also chime in with the 3m Super 77. It will eat the foam but not much....
I have found the best method is to spray a light coating on both pieces to be joined, let sit for about 3-5 minuets (adjust time depending on temp, just to tack up a bit and flash most the solvents off) and carefully assemble.
Once the form is made and smooth (*drywall mud works well if you need to add material providing its not too deep) coat the mold with aluminum foil (*again spray with 3m 77) and roll the foil smooth with a laminate roller.
THe foil will act as a barrier to prevent release agents, chemicals, epoxy or other from attacking the mold.
After that you can glass or carbon fiber away.
Good luck.
~JH