Tips on working with lightweight foam
Thought I would give this a try and see where it goes.
Anyone that has discovered, heard of, and tried an idea to help improve foam building techniques please contribute to this thread.
Although it is well known that forming, baking, creasing, curving, etc will enhance the strength of a structure, lot's of builders are new to all of this. This might just make a good referance for those with learning new skills.
I'll start one with forming a duct I made for a 30mm EDF unit. The 2mm depron I used was light, plyable, but would not hold it's finished form well, and was too 'soft' and 'squissy' when done.
I came up with making a composite structure, in other words, I mixed two different building materials into one. The solution was as simple as tissue paper. Yes, tissue paper laminated to the foam made the structure 3-5 times as strong and added very little weight. In fact tissue paper can be used in other structures with good effect too.
Here is what I did.
1. I ran hot tap water over a sheet of 2mm depron, and preformed a curviture over a 1 1/4" PVC sprinkler pipe.
2. I made a form the diameter and shape I wanted my finished duct, or tube.
3. After cutting the sheet so the edges would align when stretched around the tube, I applied foam safe contact cement to both edges. (CyA would work too, but we want something that sticks instantly without holding the edges together for a long time).
4. I wrapped a standard sheet of copy paper around my tube, glue stick sealed. I then wrapped a sheet of mylar/plastic around the paper. All this makes it easy to remove your assembly later, and the plastic is a glue release agent.
5. After treating some tissue paper with Krylon clear paint to seal it and make it wrinkle resistant, I added this, one layer, on top of the plastic wrap.
6. I coated the inside face of my Depron with a very thin coat of white glue. Wrapped this around the prepared tube, pressing the edges together. One more wrap of about 2 layers thick of copy paper, snug, tape the edges so it won't unroll.
7. Pop it in an oven, set the temp to 170-180 degrees F., and let it heat to temp. 20 minutes, remove from oven, let completely cool. Remove it from your form, and peel the plastic from the tissue inside. At this point you can also re-seal the tissue with WBPU if you like.
One 6" long duct I made was: 1.5 gram without tissue, the duct became 2g with the laminate and almost bullet proof. You can make nacelles, fuselages, etc in a similar way and then you need few, if any formers except where wings, firewalls, and tail groups get added.
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something i do when building fuselages is i microwave them. i think i got is from mcross. i use 1mm depron too cause 2mm just doesn't work when i use it. i cut out the pieces and tape it all together. a couple light folds help keep it the right shape. i then stuff a moist (not dripping) inside then i microwave it for aobut 30 sec on high. any longer and it destroys it. it comes out crisp and well formed, it wont unroll when you take the tape off. it also adds some strengh to the foam.
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