RugbyFuture
Lord Logo
any hobbyists/designers out there want to give me tips on modelling high density foam. been a year and a bit at uni now and still not getting the hang of it. i know the basics like hot wire cutters etc but still.
modelling foam
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waratahjesus
Greg Davis (50)
what are you modelling, what frames are you using etc?
What are you modelling?
I used to be into R/C aircraft and we built wings out of high density foam. Built our own cutters with high resistance wire from Dick Smith and jumper leads to a car battery. The trick to a good cut was patience - let the wire melt the foam and don't force it, and above all a good template. We used craftwood in the shape of the cross section with progress numbers every 10% of the distance. The templates had to be smooth to stop the wire getting stuck, and we'd read the numbers out as we went. The toughest part for us was the leading edge of the wing as it is quite a sharp curve, so we started at the tail and went forward to get our rhythm right at the end.
Once you've done a good cut you still need to lightly sand the foam.. and you've no doubt noticed how bulky the offcuts are, we used to disolve them into an icecream bucket with a bit of 4 stroke, suprising how flamable this mix was..
I used to be into R/C aircraft and we built wings out of high density foam. Built our own cutters with high resistance wire from Dick Smith and jumper leads to a car battery. The trick to a good cut was patience - let the wire melt the foam and don't force it, and above all a good template. We used craftwood in the shape of the cross section with progress numbers every 10% of the distance. The templates had to be smooth to stop the wire getting stuck, and we'd read the numbers out as we went. The toughest part for us was the leading edge of the wing as it is quite a sharp curve, so we started at the tail and went forward to get our rhythm right at the end.
Once you've done a good cut you still need to lightly sand the foam.. and you've no doubt noticed how bulky the offcuts are, we used to disolve them into an icecream bucket with a bit of 4 stroke, suprising how flamable this mix was..
RugbyFuture
Lord Logo
well currently (due tommorrow) im modelling a camera i designed based off hasselblads and a military scope, using paper and cardboard templates i make myself
Hey Thomo, I've done a dodgy mspaint picture...... the thing about our process is we were in school at the time with very little cash, so everything was done as cheap as possible.
What's a 505?
Our wingspan was about 1800mm, we were making smallish gliders to throw off cliffs.
While the standard wing aerofoil is double-sided, we found it easier to make them with a flat bottom and then shape the leading edge manually. We'd use a long cheap hobby knife to cut along the red line, then sand it to be round along the length of the wing.
The green circles are for nails, they hold the template to the foam.
The numbers are read out as you're cutting, we'd say 1/4 ... 1/2 ... 3/4 ... 1. If one bloke gets ahead then the other guy has to catch up. Trick is to go real slow, let the wire cut rather than tear it through the foam.
Once we've got the wing shaped, we'd cut the wing and insert a wooden spar then glue it in with a two-part 5 minute epoxy (araldite). We'd also cut a slight angle in the middle so when the two halves of the wing are put together there's a slight (say 5 degree) V in the wings. We'd also make a hardwood wing joiner that would be maybe 6 inches long on each side and join the two halves near the spar.
Then we'd sand it nice and smooth, and it's ready for covering, which we'd do by mixing a PVC glue (aquadere) with water then painting it on the wing and sticking brown kitchen paper to the foam. This was a lightweight covering that also strengthened the foam quite a bit. Then we'd paint it and it's ready.
What's a 505?
Our wingspan was about 1800mm, we were making smallish gliders to throw off cliffs.
While the standard wing aerofoil is double-sided, we found it easier to make them with a flat bottom and then shape the leading edge manually. We'd use a long cheap hobby knife to cut along the red line, then sand it to be round along the length of the wing.
The green circles are for nails, they hold the template to the foam.
The numbers are read out as you're cutting, we'd say 1/4 ... 1/2 ... 3/4 ... 1. If one bloke gets ahead then the other guy has to catch up. Trick is to go real slow, let the wire cut rather than tear it through the foam.
Once we've got the wing shaped, we'd cut the wing and insert a wooden spar then glue it in with a two-part 5 minute epoxy (araldite). We'd also cut a slight angle in the middle so when the two halves of the wing are put together there's a slight (say 5 degree) V in the wings. We'd also make a hardwood wing joiner that would be maybe 6 inches long on each side and join the two halves near the spar.
Then we'd sand it nice and smooth, and it's ready for covering, which we'd do by mixing a PVC glue (aquadere) with water then painting it on the wing and sticking brown kitchen paper to the foam. This was a lightweight covering that also strengthened the foam quite a bit. Then we'd paint it and it's ready.
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