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Old Jun 19, 2011, 01:40 AM
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New Zealand
Joined Jul 2009
54 Posts
Question
how smooth is smooth enough?

So I tried vacumm bagging a layer of carbon over the tail wings of my fly fly salto h101 2.68 this afternoon.

This is going to be a sloper, so im not too concerned about adding a little bit of weight, and i have lots of scraps of carbon that are too small for anthing but making models out of- so thought I would try it.

These being built up balsa wings, I had to run a pipe into the inside of the wings, which vented to outside the bag, so the vacumm pulled against the balsa sheet, and not the wing itself, (which of course would crush it.)
This worked very well- the wings went from 36g to 44g- not too bad given these are 270mm long, and i was using 200gsm carbon.

The question I have- it how smooth is smooth enough? - Given it was tricky enough to get everything sorted with vent pipes etc- I chickened out of using mylar, and used peel ply & choppy fibreglass over, a method I'm much more familiar with.

So the wings not have the rough peel ply finish, which i will sand off, but will still have the cloth weave & pin pricks, unless i paint them, which i dont want to do - I hate painting, and I don't want to add any extra weight if i dont need it.

What are o peoples thoughts, and should i do this to the main wings as well....
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Old Jun 20, 2011, 01:56 AM
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South Africa, WC, Knysna
Joined May 2006
1,321 Posts
imo if you havnt tried mylars yet ? now is the time to , even if the mylar doesnt come out perfect it will make a LOT less work sanding prepping from a mylar finish compared to a peelply finish

you dont want to paint ? then they gonna stay black ? if you do paint then they will have a colour and a little bit more weight ...erm
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Old Jul 20, 2011, 01:48 AM
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Jim.Thompson's Avatar
Australia, NSW, Bellingen
Joined Aug 2008
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Quote:
Originally Posted by jason128 View Post
So I tried vacumm bagging a layer of carbon over the tail wings of my fly fly salto h101 2.68 this afternoon.

What are o peoples thoughts, and should i do this to the main wings as well....
I'm impressed with your internal venting arrangements in order to vac bag a sheeted built up wing! Good thinking.
However finishing a surface with peel ply is not such a good idea like has been said above. And 200gsm cloth for tail surfaces is too heavy I would have thought. That will add a lot of weight to the wings if you do them in that.

How smooth? Well when you try mylars you will have a smooth result. The full answer is as long as it is smooth enough for you. You have to live with it and fly it.

And bare black carbon does not have good thermal properties, it gets too hot for the ideal conditions for epoxy resin. This is very often not understood or taken into consideration.

I would say, get some mylar and lighter fabric, preferally glass, for the wings. Save you carbon for when you are much more experienced I suggest. Glass still adds a lot of strength for a sloper.

I have looked at that Salto. Please keep us updated with how it flies and such.

Jim.
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