By John Hovell - 8/26/2020 7:06:53 PM
Hi, having watch your excellent videos I seeking advice on building model glider fuselage pod (the front part of the fuselage, the rear being a commercial boom). This is for a large (4m span) competition glider.
I have made a few pods using a “lost foam “ technique. Whilst I have been reasonable pleased with the results, I feel you may be able to help improve.
The pods are 750mm long, 28mm dia at the nose and 12mm dia at the rear. The widest point is 51x35mm. They include a concave figure grip under the wing location. See attached CAD drawing.
I appreciate that the traditional way to make such an item would be to make a mould, but I don’t want to go down that route as it doesn’t allow design changes from one build to the next. Also, it is very time consuming.
I cut the foam (Extruded Polystyrene (XPS)) in 50mm sections using a CNC foam cutter and thread them on a rod to make the core ridged. I wrap the core in parcel tape to prevent the resin soaking in
Then do a wet layup:
• 100gsm 2:2 twill glass bias cut
• Longitudinal reinforced with 300g uni attached with 3M77
• Bias Cut Black Stuff Carbon Fibre 2/2 Twill 3k
• Wrapped in peelply
Then Vac bag, when cured dissolve the foam out and pull out the parcel tape. See photo of finished pod
The issues I have is one that the whole process is very messy, this makes it difficult to get a neat wrap. Secondly the vag bag introduces the occasional wrinkle in the carbon where it meets, this weakens the structure.
So, my thoughts are: less vac, use heat shrink tape rather than vac bag, use your XCR process.
Sorry for such a long mail but I would appreciate your comments
Thanks
John h
 
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By Hanaldo - 1/22/2021 3:07:46 AM
Great result. Mouldless construction is not easy, so you've done well.
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