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

Remember that shrink tape will leave slight ridges on the tape edge.  My only concern with that would be around the flat area that potentially the consolidation may be uneven due to uneven pressure from the tape.  However that should quickly sand off and be covered with XCR resin.

Just be careful how much resin you add as you don't want a thick layer of resin as it is just excess weight.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

And what about using the carbon braided sleeve?
Apply directly on the XPS core a number of plies, don't use tape or better use epoxy like a
I have made a carbon

or...it seems there is a inner radius surface on the outer surface, using shrink tape will not works - not copy the surface on this location.
Use the heat shrink tube (electrician wiring) instead tape, the surface will be smooth, no ridges....

Thanks both for you comments, more for me to think about.

I have reached a few conclusions:
1.    A vac bag is not a good idea as the pressure causes the layup, and probably the foam, to compress and wrinkle out at the line where the bag top and bottom meet.
2.    Given no vac bag then concave curves are not practical, shame as they provide both strength and a good hand hold, but they will have to be designed out.
3.    Using shrink tape to provide the pressure is not ideal for the flat surface but I will have to make do. Maybe I can add a flat piece of wood onto the flat surface after the first layer of tape and then tape that down.
I like the sock idea, I never thought of a sock on something of this diameter, but have used them on wing spars.

It will be a while before I get round implementing this, I’m currently working on ideas for this winter build. I will keep you in touch with progress

After 5 months I’ve eventually got round to making another glider fuselage pod taking into account your comments. I am very please with the result. Although the finish is not as good or accuracy as a mould, this method is quick and cheap for one offs and experimental designs.

The plug was designed using “DevFoam” and hot wire cut from Blue Foam in 50mm sections using a homemade CNC foam cutter. The sections were threaded onto a 10mm dia rod to stiffen the plug. It was lightly sanded and the odd dint filled. I then coved it with some thin laminating film to prevent the foam absorbing any resin. Laminating film has a heat activated glue and heat shrinks, i.e., can be ironed on.

I then attached a layer of glass cloth with spray adhesive, wetted it out with Laminating resin. Applied length of uni carbon for longitudinal strength and wetted. This uni was longer than the plug and taped to the protruding stiffing rod. I then pulled over a carbon sock, taking care that it was tightly stretched over the plug. This was also taped to the stiffing rod and wetted out.

I then wrapped in heat shrink tape, this needs to be done in several pieces as the tapered plug causes the spiral to lengthen out. The tape was tightened with carefully with a heat gun (don’t want to melt the foam core). I then vag bagged it for a few min on a very low vac to be doubly sure that the layers were compressed.
Let it cure, remove the tape, dissolve out the foam and lightly sand and polish. The final product is a strong, light weight fuselage pot that will form part of my next competition model

Great result. Mouldless construction is not easy, so you've done well.