Barry_DVRC

I have a plan for a built up model. I'd like to have a fiberglass fuz version. I know the plug must be made up of a close grain wood. Should I buy a block of such a wood or should I built the Fuz as usual with internal formers but plank the outside with the close grain wood and not balsa? I've never molded anything before and I don't wish to start out the wrong way.

Thanks

Barry

soarrich

My Feedback: (98)

Barry
Small world I grew up in Concord.
To you plug question, there's lots of ways to make plugs and molds. First how big is the fuse? How many fuses do you want to make?
For starters look at this:
http://www.rcgroups.com/forums/showt...ht=ultracal+30

Barry_DVRC

Hi Rich,
Size, it's a "vintage" FAI pylon racer call Maneater, 40 powered and about 40" long. I'm only making them for me and a buddy so maybe 6 total. However this is a learning thing and I'd like to learn to build future molds for 25 or more copies. I have a good (large) bandsaw and figured wood was the way to go. I did however read the link you provided and own a CNC foam cutter.

So if wood is the way to go.....question still stands, hollow and built up or solid wood?

Barry

soarrich

My Feedback: (98)

I'd go solid wood. Basswood is cheap and easy to sand, mahogany is dimensionally the most stable.

Barry_DVRC

What do you mean by most stable? Do you mean the plug will still be good in 10 years after I wipe the dust off?

Barry

Barry_DVRC

I've also seen poplar suggested because it comes in longer lengths. Any thoughts?

Thanks

Barry

soarrich

My Feedback: (98)

I think basswood and poplar are the same thing, if not I can't tell them apart! It seems if you buy it in a hobby shop it's basswood, in HomeDepot it's poplar. In the HD by me you can get it up to an inch thick, but if I was going to carve a plug out of it I'd buy it in 1/4 inch thickness and laminate it together using epoxy. The piece would then have lines that would help for seeing the contour.

Mahogany is the most stable means that it stays the same size, other woods expand and shrink with changes in humidity. Look at you kitchen cabinets, the doors are made with like a picture frame surrounding a center flat wood piece that is free to float in the picture frame, that's so it doesn't warp from temp and humidity changes. Mahogany was the plug of choice for molding until they came out with some highdensity foams that are better, but unless you want to spend 2K on foam for a plug you don't need it.

Barry_DVRC

2k on foam - not in this life time.

Thanks for the info.

Barry

dld

Barry,

You can make the plug out of almost anything, as long as you make it very smooth before you make the mold. If you smooth the surface with at least 600 grit paper, wax multiple(5 or more) times and use PVA, your mold should come off the plug with very little if any damage. I have made molds from plugs made of foam with glass over it, built up wood with monokote covering, built up wood with fiberglass over it, and solid wood. The only thing that really makes any difference is how accurately it was made. Make your mold at least twice as thick as the part you want to make, and build the flange area up even more. Epoxy and fiberglass are relatively cheap, so I tend to make my molds fairly thick, especially something like a race plane mold, where accuarcy is paramount.


Good luck,

David Layne

charlieoneseven

Barry,

I have made molds from built up parts before and it sounds like you have the plans to make the plug out of a flyable fuse.
Planking the fuse frame with balsa strips 1/16x1/4 on the curved surfaces and 1/16 planks on the straight sections gives the best results. I like using 1/2" tubes for alignment in the frames and a jig board to hold everything straight while planking. Hardening the exterior wood with CA and .3/4 oz cloth and primer is what I did. Sanded it smooth, primed, waxed it up a few times and made a parting plane down the centerline where I wanted it to release out of the mold. I filled the gap with bondo and more wax on both the plug and parting plane. Here is a great build using the same methods www.su27.de
Harald went into surface detail after planking was complete with metal skins on the plug, you can skip that part since your plane is modeled after a composite ship. I re-read this project for inspiration with I get stalled in the shop and it lights my fire to do as well.

The other method CNC a foam plug and glass over it, prime, wax and your in business either way!

Best of luck,
Charlie

Barry_DVRC

I was not planning to use a flyable fuz but instead using the same construction as the plan but with Basswood or similar, hoping to cut down on the shaping required and by limiting the shaping to get a more accurate shape. It seems that I might just try a solid poplar plug rough shaped on my bandsaw. I've been thinking about this and the order I should go in.
I also think that having a flat and solid shape at first, will aid in wing cutout, cowl line and fin location.

The Plan

1. Cut wings so that the hole in the Fuz fits the actual wing to be used.
2. Join up a block of poplar wood.
3. place outlines of fuz on block.
4. Cut a long notch in the rear and insert a 1/4" plywood fin.
5. Cut nose off and lightly glue back this will be the cowl line.
6. Cut the wing and belly pan from the fuz.
7. Cut the belly pan from the wing.
8. lightly glue wing piece back in place
9. lightly glue belly pan back in place.
10. Rough cut shape of fuz with bandsaw
11. Carve and sand fuz (easy when you put it like that.)
12. Break glue to remove wing piece with bellpan attached
13. attach to real wing and build a fairing on top of wing.
14 break glue to remove cowl. add 1/4" spacer to front of fuz slightly smaller that it's current size. This will locate the cowl.

Did I paint myself into a corner anywhere?

Barry