Scorpion Racing

More pics prior to clean up:

Scorpion Racing

Well, 36 hours after lay up and I am suprised at how stiff this thing is! Total weight without the firewall, wng bolt blocks and landing gear blocks is 5 3/4 oz. (162 grams). I will use this fuselage to mold the v-tail, finish the main wing center section and size all the wood parts; then I will be ready for some flight testing!

I still need to find some thin carbon fiber cloth that I can afford. Any of you guys have access to some small quantities or scrap carbon fiber? 3" x 12" strips are about the biggest pieces I would need.

Thanks!

Kevin Matney

My Feedback: (1)

I will sell some the 4.3 uni carbon for $50.00 a yard and it is 30" w

Scorpion Racing

Thanks Kevin, I found some at Aircraft Spruce (thanks to Petec!) and will try it. I need to order some more resin anyway, so I can just add it to the order. It is 5.8 oz., so I will use it as a second layer and it should work out fine.

Thanks guys, I am finishing the v-tail and main wing now, and will be molding them as soon as I can. I can't wait to bolt my Nelson on this baby when it is all composite!! The woodies with the Nelson fly great, so this thing should be awesome!

Thanks again.

Atlanta 60

My Feedback: (18)

Well Done!! [8D]

Scorpion Racing

Thanks! I have a question for you guys; have you ever used a gelcoating pigment in the first coat of resin in the mold when laying up the parts? My thought is to add a white pigment to the first coat (the one on the mold with the carbisil added) and then lay up the fuselage. This way it is colored (white) and no paint is needed. If that works, there are quite a few colors available.

Any ideas?

Kevin Matney

My Feedback: (1)

You will find out the mold is real hard to read the resin and glass with traped air. I like a gray mold, it is the best for me to read. I have a feww molds that are black. I spray gray primer in it to make it easyer to read.

Scorpion Racing

Kevin, so you say that if I pigment the resin, it will be more difficult to read the layup? I guess that makes sense. But how would it be any different than painting the color in the mold, and then laying the part up? I was thinking that pigmenting the resin (say, white or whatever color you want the final part color to be) would be the same as painting the mold (white again, or whatever color you want the final part color to be) and then laying up the part. Only the outer resin coat would be colored; the laminate layers would just be clear resin. I will paint the wings in the mold as they will have more than one color, but the fuselages I usually just do a solid color. Thus, the pigmented resin first (outer) coat idea.

Does that influence your opinion any?

Thanks

Kevin Matney

My Feedback: (1)

Scott I send you a PM

AllanU

Gents

I have built a mold using the same method and have a couple of questions. My seam did not turn out well. It can be fixed but the fuse is already 8 oz. Mostly because I think I overdid the firewall and nose section.


1. When laying up the 2 parts I understand that you leave the glass long on opposite sides so that it makes the overlapping seam. You put it together wet. How do you trim the other sides flush while wet? Or what do you use trim the glass flush.

2. How do you do the firewall? Do you leave the molding plate off the firewall while rolling down the seams and then put the plate on and glass it from the inside as a last step?

3. What kind of tools do you use to complete the seam?



Thanks.

Scorpion Racing

Well Allan, I will tell you how I did it! I layed it up as two parts; the big piece with the firewall piece attached, and the smaller bottom piece.

I made templates for all the glass pieces I used in the lay up. I made a template for the Top, sides and bottom pieces. I added a flap on the side and top templates for the firewall for the layers I want to add this to. For the layers I omit this from, I just fold it up out of the way.

I then cut out 1 top (with firewall), 2 sides (with firewall) and 1 bottom piece from 2oz. fiberglass for the first layer.
I then cut out 2 tops (1 with firewall), 2 sides (with firewall and 3/4" on bottom for the lap joint with any relief cuts for corners and tapering at the rear) and 2 bottom pieces from 6oz. fiberglass for the next layers.
Cut your carbon fiber pieces for the sides. I put this in as the middle layer, and will use 5.7oz. from Aircraft Spruce.

For the lay-up, I start with the big mold and painted it with a resin and carbosil mixture (about as thick as catsup) to coat the mold. Add some cotton flock to the mixture and paint any sharp corners with this. I lay in the 2oz. top piece (with f/w) and then the 2 sides (2oz. with f/w) and wet them out with resin. I align the side pieces so they are flush with the mold flange edge. Next add the 6oz. top and then sides (all without f/w) and again make sure the fiberglass sides are flush with the mold flange edge.

I now go to the bottom mold and painted it with a resin and carbosil mixture (about as thick as catsup) to coat the mold. Add some cotton flock to the mixture and paint any sharp corners with this. I lay in the 2oz. bottom piece and then the 2-6oz. pieces and wet them all out with resin.

You should now be left with 1 top piece (with f/w) and 2 sides (with firewall and the extra for the lap seam). Put in the top piece, followed by the 2 side pieces (making sure the lap joint pieces are positioned where you need and wet it out with resin. I now add some carbosil to the resin (about as thick as catsup again) and run a thin bead of this between the mold joint edge and the extra flap for the joint seam. You can add the actual wooden firewall now (add a little cotton flock for added strength) and make sure it is tight and has resin mixture all over it where it will join the bottom.

The moment of truth! Take the bottom piece and place it on top of the big mold and seal it tight. I flip the closed mold over and now use a brush on a long stick to go over the joint seam (the flap) with some plain resin thru the main wing mount hole and the tail mount hole. You will need some good lights to see in the mold, but make sure you can run the brush down all the seams and they are flat.

Whew! If you did all of that, you are now about 2 hours deep and need a break. So let it set overnight and try to clean up the mess! When you pop the mold apart, you should see a thin flashing around the seam where the mold pieces go together; this is good! the flashing can be trimmed off with a razor knife, and cleaned up with some 400 grit wet sandpaper. If you are happy with it, some rubbing compound followed by some polishing compound will make it shine like the finish on the rest of the plane.

Good luck!

Ed Smith

Allan,

From your picture it appears you do not have a hole in the mold at the wing saddle position. Is this so? I access the inside of all my molds through the wing saddle hole. The hole is as big as I can make it while allowing a say 1/2" wing seat flange.

Ed S

AllanU

Thanks Ed

I should of attatched a different picture. That picture was taken before I cut the hole in the wing saddle and the stab locations. I could make the hole a little larger to give more room, like you say for a 1/2" wing seat flange.

Al

wkevinm

Al

The last fuse I made (my best to date) I made templates as well to cut the glass in a more accurate fashion so to have the glass flush with the seams. I then add a ribbon of cloth so it it proud by 1/2 the width. I do this when the fuse layup is still wet. I tried to do cloth on either side, never worked for me so I put the ribbon on the main mold, and push it down before joining, it tends to spring back a bit. I also apply a this line of cabosil along the joint line, most will be cut off as flashing later. After joing the 2 mold halves I run a 1/8" wire (that has a loop on the end about with a 1/4" radius or so to push the cloth onto the other half along the 1/4" radius of the fuse, I do this through the firewall opening. Once happy with the joint line, I install the 1/4" firewall with a generous coating of cobosil. The firewall has a whole in it and is pre-threaded for a screw that the front mold plate pulls into place. Of the 2 fatal crashes I have had the firewall has never given way.

I use West epoxy, slow hardener. I use various cloth weights mostly 2.5oz, and SIG 6oz cloth (tight weave, wets out nice). It costs a bit more but still cheap given the amount needed. I use 5oz CF for the nose sides and gear supports. I use 1/8" aircraft grade plywood for gear supports and wing blocks.

Kevin M

AllanU

Thanks Kevin

I never thought of the wire with a small loop in it. That should work good. I will see how #2 works out.

Al

dsquire

I Have read where others have placed a small wheel on the end of a long piece of wire and then roll the seam down when joining the two halves together.

Just my 2 cents worth

Cheers

Don

diggs_74

That's how I've been doing it.. Seems to work ok.. Just find a tail wheel for a .25 sized plane, a 4-40 piece of wire and a used carbon arrow shaft that's long enough to get the full length of the fuse..

AllanU

Wrong thread post Sorry
Al