My very own Go Devil 38 build

Today I want to epoxy my plies onto my rocket for real. My best friend is coming over and I think he will be my camera man while my hands are sticky with epoxy. First I want to relate what my RC airplane friend,Ben, just experienced doing vacuum bagging. He and I are getting into it at the same time. He introduced me to his RC build group and I picked up a lot of tips. Ben's first attempt left a little to be desired. The good news is he can throw the first vertical and horizontal stabilizers he made away and it won't hurt his airplane. When applying plies to your rocket it's all or nothing. If you want to start over you have to order a new sustainer tube and fins and begin again. I can't afford that. I want to fly at LDRS so failure is not an option. Hence preparation.

Here is Ben's first attempt.
He knife edged 1/8 in balsa cores. He put a 2 inch strip of unidirectional tape over the leading edge and laid 5.7 oz plain weave carbon cloth over that. I think the first attempt also included 1.4 oz fiberglass. Over the composite he put a 2mil non-porous release ply then paper towels as a bleeder cloth. Finally he has 2 mil vacuum bag.
You can see the edges of the uni-tape under the other layers as you would expect but notice how lumpy the surface is. The release ply didn't pull the carbon down onto the balsa uniformly. It took on the lumpiness of the towels. That is unsuitable. He showed it to me yesterday and at first I thought he was proud of it and wanted me to admire it. Then he let me know he was warning me.

In the RC world they always use .014 Mylar over the wings so the composite takes on the finish of the Mylar. That thick Mylar also bridges over the edges of plies and reduces the amount of time you need to spend finishing.
I didn't have any Mylar for my job so Ben came to the rescue. He found unused ancient Mylar view foils from the stone-age...I mean the 90's. He took some and gave me the rest. This stuff looks to be 5-7 mil. Nice and flexible so it can take a fillet corner but stiffer than release ply. I'll show you what he produced next last night.

Here is what he wrote me:

These are all the pics I took - also included pics of the bumpy first attempt. Sorry I didn't get any shots of the dry cloth before layup, but I'll list the layup order from balsa-core to vac-bag:

(symmetric)
- 1/8" Balsa core shape
- 2" wide Uni-carbon tape (LE reinforcement)
- 5.7oz plain weave CF (main strength)
- 1.4oz fiberglass (better top surface)
- 2mil release film (non porous)
- Transparency film
- Paper towel
- Vacuum bag

All cloth layers were cut with ~1/4" perimeter-excess; except for LE, LE is wrapped around.**Release film is cut just outside the cloth. Transparency film is cut to exactly the same as balsa core.

I stuck all the layers on dry with a light-dusting of 3M77, then wetted the entire thing and squeegee'd until I felt it was saturated (I did a better job the first time).

Once saturated, release film laid on, squeegee again to eliminate air bubbles. Then lay on transparency, then put in bag between paper towels.

Here are his pics:
An example of the view foil material

The bagging rig

The finished product

It's not Jarvis but is beats the snot out of the first attempt. It is shiny and smooth.

That's what I want to do this afternoon.

I started getting ready this morning. I had to take the bag off my rehearsal setup and get my un-epoxied plies out and clean off the rocket in preparation for really bonding them on.
The bag wouldn't come off without tearing so I cut it off. I stripped everything off down to the bare airframe and fins and I will redo all the masking tape and the yellow sticky sealant tape. I think I will move the aft fin guide off the end of the body tube onto the payload section. Remember I extended the aft end of my sustainer with my coupler and payload section. This puts the fins in the middle of the setup and I can support my rocket in my stand and make my work easier. Yes I know I have to make sure epoxy doesn't leak into the joint between the sustainer and the payload section. I'll cover that in a layer of non-porous bagging material.
I also bunged up my outer plies a bit peeling off the masking take that held them on for the rehearsal. Since they will be visible and I won't paint I will cut new ones. I will also be extra careful taking the edge tape off. I want that Jarvis look!

More after lunch.

Here is how I used my fin guides to support the vacuum bag.

I glued on a mast to hold my vacuum fitting. You can see how I used the screwdriver to push yellow sealant tape through the fin slots. That held the sealant on the inner faces to the fin guide. It turns out that highly sticky sealant doesn't stick to plywood well but it sticks to itself.

I used 3M-77 spray glue on the back side of the first plies so I could tack it in place.

When I peeled the tape from the edge of the ply I got mixed results. Must of my edges frayed.

I saturated each ply with epoxy and the added the second plies.

I also used a spatula on each ply to get rid of excess epoxy

The last plies I figured I'd leave the tape on the edges that overhung the fins since that will be cut off anyway.

I put on the release plies

Then the bleeder plies made of shop cloth

I was able to get the blender plies to stick to the ring of sealant around the body tube.

Finally I put on the bag.
I had to cut a hole for the vacuum fitting first. Then I tacked it to the sealant.

I want to thank my friend Jim for his help. He rolled the rocket. For me for each stage and took pictures with his clean hands.

The finished bag

I applied vacuum and could only pull 15 inches of mercury. P
I added sealant and listened to the bag up close. Eventually I found the leak. I got 27 inches.

I wanted to use the thin Mylar Ben gave me but it didn't work. It stuck to my outer plies and the. The Mylar flattened out. It pulled the plies from the rocket so I had to get rid of the Mylar. Too bad. I have lumps and wrinkles.
I tried to straighten the wrinkles out after shutting off the vacuum but no good. We shall see in a few hours. I want to pull the bag after four hours and trim the still soft epoxy. It is like vinyl at that point.

It's been an hour. I can see the bleeder cloth getting saturated with epoxy.

I forgot to mention my most important helper. Cisco.

He is an English Cream Golden Retriever. Pure bread and awful health. We call him Cisco the Lard Dog. Here is proof that A) lard floats and B) it doesn't dissolve in water.

Two and a half hours. Check out the bleeder cloth saturation.

The epoxy is warm to the touch. It's exotherming.

You can see the epoxy making its way through the bleeder cloth towards the vacuum fitting.
Even though I am convinced I will have lumps and wrinkles I am excited. This is quite a learning experience. I am already thinking of ways to defeat my issues next time.

Good news. I peeled the bag off and the underlying composite surface is much better than I thought. I may have some issues with the fillet on the left in this picture but it also may just be the release ply coming loose.
The other sides look much better. I left the release ply on because the epoxy is still too tacky. This stuff cures much more slowly than my last batch.
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I'll check again in a few more hours to see if it has lost its tackiness, then I'll trim the fin edges.

This is so awesome! I started vacuum at 3:30 yesterday, and had good vacuum by 4:00. I checked at 6:30 this morning and the carbon was the consistency of leather. So I rough trimmed it with an exacto knife. It cut easily. I peeled off all the yellow sealant and masking tape. This is what I ended up with.

Way cool!

Looks pretty good for a first time Tom! I wish I had the means ($) to do mine.

Next time u need to use more breather bleeder fabric. If ur fabric is that saturated it means it only pulled out so much epoxy. My recommendation is use 2 layers of breather bleeder fabric. U have extra epoxy in ur laminate that is costing u weight and ur not gaining any strength. When I do 2-3 layers of carbon or fiberglass I use the extra breather because that gets all excess epoxy out. The breather I use is 4 oz from fiberglast.com. It is specifically made to full a vacuum and soak up extra epoxy. I would not use shop towels. Just my 2 cents.

Andrew. That was two layers of shop cloth. I just looked at Fiberglast and saw that the 4 oz bleeder cloth is $4.95/yd. Not a bad price. I will try to get it from Airtech though. They are located a mile from my house (Huntington Beach). When I tried to buy vacuum bag material from them they gave me a 60 in by ten ft roll of 2mil stuff, a roll the same size of 1 mil perforated release ply, and a box of yellow sealant tape with three 25 ft rolls. Free. Maybe I can get bleeder cloth for the same price.

I am going for the gleaming carbon under the clear coat. I am using the 550 degree Engine Enamel Gloss Clear from VHT.

The effect is quite nice. It dries in a few minutes. Even if I spray too much I can use my halogen shop lights and get it to cure to the point that I can sand it in a few minutes. Great stuff.

However I am suspicious of the job I did on my carbon plies. There were divots between the tows that took forever to fill with the clear coat. I eventually resorted to epoxy and a spatula and lots of sanding.
Here is the result. I haven't polished it yet.

Got any suggestions for polish?

I can see from my above post I need some more posting skills. I can't delete those last two images.

So I'll talk about them. I am an aerospace engineer with a laptop that has CATIA loaded on it. I do CAD all day. So it is an easy task for me to design a sled like this. I uploaded the file on Shapeways.com. It will take an Eggfinder, a 400 mah LiPo battery and a magnetic switch and fit it into a Go Devil 38 nose. The file is on Shapeways under my id: scoutertom58. Anyone can order a print of it now that it is up. I uploaded the battery cover too. The whole thing comes out under $30 shipped. I should get it in the mail about the same time I get my soldered Eggfinder from Connor McGrath.

TomSmith58 said:

I can see from my above post I need some more posting skills. I can't delete those last two images.

So I'll talk about them. I am an aerospace engineer with a laptop that has CATIA loaded on it. I do CAD all day. So it is an easy task for me to design a sled like this. I uploaded the file on Shapeways.com. It will take an Eggfinder, a 400 mah LiPo battery and a magnetic switch and fit it into a Go Devil 38 nose. The file is on Shapeways under my id: scoutertom58. Anyone can order a print of it now that it is up. I uploaded the battery cover too. The whole thing comes out under $30 shipped. I should get it in the mail about the same time I get my soldered Eggfinder from Connor McGrath.

Click to expand...

Thanks for this. I've been putting off building my kit of this rocket contemplating how to solve this problem. This is perfect!

ETA: Not showing any creations under your account.

You said
ETA: Not showing any creations under your account

Let's see if I can fix that

OK, you should be able to order one now

I created a hand powered "Dremel" tool to scuff up the interior of my sustainer tube in preparation to glue in my motor retainer.

It is a piece of PVC on a 3/4 dowel.

I used strips of 3/32 basswood as a spacer. I stuck it 8 3/8 into the tube and rotated it by hand. Here is the result.

You can see the ring of dark. It looks like it's a mile down the tube but that's iPhone photography for you.

I'll bring the tool with me to LDRS. I need to get the 6G-XL motor casing and propellant load I bought from Bay Area Rocketry before I glue the retainer in. I will use the actual motor as the tool to locate the retainer. So I can't glue it in till I pick my motor up at LDRS.

Which of these would you chose?

I want to solve the issue I had with my Mariah where the shock cord cut at the lip of the body tube. I also want to make sure I can remove my cord if I want to. So I want a harness where there is something permanent but strong attached to the eyebolt in my engine mount and I want that same harness to stick out the body tube where I can attach my shock cord to it.

First idea; use a single loop of 5/16 Kevlar woven tube.

I tied a square knot in the Kevlar tube and I passed the 1/8 in line through the sewn loop at the end. The 5/16 tube should never break on the edge of my body tube. It is long enough to stick past the end of my body tube and it will take the abrading, not the shock cord. This is strong as hell but bulky.

Second idea; use a double loop of 1/8 Kevlar line.

Here I have a 40 inch long line tied in a single square not. I fold that loop in half and pass one half through the eye bolt. I then tie my shock cord by passing it through the sewn loop as in the previous design. This design has four times as many cords passing over the lip of the body tube. It should be less bulky than the first design.

Finally, I tie a butterfly knot 18 inches from the end of my shock cord and I just use the shock cord with no other cord.

Here I show off my Boy Scout skills. A butterfly knot is strong, can be tied anywhere along the length of a rope, and it takes load in any direction. However, now that I think of it I can't use this knot as shown. I had to pass the motor retainer through the knot twice to get the sewn loop to attach to the knotted loop correctly. I will have the retainer glued into the body tube by the time I ever want to take this knot off. I would be forced to cut the shock cord. This design has another drawback. This is the same size shock cord as broke in my Mariah. I am not much better off. The one thing this has going for it is there are two lines passing over the lip of the body tube instead of one. If I do want to use this design I would have to use a quick link to attach the loops. Quicklinks are heavy and bulky. It's OK to do but I want to avoid it.

I am leaning towards the second design. What do you think?

IMO I think the first one, more surface area across the lip. You can also file / Sand a bevel on that inside lip of the sustainer to reduce the chances of cutting the cord

OK, got my sled in from Shapeways today. Initial quality looks OK. I chose Pink Strong & Flexible Polished Bright pink, richly colored nylon plastic with a smooth finish for mine, mostly because I wanted it to stand out really well. Not being very smart on 3D printing material, I expected something like the PLA sleds that MissileWorks/Landru uses. It's not. The Shapeways stuff is lighter and a LOT more flexible, the finish has no printing lines, and is matte in appearance (polished???). Should work ok.

I'll take a better look at everything later this weekend when I have more time. First blush thoughts: Cool.

Initial look-over wants: Larger battery box to accommodate this ever popular battery: https://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=28646, and pads down low to mount a screw switch to access through a hole in the cone shoulder.

More to follow.