New tandem tractor design and build

Jean Claude

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Michael,
Have you chosen another engine?
This cover does not look like that of the radial engine.
 

ILikeJetsToo

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Have you tried the Frekote mold release agents? I only use those now, and have never stuck a part of mold.

http://www.henkel-adhesives.com/industrial/brands-5497.htm?nodeid=8797571973262

Also, have you ever tried Duratec easy sanding primer for plugs?

http://www.adhesivetechnologies.co.nz/duratec.html

It sprays or brushes onto the foam or wood and hardens fast, ready to sand within an hour. Make a hard surface on the foam and pull a mold right off. Fastest way to make a plug I ever found. I even machine a temp mold out of stacks of high density practical board and spray with Duratec and sand it, then using FreKote, and can pull 50 parts at 50F.

They also have in-mold primers for low or high temp.

Thanks for the info Dennis. I have not tried either of those before. I'm always looking for new material options, so I'll check them out for sure.

Thanks,
Michael
 

ILikeJetsToo

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So what is the process now? When you say you are making a tool, does that mean you press the tool into the CF or do lay up the CF around the tool?

Hi Jordan,

For this part, I’ll be laying-up the carbon/epoxy around the outside of that foam tool.

There are a ton of different ways to make composite parts and tools. I like to try different methods and experiment as I go. For me it’s usually a balance of time, cost, and part finish.

Often, people will make a male tool (called a plug) that looks just like the final part, and then they will make a female mold from the surface of that plug. Then they can make many parts in the mold that will look just like the plug. It's a good way to make multiply parts and parts that will have a nice outer surface. If you scroll back a few pages, that is how I made my landing gear ribs. On those ribs, I went to the effort of making a fiberglass female “hard” tool because I wanted to make two identical ribs.

For this cowling, I'm just making one part. It's also a big part, so I'm trying to make the tool as inexpensively as possibly. I made the plug out of low cost white expanded polystyrene (Styrofoam) foam. I think styrofoam is pretty yucky stuff to work with, but it’s very economical. The foam is delicate, but I only need to have it last for one part. To keep the cost low, I'm just going to prepare and release the surface of the plug and layup the carbon/epoxy right on the surface. It is the same method that I used on the fuselage, but this time I can just pull the part off of the tool when finished.

For this disposable tool, here is the basic sequence:

Tool:
-- Machined expanded polystyrene foam to cowling shape (you can hand shape it too)
-- Fix small surface blemishes with drywall compound (Let dry)
-- Seal surface with latex primer (Let dry)
-- Seal surface with two coats of epoxy resin (Let cure)
-- Release surface with three coats of Partall Paste Wax or Meguiars Carnauba wax (Let dry then buff)
-- Spray wax surface with three coats of polyvinyl alcohol releases film (Let dry)

Layup:
-- Wet epoxy one ply of Dacron “peel ply” to polyvinyl alcohol released surface (remove peel ply later for nice bond-ready finish)
-- Layup carbon/epoxy on wet peel ply
-- Layup one ply of peel ply over last wet carbon ply (remove peel ply later for nice bond-ready finish)
-- Vacuum bag as needed
-- Cure overnight (or longer based on temperature)
-- Post cure part on tool at 140 F for 10 hours
-- Remove part from tool
-- Trim edges of part
-- Remove peel ply from part surface

There are so many ways to make composite parts. They all have pluses and minuses. This method works pretty well for one-off parts this size.

Michael
 

DennisFetters

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Thanks for the info Dennis. I have not tried either of those before. I'm always looking for new material options, so I'll check them out for sure.

Thanks,
Michael

It looks like you are using Styrofoam instead of Urethane foam. If so, you can use the spray made for Styrofoam, and then cover it with the 1041 for easy sanding;

www.youtube.com/watch?v=Q4oCkrvyk3U

www.youtube.com/watch?v=lOxnCg0-7iU

I can't say enough good things about Duratec products.
 

ILikeJetsToo

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Michael,
Have you chosen another engine?
This cover does not look like that of the radial engine.

Hi Jean Claude,
I'm still using the Rotec Radial R2800. This boot cowling is just the bit that covers the engine mount and accessories on the back of the engine.


Michael
 
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bryancobb

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I have been learninq a LOT about composites manufacturinq durinq my year at Meqqitt. Michael`s project is every bit as complex and every bit as beautiful as our C-53k inlets or our V-22 rotor blade heat blanets.

He amazes me with the success of the project thus far. Michael, I think we would be amazed and you would have braqqinq-riqhts even more if you made it a standard feature of your posts to provide the finished weiqht of each part as you made them and the cumulative weiqht of everythinq that will leave the qround when the project is done. :)
 

ILikeJetsToo

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It looks like you are using Styrofoam instead of Urethane foam. If so, you can use the spray made for Styrofoam, and then cover it with the 1041 for easy sanding;

I can't say enough good things about Duratec products.

Awesome. Thanks for the info Dennis. I'll totally get some and give it a try on my next plug. I get material from Fibreglast all the time, so I'll take a look.

Michael
 

ILikeJetsToo

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I have been learninq a LOT about composites manufacturinq durinq my year at Meqqitt. Michael`s project is every bit as complex and every bit as beautiful as our C-53k inlets or our V-22 rotor blade heat blanets.

He amazes me with the success of the project thus far. Michael, I think we would be amazed and you would have braqqinq-riqhts even more if you made it a standard feature of your posts to provide the finished weiqht of each part as you made them and the cumulative weiqht of everythinq that will leave the qround when the project is done. :)


Thanks for the support Bryan!

I can totally start posting part weight. I'll put some thought into it and try to pull some info together. Maybe I'll list part weight and weight per surface area.

Michael
 

ILikeJetsToo

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I just finished the gyro cowling. I need to trim it to fit the firewall a little, but overall it turned out really well.

The cowling is actually a pretty large part of the aircraft. I was surprised how large the part is in real life. The part is carbon and fiberglass, so the weight wasn't particularity impressive. The weight below includes bodywork and two sprayed layers of primer.

Surface area:1,953 in^2
Final weight: 7.7 lb
Material: Carbon-282, Fiberglass-7725, Aeropoxy
Bodyworking: Fast West, West phenolic micro, Polyprimer
Layup: C-45, G-45, G-0/90, G-45
Time to fabricate part: 34.25 hr (including tool prep after CNC milling tool)

Michael
 

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TJPUMPHREY

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Your tractor Gyro looks great. Do you have any updates on how the project is coming along. Also, what CAD software did you use. I have not had a chance to check your earlier
post.
 

ILikeJetsToo

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Hi everyone. I've had several requests for an update on my tandem tractor gyro.

I have sold the project to another forum member. I look forward to seeing him conitnue the project with new desgin ideas and energy.

Michael
 

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