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Mold trick

wirejock

Well Known Member
I have some down time while parts cure for the plenum inlets, so I decided to try and fab a plenum for the oil cooler air supply. How to fab a twisted and turned 4" tube?
I took a 4" closed cell foam backer rod. Basically a pool noodle. Sliced pieces off. One end is cut 30°, one end 90°.
Take the slices and arrange them by stacking and rotating till the mold takes shape. Draw a line on one side and two lines on the opposite side. Number them. Spray ends with 3M 77. Reassemble lining up the alignment lines. Remove, sand to shape and layup the glass. Kinda fun and might just work.
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How do you get a smooth contour at the intersections?

Dave

I plan to rough sand the exterior to smooth the joints. I will loose a little volume but the smooth interior should help. Other option would be judicious application of tape.

Hopefully the resin doesn't eat your foam before it cures.
That's no problem. I use packing tape. Wax the tape. Layup the glass. Cure. Carve out the foam till the mold pops free. Done it many times. Fast. It's a sacrificial mold.
 
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Or cut the part in to 2 semi-circular parts, smooth out the internal profile and glass back together. Good thinking to use sections of stiff foam.
 
Or just carve a finished mold and spend half the time for a better part.

Composites Rule #1: Time spent on quality molds and forms pays significant dividends in weight and finish.
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Or just carve a finished mold and spend half the time for a better part.

Composites Rule #1: Time spent on quality molds and forms pays significant dividends in weight and finish.
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There's some good advise. Exactly what I did with the plenum inlets. Except, I can't carve a stick into kindling, so they still need work. :D
 
Etc.......
 

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Actually not much carving. I rarely cut with anything more complicated than a hacksaw blade or hand saw. It's mostly sanding. Make templates when necessary.
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Actually not much carving. I rarely cut with anything more complicated than a hacksaw blade or hand saw. It's mostly sanding. Make templates when necessary.
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I didn't realize your aircraft was equipped for CAS/COIN missions... :)
 
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Oil cooler plenum

The mold worked great. Unfortunately, I didn't check clearance before adding the fiberglass. I thought it was well inside the top cowl. Top cowl won't clear. I trimmed but lost too much volume so I tossed it. Bummer. I'm going back to SCAT.
 
Parts

I hate to ask a dumb question but why are you manufacturing your own parts?

Dumb answer? Because I can. Not my first rodeo. I also made one piece canopy skirt and windshield trim plus a few other mods.
Real answer? Because it's a modification not in the plans. The oil cooler is mounted to the firewall and requires a duct and butterfly valve from the baffle. A plenum would have been more efficient and significantly lighter than SCAT or SCEET. I may fool with it again later.
This is nothing. You should see the plenum and inlets! That was a project.
 
I hate to ask a dumb question but why are you manufacturing your own parts?

Larry learns new skills with every attempt at creating a custom part. It doesn't matter if the part is ultimately rejected; even failures teach something. The best airplanes often have a pile of trash parts back home.

Have you ever seen Mark Gilmore's Marquart Charger on the flightline at OSH? Former Gold Lindy winner, and still flawless. Mark's favorite part is the vintage sectional windshields. He made three or four sets...doesn't remember, and doesn't care.
 

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50 years of Vans RVs

I hate to ask a dumb question but why are you manufacturing your own parts?

How things have changed! In the beginning, everyone manufactured many of their own parts, because that was the way the Vans kits worked.
Now, CAD/CAM and CNC machines do a lot more of the work for the builder, or assembler. :p
 
Fun

Isn’t that the fun of E-AB ?

Totally. Some days, you get the bear. Some days, the bear gets you! Today the bear won. Not the oil cooler plenum. The engine plenum inlets. Had to cut it up and re-glass. That's the real beauty of fiberglass. Everything is repairable. :D
Tomorrow will be better.
 
Multiple parts

Larry learns new skills with every attempt at creating a custom part. It doesn't matter if the part is ultimately rejected; even failures teach something. The best airplanes often have a pile of trash parts back home.

Have you ever seen Mark Gilmore's Marquart Charger on the flightline at OSH? Former Gold Lindy winner, and still flawless. Mark's favorite part is the vintage sectional windshields. He made three or four sets...doesn't remember, and doesn't care.

Some years ago Mark Gilmore had his MA-5 at Blakesburg Antique flyin. I was talking to his wife while he was showing off his Marquart. She claimed the neighbor took Mark’s throw away parts and flew his plane before Mark flew. Unbelievable craftsmanship!
 
Isn’t that the fun of E-AB ?

Certainly for some.

Let's showcase an example. Dave Howe recently posted about an insurance rate jump after 20 years with no incidents. Twenty years ago, RV's were not tab A, slot B, Rockets were really special, and nice airplanes were more about shop skills than checkbooks.

https://www.danhorton.net/Misc/Dave Howe Sport Aviation.pdf

Trust me, every builder should undertake at least one entirely custom part. Doesn't matter what, as long as it makes you grin every time you look at it.
 
Oil cooler plenum

I had a break while parts were curing and pulled out the oil cooler plenum. The offending area was cut to clear the top cowl. The area needed a filler to layup the repair. Balloon to the rescue. I inflated it inside the plenum. Some waxed tape was already in place to span the gap so I just left it.
Just a little fabricating fun.
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OOPS - - -

No matter, I made 5 plenum covers before learning how to do it right.

Keep them coming, Larry.
 
Oil cooler plenum

Not as pretty as Dan's fiberglass work. The balloon died a horrible death sometime during the cure but fiberglass was hard enough already. It still needs some finish sanding and fitting. It was just a fun little project in between waiting for other parts to cure. I hate sitting still.
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David Howe

Dave is one sterling fellow ....he took time out to contact me personally around a question I had posted on VAF . His knowledge , understanding and old fashion homebuiding encouragement have been greatly appreciated! I was fortunate enough to grow up in a homebuilding family .....my late father was very good friends with George Bogardus ,arguably..perhaps THE most important individual ever in the hobby . George would have liked Dave very much as he fosters the spirit of innovation ,the very foundation of the movement .
 
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