Mo(u)lded plywood construction?

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Aviacs

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WR cedar bends fine.
In any lamination, choose or saw for grain run-out.
I've bent thousands of feet of it and redwood for ourside architectural projects.

This project is redwood, which is arguably more brash than cedar. I had a pile that i didn't want to store anymore.
(Cedar is stronger and more stable. Those attributes were not a factor for bent-lam arches. Hence, save the cedar, use up the 4/4 redwood)

As can be seen, the laminations don't even need to be that thin for stuff like this.
Saw it thinner, and thinner bends work well. Again, sorting/sawing to improve grain run-out.


AFA strip planking an aircraft fuselage, it would seem to be too heavy?
To get any strength across the grain would require glassing both sides = weight.

The old method included laminating 3 to 5 plies of birch to a total thickness under 1/8" IIRC?
Though it seems some skins for some planes were locally thicker in areas of higher stress.

smt
 

Aviacs

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Fresh cut cedar posts for fencing has been used in the south since back in the early 1800's. I've worked fence sections that had cedar posts in place for nearly a hundred years and the posts were still good!

Just curious - Cedar, or Juniper?

Cedar for strip canoes is Western Red Cedar which grows in huge, straight logs.
My experience of "cedar" in the mid atlantic and south, is Juniper which grows prolifically in the region, but is smaller logs with more knots than knotty pine. Juniper is the "aromatic" cedar of closet & hope chest fame. Heartwood trunks last seemingly forever. Junipers were also sometimes grown as self-fences for small areas. Close enough and weedy enough to keep larger animals in or out.

Another aside, the south had cypress as well. My experience is that current stuff is not particularly rot resistant, though. IIRC, heartwood may be close to sitka spruce in technical spec.

smt
 

karmarepair

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I think it was Molt Taylor who pioneered using craft paper as a core.
I wondered when this would come up.

I recently got the book on TPG from Jerry Holcomb, he included some small samples of the "core" materials. Which is good, because I'm having a hard time finding them in retail quantities.
While the handbook has long been sold out, I could photocopy the original manuscript and round up some samples of both types of laminated paper and the type 1528 fiberglass that I used to construct the three airplanes using the technology.

I can also send you a Perigee (N9XH) information package that compliments the handbook. By far, N9XH was the most successful of the three airplanes that I built, but neither construction drawings nor any of the kit parts that I once sold are available today.

The handbook and material samples are $20 and the info pkg is $10. I haven't mailed a set for some time now, but $5 should be close enough.

You can mail me a check or PayPal to [email protected]

Best regards,

- Jerry Holcomb
1010 NE 122nd Avenue
Vancouver, WA 98684
The manual is strong on technique, and light on engineering data, like, how much does it weigh? The Perigee looks like a really neat plane. The Cuyuna it was designed around went Out Of Production, Jerry started replacing it, but never got to done. The airframe is still under cover in his back yard.

I mentioned the supply problems I was running into.
Ryan, yes, we encountered the same kind of resistance from container board mfg/distributors when Molt and I came up with the idea of building paper airplanes. Luckily, the materials were produced locally, so a few "butt,-rolls" (the relatively small diameter final portion left over from the huge rolls) fell out their back door ... and accidentally landed in the back of my truck.
I've done some preliminary cost and weight estimates. I'm skeptical this is the answer to any pressing aviation question/problem, but I'm still rolling it around in my mind.
 

Chilton

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Early Mosquito used Casein glue, the first ones sent to India came unglued due to humidity, De Havilland changed to Aerolite for the majority of the type as a result.
 

rotax618

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My father was in the airforce during WW2, he was the one who told me about the casein glue, apparently they did repairs to the airframe using casein but I believe they used aerolite on all later models.
 

TFF

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Kermit Weeks Mosquito is grounded at Oshkosh because of glue. His is a late one He doesn’t trust it anymore. I believe one broke up in the air a couple of years after he got his and that was that. If you go look at it close things like the flap hinging is just varnished wood painted over. They were never designed to be around today or were kept up like expected to originally. The one that’s been flying to Oshkosh a couple of times is almost 100% new.
 

Vigilant1

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Similarly, lots of metal parts in aircraft were produced with little concern for dissimilar metal corrosion issues. Concerns about corrosion took a back seat to production volume. There's not much point in building for a 30 year service life when some models had an average service life well less than a year.
 

Saville

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I've seen the build videos of the main fuselage many times but I wonder how they handled the nose with the sharp compound curves.
 

mcrae0104

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Early Mosquito used Casein glue, the first ones sent to India came unglued due to humidity, De Havilland changed to Aerolite for the majority of the type as a result.
Thanks, I wasn’t aware of that.
 

karmarepair

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TPG is ghastly heavy & weak, but can make a cheap plane in one weekend.
Please share your data.

Here are my calculations, looking at rib gusset alternatives, the drywall tape alternative numbers are actuals, all else is speculative or catalog data.
"Light" TPGGrams/M^2Cost, $/ft^23mm Birch Plywood (1/8")1.5mm Birch Plywood (1/16").020 aluminum3 layers of drywall Tape, saturated with Tightbond III"Fish Paper", 0.01" thick, used in WWII for Aeronca rib gussets
90# Linerboard245.00$0.09
1528 glass cloth204.00$0.96
Polyester resin to saturate cloth204.00$1.83
Resin soaked by linerboard29.14$0.26
Single sided glass, about .034 finished thickness, .83mm711.29$3.41
Cost of alternatives, $/ft^2$5.23$3.10$2.31$1.34$6.25
Double sided glass, about .040 finished, 1.01mm1,364.29$6.21
weight of alternatives Grams/M^22000100056632000293
sealed both sides2,058.291,058.29
 

Fiberglassworker

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So How bright does the light have to be exactly? I mean I watched my grandmother candle eggs as a child and she did it in the root cellar, but an egg is one thing candling plywood another thing.
Depending on the thickness of the plywood a 500 watt to 1000 watt bulb is used in a light reflecting box, and it is just like candling an egg.
 

Fiberglassworker

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I believe the glue used to build the Mosquito was casein glue, it is derived from milk protein.
The first few were made with casein glue, De-havilland quickly discovered that these did not do well in the far east because of heat and humidity and switched to aerolite 300 a premixed urea formaldehyde resin glue.
 

Lendo

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Any core material that holds/absorbs resin, is going to add unnecessary weight. Any material with a fine grain will be best as the resin is primarily maintaining the strength of the composite and only bonding to the core.
George
 

Sraight'nlevel

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Carving blue foam and vacuum bagging the plywood over that foam plug would be the only reliable way to get 3D curves. However, once you've gone that far, you can probably substitute glass cloth for the plywood and save some money :)

I believe Sonja Englert, who is or was a participant on this forum, made her own motorglider fuselage mold pits out of dirt. In her back yard IIRC. She realized that for a one-off fuselage, she saved more time this way than she lost by sanding bondo later. So there is a potentially viable idea to use this kind of "pit mold" in dirt and perhaps plastic sheeting over the dirt.
I bet there is no need for blue foam. Like said before you comments the form will come if the design is made to look like it is curved. Plywood in Mosquito was made in situ, but was also very thick, nowadays thinner layers bend really easily like 1 mm. You can have several of those if you will.
 

Sraight'nlevel

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The first few were made with casein glue, De-havilland quickly discovered that these did not do well in the far east because of heat and humidity and switched to aerolite 300 a premixed urea formaldehyde resin glue.

I agree, the epoxy came too late to save De-Havilland wood worx.
 
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