# Mo(u)lded plywood construction?

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#### Aviacs

##### Well-Known Member
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

##### Well-Known Member
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

##### Well-Known Member
HBA Supporter
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.

#### Fiberglassworker

##### Well-Known Member
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

##### Well-Known Member
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

##### Well-Known Member
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

##### Well-Known Member
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

##### Well-Known Member
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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