Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cluttonfred, May 8, 2011.
In VP-1 plans you can extend the 1/16 aircraft ply in the center wing section to cover leading edge, is that replacing the aluminum in that section or in addition to? And is it kosher to replace the entire leading edge with 1/16 aircraft ply?
The 1/16" replaces the aluminum. And yes, you can use 1/16" instead of aluminum for the whole LE.
The infamous glue question … again. I like Smiths … http://www.glueoakandteak.com/ … have had good success with it. Is there anything that makes T-88 superior?
Besides history, T-88 has a high service temperature tolerance which is probably why it gets the nod. And while a few get picky on mixing, the vast majority just want squeeze and mix, which T-88 was invented for. They claim 160F max service and 119F temperature deflection. The stuff was made for boats about thirty years ago. It just works.
It would be interesting to put some thermometer probes at various places inside the wing of a GP-4 or Falco--especially right on the inside of the skin at the spar. Is suspect it might scare a lot of folks right back to the stone-age days of resorcinol.
I suppose it's a matter of perspective. I'm searching for an alternative to T-88 because of it's low temperature tolerance.
The OD Green fuselage on my VP-1 exceeds the max service temp for T-88 on a cool day (65f). The whole airplane exceeds the deflection temp limit on a cool day.
Resorcinol can’t be beat for heat.
Remember wood is a terrible conductor of heat. The surface temp can be high and the glue joint not close to its max. I believe someone took temps on their Tailwind wing and internal was not close to being scary.
Wood is a good insulator but there's only a 1/16" of an inch of it between fabric that's glued to it and the T-88 glue line, and it forms a closed box (oven). If one side of a piece of 1/16th ply is uncomfortably hot, the other side isn't far behind.
Bottom line: T-88 has poor temperature tolerance.
The big draw back to resorcinol seems to be getting a good fit. Is there a way to modify it's gap filling properties by mixing in something like really fine sawdust, kind of like we to with epoxy and flox/milled glass?
I'm going to use resorcinol on my laminated parts but it would be nice to be able to use it with the same fit tolerances as T-88 on the rest of the parts and just use one adhesive.
Does anyone here have knowledge and experience with the Hughes FPL-16 and other "resorcinol replacement options" that were developed over the years?
Also, I know for a fact that there are now several higher temperature epoxies used in composite construction. (I personally saw what was clearly some kind of a carbon composite jet exhaust duct on the later jet powered Predator drone a couple of years ago at one of their facilities)
Can one of these "laminating" epoxies be thickened slightly to create a structural gap-filling adhesive with higher temperature tolerances?
I wrote Smiths for a technical data sheet, will post if they reply with one.
Here is the MDS for T88.
It states Maximum service temp is 160 deg F.
And lap/shear PSI on Maple is 1800psi, before substrata failure. 2000psi on aluminum
heat deflection temp 119 deg F
Check out Heat deflection Temp definition, and Determination:
the determination IMHO, being most relevant...
No data from Smith.
Weldwood Plastic Resin was popular. I know Craig Catto makes props with it.
Data sheet https://www.dap.com/media/74720/plastic-resin-glue30201.pdf
Resorcinol is weather and boil proof.
Is anyone aware of a documented T88 joint that failed due to temperature?
There are lots of wooden wings on airshow nd competition airplanes that sit in the hot sun, then get heavily loaded in flight. Yes, I’ve heard the claims that rapid cooling occurs on takeoff.
Resorcinol is looking better.
I don't know anything about T-88 failures. I know I am supposed to have weather and boil proof plywood, so why wouldn't I use weather and boil proof glue to stick the lumber to it?
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