Brodhead Pietenpol Association

I don’t have a garage or extra room inside my home to build. If I build a pietenpol using Sitka spruce in a portable garage, which is a tent like structure, would temperature or humidity cause problems for the wood? Thanks

Pbcyfly,

Where are you located? That may make a difference to how the question is answered.

Cheers, Ken

Ken, I'm located east of Atlanta, Georgia. Thanks

You may find that the epoxy is hard to mix if the temps in the tent are too low. The hardener, in particular, seems to get very thick when temps are low. So a heater may be essential for you to work with the epoxy. If convenient, you might keep the epoxy and hardener in your home, as they can take quite a while to warm up once they get good and cold.

I would think that in your area, a mushroom heater or something similar would probably bring the temperatures up to a comfortable working level. You'll find that as the air is warmed by the heater, the humidity will simultaneously drop. Your tent idea might work pretty well.

If you are using Sitka Spruce purchased from a source like ACS, it will already be cured to a moisture level where the pieces of wood are basically stable. So I wouldn't worry about that. You'll want to varnish ribs, tail feathers, etc., to protect them from the effects of long-term exposure to humidity. You might opt to store the finished pieces in your house as a way of protecting them from the elements until time to begin assembling all the little bits into one big flying machine.

Enjoy the journey, Ken

I built much of the wooden framing of my Flying Squirrel, and did a lot of the Aeropoxy layups on it, in my half of our garage here in southern Oregon. A lot of cold and clammy days and nights and our garage was unheated, uninsulated, and so was the garage door. What I did was get a propane-fired torpedo heater and when I was ready for a work session, I would fire that puppy off and let it bring the garage to temperature for awhile before gluing or glassing. My epoxies stayed inside the house, but even so, glass fiber wouldn't wet out as well when it was cold and the Aeropoxy would take several days to fully cure. T88 was much less of a problem curing, but once again, I kept my squeeze bottles of it in the house because in the garage, just as Ken says, the amber stuff gets very, very thick. Warming it in a pan of water helps, so does a careful beep in the microwave, but keeping it in a warm place is best.

I worked on my Squirrel, both wood and glass, over the course of maybe 5 years that way and now (about 15 years later) all the wood joints and glass layups are rock-hard and tight. It can be done in an unheated space with care, but boy is it easier in a heated workshop!

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

That’s great information. Thank you guys.

I’m a professional woodworker near Atlanta for the last 20 years...

Like mentioned, you’ll want sort of “comfortable” conditions for application of adhesives and finishes.

Otherwise, leave the wood basically in conditions similar to where the plane will live, which is a protected but non environmentally controlled area.

In theory, and basically true, if you’re epoxy coating for poly fiber process, the wood becomes inert. With no further moisture exchange occurring. If traditionally varnished, moisture level changes, but at a much more reduced rate.

More food for thought... Areas under covered things are protected from uv by the covering. Areas in the cockpit, wood struts or gear are not. So if epoxied, you should then use three more coats of spar (contains uv inhibitors) varnish as epoxy is susceptible to UV damage. Sand the gloss off the epoxy or the varnish won’t stick.

I recommend spar varnish for everything on a plane where you are using varnish.

Tools

Oh, I have a flying Piet if ya want any help or check one out..

Mike Danford
423-883-0721

Thanks, I really appreciate that and will reach out soon.