ORIGINAL: Zor
ORIGINAL: Iron Bottom
Well, water will warp any wood product I've ever seen, unless it is perfectly sealed. It will even get to the almighty woodpecker meatloaf (MDF, chip board and particle board) given time. So my thinking is that any water based product will warp wood.
Iron Bottom and all readers,
True that water (humidity) will warp any wood product if the humidity in the wood is not spread uniformly.
The work surface we use should not be subjected to wide variations of temperature and humidity.
One reason I do my building in my house that is constantly between 68 to 70 degrees fahrenheit and a relative humidity between 50% and 60%.
As mentioned in a previous posting I also have a method of checking how straight and flat is my work surface.
Now think for a moment ''<u>how much water is in the glue used</u>''.
We are buiding a wing structure. We have verified that our spar material and leading edge and trailing edge materials are straight and have no twist. They are receiving some glue at every ribs. How much water is in that glue to migrate into the wood and cause it to twist or to curve ?
I do not know the composition of the different glues I have used over the years but as I wrote earlier I never had a twisted wing due to gluing. I suspect that most glue have very little water in their composition (formulation).
I may be correct and I may be in error but I suspect that many glue formulations contain alcohol or highly volatile solvents that evaporate during cure (solidification). A good glue has to have two main properties.
It has to have inherent strength once cured and it has to have binding to the parts it is joining.
We can tell how much solids result in a glue curing (polymerism or other process) when we fillet our gluing. We can see the amont of solids left forming the fillets.
Sig-Ment glue result in about twice as much solid left after cure as compared to Great Planes PRO and Titebond III wood glues. The solids left after cure have to fill the gaps between the parts in contact. Parts in contact are touching for only a very small percentage of their areas even with all the care we take to make good fits and even when pressure is applied to the joints being made.
Conclusions _ _ _
Use a flat surface to work on and verify that it is flat.
Verify the individual components being assembled (glued) for proper shape.
Use good and proper glue for the specific assembly (fillet the joints).
Use a covering material that is light but strong in tension and does not tear easily.
In a woven fabric each thread has to break in tendion for the material to tear.
Seal the covering with coatings resisting variable weather exposures ( Think why full size fabric covered airplanes use aircraft dope).
Use coating material that is resistant to the exhaust of glow fuel if such is being used.
The above all makes good sense to me.
Enjoy solidly built models that will have minimum repair needed in the event of abnormal landings.
Zor