Re: Re: Boron / Carbon

I beleve that the amount of glue required to hold the boron in place increases with the stress applied to the component. The critical factor is of course the boron 'pinging off' under a compressive load ie the boron is buckling. I now use Duco or similar to attach the boron after degreasiing each filament with thinners. The Duco has much better initial contact strength when the boron is applied than does Ambroid so that it will remain in place while the glue is drying. This helps to avoid a dry joint. I then test each component such as wing posts or spars by bending a short section at a time to compress the boron to ensure the boron stays put. If not, reglue that bit. When I have tested both sides without failure (ie boron coming off), the component is deemed fit for use.

To attach, I wipe off excess glue with a finger  as soon as the boron is in place on the component (gjue a short section at a time).

Bob

On Jan 6 2011, Mark F1diddler wrote:



--- In Indoor_Construction_at_yahoogroups.com, "leop12345" wrote:
dI do not know how much glue is needed to hold down the boron fibers (I hope to remember to weigh a wing spar before and after sometime). Maybe Mark or someone else knows.>>


Not I! It's a personal thing according to how firmly you want it attached. Whatever glue % weight I suggest, someone else will say they use half that weight in glue, and I wouldn't doubt they do. I used to figure on about 50% of the boron's weight in glue, believing that boron *had* to be well attached all along a spar. But now believe if the boron is not buckling in the other direction (fore to aft) and it's at least attached along most of the spar's length, the boron still seems to function as a "rigging" of sorts even where not firmly attached. (Of course talking parallel spaced boron pairs here.)


> The bottom line, in my amateur opinion, is that boron fibers are the best stiffener material available for indoor planes at the current time.>>

Prolly so, and I wasn't being rhetorical in asking Bill--how do I separate a consistent strand of carbon from carbon fabric, weighing 8 mg per 24"? I have some .004 uni-D carbon, but from 1999. Will that do, Bill?
Mark F1diddler