Re: wing spars witc C grain at front?

From: Mark F1diddler <f1diddler_at_yahoo.com>
Date: Sat, 07 May 2011 21:23:12 -0000

--- In Indoor_Construction_at_yahoogroups.com, "ray_harlan" <rbharlan@...> wrote:
>
>The big reason for using A grain sheets is that they are much more consistent than C grain, since the whole sheet was grown over a short period of time and doesn't have effects from different seasons, as can C grain.>>


Good catch, Ray! However, considering how fast balsa trees grow, we are not talking different *seasons* here, but merely a few days difference. Consider a spar, just for round numbers, that is .030" X .060". The C faced spar might have grown in a period of 12 days, but the A faced spar may have grown in a period of 6 days.

(Online SIG data: "balsa trees are ready for harvest 6-10 years where could be from 12-45" diameter.") So, grabbing the middle number(28" diameter over 8 years, just for argument) would indicate average annual radius increase of 1.75", or about .005" per day.
MB
Received on Sat May 07 2011 - 14:23:20 CEST