|Howdy Burt, I Fixed Your Puny Spar|
The way I heard it, back in the 80s a fellow told Burt how he just didn’t trust the main spar. It looked a little dinky. So he beefed it up a little, adding extra layers to the spar caps. Sounds reasonable enough. More is better. What could it hurt?
Burt congratulated him for building a three-G spar.
I read in the early CPs of a wing loaded to 18 Gs before it started to fail. But this man’s innocent (ignorant) ‘strengthening’ actually created a hard, non-flexing element in the previously extremely strong, uniformly flexible wing and spar unit. It has to ‘give’.
You can do a similar demo. Take a
thin length of wood like a flexible yardstick and play with it and bow
it good and get a feel for it and maybe measure the bow flex at the center,
like where an arrow would go.
Some of us would struggle some just to do this yardstick flex demo right, much less redesign a spar. Hey, maybe we could get someone to come up with a strong, flexible, light weight, spiffy, well proven wing and spar design so we could just go fly…?
I fly with no structural concerns of my own making. The bulkheads and spars and such are per plans. My only changes would involve things like using LongEZ foam, glass and gear improvements. I have specifically benefited operationally from Burt’s elegant design, rather than something “better”.
OK, so LESS must be better?
Several years ago there was a magazine article published by a fellow that built his plastic plane, maybe a Lancair, using carbon fiber instead of fiberglass. It ended up weighing a few pounds more than standard.
It could be surmised that since I have done things with my cowls and prop, that I also surely would have “improved” the big things with carbon. No, somehow I draw a very distinct difference with the things I have done versus the primary structure. I guess I appreciate the overall design and “fit” of the airframe elements.
Also, an experienced prop guy mentioned the problems you can create when ignorantly using carbon on props. Whereas fiberglass has some give, carbon fiber doesn’t stretch much and will fail. His discussion was not technical and didn’t give me anything useful as far as the “how to”, rather just a warning that using specialized materials has two sides. Props are black magic.
Aluminum and Carbon Fiber
If you draw a straight line with a pencil on a thin sheet of aluminum, later you can go back and easily fold it right on that line and break it. The carbon eats the aluminum. I understand that Burt did some quick calculations on how long the Voyager wing fittings had been built and gave the team a drop dead date for when the fittings would have deteriorated too much. They had to fly when they did.
If all else fails, read the
I can’t believe that everyone
hasn’t heard about the total foolhardiness of changing the layers
to Burt’s design. But evidently there are those that have done it,
are doing it, and even folks planning to do it.
This is right in there with washing your skin with harsh chemicals like MEK. Or even breathing the fumes. It permeates right to the Liver. Has everyone read Burt’s admonishment to get that stuff completely out of your shop?
Is anyone slabbering micro (little hollow balloons?) in crazy places like between structural spar layers so they will be more even and look better. I’ll be back in a minute, I have to go outside and scream.
I feel a definite advantage in having
read all of the CPs and Plans and addendums. Simple understanding of the
genesis prevents mindless errant temptations, like the dark camo paint
that will allow your wings to warp. While it is OK initially to have a
goal to remove the cowls on your recently purchased EZ only once a year
during the annual, a reading of your basic documents will dictate otherwise.
Having read his stuff, at least I
won’t walk up to Burt and say something stupid, like “Howdy
Burt, in our hanger there are two more VariEzes going together!”
Bill James, Fort Worth VariEze