ORIGINAL: Nodd
Stubborn Bugger
I've not weighed the brackets but they're nothing I'm worried about, especially once I've ''Swiss-cheesed'' them. I'm getting lots of suggestions to just use fiberglass & I do intend to FG the heck out of the joint but I want something else in there too.
Fiberglass is good stuff no doubt but from experience I know it also has its limitations. For example look at what happened to my fiberglass four meter sailplane after a moderately bumpy landing...
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Fiberglass is rigid & cracks, metal is substantially inflexible but when it does move it just bends. I think a combo of both will be perfect for this application.
Fiberglass is an ambiguous term nowadays. A lot of fuselages are made with polyester resin, which in combination with glass cloth is the original fiberglass. When glass cloth is used with epoxy, we still call it fiberglass. So what's the difference between the two? The epoxy stuff is quite a bit more flexible. The polyester is more brittle. When you've got a fuselage damaged like that, how do you tell which resin was used? A professional glasser once told me you can tell by the amount of damage and how the cured resin has held around the glass. His telling advice is that if it's cracked a lot, and there is egg shelling, it was polyester. His most telling advice is you closely examine..... the cost of the product. If it was relatively expensive it is epoxy. If it was not expensive, it is polyester.
Anyway, some fiberglass IS rigid and cracks. Very few modelers make theirs with polyester resin. What we reinforce with it really isn't going to be brittle. And that's not the real problem here. And it's not the more important detail of the structure you're wanting to create either.
Just like having carbon fiber reinforcement anywhere in a model like a glider that normally flexes visibly in lots of places, having absolutely rigid structures anywhere in the glider fights that normal bending. Where the absolutely rigid support stops is where you're going to find your next crash damage. And sometimes it happens very shortly before the crash.
But what the heck. I'm not a terminally stubborn bugger. I'd like to see how your steel works out for you. I'll still suggest stubbornly that there is absolutely no value in having all that steel in the brackets. Drilling more holes in them than there will be steel left really would be worth the effort.
BTW, if your fibergalss 4M sailplane broke like the picture shows as a result of a moderately bumpy landing, I got twenty bucks says it was made with polyester resin. And the exposed section of cloth at the forward most damage suggests polyester as well. Good thing is that epoxying inside the fuselage from the wing mount forward with a couple of layers of cloth will cover the area where the stress risers from the impact did the most damage, and you'll be not only reinforcing where the stress won the previous battle, but you'll be moving the place where the next stress risers might happen farther out, reducing their leverage.