Re: Esser's Model 6 Repair
I'm sure the factory knows what they are talking about on the amount of work to replace a rear spar verses building an entire wing, but maybe they are figuring it if they were doing the work and charging what ever their shop rate is. I don't count my time as $ so if I was doing it, my concern would be how can I do it so it's good enough and at the same time not spend any more then necessary. What I would do is cut the spar off on each side of each rib, then cut lengthwise through the remaining piece of spar material in each rib and peal it out, using some heat if needed to soften the epoxy. Once all the aluminum spar material is removed, I would clean up the epoxy with a Dremel and slide in the new spar. Of course the drag brace bracket rivets would have to be drilled out to separate them from the spar as well. It's been a long day and maybe I'm missing something else as well, but you get the idea at any rate. Just a guess, but a new spar and aluminum stiffener might be about $300 not including shipping.
Re: Esser's Model 6 Repair
The wing cuff sounds interesting. Can you do some bolt-on experimentation with C-FOXD before you incorporate it into your "new" wings?
Re: Esser's Model 6 Repair
You pretty much talked about how I exactly plane to move forward Jim. I'm going to remove the tank and then cut the spar in to sections. I can't get a spar from Kitfox until August since the tariffs on aluminum started they've been hard to source. I had someone reach out who has an extra one which was very kind. I'm going to look at building a wing building jig to set everything in to build it true again.
Yeah Brian, I have some friends that made some bolt on cuff out of aluminum for their Ran's and highlanders. I might do something similar at first.
Re: Esser's Model 6 Repair
Any idea where the spars are sourced from?
Re: Esser's Model 6 Repair
Honestly, the aluminum tube used for spars is not anything exotic. A friend of mine scratch built his wings and sourced the tube from a local steel supplier (link). He had to buy them in 20' lengths to get the right length, then sold the drops to someone making wing extensions.
Re: Esser's Model 6 Repair
My concern with the source is where they are manufactured, not the specific alloy. There are reports of inferior alloys originating in China. 4130 sourced from China has experienced failures where US and German 4130 has not. My own personal experience is with aluminum alloys sourced from China. Although the data sheet for the lot said it was in spec, it did not perform to the spec and was quite different from a US sourced same alloy.
Re: Esser's Model 6 Repair
I've has the same experience, Jeff. Years ago now, I designed & built/sold (through Aircraft Spruce & others) cabin heat boxes. I used 2" dia. 6061-T6 ( I believe that's the alloy used on the Kitfox spars - might be wrong) for the inlets, & I formed a flange on those. There was variability in not only formability but also weldability between the same material even from different American suppliers, but especially sourced from China. It was junk for my purposes. One can imagine how much more critical it is when we're talking about a wing spar... and one that flexes as much as on a Kitfox makes it even more so.
Re: Esser's Model 6 Repair
You can request and receive material certs for material purchased from any reputable source. This is what Kitfox (and all other manufacturers) do.
Re: Esser's Model 6 Repair
I am aware of the certs. Thats how I determined the Chinese aluminum I was using was “in spec” but defective for any practical purpose. All is not what it seems. Especially dealing with some overseas manufacturing.
Re: Esser's Model 6 Repair
I think the key word is "reputable" source.