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Author Topic: Building Bill Gowen's CF spar LPP  (Read 522 times)
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dudpar
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« on: April 22, 2015, 07:25:14 PM »

I suppose I should have started a build thread, but I didn't. So I'm going to give some thoughts on Bill Gowen's CF spar LPP.

First and most importantly I have to thank Bill for all the help he gave me during the construction process, I asked many specific questions and he answered them all in a flash with plenty of detail. This was a great help.

I completed two models just yesterday, they will be maidened at Kent State this coming weekend Apr25 and 26- 2015. Really looking forward to seeing how they perform.

Bill's build thread and his plan really cover the process of constructing the model very well. The stacked .020 CF rod process works great, and if you are concerned about the bond between CF and balsa using Duco don't be. I found out the hard way how well they stick together. When covering one of framed up stab assemblies I laid the frame on some newspaper that had quite a lot of 77 adhesive over-spray on it---OOPS! The  frame stuck tight to the newspaper, I had to rip it off the paper tearing the ribs to pieces. Good news was all the rib ends were still stuck firmly to the spars, all I had to do was clean up the spars with acetone and they were ready to frame up again.

Not everyone will agree with me here, but I thought it was prudent to use a fairly heavy spray of the 77 adhesive on the frames since there is so little surface area on the spars for the OS film to stick to ( I hate it when film comes unstuck). Don't think it hurt us much for my weights were right in line with Bill's.

The wing tip plates and stab tip plate process works like dream, just be careful when cutting off the excess CF rod below the bottom of the plates after they are attached to the wing and stab. I had one rod that I didn't cut cleanly with the side cutters and when I removed the cutters I made a mess of the side plate because of the snagged cf rod. More rebuilding....

I've only been involved with indoor rubber for a year now and this has been my most ambitious project, the hardest lesson I learned building these two models is that you must ALWAYS make sure that a wing assembly left on the workbench has to be weighed down with a scrap  of balsa or something.
I had just completed the second wing and I noticed the shop was getting a little warm so I turn the AC on. Walked back over to the bench and felt something brush against my foot, yep it was the wing D**N!!  I wiped out both of the tip plates, fortunately the main wing frame came through unscathed. More rebuilding.

Both airframes came in around 2.245 grams, so we expect to add just a bit of ballast to make weight.

Wish us luck and hope to see you at Kent State

Dudley




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Building Bill Gowen's CF spar LPP
Building Bill Gowen's CF spar LPP
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Olbill
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« Reply #1 on: April 22, 2015, 11:07:21 PM »

Those models look really great!

Being a klutz, I wiped out one of my new wings at West Baden. I can't remember how the problem started but the first part of the damage was a broken tip rib. Then while trying to put a speck of CA on the break I touched my applicator to the film on the tip plate. The CA ran down onto the wing covering and the capillary action pulled the covering off one of the spars. then when I tried to get the CA applicator off of the tip plate the covering on the tip plate ripped. At that point I took out my other model and finished the contest flying it.

Tonight I cut the tip plate off, removed the covering from the last rib bay of the wing, removed the broken tip rib and glued in a new rib. Then I borrowed an idea from Maxout's covering method. I coated the end bay spars and ribs with 3M77. I used a small covering frame that has an arc shaped cutout in one end, put the film on the frame with liquid soap and pressed the film down on the wing. This worked great and gave me a pretty neat patch on the last rib bay. Then I took the uncovered tip plate and glued the bottom ends to the wing. When this was done I coated the outside edges of the tip plate parts with 3M77 and pressed it down onto some film that was left on the covering frame. The end result was a wing that looks good from a couple of feet away and that didn't gain much weight.
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