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Old Aug 24, 2014, 07:23 AM
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To all the viewers on this thread:

Here are two link headings to "how to" stuff on my Skybench web I wrote concerning adding carbon to spar construction and wing construction from start to finish. They are located on the web's front page, hope this helps..

Wing Construction Tips

Add Carbon to Spars ???

I asked the designer of one of my kits, "Challenger", why he never bowed the wings during launch regardless of wind velocity . His reply, " I took it easy on the winch" . In other words, he managed the line tension based on wind velocity. He always had the highest launch in contests. His Challenger had 1/8 x 1/4 spruce spars, span is 144 inches. In the beginning of sailplane contests we used 6 volt winches with 120 LB test line, contests now use 300 lb test line , 12 v winches that have been souped-up to accommodate the $2500.00 + moldies.

With today's interest in putting the winch in the nose, we have to re-think wing strength in WOODYS for normal soaring activities. The builder has to decide what world he will fly his plane in and build the wing accordingly. I broke the two 5/16" carbon wing rods in my Challenger on a souped up contest winch this summer, I usually had a steel front rod and rear carbon rod. With all the testing I did prior to the contest, the two carbon rods seemed to work. My conclusion is, I have changed the wing rods in my personal E-Powered planes to carbon. But ... you have to continually check the carbon rods for scratches caused by the ends of the wing tubes. Carbon rods break, steel rods bend.

Ray
Woodys Forever
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Old Aug 24, 2014, 08:20 AM
ahh crap! crunch..
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Australia, QLD, Fraser Island
Joined Nov 2007
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^Still use the old sidchrome screwdriver shaft for my OIII Ray, never bent come hell or high water. Wings still good, still taking more than they really should. 144" and the rod is a bit shorter than it could be by about 20mm. I am still in awe of what my old Oly can do and go through, it's 7 years old now and still cranking after 400? launches. Survived plenty of sloping too. Cheers mate!

edit; Yes carbon caps on spars for sake of asks. just be sensible, it'll never be a world beater for pure F3J, but a hell of a woody even with foil adaptions.
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Old Aug 24, 2014, 08:28 AM
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United States, OK, Perry
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Thanks Ray, I tried the one about laminating 1/16 ply to 1/16 carbon and they all bowed severely. I used plenty of weight and they were weighed down for about a week. When I took the weight off.....they all bowed up....about 3" in the center of a 40" span. So even though the bows would be opposing each other, I was concerned they might manifest the tension in a longitudinal warp. So, I went back with your original spars.
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Old Aug 24, 2014, 08:45 AM
ahh crap! crunch..
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Australia, QLD, Fraser Island
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That pre-tension could have been a benefit, as described by very academic people here already in the boards. Consider the counter-acting force of the vertical grained sheer webs easily holding that force in? with D or full sheeting the warp factors are minimised and contained for use within the structure forces, in launching and flying, for flex.

Don't mean the whole thing can't go Pop though. all things being equal.

Good luck, and please take advice from folks like IHAVA and such.

Steve.
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Old Aug 24, 2014, 09:38 AM
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Thanks Steve,
I agree with you, but after doing this for 40+ years, I've learned to not take Murphy for granted. This is too nice a kit to run the risk of screwing up the wings on something that I'm really not going to benefit from. I'm keeping those spars around in case I want to build a second set of wings.
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Old Aug 24, 2014, 08:15 PM
fa2
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"I broke the two 5/16" carbon wing rods in my Challenger on a souped up contest winch this summer, I usually had a steel front rod and rear carbon rod."

oh no!!

I think i'll use the steel ones that you send with my kit - in texas, the wind is usually blowing so they can be considered ballast - right

sorry to hear about your challenger accident ray
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Old Aug 26, 2014, 11:17 PM
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Wednesday afternoon I will be ready to join the left inboard and outboard panels...YEAH!
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Old Aug 27, 2014, 01:37 AM
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I always install the wing rod tubes before adding the tips due to the size of my building area , but it also seems easier working with just the inner panels rather than the whole wing.

Ray
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Old Aug 27, 2014, 01:47 AM
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Quote:
Originally Posted by fa2 View Post
"I broke the two 5/16" carbon wing rods in my Challenger on a souped up contest winch this summer, I usually had a steel front rod and rear carbon rod."

oh no!!

I think i'll use the steel ones that you send with my kit - in texas, the wind is usually blowing so they can be considered ballast - right

sorry to hear about your challenger accident ray
I'm in luck, I have Otto's unfinished fuse he was working on and only one wing needs repair. Sorry about the delay in shipping the two Challenger kits. I'll go back to using the steel rods.

Ray
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Old Aug 27, 2014, 07:11 AM
fa2
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otto used steel - maybe the old master knew best, huh
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Old Aug 27, 2014, 07:13 AM
fa2
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the repairs on a sailplane are "badges of courage" - right!!

Carpe diem is a Latin aphorism usually translated "seize the day", taken from a poem in the Odes (book 1, number 11) in 23 BC by the poet Horace.

right ray!!

in my life, all the success I have had has been a result of pushing the envelope

your challenger was brave, huh
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Old Aug 27, 2014, 07:15 AM
fa2
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your challenger trusted you, but it will also forgive you
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Old Aug 27, 2014, 09:47 AM
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I agree Ray......I installed the wing rod tube before I even capped the trailing edge or glued the lower LE sheeting to the ribs. It is a lot easier to handle the shorter panel.
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Old Aug 27, 2014, 11:09 PM
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Inboard and outboard left wing joined together!! yeah!
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