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Building Tips and technical articles. => 1/2 A building. => Topic started by: Robert Whitley on October 13, 2019, 06:17:59 PM
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Since we got weathered out for the Ringathon weekend, I decided to build a replica of my original baby Ringmaster from the 1970s.
Including making plans and templates, the build stretched out over about three days. I know - pretty slow for a 1/2 A.
I did it in my original colour scheme but cheated and used monocote instead of dope and silkspan. I did re-use the original main gear and bell crank.
Specs: 21-1/4" wingspan, 5.4 oz RTF, COX BABE BEE .049.
Looking forward to first flight and hopefully the snow stays away for awhile longer.
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Pictures
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more pictures
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pictures again
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yet again with the pictures
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Last one!
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Beautiful job!
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Thanks.
I sure had a lot of fun back then with the original and hope to repeat a bit of those good times with it.
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That looks gorgeous. Did you use a wing jig back in the day? I know I didn't as it was a lot of pins and tape with the old Ambroid glue. H^^
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As a kid in the seventies we wouldn’t have recognized a jig if it bit us.
Yep, a re-purposed door for a bench with some sort of ceiling tile board to shove pins into and usually glued with Testors since that was the most readily available brand around here.
Good carefree times.
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Very nice! Wish I could do wingtips with Monocote as well as you can!
I'll bet your original Baby Ringmaster didn't look this good! :)!
Andre
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Thanks Andre,
Actually the original did look as good overall.
It was done in silkspan and dope with the base colours and sunbursts reversed again on the lower surfaces which looked quite sharp with the colour transition all around the leading and trailing edges of the wings and stab/elevator.
I planned that again but foolishly automatically flipped my patterns as per a normal covering application and didn’t want to waste any monocote.
I still have the original two piece metal motor mount but didn’t use it because they look so cheap and ugly.
Maybe I’ll build another with the old Golden Bee and do another dope finish.
I made a full set of ply patterns so another one would probably only be a one day build.
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Indeed I did boil it.
They’re much chewier that way.😀🤪
In case of too much propellor lawn mowing I still have about a dozen of these props to go through.
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Very nice, did you boil the prop?
Seems like I've heard of doing that before, but can't recall why? ???
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It helps relax the stiffness that older plastic props develop.
I don’t think the time they boil is any constant. I just do it until they feel somewhat more flexible and if they have a slight bend it usually straightens them.
Back when we would even do it with new props since who knew how long they were sitting on the LHS’s shelves.
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Well, kind of sort of.
You might think of boiling your prop as a tempering process, except of course it's not a metal, and the analogy breaks down. What you are doing is trading strength for toughness, brittleness for flexibility. (Whereas the elastic modulus of metals is essentially independent of heat treat/temper.) And old, bad material is just that: either bad to begin with, or now too old to be "fixed" by boiling. For example, if it has micro-cracking, boiling isn't going to make that go away. I would be particularly wary of the old Cox gray performance props. Many reports of them being extremely brittle all these years later.
Here's a pretty clear explanation from a materials scientist about moisture content vs. properties for common nylon materials. I believe it is a reputable source in the industry.
https://www.plasticstoday.com/materials/materials-analyst-part-85-fixing-brittle-nylon-product-water/141225133500
I find the long term equilibrium discussion to be most interesting. What he is saying is that you can temporarily increase the toughness (flexibility) but that if you do so, be aware that it will return to a more natural equilibrium of ~1.5% by weight of water.
Dave