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General control line discussion => Open Forum => Topic started by: Stew Robinson on January 29, 2016, 02:43:40 PM
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I'm just getting back into CL flying after a 40 year leave of absence and dragging my son in law along with me. I bought him Skyray 35 and an NIB 20FP for Christmas. I keep reading that the plane will be better with the plywood ribs replaced with balsa, but I'm afraid that having to fabricate them will scare him away. Hopefully, someone sells balsa replacements, but I can't seem to find them. Any help will surely be appreciated. Thanks , Stew
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Get some 3/32" balsa sheet and cut him up a mess of ribs.
Or, just go with the Lite-ply ribs. Yes, Balsa Flies Better, but the plane will be OK with Lite-Ply.
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Stew you might check with Eric Rule at RSM Distribution.
Mike
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It will fly better with lighter balsa ribs however more importantly in this case is giving him the experience of building the plane w/minimum hassles. Even with the stock lite-ply ribs it will be the best flying plane he has ever flown and fully capable of teaching him the basics, including basic maneuvers. I would even keep the single wheel LG. That way if (when) he smacks it in it won't put a hole in the wing but just collapse against the fuselage.
Before assembling, cut out a set of ribs using the plywood ribs as templates, very easy to do. Then trace all the other pieces. Cut them out in your spare time, add stringer and sheet. After he wears this one out present him with a new and improved Skyray Mk II kit complete with light, balsa ribs and this time, two wheeled gear. Hopefully this will be just the first of many C/L projects. Just my take. 8)
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I'm just getting back into CL flying after a 40 year leave of absence and dragging my son in law along with me. I bought him Skyray 35 and an NIB 20FP for Christmas. I keep reading that the plane will be better with the plywood ribs replaced with balsa, but I'm afraid that having to fabricate them will scare him away. Hopefully, someone sells balsa replacements, but I can't seem to find them. Any help will surely be appreciated. Thanks , Stew
Make him a template (or series of templates) to cut them out with. I usually use two templates - one to cut the spar slots, and a second to cut the shape. Cut the slots first, then the shape, to avoid splitting the wood. They should be keyed with pins to line them up and keep them from slipping. It takes about 15 minutes to do a set for a Skyray once you set it up. You might need a 3rd template to cut the center-section ribs. I use a balsa stripper to cut down from regular to center section ribs - it takes some skill to keep it tangent to the surface but any mistakes are in the direction of cutting them too large, which can be sanded down. Leave the centers in the ribs, and use the pin holes to line up a stack for stack-sanding. Only then, cut our the leadout holes using sharpened brass tubing and an exacto knife. You can use a single template as long as you are careful cutting the spar slots - use a single-edged razor blade and a "chopping" action rather than a conventional cut to reduce the tendency to split.
The best reason to make if from balsa is not the flying (which, with the engines you are talking about, won't make much difference) but the durability. My plywood version converted itself to a pile of parts on the first crash, because it was so heavy that the wingtips just kept going when it hit, breaking every single part in the wing. The balsa version survived many crashes nose-in into dirt/grass, and only finally had to be rebuilt again after the Monokote got brittle to the point it cracked when I was wadding it up.
Laser-cut makes a lot of sense for a tapered wing but with all the ribs the same, it's much faster and quicker to do it with a template. Once you are done with the ribs, that's the only significant work to be done, cut the fuse and the doublers with a scroll saw.
Brett
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Check with Walter Umland, he can be found in the Vendor section here on the forum.
builtrightflyright.com
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Just hand-cut some balsa ribs for the inboard and use the plywood outboard. You need tip weight anyway. The ply ribs are good templates for stack-sanding. You can do the job in 20 minutes.
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Just hand-cut some balsa ribs for the inboard and use the plywood outboard. You need tip weight anyway. The ply ribs are good templates for stack-sanding. You can do the job in 20 minutes.
That will end up with you needing *a bunch* of tipweight on the inboard side, and will render the outboard wing to confetti on the first crash. The weight difference from plywood stock wing to the balsa replacement was about 6 ounces. Both before and after, mine needed something like 1/2 ounce of added weight in the tip, because the engine and tank are almost enough by themselves. Having an additional 3 ounces on the outboard and you would need to add something like an ounce and half to 2 ounces on the inboard tip.
Interestingly, reducing the weight by ~6 ounces hardly made any difference in the performance when using the 20FP. The cornering was and is still limited by the length of the tail more than lift, and the engine is certainly able to get adequate vertical performance in either case. I could baby it through a full pattern at 36 ounces with an L&J Fox but to be frank, I suspect most people would have had difficulty. I *did* crash one using an Enya 29 baffle-piston engine which is even wimpier; just ran out of corner (and skill) - in a round 8!
Brett
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The cornering was and is still limited by the length of the tail more than lift,
That's an interesting thought on the Skyray. To better it, would you suggest lengthening or shortening the tail?
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Great basic tips here, not often posted...'Basic' points re 'cutting', or 'mfg.' ribs and parts.
Most of us went through this way back, but these ploys are seldom brought up...
Kudos to Brett and others for explaining grass roots stuff taken for granted.
(often avoided questions due to, "Will I look foolish in asking?")
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That's an interesting thought on the Skyray. To better it, would you suggest lengthening or shortening the tail?
Sorry to pull this discussion away from wing ribs.
The Skyray is an excellent plane for Beginner to Intermediate pilots. Not being able to turn too sharply in the corners is, IMHO, part of that excellence.
From Beginner up to the bottom half of Intermediate the pilot with a Skyray will be limited almost entirely by their own ability. Moving to something flapped might get them a few more points, but not as much as the normal point spread between 3rd and 4th in a contest. If you're still crashing all the time it's simply not worth flying something more complex.
Once a pilot gets to the point where they aren't crashing all the time, then they should move to some nice basic profile or a Hobo -- I'd recommend a Twister, Banshee or Hobo for people who are still worried about crashing (the wing structure on those planes is similar, and nicely crash resistant). If the pilot is beyond crashing or wants the warp resistance of something like an Oriental wing, then they should go for it, recognizing that the plane will be harder to fix after a crash.
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I've never done this, but taking a Skyray kit wing rib and hardening it with CA on the edges, then sanding it smooth, should make a pretty good rib template. It won't be as durable as using aluminum or steel sheet, but it'll be a heck of a lot easier to fabricate.
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Stew
I know what you mean....Laser cut are so much better than we all remember with the die cut..IF the cut outs and dimensions are accurate
I have done it both ways ...as suggested...and although I am good at using a template and cutting out two or three rib sets at a time...I find I prefer the laser cut ones as just slightly more accurate
There are several vendors here that will use your template, or already have it, and LASER cut sets of ribs reasonably inexpensively
With templates the outline profile is easy as are the spar slots...... but I really like the EXACT location of lead out and lightening holes the LASER can produce....MY sharpened brass tube method works but is tedious and not as clean looking as the laser guy can do
I also agree that some of these kits with PLY ribs are better redone with good balsa
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Thanks a lot guys, especially Brett for the hints on making my own. I just completed my S2 Mustang from the late 80s, but I built up the wing 30 years ago and don't remember a whole lot about it. I'll make templates from sheet brass, (because I have it).
Mark will be building his Skyray across the table from me as I stumble through my Twister. I'd rather crash the Twister than the old Sterling that my brother gave me so long ago. We've been flying 1/2A Skyrays this Summer.
If Mark can figure how to post photos, I'll share some as we build the pair......Stewie
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A little more on using the kit plywood rib. As stated harden it with CA. Clamp the balsa that is rough cut between the two ply ribs and start sanding. You can even do it with the center ribs. Before you know it you could have enough ribs for several planes. By the way leave the lead out pieces in the ribs you are going to use. Use bolts long enough to do half dozen ribs. Don't worry about the spar notches yet.
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Stew: Can't go wrong with Brett's advice !! and the fun you and your son-in-law will have doing it together will be fantastic !!