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I'm on track! Getting prepared for contest season in 3 weeks

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I'm on track! Getting prepared for contest season in 3 weeks

Post  RknRusty on Thu Apr 07, 2016 11:37 pm

Well it's that time of year again, when I get preoccupied with preparing for contest season, so everything else, including Mister Twister is barely simmering. I really hate to back burner it when I was on such a roll. But the good thing is, I'm on pace to be completely prepared a couple of weeks before Huntersville, and can possibly turn the heat back up on the Twister. And if the wind doesn't settle down I'm not likely to have the chance to wreck my stunters Lol. But I really do hope I do have a chance to practice because I've made some changes to both planes.

I was afraid I was only going to have the Cardinal, which is a bit rickety but dependable and I fly it well. Its only problem is it needed a bigger fuel tank. If I run it fairly lean, it'll do the whole pattern on 4.5 ounces, but flies too fast, and it's already on 62' lines. And the engine runs happier a little slower too. So I bought a Sullivan 6 oz. clunk, but couldn't assemble it until my hand healed from its February surgery. I got on that job this week and finished installing it today.
These things look easier than they are to get a perfect fit and clunk action, but I did a good job. I cut the outgoing lines to length and sealed it up and strapped it on this morning.


I've never had any luck making a uniflow follower, so I did what worked well on the Osprey, making the two vents Siamesed. The tank is mounted with the wide side against the fuselage and the vents are installed in the same configuration as shown laid out in the bottom picture, ignoring the bump meant for the vent tube(in its intended orientation), and rather turned up towards the the top narrow side. On the Osprey, the engine run was just like Uniflow, with no change in mixture from start to finish, and no lean pre-cutoff warning. I'm expecting this one to behave the same. But I need to fly it, get a tach reading on my preferred launch speed, and figure how much fuel it needs to give me 8-10 laps after the Clover. Please, just one good flying day is all I need. Two would be better so I can practice my pattern with all that testing and tuning behind me.

The Cardinal had one other problem I've neglected too. The 12x4 prop has no ground clearance. With the buzz-cut grass at the Fort, I can do a fair takeoff roll-out without striking the ground, but do lift it a little early... which is a points deduction in a contest. But with the taller grass at Bob's on Sunday, I mowed a strip of grass on every takeoff. That won't do. Huntersville's grass circle is taller and bumpier, so this problem had to be addressed in case we fly Intermediate Stunt Sunday on the grass. profile Saturday is usually on pavement, which I dislike, but my takeoffs usually score much higher. The existing wheels are 2-1/4" tall. I went shopping today for some 2-3/4" wheels, and came home with 2-1/2" inchers. That gives me a hairy 1/8" extra clearance. It'll have to do, unless someone at H'ville is selling 2-3/4" wheels.
I also bought some black and clear checkered Monokote Trim for the Twister's white wings.

That brings us to plane #2. As I recalled earlier this week, in my weekend flight report, the Oriental had been frustrating me since October after its extensive repairs, and the engine decided to run wild and lean. I feared it was vibration from my RC engine mount, even though I took serious precautions to make it rock solid with 1/8" ply added to the firewall and reinforced with medium fiberglass, and every batch of epoxy set up just perfectly. Ken built a nice tank for it, which simplified my plumbing, and my wing root repair seemed adequate. Bob looked it over pretty thoroughly and was convinced it was solid and not the result of vibration. He took my spare head to modify, while I rebuilt it with a new crankcase given to me by Dane Martin of the Las Vegas CL gang. Bob opened up the combustion chamber considerably to tame the engine, and here's his comment on Stunthangar:
Robert Zambelli wrote:I've been experimenting with FP combustion chamber configurations for quite a while and I feel that I've optimized the design.
I found it interesting how small changes in shape made noticeable differences in performance. What really surprised me was how angling the squish band upward improved the four-two-four break.
I've done this mod on quite a few Schnuerle ported engines, all with favorable results.
Like magic, this thing runs an old style 4-2 break like Swiss timing, just as well as my Max-s .35 does. Ron Cribbs got to enjoy a couple of flights on it back in the Winter. It's really sweet, but it too, needs to be re-tached and fuel metered. So again, lets wish for a couple of good flying days before April 29th.

But that ain't all. The outboard wing started flapping in flight. Thank goodness Bob noticed it, and we took it into his shop to have a look and perform some surgery. It involved cutting a section out of the top of the fuse. If I'd followed Ken Cooks advice and cut the fuselage open a long time ago, I would have found the top spar shattered, having broken in half at the point where the manufacturer had deeply notched the spar to make room for the bellcrank top nut. But not being confident with full fuse architecture, I tried a fiberglass "bandaid" patch outside at the wing root. Bob cleaned it up and used some CF string to twist up, soak with CA and make two custom shaped rods to span the broken spar. Now it's stronger than it was when new. He also reinforced the crutch(bottom right in the pic) to the inside of the fuselage with some 1/2 oz. fiberglass.

All I had to do is glue the top section back in place. I did that Monday, and she's hanging up in my hangar ready to fly. So it looks as if I had two strong planes now and only need to test, tach and tune, and get re-acquainted with flying it.

There's more. My disposable Dubro NiCd glow igniter died and I've ordered a new one with a replaceable battery. I will immediately toss out the supplied 1300Mah NiCd and replace it with a 4000 Mah NiMH battery which is far far superior to the junk battery that comes with it. For more on that, read the article I wrote in my March MCLS club newsletter Follow this link and look for the article on Page 3.
https://www.dropbox.com/s/3nkdgdl4ot27n7z/Pitts%20Special%202016-3-March.pdf?dl=0

Time for bed now, so I'll catch y'all tomorrow. And tell me if the link to the newsletter gives you any problems. I'm just now learning about Drop Box file sharing.
Rusty

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Re: I'm on track! Getting prepared for contest season in 3 weeks

Post  pkrankow on Fri Apr 08, 2016 1:01 am

Put bigger wheels on it. 1 inch of larger tundra tires will give 1/2 inch ground clearance and a better takeoff roll on the rough grass.

Phil
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Re: I'm on track! Getting prepared for contest season in 3 weeks

Post  getback on Fri Apr 08, 2016 8:00 am

OK that's a interesting repair what the heck is CF STRING ? Good thing that happened before the contest and was able to get the repair without too much difficulty , hope you can get some fly time in soon if adjustments are needed that take time / Rusty I got a set of DU-BRO 2.75 T Tires if your interested let me know . Eric Very Happy
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Re: I'm on track! Getting prepared for contest season in 3 weeks

Post  fit90 on Fri Apr 08, 2016 8:11 am

Wow, it looks like competitive control line is a lot of work. But, it looks like you have it down to the fine details. Glad you caught and repaired that spar before it got too much worse. Hope you get some good practice time in soon.
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Re: I'm on track! Getting prepared for contest season in 3 weeks

Post  pkrankow on Fri Apr 08, 2016 11:01 am

I would guess Carbon Fiber Tow. There are a number of sellers on ebay who have it at $1/10ft (plus shipping) which seems a good price for small quantities. Typically it is bound with styrene which is dissolved by epoxy or polyester resin, or most solvent glues, allowing the fiber to wet and bond.

I have only played with it a little and I like it.

Phil
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Re: I'm on track! Getting prepared for contest season in 3 weeks

Post  RknRusty on Fri Apr 08, 2016 11:16 am

fit90 wrote:Wow, it looks like competitive control line is a lot of work. But, it looks like you have it down to the fine details.  Glad you caught and repaired that spar before it got too much worse....
It is a lot of work for me. Some people make it look easy, and I'm getting the hang of it, prep-wise anyway. Mainly you just need to know what flight speed you want and what launch RPM gives the engine a happy stunt run. Combine prop type and line length to get there. Then know how much fuel will complete the pattern and not go over-time. That changes with location, just for added madness. Or go electric... nah.

Eric, I just remembered the Magnum might have big wheels. I'll check. Thanks, but I'm probably okay. I appreciate the offer though.
Rusty

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