Rubber Speed Event

The lighter side of things

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Re: Rubber Speed Event

Postby kittyfritters » Sat Feb 16, 2019 3:51 am

Finally, I got to work on my model, the Speed Merchant.

I decided to go with the rolled tube version since Bill Watson gifted me with a rolled tube he made for his model that apparently did not meet his specs. I found it to be a very nice tube. He made it the way I do by rolling the wet balsa and a layer of wet silkspan around a mandrel. He lets his dry overnight. The silkspan drys first and wicks the moisture out of the balsa. I'm not that patient so I bake them in the oven. Since my wife is not retired and I am a house husband I can get away with it.

SpeedM1.JPG (83.47 KiB) Viewed 1396 times

Now to make the nose cone and tail cone. As it turned out I had the nose cone already made, I found it in my junk box. It was the nose cone from my "Unintended" P30 that was destroyed in the opossum invasion last year. It was for the same diameter rolled tube fuselage.

SpeedM2.JPG (65.08 KiB) Viewed 1396 times

All I had to do was replace the prop with the aggressive Ikara prop that I have been testing and install a new prop shaft.

SpeedM3.JPG (104.31 KiB) Viewed 1396 times
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Re: Rubber Speed Event

Postby kittyfritters » Sat Feb 16, 2019 3:54 am

The tail cone I had to make. I cut a 1/64" plywood base disk using a compass then rough cut out six 1/8" thick disks also with the compass. Using the compass left a hole in the center of each disk so I could put a pin through it to line them up for gluing with CA. When the CA had set, about a minute later, I put the stack on a Dremel tool mandrel and chucked it into the tool.

SpeedM5.JPG (73.72 KiB) Viewed 1396 times

I put on my mask, turned on the tool, grabbed my sanding block and 90 seconds later had a tail cone.

SpeedM4.JPG (99.04 KiB) Viewed 1396 times

SpeedM7.JPG (57.87 KiB) Viewed 1396 times
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Re: Rubber Speed Event

Postby kittyfritters » Sat Feb 16, 2019 3:58 am

Now, all I had to do was key the tail cone, run a prop shaft through it as a rear hook, and I had a fuselage.

SpeedM8.JPG (81.71 KiB) Viewed 1396 times

SpeedM9.JPG (82.5 KiB) Viewed 1396 times

SpeedM10.JPG (79.02 KiB) Viewed 1396 times

Next wing, tail feathers, cockpit, landing gear and it's finished. The wing is two inches longer than the test hack so it should fly on six strands on 1/8" flat, tan Super Sport rubber.

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Re: Rubber Speed Event

Postby kittyfritters » Sun Feb 17, 2019 10:37 pm

After the flying my test hack (henceforth known as "The Hack") I decided that the wing needed two inches more span to handle the torque on takeoff. I simply enlarged the drawing spanwise. The original drawing had too many ribs so I decided to make the wing and the tail surfaces out of 3/32" stock and simply sand to a symmetrical airfoil. I flexed the structure and added gussets where needed. The covering was red Esaki tissue applied with glue stick. It was shrunk with rubbing alcohol but not fixed.

SpeedM11.JPG (136.87 KiB) Viewed 1375 times

The tail section was simply glued to the tube. To attach the wing I glued two lengths of 1/8" square stock to the bottom of the wing a quarter inch to either side of the center line. I wrapped a piece of fine sandpaper around the tube, set the wing on it and moved it back and forth until the wing sat flush on the tube. The 1/8" square stock was now contoured as a wing saddle.

The tether wire was wrapped around a dowel the same diameter as the tube and then slipped over the tube. The landing gear wire was bent like it was made for an ROG model with a 1/8" stick, then the top section was bent back about 85 degrees and bound to the bottom of the tube with thread and CA. The rules said it had to have a canopy so I glued an old Enterprise bubble canopy on top of the tube.

Now I put rubber in the fuselage, wound the motor and let it unwind, and found the CG. I slid the tether wire to the CG and tacked it in place with CA, then positioned the wing and glued it in place.

Speedm13.JPG (93.78 KiB) Viewed 1375 times

Ready for the contest!

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Re: Rubber Speed Event

Postby kittyfritters » Mon Feb 18, 2019 12:30 am

The contest was, if nothing else, a lot of fun! The attendance was a bit disappointing, but I'm sure that it will be better the next time we try it after the club members get the report on it at the next meeting.

20190216_210636.jpg (133.24 KiB) Viewed 1371 times

Since most of the Black Sheep members are in the San Fernando, Simi and Conejo valleys, it is a 45 minute to an hour (or more) drive to Duarte in Saturday night traffic. I realized that some of the more enthusiastic members, who are also in O.F.F.C. can no longer drive at night. They can't come to the Duarte sessions if they can't get a ride. We may have to work out a shuttle to get them there for contests. There were spectators since we share the site with the Santa Fe Dam RC fliers. We had the timing pylon set up in the northeast corner of the gym and the "low tech" pylon set up in the northwest corner for practice and trimming. This left space for some free flight and RC activity to take place in the rest of the space.

RTP1.JPG (135.37 KiB) Viewed 1371 times

RTP2.JPG (132.48 KiB) Viewed 1371 times

The flying was, if nothing else interesting. And, if the number of contestants was disappointing the number of models was not. No one showed up with less than two models. The faster models had two lap timings right around 3 seconds. Jim Leuken was to only one to get a sub 3 second time by the "brute force method". I don't know how many strands of 3/32", flat, tan he had on that flight but he used a Starlink Flight Tech motor strander, the same one he used for his Wakefield motors, to assemble it. And, that motor only worked for one flight. All of us were making motors all night. After a few flights we were using short, well lubricated, 4, 6, and 8 strand motors with about 600 to 750 turns. A motor would give about 3 competitive flights before going dead. I had a few feet of carefully stored Pirelli rubber left and I used it because it has a lot more torque than the F.A.I. tan at the start of the run. The problem with that was a bad launch was made even worse with all that torque. We also discovered that the rolled tube fuselage models were too small in diameter. They need to be at least 1-1/2 inches in diameter to hold more than a four strand motor. That doesn't mean they are not fast, a single loop of 1/4" Pirelli got my model into the 3 second (1-1/2 second laps) range with no trouble.

Those lap speeds caused another interesting problem. When you launch the model from the floor with the ten foot tether and the three foot pylon it's about 100 inches from the center of the circle. When it comes around again it's flying level with the pylon and it's 120 inches from the center of the circle. That means if you kneel down to launch the model and, stop to watch that it is flying stably when it crosses the timing line, 3/4 of a second later it's coming at your head at over 30 mph! (I don't care that the model only weighs 20 grams, it would still hurt!) I did that and ended on my ass avoiding getting hit, much to the amusement of everyone else. (Fortunately, no one got a video of that one.) The correct technique is to bend over to launch the model and take a step back.

Another thing about the launching is something that Jim Leuken, with experience flying control line speed models, picked up on. The model should be level when launched. That's why his models had under rudders to give them a level stance on the ground. He were the only launches that were consistently without drama. Some of the others occasionally ended in a wingover if the line did not stay taught. There were some flights that ripped up the course interspersed with some spectacular crashes and an occasional failure to fly resulting in an extremely fast taxi. All during the contest we were helping each other giving advise gleaned from our last flight. There were also some real surprises. Bill Watson's push-pull full fuselage model was not performing well, but he had also brought a box of Embryos in case he got the chance to do some free flying. (He did impress the RC fliers with his indoor towline glider!) He had built one of my Wright Amount of Wrong Embryos and saw that it had a long, skinny fuselage so he assembled it with just the bottom wing, rebalanced it with a more powerful motor, put a pin in the wing tip to anchor the tether, and finished third in the full fuselage class!

RTP7.JPG (118.79 KiB) Viewed 1371 times

The results were:

1. Jim Leuken
2. Bill Watson
3. Howard Littman

Covered Motor
1. Howard Littman
2. Dave Gee
3. Bill Watson
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John Webster
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Joined: Thu Aug 18, 2016 7:18 am

Re: Rubber Speed Event

Postby John Webster » Thu Feb 21, 2019 2:40 am

That looks like it could get hilarious.
You begin flying with a full bag of luck and an empty bag for experience. The object is to fill the bag of experience before you empty the bag of luck.

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