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How to build model airplanes >> Free Flight Indoor >> Speed Merchant - RTP Rubber Speed Model
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Message started by Kittyfritters on Jan 13th, 2019 at 3:59pm

Title: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Jan 13th, 2019 at 3:59pm
OK, so this is not quite free since it flies around a pole but it still fits here.

Here is the preliminary drawing for The Speed Merchant, my Round-The-Pole rubber powered speed model, for the contest at Duarte on February 16th.  Before I cut wood I'm considering moving the wing to the bottom of the fuselage.  the tether wire will go from the right side of the fuselage, embedded in bottom of the wing about half way between the leading edge and the spar, to the left wing tip where it will have a loop.  Will test both two and four blade prop.  If other obligations permit I will have both the built up fuselage and rolled tube versions ready for test flying at Duarte on January 19.
Speed_Merchant_Plan_P.png (84 KB | 13 )

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by bigrip74 on Jan 14th, 2019 at 8:33am
kf, what is the wing span?

Bob

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by strat-o on Jan 14th, 2019 at 9:26am
Interesting.  What are the rules?  Could you make the rolled-tube version push-pull?

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by pb_guy on Jan 14th, 2019 at 10:14am
Speed models have a long history it seems. The Comet Racer by Don Orman had a 9" wingspan and appeared in the August 1938 issue of Air Trails. Speed models might raise the interest of some of the younger generation.

Quote:
Models of this design have been clocked at 91.4 miles per hour over a 120-foot course. A second model with slight modifications turned in a speed of 96 mph. It averaged 80 mph for seven flights over the course

Model on Outerzone: https://outerzone.co.uk/plan_details.asp?ID=9859
ian
comet_racer.jpg (44 KB | 24 )
comet_racer2.jpg (61 KB | 33 )

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by bigrip74 on Jan 14th, 2019 at 2:18pm
Ian, I have that plan, but never found anyone to be a mentor to build one and as strat-o stated what are the rules.

Bob

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Sky9pilot on Jan 14th, 2019 at 4:24pm
Interesting model...and category.  I think it kinda reflects the FAC B.L.U.R. (Bee Line Unlimited Race ) You can see the rules on page 17 of the FAC Rules Book  Click Here

Looks like a lot of fun...please keep us informed!!! [smiley=thumbsup.gif]

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Jan 14th, 2019 at 6:58pm

Sky9pilot wrote on Jan 14th, 2019 at 4:24pm:
Interesting model...and category.  I think it kinda reflects the FAC B.L.U.R. (Bee Line Unlimited Race ) You can see the rules on page 17 of the FAC Rules Book  Click Here

Looks like a lot of fun...please keep us informed!!! [smiley=thumbsup.gif]


The B.L.U.R. race is for scale models.  (And when I have seen it was fun to watch.)  The RTP race is for pure speed models.  The Covered Motor  class simply has to have a canopy, that's for "plausible scale".  The Unlimited Class can be a motor stick model.  Push/Pull designs have been suggested but they must R.O.G.

The Speed Merchant is a similar model to the Comet Racer, and other speed models of the 1930s, with a 9 inch wing span and is 22 inches long.  The difference is that is intended to be tethered at the wing tip to fly in a circle.  This is something the Black Sheep Squadron did many years ago and it was decided that it would be interesting to revive the contest.  I might also be fun to fly these things outdoors on a B.L.U.R. course.

Here are the rules:

RUBBER POWERED RTP SPEED EVENT RULES
(Preliminary)

Pole

    The pole will be three feet tall with a headed nail in the top.
    The line will be fine sewing thread with a paper clip at each end as a swivel and a hook. The swivel to hook length, including the paper clips is 10 feet. This gives a circle of 62.83 feet.  (1 second lap equals 42.84 mph.)
    A 1/8 inch high, foam, curb is placed across the path of the flying circle at one side as a timing point.
    Three people with stop watches will do the timing unless there is an electronic timing system


Models

    Classes

    Covered motor
        “Plausible scale” (i.e. must have a cockpit)
        Motor completely enclosed by fuselage
        Flying surfaces built up and tissue covered
        Landing gear has rolling wheel(s)
        Detachable dollies allowed
        (If you think you can make that work!)
        Hook attaches at wing tip

    Unlimited
        Motor sticks allowed
        All balsa flying surfaces allowed
        Landing gear has rolling wheel(s)
        Detachable dollies allowed
        (If you think you can make that work!)
        Hook attaches at wing tip

Competition

    For a qualifying flight the model must ROG, from the floor, from any point past the curb and must be airborne and clear the curb at the end of the first lap.
    The timing starts when the model crosses the curb at the end of the first lap. The model is timed for the second and third lap and the speed is calculated.
    Winner in each class is the fastest speed.


These rules are preliminary and will be revised after flight testing and experimentation.

KF



Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by bigrip74 on Jan 14th, 2019 at 8:48pm
kf, interesting rules. I assume some photos will be posted of the attempts to help us?

Bob

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Jan 14th, 2019 at 10:17pm

bigrip74 wrote on Jan 14th, 2019 at 8:48pm:
kf, interesting rules. I assume some photos will be posted of the attempts to help us?

Bob


With videos if I can get good ones.

KF

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by bigrip74 on Jan 14th, 2019 at 10:36pm
No rush KF, I was wanting to see this in action.

Bob

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Jan 24th, 2019 at 3:24pm
Here's a video of my test hack at OFFC Wednesday morning. Couldn't get it over 13.5mph at Duarte last Saturday, Changed to a smaller prop and cut the wings back down, in stages, to the original span and got a 24.43 mph flight out of it, probably the limit for that airframe, The vid was taken at the end of the session when the rubber was getting tired. It's only doing 16.34 mph in the video, Has too much incidence, jumps off the ground too soon and flies too high, but I think it give me the parameters for my real racer. Oddly enough, I think a scale D-12 Bonzo would do quite well.
https://www.youtube.com/watch?v=1MoqCCBgFmc

More Later!

KF

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Sky9pilot on Jan 25th, 2019 at 6:46pm
Very interesting Howard...I look forward to your next model.  Thanks for sharing the video!
Tom

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Feb 17th, 2019 at 3:16pm
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.

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.  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. 
SpeedM1.JPG (83 KB | 25 )
SpeedM2.JPG (65 KB | 23 )
SpeedM3.JPG (104 KB | 22 )

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Feb 17th, 2019 at 3:17pm
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. 

I put on my mask, turned on the tool, grabbed my  sanding block and 90 seconds later had a tail cone.
SpeedM5.JPG (73 KB | 25 )
SpeedM4.JPG (99 KB | 24 )
SpeedM7.JPG (57 KB | 22 )

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Feb 17th, 2019 at 3:19pm
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 KB | 26 )
SpeedM9.JPG (82 KB | 26 )
SpeedM10.JPG (79 KB | 23 )

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by Kittyfritters on Feb 17th, 2019 at 4:19pm
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. 

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.

Ready for the contest!

KF
SpeedM11.JPG (136 KB | 22 )
Speedm13.JPG (93 KB | 19 )

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by shipwreck on Feb 27th, 2019 at 7:28pm
That looks cool 8-)
Paul

Title: Re: Speed Merchant - RTP Rubber Speed Model
Post by bigrip74 on Feb 28th, 2019 at 1:55am
KF, I LOVE the looks of that RTP.

Bob

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