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Author Topic: Welkin Pseudo-Dime  (Read 534 times)
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bobson
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« on: August 18, 2018, 10:00:08 AM »

Inspired by Megow's twin dime scale P-38 and Skyrocket, I drew up plans for a pseudo-dime Welkin. It really doesn't have much wing area, but I'm hoping if I can keep it to 10 grams or so it'll fly. Structure is 4# 1/16" for the most part; the gray is white Esaki chalked on the dull side with a pan pastel and the blue is domestic Easy Built tissue. I'm planning on making counter-rotating props from laminated balsa slats. I haven't done this before, but thought plastic would be too heavy and FAC rules don't allow composite propellers.
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Welkin Pseudo-Dime
Welkin Pseudo-Dime
Welkin Pseudo-Dime
Welkin Pseudo-Dime
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Crabby
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« Reply #1 on: August 18, 2018, 10:16:17 AM »

Bobson really interesting looking plane, I have a 17 ws S'with Tripe I was trying to keep around 10 grams but it exploded the scale when I succumbed to the temptation to shrink and dope. It cost me 5 grams. I really like the lines of your Welkin and I concur on balsa props. How much rubber will the nacelles hold? What is the scale saying at this point?
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MKelly
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« Reply #2 on: August 18, 2018, 04:09:04 PM »

Very cool!  I built the Megow Skyrocket dimer, came out about 17g with motors.  It flies, but I haven't yet found a truly suitable motor-prop combination.  Props on the plan work but the pitch is so low motor run times are quite brief.

Your Welkin looks great - please update as you finish up and get it flying.

Mike
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bobson
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« Reply #3 on: August 21, 2018, 10:19:52 AM »

Thanks, Crabby and MKelly. Not sure about how much rubber I'll get before bunching becomes a real issue, but I have 3 1/4" hook-to-peg in the nacelles, which are slightly enlarged from scale. I'm carving the props at a reasonably high (compared to plastic props) P/D of about 1.3/1, and I'm hoping I can use a shorter loop of higher cross-section than would be used for plastic props and get a good lower-RPM run. It's just about ready for finishing; I'm going to give it one light coat of Krylon and then glue on the canopy. 6 grams as it is now.
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Re: Welkin Pseudo-Dime
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bobson
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« Reply #4 on: August 30, 2018, 08:02:17 PM »

The Welkin is finished and flying! I was able to go to Wawayanda for a trim day this past Friday, and it happily turned right with a small amount of rudder warp. It came out to 8.5 grams without rubber, finished with a light coat of Krylon. With an enlarged stab and DeLoach's TVo calculations, the CG came out to just aft of 50%; luckily, the plane balances here with no extra weight. I carved two counter-rotating balsa props using the fan method with 5" diameter and 6.5" pitch, and finished them with a coat of medium CA sanded and then Design Master Colortool black. Freewheelers are two 1/8" aluminum tubes with ramps carved in; they work fine with the lightly braided 1/16" motors this plane uses. Trimmed out, it was flying with 10" motors in each nacelle, wound to about 1400 turns. It's light enough to really respond to lift, and its best flight of the day was over 90 seconds.

I uploaded the plans to the gallery; they don't seem to have loaded yet, but I'll post a link when they have. Here's a video with a flight and building slideshow:

https://www.youtube.com/watch?v=oBxScudqTqY
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PB_guy
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« Reply #5 on: August 30, 2018, 08:19:18 PM »

A very rewarding flight! Congrats.
ian
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calgoddard
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« Reply #6 on: August 30, 2018, 09:38:47 PM »

bobson -

Marvelous!
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bobson
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« Reply #7 on: August 31, 2018, 07:38:47 AM »

Thanks, Cal and PB. The plans are uploaded, here's a link:   http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=10652
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