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Thorpe F-20 build

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Old 12-30-2011, 10:02 AM
  #126
tlj125
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Default RE: Thorpe F-20 build

Per the Wren website, the Wren 44 burns 5.8 oz of fuel per minute at full throttle. My current plan is to install two 11 oz ducted fan tanks along with the 17 oz Kavan center tank for a total of 39 oz. Flying at or near full throttle would result in a 6.7 minute flight time. With some throttle management I should be able to get 7-8 minute flights.

My concern with the 44 is performance at take off and going vertical. I remember Bob's F-100 and it flew with authority. What a neat model it was. I am currently flying a Tam F-16 with a Wren 75 and I would prefer better take off and vertical performance than that combo.
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Old 12-30-2011, 10:29 AM
  #127
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Default RE: Thorpe F-20 build

Ron- I fly from a paved runway. The video below was taken at our club field.

http://www.youtube.com/watch?v=KOfn8LKozbc
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Old 12-30-2011, 10:48 AM
  #128
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Default RE: Thorpe F-20 build

Hi Terry, Good video. Personally I would be more than satisfied with a performance similar to your F16. I assume you have fitted a good thrust tube to maximise the available power. I imagine acceleration will be a little slower than the F16. I fly an Avonds F15 with a wren 70, great turbine. Ron.
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Old 12-30-2011, 01:03 PM
  #129
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Default RE: Thorpe F-20 build

The 44 gold will be perfect for this model.
No issue at all.

Paul G
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Old 12-30-2011, 02:34 PM
  #130
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Default RE: Thorpe F-20 build

I plan to use a Tam pipe I got from Yellow Aircraft when I bought a Starfire years ago. It is rated for a 10-12 lbs turbine and the length is about right.

Sheeting the main hatch with 1/16 balsa. First piece was the center section and it was glued and pinned with 30 minute epoxy while the hatch was in place on the fuse. The second sheet was glued with medium CA without being attached to the fuse. Sanded around the edges and the fit so far is pretty good. A bit concerned about the shape of the hatch when viewed from above. Has an hour glass shape. Probably would not have looked this way if I had built the hatch and sheeted it with the fuse and cut it free as described in the building instructions.
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Old 12-30-2011, 05:49 PM
  #131
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Default RE: Thorpe F-20 build

Finished sheeting the hatch and rough sanded it for a tight fit. The hatch latch and locating pins work very well. This was different than what the plans called for. I decided to go this route to avoid having two hatch pins sticking out of the top of the model and to give the hatch a solid locating point.
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Old 12-30-2011, 10:19 PM
  #132
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Default RE: Thorpe F-20 build

Sheeted the rear of the fuse that I was using for access to the hatch screws. Also sheeted the small flat area near the wing roots. Use 1/16 balsa and 30 minute epoxy.
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Old 12-31-2011, 01:39 AM
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Default RE: Thorpe F-20 build


Quote:
ORIGINAL: tlj125

I plan to use a Tam pipe I got from Yellow Aircraft when I bought a Starfire years ago. It is rated for a 10-12 lbs turbine and the length is about right.
I would use a Wren tailpipe, very light, and more thrust than a Tam due to the way it is designed.
You need to keep the weight down in the rear and get the engine as far forward as is reasonable.
Price is around £50.0 i think, check with Wren they do different lengths.

Paul G
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Old 12-31-2011, 08:50 AM
  #134
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Default RE: Thorpe F-20 build


Quote:
ORIGINAL: tlj125

I plan to use a Tam pipe I got from Yellow Aircraft when I bought a Starfire years ago. It is rated for a 10-12 lbs turbine and the length is about right.
You might want to consider a Wren/Wright pipe. Wren sells single wall versions, Gary Mueller at Jet Tech makes a dual wall that is super light, designed for the '44. You will see a 5% thrust gain over a straight '44 pipe.
Greg
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Old 12-31-2011, 09:14 AM
  #135
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Default RE: Thorpe F-20 build

Paul and Greg- Thanks for the info on the exhaust tubes. I realize there may be better exhaust tubes out there but I have already paid for this one. I am trying to keep cost low on this plane. If I like they way that it flies, I may make a mold and build another one out of fiberglass and go all out with it.
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Old 12-31-2011, 09:29 AM
  #136
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Default RE: Thorpe F-20 build

ron-hows the maverick?
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Old 12-31-2011, 11:39 AM
  #137
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Default RE: Thorpe F-20 build

Currently static. Just built a Quaker Flash and half way through a big Tucano during the recent non flying weather,,,,,,,,,,,,,,, but we digress.

Terry what are you going to do about the hatch distortion. When I built mine I never thought of sheeting the fus'. I planked mine with 1/4 x1/8 strips. Your flying site looks great and should be great for the F20. I will be interested in your retract installation. A little bit of positive incidence in the ground angle will help with rotation. Ron.
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Old 12-31-2011, 01:59 PM
  #138
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Default RE: Thorpe F-20 build

Ron- I am not planning on doing anything about the hatch. Doesn't look that bad to me. Retracts will be Spring Air #305. Ordered them several weeks ago. They have not arrived as yet. Planking with thicker balsa sounds interesting. Would leave more material for sanding.
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Old 12-31-2011, 05:47 PM
  #139
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Default RE: Thorpe F-20 build

Glued on the second base for the rear of the fuse. It is made from gluing together 3/8" x 4" sheets with medium CA and cutting to shape on plans. Then gluing it to the bottom of the fuse with 30 minute epoxy and pin in place.
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Old 12-31-2011, 05:53 PM
  #140
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Default RE: Thorpe F-20 build

Before making the ailerons, wanted to match wing tips and aileron pockets. Made a pattern from scrap balsa sheet of the wing trailing edge, wing tip, wing root, and aileron pocket. Then compared to the wings on the model. One side was close. The other was about 1/4" off. Glued some scrap balsa to the wing tips to make them longer to match the pattern.
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Old 01-01-2012, 07:30 PM
  #141
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Default RE: Thorpe F-20 build

Trimmed and sanded the wing tips and aileron pockets. Made several measurements to check the accuracy of the wings and how they matched up from one side to the other. Got them to match within 1/16" feature to feature. Then traced out the wing tip on 1/16 plywood and cut the caps out on the scroll saw. Glued them on to the wings with 5 minute epoxy. Sanded them flush after the glue cured.
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Old 01-01-2012, 07:39 PM
  #142
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Default RE: Thorpe F-20 build

Made the ailerons from 1/2 and 3/16 x 4" balsa sheet sandwiched together with 5 minute epoxy. Fit them to the wing pockets and put two Robart hinges in each one. Put a piece of balsa shaving in the gaps at the trailing edges and touch zapped with thin CA. This holds the aileron in place during shaping and sanding.
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Old 01-01-2012, 07:45 PM
  #143
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Default RE: Thorpe F-20 build

Used a small hobby plane to get the left aileron into rough shape. Then sanded with 150 grit on an aluminum bar until flush with the wing.
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Old 01-01-2012, 09:38 PM
  #144
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Default RE: Thorpe F-20 build

Same method on the right aileron.
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Old 01-02-2012, 08:46 AM
  #145
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Default RE: Thorpe F-20 build

Cut the ailerons free with a hand saw. Sanded bevels on the leading edges to get the proper throw listed on the plans- 3/8" up/down. Made control horn plates from 1/8 ply and carved out pockets for them in each aileron.
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Old 01-02-2012, 08:49 AM
  #146
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Default RE: Thorpe F-20 build

Glued the blocks in with 30 minute epoxy. Made blocks for the elevator and rudder the same way.
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Old 01-02-2012, 10:52 AM
  #147
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Default RE: Thorpe F-20 build

Terry, happy new year. Don't worry about the lack of response, your building faster than we can post, great work. Ron.
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Old 01-02-2012, 11:54 AM
  #148
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Default RE: Thorpe F-20 build

Thanks Ron. In case anyone is interested, the plane weighs 4 lbs so far.
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Old 01-02-2012, 04:46 PM
  #149
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Default RE: Thorpe F-20 build

Removed the glue clamps and sanded the blocks to give a clean and flush feel. Dremel sanded the block if it stuck out too far. Mounted the control horns onto the ailerons, elevator, and rudder. Used #2 x 3/8 wood screws. Predrilled the holes with a 1/16 drill. Tried to line up each control horn straight with the control cable at the central position of the flying surface.
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Old 01-02-2012, 04:53 PM
  #150
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Default RE: Thorpe F-20 build

Cut former F12 from 1/8" plywood on the scroll saw. Traced the tailpipe on the ply to ensure a good fit. Used a sanding drum on the dremel to fine tune the fit. Glued in place with medium CA.
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