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50 Caliber

Old 10-11-2014, 02:50 PM
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vertical grimmace
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Default 50 Caliber

I am just about to start building a 50 Caliber designed by Dick Sarpolous. I am wondering if anyone would be interested in a build thread? I have my engines ready, and have started the engine nacelles. This will be my first twin, so comments, suggestions would be welcome. I will be using 2 OS .25 FX engines. The wing will be a foam core, sheeted with 1mm poplar. I am going to vacuum bag the wing, and fiberglass the entire airframe. I will also be converting this aircraft to a tail dragger as it is a practice plane for a larger WW2 twin warbird.
Old 10-11-2014, 03:45 PM
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R8893
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I have built five tail dragger twins (with a sixth coming up this winter). I have found a twin tail setup, with each rudder in the propwash, to be more effective for ground handling/takeoff than a single central fin and rudder. May not apply to your warbird project.
Chuck
Old 10-11-2014, 04:43 PM
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I am planning on build an ME 410, which is a single tail, tail dragger. So any negative ground handling aspects, I would like to duplicate. I have to think that counter rotating props would help on the ground. The 50 Caliber will not be counter rotating, but the ME 410 may be. I need to look into changing the timing on the gas engines I plane to use and see how feasible it is.

One question I have out of the gate is.....how should I orient the thrust on the engines for the 50 caliber? The plans do not show any as far as I can tell. I seem to recall it is beneficial to have a fair amount of right thrust in case of an engine out. What is the prevailing thought on right thrust (or left) on a smallish .25 powered twin like this?
Old 10-11-2014, 04:43 PM
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Originally Posted by R8893 View Post
I have built five tail dragger twins (with a sixth coming up this winter). I have found a twin tail setup, with each rudder in the propwash, to be more effective for ground handling/takeoff than a single central fin and rudder. May not apply to your warbird project.
Chuck
Which models have you built?
Old 10-12-2014, 05:25 AM
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VG,
My scale twins have been a Me-110, and Handley-Page O-400. Non scale: my first twin, a conversion of a Midwest Strikemaster to something that looked like a Navy patrol plane (trike gear), Super Kaos conversion painted as a dH Hornet, and a Direct Connection Sea Fury bashed to a twin inspired by Russian Pe-2 dive bomber. Looks like I should have said 4 tail draggers. I have always set my engines straight ahead. I personally don't like the look of offset engines, especially on a scale model if the prototype did not have them. I sold the Kaos conversion. Attached is a photo of it and the Sea Fury conversion flying together. HP O-400 bomb run.

This winter I am going to build another dH Hornet and will use left and right handed engines. It only takes a couple minutes to change the ST 2500's I will be using and there are appropriate pusher props available. I also going to check out the Twin-Sync device.

Chuck
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Old 10-12-2014, 09:46 AM
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Some progress. Started with the engine nacelles. I got the main structures framed up, and now the engines mounted. I like to side mount my engines to put the carb in the right location relative to the fuel tanks. I really like these OS aluminum mounts. Makes life easy being pre drilled and tapped. Also those little barbed T-nuts are really nice. I just wish they would have provided allen head bolts instead of phillips, as they will strip out eventually. It would also be nice if they put center line marks on the mount themselves.
I have always had really good luck with the OS .25 FX engines. I have a lot of experience with them from my RC combat days. I do not think I have ever had one deadstick on me. They have a lot of power as well.
I have a kit coming for this model from Eureka aircraft. It is a short kit wood wise, and includes a foam wing. I can expect it to show up at the end of the week. I decided to just pull wood out of my supply to scratch the nacelles as I wanted to get started.
The nacelles are going to be independant items in that they will have the fuel tanks and throttle servos installed within them. I cannot imagine in the old days having to run bellcranks or cables to the engines. We have it so easy now!
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Old 05-13-2022, 10:51 AM
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Default Electric Fifty Caliber




I have aquired one of these from a clubmate who converted one to electric powered by two Power 25 (1250kv) motors in keeping with its name. Originally, it was not a pristine build, but it is structurally sound and aerodamically correct and my clubmate spent many an hour to bring it to flying condition. With it's 8x8 counter rotating prope it flies like a dream, is fast and performs perfect axial rolls without any elevator input. It was originally constructed to be a tail dragger but the landings gear was not placed forward enough so I had to rake the gear forward some 30 degrees. I am flying it with a 5000 mah 4s battery with the timer set at 3.5 minutes. I examined and can further modify it to accept two 3700 4s batteries for a total of 7400 mah but I need to evaluate what the wing load will be before deciding whether to proceed.

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