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Thoughts on building/flying the Brodak F-82?

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Thoughts on building/flying the Brodak F-82?

Post  YellowJacket on Wed Feb 27, 2019 9:58 am

Hello all,

My wife just finished her first plane, a Sig Staggerwing Beech, and it looks great. She is now working on a Sig Mini-Zilch to learn about built up wings. That kit is a simple build and she will done with it quickly.

I showed her a pic of the Brodak F-82 twin Mustang with 2 engines which she thought was uber-cool and wants to build it next. I have two extra reed valve motors not dedicated to anything right now, a Black Widow and a Golden Bee, both with the 8cc tanks.

So, does anyone have any advice about this plane with two motors like: 1) should one of these motors be inboard and the other outboard? Should we purposely allow one engine to run a tad longer than the other to aid in landing, and if so, should it be inboard or outboard? Will this plane perform most or all of the AMA stunt pattern (not sure what all that entails at the moment but wanted to ask about its limitations vis a vis the Staggerwing and Mini-Zilch).

Thanks for any and all thoughts on this?

P.S. I was also eying the RSM "Miss Ashley" for her as I do have a extra baby bee that could go on it Flying
P.P.S. I would have attached a couple pics of her plane but I don't see an "attach file" button.

Greg
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Re: Thoughts on building/flying the Brodak F-82?

Post  Marleysky on Wed Feb 27, 2019 12:04 pm

Hello! Greg and Wife, WELCOME to the CEF. There is a time period that new members have to pass thru before you can post pictures. The F-82 Twin Mustang is one of my favorites just behind the P-38 Lightning. There have been threads on flying them and the problems caused by having one engine stop during flight. We will have to do a search for twins or P 38 to find those flight reports.
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Re: Thoughts on building/flying the Brodak F-82?

Post  getback on Wed Feb 27, 2019 12:47 pm

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Re: Thoughts on building/flying the Brodak F-82?

Post  Oldenginerod on Wed Feb 27, 2019 2:48 pm

Just guessing, balancing things out with a Black Widow and Golden Bee will be difficult.  From a flight performance point of view, it would be best to have the more powerful engine, being the Black Widow, inboard to help maintain line tension, but it is also desirable to have the outboard engine cut out first for the same reason.  This will be your problem because the Golden Bee will be more fuel efficient than the Black Widow and will run longer, the opposite to what you need.
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Re: Thoughts on building/flying the Brodak F-82?

Post  Ken Cook on Wed Feb 27, 2019 3:56 pm

I have built 3 of them to date and I like them a lot. I had two black widows on the 1st one which crashed coming out of a wingover when one engine quit. This is the problem with integral tanked bees. The gear is lacking and it collapses and I redesigned using my method. With two black widows, I needed some tail weight. I would also not limit the controls and use the outer hole in the bellcrank vs the inside which makes the controls a bit slow and not enough deflection. The other problem is the wing itself, it flexes a lot in between the two fuse's. I didn't do this on my last one and regret not sheeting the center. My 2nd one had two Golden Bee's.  My versions were not single ported Bee cylinders but dual so they offered good power.

         Main thing is to get two reliable engines that audibly sound equal which helps needle setting. Many seemed to be over concerned with starting one engine first , seeing that the outboard runs out first etc. I have never encountered that to be a issue ever. I always start the inboard first for safety reasons and then the outboard. I have twins from .020 - .40. Two black widows fly very well on 42' lines. I have used as much as 50' but the run time was too short. I have since switched to product engines.

       Here's a pic of my latest, I had it out this weekend. My flying partner and I fly these together as his has 2 TD's on it. He nipped my rudders because were were fooling around and got a bit too close so I need to paint the slugs of wood I put in there. I feel mine is more maneuverable. I shortened my fuse on the nose.
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Re: Thoughts on building/flying the Brodak F-82?

Post  YakNine on Fri Mar 08, 2019 6:55 am

Hey Ken , are those #2 3/8 oz. tanks , what kind of run time do you get ? also where do you get your copper tubing for the tank fittings ? Thanks TJ
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Re: Thoughts on building/flying the Brodak F-82?

Post  getback on Fri Mar 08, 2019 8:24 am

I was wondering how that plane flew after watching the change , good to hear it did well Ken .
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Re: Thoughts on building/flying the Brodak F-82?

Post  Ken Cook on Fri Mar 08, 2019 4:00 pm

TJ, my tanks are 1/2 oz. Perfect uses a brass tubing that usually splits on the seam and you can't see it internally. This is when you find out that Perfect tanks are not so perfect. Often they use a very small tubing which is also no good. That goes out in the trash. All tubing replaced with K&S 1/8" copper. I replumbed the tank for uniflow. Bottom vent only gets capped during flight. Most situations has proven to me that the uniflow pipe even though 1/8" is too large. I necked it down with a piece of 3/32" tubing that when cut with my tubing cutter closes the hole even further.

I haven't flown the model on uniflow to date as it got too cold here when I completed it. On the days that were worthy of flying, I had other models out. I never had a lot of luck converting a wedge tank to uniflow, it usually becomes problematic in the later part of the flight. I may even have to increase the tank capacity because I would like to fly the pattern using this one. If I choose to do so it will be plastic tanks.
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Re: Thoughts on building/flying the Brodak F-82?

Post  rsv1cox on Sat Mar 09, 2019 6:56 am

I have flown my scratch built P-38 many times using both Golden Bees and Black Widows but never mixed the two.

I would invest in either another stock Golden Bee or Black widow. Just top off the interior to the circle engine last and you should be ok. Mine flew fine on one engine.



Good luck with your build.

Bob
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