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Old Feb 08, 2014, 06:59 PM
100% electric since 1990
twest's Avatar
United States, MA, Ware
Joined Jul 2001
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Jr Models B-25

Hello, here is a blast from the past "kit". The Jr Models B-25. This used to be sold by Hobby Lobby. This may have passed as an "almost ready to cover" plane back in the late 90's, but it really is a kit, just one with a fiberglass fuselage (gelcoated, like most European kits) and the wing panels already built up out of balsa.
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Old Feb 08, 2014, 07:13 PM
100% electric since 1990
twest's Avatar
United States, MA, Ware
Joined Jul 2001
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The decals do not fit the plane- the kit builds into a B-25 B, C, or D model. "Pacific Princess" is a B-25 J (actually, it is a navy PBJ, but the point is, the gun turret is in the wrong place).

I plan to build a B-25 B, most likely a Doolittle raider.

I chose to fiberglass all the wooden parts, since they are already sheeted. This way I can paint the entire plane as one piece. I don't like to match monokote to paint, and I hate painting over monokote.
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Old Feb 08, 2014, 07:17 PM
100% electric since 1990
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United States, MA, Ware
Joined Jul 2001
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So far, I have all the balsa bits fiberglassed, and the vertical stabs are spot-glued on with ca to test the fit. I will permanently glue them on with epoxy after filling the fiberglass weave.

I might decide to hinge the rudders, and I might decide to make the vertical stabs bolt on, but this is meant to be a simple, fun project.

I have already decided NOT to install retracts, as many have in the past.

I want this project to be fun, not take a thousand hours. (Can you tell I'm trying to remind myself not to do too much?)

It seems that most people who installed retracts ended up hand-launching and belly-landing anyway. I fly from grass so I've made up my mind.

I might build a set of removable dummy landing gear for when it sits on the ground.
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Last edited by twest; Feb 08, 2014 at 07:25 PM.
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Old Feb 08, 2014, 07:23 PM
100% electric since 1990
twest's Avatar
United States, MA, Ware
Joined Jul 2001
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It is about 55 inches (1350 mm) in span, and would weigh about 3.5 lbs (1.6 kg) if powered by 2 geared speed 400's and 10x 1700 nicads. Actually, most people found that this plane was a bit heavier than that. With retracts, lithium cells, and 2x outrunners, most people came out at about 5.5 lbs (2.5 kg).

I'm going to power mine with 2x astro 19 inrunners, 2x 9.5 props, and 3s lithium.

Here it is so far.
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Old Feb 09, 2014, 12:12 AM
buy a lot, fly a little!
stuart warne's Avatar
Hong Kong, Hong Kong Island, Central And Western District
Joined May 2001
5,810 Posts
Hi Twest, glad to see someone finally doing a modern build of these beautiful Czech/European kits. I'm a big fan for these and have a NIB B-25 from JR also along with NIB HVP Catalina, Beaufighter and Henschel all of which I plan to start in the next couple of years.

Are you going to fit retracts? I was pondering this myself and for now I'm still of the mind to keep it light and simple and without the retracts, but I might change my mind again once I finally come to build it, though hard mounting points and reinforcement for the LG could be more work than its worth.

As to rudder, I was considering these too, but then Tom Hunt showed me just how effective variable thrust on twins (on the Durafly Bf.110 which has basically the same tail config as the B-25) can be in place of working rudders, so I think this will be the way I most likely go with my B-25. Have you considered it?

Look forward to seeing more as it looks like your approaching this build they same way I would.

Stuart.
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Old Feb 09, 2014, 08:57 AM
100% electric since 1990
twest's Avatar
United States, MA, Ware
Joined Jul 2001
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Hi Stuart,
I plan to not use retracts. I might build a set of dummy gear that plug in just while the plane is on the ground.

A local guy built a 100" span B-25 about 10 years ago, and he loaned out to me all of his scale documentation.

Do you have a link to how to set up the differential thrust?

Thanks
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Old Feb 10, 2014, 05:11 PM
got any foam to bash?
Tom Hunt's Avatar
Lake Grove,LI, NY
Joined Aug 2000
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HI Tyler

long time no type!

Whens the last time you came down to the NEAT Fair?

Dif thrust is pretty easy to do.

Plug one of the two ESC's into ch3 (or throt if Spek) and the other into an unused channel (except rudder!) Lets say 6

Pmix chan 3 into 6 at 100%

Pmix chan 4 into 3 at 25%
pmix chan 4 into 6 at -25% (or however your radio does the opposite)

This should speed up one motor and slow down the other at anything but idle and full throttle. If the wrong motor speeds up, just swap the ESC's at the RX.

you also might have to "null" channel 6 so that it can't effect the one throttle accidently.

practice set-up with servos in the channels before plugging in the esc's!

Tom
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Old Feb 11, 2014, 10:26 AM
100% electric since 1990
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United States, MA, Ware
Joined Jul 2001
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Thank you very much. Sounds much better than snaking a flex cable through the horizontal stab.

My wife's birthday is September 15, we went to a couple of NEATS together about 12 years ago but she doesn't want to spend her birthday weekend camping out and flying planes. I don't know why- we do that most other weekends!
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Old Feb 11, 2014, 11:27 AM
got any foam to bash?
Tom Hunt's Avatar
Lake Grove,LI, NY
Joined Aug 2000
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Quote:
Originally Posted by twest View Post
Thank you very much. Sounds much better than snaking a flex cable through the horizontal stab.

My wife's birthday is September 15, we went to a couple of NEATS together about 12 years ago but she doesn't want to spend her birthday weekend camping out and flying planes. I don't know why- we do that most other weekends!
Ah.. fortunately my wifes the 27th! NEAT never gets that far out. 2015 will be 18,19,20 so you won't have an excuse then!

Tom
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Old Mar 28, 2015, 10:47 AM
100% electric since 1990
twest's Avatar
United States, MA, Ware
Joined Jul 2001
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Well, more than a year passed, now I'm back at it. All fiberglassing done, and most of the plane has been primed. The model will be the "ruptured duck" famous by the doolittle raid and the movie "30 seconds over Tokyo".

As a friend of mine pointed out, yes, a roll of toilet paper makes a very good plane stand.
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Last edited by twest; Mar 29, 2015 at 11:29 AM.
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Old Mar 28, 2015, 01:29 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
14,409 Posts
My scratch built B-25, now 22 years old and still flown.

Not true scale, but based on a 3-view for a silhouette scale. Gun nose and a bomb bay

93" span, 95% balsa build, mechanical retracts, 560 watts total, 9Lb -11oz, just under 60 watts/Lb, (who says you need 100 watts/Lb ).

B 25 #3 (3 min 43 sec)
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