RE: Berkeley B 26  
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All Forums >> RC Airplanes >> Twin & Multi Engine RC Aircraft >> RE: Berkeley B 26
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RE: Berkeley B 26 - 6/8/2006 10:15:10 PM   
50%plane



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Cool!! Thanks so much!!

Now onto the model. I have a total of 10 hours into this plane now. The fuse it just about ready for sheeting and carving. The only problem is I don't have any carving blocks, so I'll have to get that.

I've never used retracts before and so it would be pointless to do any more work on it until I have retracts. Does anyone have any suggestions for this? Would GP's cheap mechanical retracts work?

I don't have many motors laying around.(Hey! I'm only 19) I'd love to run the O.S. Wankels, but at this time I'm a low budget builder/pilot. I'm thinking the O.S. .25 FX, but maybe the .25 LA.

Spun aluminum cowls for this plane are a bit hard to come by, so looking at the current state of models, there's got to be a .40 size Yak54 cowling out there. I don't have any experience making my own 'glass cowls, so I'll have to buy it.

I'll be using Monokote for the finish as it's the best stuff out there. I had thought about painting with roof paint, but this plane looks to have a nice chrome finish.


50%

< Message edited by 50%plane -- 6/9/2006 1:20:05 AM >


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RE: Berkeley B 26 - 6/9/2006 4:09:54 PM   
50%plane



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Here's some build pics!! All formers are hand cut with a knife. The "spars" on the sides of the fuse are spruce, but everything else is balsa. The plans look like they call for 1/8" ply formers, but I used 3/32" balsa. Total build time shown is 9-9.5 hours.



Edit: BTW, the fuse IS straight. the floor isn't.

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< Message edited by 50%plane -- 6/9/2006 6:35:02 PM >


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RE: Berkeley B 26 - 6/9/2006 11:43:02 PM   
whatiwork4


 

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Hi,
you will note that the wing is set at positive incidence for radios in use back then,non porportional,ruddwr only.only way to get the plane to lift off the ground.set the wing to 0 degrees as well as the thrust on the engines.3-5 degrees of out thrust on each engine will be bene ficial also.as far as the wing ribs go there is a program called profli that can produce the wing ribs for you if you know the airfoil.anaca 2415 should be close to the original if you do not know.print one up at the size you have of the original and see if it matches.with the weight of this plane you are going to need heavy duty retracts with 3/16 music wire struts.spring airs would be the easiest especially firewall mounted mains that retract rearwards like a non steering nose gear.rhom used to offer these for the royal p-38 and b-25 kits.

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RE: Berkeley B 26 - 6/10/2006 12:38:54 AM   
50%plane



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Thanks Whatiwork!

I actually already cut the fuse formers for the CL version, so I'm thinking that it's probably not that far off. As far as Profli, I've heard of it, but I've never found it. Do you know where I could get it? I'm hoping to start on the wing here soon and I might just scan and resize the ribs that I have.('bout time I used that calculus) As far as retracts, I'm not familiar with Spring Air's. Do you have a link?


THanks
50%

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RE: Berkeley B 26 - 6/10/2006 12:51:01 AM   
50%plane



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These retracts have 5/32 wire. They look like they go in the right direction to me, but I don't know. I could make it work if I had to.

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXUY33&P=7

Has anyone actually used these? I can't spend hundreds of dollars on a retract system.


50%

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RE: Berkeley B 26 - 6/10/2006 1:16:10 AM   
CoosBayLumber


 

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I laser cut up a set of 1/8" ribs for the B-26 back about eight years ago. Not all ribs are shown on the plan, and don't trust the cross-sections either, for they are not accurate.

Awfull lot of 1/4 inch square being used in the kit.

You going to install the design retracting gear too?


Wm.


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RE: Berkeley B 26 - 6/10/2006 1:47:32 AM   
50%plane



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I'm not planning to do the design retracts. I think I'd rather use some modern technology there.(I tried to do the retract on a Comet Sailplane and it didn't work that well ) I might do it though if I get desperate.

Would you be able to email the patterns for the ribs to me? I would really appreciate it.


Thanks,
50%

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RE: Berkeley B 26 - 6/15/2006 5:51:31 PM   
50%plane



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Update:

I just bought two O.S. .25LA's for the plane. I don't know what to do as far ar the nacells go. The motors are mounted on two beams with tons of ply support. I'm not doing that. Does anyone have a pic on how to do it the "modern" way? I will be starting the wing here soon. I will hopefully get the stabs done today. Does anyone know what the dihederal of the stabs should be? I'm going to the 22'nd annual Ray Gordon Memorial Fly-in tomorrow through Sunday, so I won't get that much work done on it, but I hope to have all the ribs cut. I'm still deciding on the retracts. I want to run the SpringAir, but I don't know if I want to spend the money.


50%

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RE: Berkeley B 26 - 6/15/2006 6:52:35 PM   
William Robison



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Chris:

Let’s talk retracts for a moment. Everyone knows Robart, Century Jet, Rohm, and Spring Air. All these except Spring Air, until recently have been air up and air down. The popularity and safety of the spring extend from Spring Air has caused Robart to add air up spring down to their line.

On the mechanical side, directly servo operated, all the pattern fliers know the MK retracts sold by Gator R/C. And everyone has seen cheap unreliable mechanical retracts, and also some junky pneumatics from other suppliers. Most of the retracts supplied with ARF planes fall into the junk category.

The one “Nobody” knows about is the B&D brand retracts. I’ve been using them for a long time. They give you only one option, you can pick air operation or straight mechanical. No strut selection, no bigger or smaller set, all the same size. No selection of different struts, they are all hardened steel wire, but the mains as well as the nose wire have springs for landing shock. If you don’t like the steel wires, pull them out (retained by a set screw) and install a set of titanium wires from MK. You can also cut the wire off and attach a Robart or other strut if you wish, their maximum load rating is around 15 pounds – they don’t state a specification for this.

Two things make them an excellent choice for a plane in this weight range. First, they are guaranteed for life against ANY failure. A vertical landing from 300 feet with everything including the engines shattered? No problem. Gather up the remains of the gear, B&D will replace them. Get worn pivots in a set of CJM? CJM wants another $600 to replace them. Worn B&D? Free.

And best of all, call Tower Hobbies to buy a set:

B+DQ1070 B&D Pneumatic Retracts Tricycle 1 $82.99

That price includes the retracts, wire struts, the air valve, the hose needed, disconnects, charging valve, and the air tank. All you need to add is a pump to charge the system. Let’s see Robart match that. CJM match it? They’ll never come close.

Bill.


< Message edited by William Robison -- 6/15/2006 7:08:37 PM >


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RE: Berkeley B 26 - 6/15/2006 7:15:05 PM   
50%plane



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Thanks Mr. Robison! Those look great. I will probably get those.


50%

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RE: Berkeley B 26 - 6/15/2006 10:50:23 PM   
Ichy


 

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"Does anyone know what the dihederal of the stabs should be?"

I'll measure mine and let you know.

Interesting those retracts! Will have to check themn out.... thanks!

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RE: Berkeley B 26 - 6/16/2006 11:48:25 PM   
aerowoof


 

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as far as the nacelles go .use 1/8 or 3/16 birch ply for a firewall and mount an engine mount to it then the engine to the mount.with the stringers and sheeting it should be fine with the .25.but an 87" span plane using twin .25's may be a bit underpowered.my duelist has a 60 = span and uses 2 hp 40's weighs 10+ pounds with retracts.by stafford b-24 has 90' span weighs 13 + pounds use 4 fox .25 with 9 servos.i would think something in the .45-.50 range would be about right unless your plane weighs under about 8 pounds.

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RE: Berkeley B 26 - 6/17/2006 1:17:15 AM   
50%plane



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quote:

ORIGINAL: aerowoof

as far as the nacelles go .use 1/8 or 3/16 birch ply for a firewall and mount an engine mount to it then the engine to the mount.with the stringers and sheeting it should be fine with the .25.but an 87" span plane using twin .25's may be a bit underpowered.my duelist has a 60 = span and uses 2 hp 40's weighs 10+ pounds with retracts.by stafford b-24 has 90' span weighs 13 + pounds use 4 fox .25 with 9 servos.i would think something in the .45-.50 range would be about right unless your plane weighs under about 8 pounds.

Thanks! I'm planning to keep the weight down on this plane. Can anyone tell me what the stock weight of this plane should be? I have significantly lightened the plane and don't have a scale. I can only judge by how much I've probably lost.


50%

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RE: Berkeley B 26 - 6/17/2006 3:05:26 AM   
aerowoof


 

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well start with the radio at about 12 oz,2 engines at about 12 oz each,retracta are about 1 pound that's three pounds all ready with out the airframe tanks and linkages or finishing.you really cannot go by weight of the original as the radio used back then was extremely heavy considered by todays standards,tubes no transisters and large heavy batterys.

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RE: Berkeley B 26 - 6/17/2006 4:27:15 AM   
50%plane



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Actually I was thinking more along the lines of empty or CL. Weight of the radio will be 9.4 oz. less servo extensions. Motors are 9.5 ounces(each) with mufflers. I'm taking 1/32 worth of wood off the exterior. I have some 1/16 just laying here and I'll use the 3/32 for the ribs. I'm going to just cut my own ribs out from an airfoil. Since I have Realflight G3, I will copy the airfoil off of there and resize it for my purposes. I'm going to significantly lighten the ribs also.(especially after the motors) I'm going to go ahead and cut the nose gear plate out so I can sheet the plane. Does anyone know how much wood would be good left there?(It's way to big on the plans)

Also, as far as cowling goes, the cowls are 6" I believe. I'm thinking about using a 3 liter bottle and cutting them out of there, but I haven't measured. Does anyone know of a good source for a 'glass cowling? I prefer 'glass to plastic.


50%

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Model Airplanes don't kill people. Chuck Norris kills people.
Christopher A. Todd AMA# 637636

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