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RE: B25 - 6/13/2004 2:40:27 AM   
R/C Lee


 

Posts: 162
Joined: 12/21/2002
From: Black Butte Ranch, OR, USA
Status: offline 		Shawn, it's good to hear from you again. I spent 17 years at HP in San Diego - seems like years ago. With this economy, it's good to hear that you are forging ahead. Re my B-25, all I can say is that the tail assy is done, but good weather appeared and the yard called. Our weather here in Central Oregon is always marginal at this time, but it looks like it's time to start flying again. Maybe the B-25 will get started again in the fall

(in reply to 1wolf-RCU)
       Post #: 501

RE: B25 - 6/14/2004 3:48:36 AM   
Bundy



Posts: 57
Joined: 12/20/2003
From: BundabergQueensland, AUSTRALIA
Status: offline 		HI

Here is a pic of my electric powered B-25 which I hope to have finished by the end of July. Anyone else in Australia building one or has built one? I've had so much trouble finding the bits I've needed from our local hobby shop and would have been near impossible to build this one without the links, ideas and inspiration from Randy Linderman's excellent site - thanks heaps!!

I'm covering it in brown paper and 50/50 PVA. I tried this method on a sport scale Spitfire and loved it. Anyone tried it?

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(in reply to 1wolf-RCU)
       Post #: 502

RE: B25 - 6/14/2004 4:26:15 AM   
RandyL


 

Posts: 366
Joined: 2/1/2002
From: Silver Lake, KS, USA
Status: offline 		Bundy, What a fabulous project you have going! I'm very happy to hear that some of my experiences have helped while working on yours. The pictures you posted are great. I pick a lot our of them and you are doing great.
I've tried the paper / pva covering twice on smaller projects but somewhat failed both times. I simply am not doing it right and I know no one around here to teach me. I may well get ahold of you in the future when I get to a project where I would want to attempt it again.
Please tell us more about what will power yours. I am very interested!

I hope your nylon ball link connectors work for you. I first tried to use nylon clevis on some of my air cylinders. I found that the cylinders were so strong that after a few cycles the cylinders pulled the threads out of the self tapping nylon clevis. I finally used good quality metal clevis that interlock at the seam and had no more problems.
Not sure if my site tells what I use for cylinder stops but I did find an easy solution to pulling too hard on the doors when they are shut.
Your project looks great! Hope some of the other guys start posting again...

Randy


_____________________________

Randy
Flying the Friendly Skies of Kansas

(in reply to Bundy)
       Post #: 503

RE: B25 - 6/17/2004 6:49:49 AM   
Bundy



Posts: 57
Joined: 12/20/2003
From: BundabergQueensland, AUSTRALIA
Status: offline 		Hi Randy

Thanks for input and comments. It is good to hear what problems other have had and how the they have dealt with them. Hopefully safe us from repeating them and reinventing the wheel.

I've used Gene Barton retracts and don't know if Robart are the same but the center line of the wheel sits about 1/4 inch outboard of the the nacelle center line so it will all fit in (see attached pic). This meant a fair chunk of the undercarriage door had to be cut out from the outboard door to allow for the wheel blister which made what was left of the door very flimsy especially with the pull of the air cylinder. I'm planning to use a length of air tube slid over the cylinder arm to act as a stop and have cast fiberglass doors to give them some strength and stop them distorting under the load from the cylinder. Will this work? I haven't had the nylon clevis strip yet but will closely look at this. There isn't much thread on the cylinder arm to bite into. Thanks for the tip tho.

Brown paper has worked really well for me. I use thick wrapping paper, 50/50 PVA, brush it on the sanded balsa (less than 3/32!QUOT! needs sealing to stop warping), dip the brown paper panels in the glue/water, wipe off and apply to the plane. I then use an old credit card as a squeegee to firmly press the paper on and remove all excess glue leaving the paper quiet dry. A second coat of the 50/50 mix brushed on, a good sanding when dry and then on with the rivets. Sure is a lot less mess than glassing!

Electric power will come from 2 Plettenberg 370/50/A3 turning 3 bladed 18!QUOT! variable pitch Solo props. I've used these motors in a 1/3 Crackerjack and a 1/4 scale Tigermoth and really can't fault them. Still waiting for the props to arrive but will give some actually figures as soon as I can. They easily handle 1500 watts each which with an AUW of 35lb will give a power loading of around 85watts/lb which more than acceptable for this sort of plane and the 10S4P Lipos promise 20min flights. Time will tell!

I will post more details and pics as things progress. We have an electric fly in here on August 22nd that I hope to ready for - better get building!

Richard
Bundaberg, Queensland Australia

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(in reply to RandyL)
       Post #: 504

RE: B25 - 6/19/2004 1:24:28 PM   
RandyL


 

Posts: 366
Joined: 2/1/2002
From: Silver Lake, KS, USA
Status: offline 		Richard... That is serious electric power! I am very interested in hearing more at time goes forward. My largest electrics are a converted Telemaster with an Astro 40G on 16 cells, and a B-29 with 4ea spd 400 direct on 8 cells. Miniatures compared to what you are doing. I'm doing a bit of indoor with Li-po's so I'm learning that also. Maybe someday, a project like yours. Are there paticular web pages you would send me to to learn more about the motors you are using. I am not familiar with them.


_____________________________

Randy
Flying the Friendly Skies of Kansas

(in reply to Bundy)
       Post #: 505

RE: B25 - 6/19/2004 1:37:55 PM   
RandyL


 

Posts: 366
Joined: 2/1/2002
From: Silver Lake, KS, USA
Status: offline 		Richard, I forgot to mention that you are using the same cylinder stop idea. I cut soft brass tubing and slid over the piston rod to act as a stop and it worked very well. I like your idea of using airtubing as long as it maintains its strength on a hot day.
KS tubing makes hard and soft brass tubing. Use the soft and lay it on a flat table, use a single edge razor blade to cut the tubing by setting the blade on the tubing and rolling back and forth. Makes a nice, clean, smooth cut. Hope the air tubing idea works as well, it would be easier to use.


_____________________________

Randy
Flying the Friendly Skies of Kansas

(in reply to RandyL)
       Post #: 506

RE: B25 - 6/19/2004 10:51:12 PM   
Bundy



Posts: 57
Joined: 12/20/2003
From: BundabergQueensland, AUSTRALIA
Status: offline 		Hi Randy

David Theunissen's large electric page at http://www.flyelectric.ukgateway.net/largesum.htm is a good place to start and see what other people are doing. It also includes basics details of what makes these big electrics fly and some interesting links.

Gordon Whitehead wrote a series of excellent articles starting in Sep 2003 Scale International mag on how to choose the right power setup for electric planes. If you would like help getting hold of these just give me a yell.

Etienne from ICARE at www.icare-rc.com has been extremely helpful at suggesting suitable motor/ESC combinations. I've bought nearly all my brushless motors thru them, have excellent service and a vast range of whats available. This is a link to the motor I'm using http://www.icare-rc.com/plettenberg-hp370-50.htm

I hope to get a bit of building time in today so I plan to give these undercarriage doors,ball links and stops a good test and see if I make something fail.

Thanks again for the input

Richard
rap61@interworx.com.au

(in reply to RandyL)
       Post #: 507

RE: B25 - 7/2/2004 5:50:54 AM   
Peter G.


 

Posts: 293
Joined: 8/1/2002
From: Terrace, BC, CANADA
Status: online 		What a great thread. I hope if I post this question it will not get lost, being that the thread is so large.

I am building a Ziroli B25 and have it all framed up. I have sheeted the underside of the wing. I am building the wing as one whole piece. On the real B25 the flaps were one piece on the outer section (beyond the engine and wheel nacelle). I can't figure out how this would work since the wing changes dihedral and would bind the hinge line. What did you guy's do????? This one has me frustrated

(in reply to Bundy)
       Post #: 508

RE: B25 - 7/2/2004 8:37:40 AM   
Bundy



Posts: 57
Joined: 12/20/2003
From: BundabergQueensland, AUSTRALIA
Status: offline 		Hi Peter

Have you seen Randy's excellent web site detailing his B-25 build? If you have a look at the photos at http://flyinglindy.homestead.com/b25wing.html the method of attaching the outboard flaps should become clear. Basically the outboard flaps are only hinged to the outer wing panels and not across the dihedral break but Randy's photos will show this.

How about posting a few pics of your progress and we'll try and keep this thread alive. I hope to start applying the rivets to the fuselage this weekend and will try and get some more pics.

Bundy

(in reply to Peter G.)
       Post #: 509

RE: B25 - 7/2/2004 4:24:40 PM   
Peter G.


 

Posts: 293
Joined: 8/1/2002
From: Terrace, BC, CANADA
Status: online 		Thanks Bundy;

I would have sworn those flaps would bind. I am not making the ends of my wing detachable. I guess I'll just proceed the way I have. I also noted that Ziroli used robart hinges on them in a fashon like the fowler flap, this is not scale however. I wonder hinging in this way reduces the binding.

(in reply to Bundy)
       Post #: 510

RE: B25 - 7/25/2004 10:42:02 AM   
Bundy



Posts: 57
Joined: 12/20/2003
From: BundabergQueensland, AUSTRALIA
Status: offline 		HI All

My Mitchell is about a week away from first tests. Thanks Randy for the stacks - they were excellent. I used the spare ones for air scoops. The lipos are in the mail now and I should have them next week, then a bit a balancing act to see where everything should go, a few more details and decals and then the final checks. My large model inspector has looked in to every nook and cranny and is happy so it's an exciting time.

Any first flight advice? AUW looks like being very close to 35lb - how much flap for take-off? I'm thinking about 10 degrees and 35 for landing as a starting point.

Richard

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(in reply to Peter G.)
       Post #: 511

RE: B25 - 7/25/2004 1:50:55 PM   
Connery



Posts: 781
Joined: 4/25/2004
From: Chandler, TX, USA
Status: offline 		Looks nice! Makes me remember a funny thing that happened a few years ago (before digital cameras lol). I was at the big CAF airshow in Midland, TX and took a lot of pictures. The only one that the photo place WOULDN'T print was almost the same shot of the nose art on the full size Yellow Rose.

(in reply to Bundy)
       Post #: 512

RE: B25 - 7/25/2004 10:16:05 PM   
RandyL


 

Posts: 366
Joined: 2/1/2002
From: Silver Lake, KS, USA
Status: offline 		Richard, That looks outstanding! I'm very happy to hear that you used the stacks and that they were to your satisfaction. I wished I could send them out free but as you know, everyone would want them even if they never used them, hence I had to set a price on them.
I suspect I have your e-mail address here some place but if you want to send me a note at Flyinglindy@cs.com I can reply to it with my concerns about test flight. It is a note I wrote about my experiences and I saved it. I'll send it if you want to read it.
All the folks I have spoke with over the last few years make me believe that you do not need or wan