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-   -   Top Flite B-25 ARF (Tecnical, tips, suggestions) (https://www.rcuniverse.com/forum/arf-rtf-75/6494380-top-flite-b-25-arf-tecnical-tips-suggestions.html)

Quigleywins 01-06-2009 07:58 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 


ORIGINAL: flaviosi



Thanks for the tips, pal. If OS is less messy, I'll go for it... :) I'm ordering the stuff and start to get the darn thing going... :) What other foruns are you hanging around, Normand?

Flavio
I fitted the OS81 they fit perfect and with the 90deg exhaust bend fitted the exhaust exits on the other side very neat with no extra cutting of the cowls for the exhausts. Rocker covers and prop nuts neaded to be removed to install cowls .
PS. Try not to lose the woodruf key in the crankshaft. They fall out so easy.
Yours Paul T

CCFPILOT 01-06-2009 11:49 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
put some blue locktight on the woodruf key, works great. This tip from the "Oily Hand" in RC Report Mag.

Mirco 01-07-2009 03:40 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Hi

First: nothing new

Still waiting for 2 Lipos from hobby city, pilots from UK and fuel.

BTW. First engine run is not possible without fuel an temperatures below -10°C (the engines and no fuel are not the problem, but I am, brrrrr)

regards

Mirco


CCFPILOT 01-08-2009 04:50 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Does anyone know where the four 3/8" X 12" foam wing seating tapes are used?? Top Flight Technical Help says "the tape is used to put the wings onto the fuselage. Thanks." This must just be a bonus, as no tape is required on the wings of this model. Could go under the stab? No, I don't think so.

rnordeck 01-08-2009 06:43 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
CCFPILOT,

Yeah, I scratched my head on that one too. But, it's there on P. 21, #13. I found it after I had already applied fuzzy sided velcro pads!!

My build tip for the day: Order a package (or two) of #0 X 3/16 Button Head screws (STP0003B) from http://microfasterners.com. Work great for attaching top turret, canopy, nose and side waist gunner windows and the wing top carb intake fairings. Note that U will also need a tiny .035 Hex Key (BL02).. I also ran out of #2 X 3/16 screws so consider 'nother hundred black #2 X 3/16 (STP0203B).

BadBob

norm 01-08-2009 08:59 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
ccf,

the btape go on the styrofoam stand supplied to sit the plane...2 on each stand...the instructions are clear on that!

Normand

harleydoberman 01-14-2009 08:01 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Tim

I have assembled the b-25 as per instructions with two OS 81 engines and robart retracts. When I balance at the 5" cg point with retracts down I am still slightly tail heavy with 3 oz of lead in the nose, but with the retracts up up the plane goes nose down very slightly. As I am new to planes of this size with retracts could you tell me if this is normal. I have a 4700 suc c NIMH battery in the cockpit behind the piolt seats. I would be greatful for any info.

Tony

Thomas B 01-14-2009 09:16 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 


ORIGINAL: harleydoberman

Tim

I have assembled the b-25 as per instructions with two OS 81 engines and robart retracts. When I balance at the 5" cg point with retracts down I am still slightly tail heavy with 3 oz of lead in the nose, but with the retracts up up the plane goes nose down very slightly. As I am new to planes of this size with retracts could you tell me if this is normal. I have a 4700 suc c NIMH battery in the cockpit behind the piolt seats. I would be greatful for any info.

Tony

I always set the CG with the tanks empty and the gear down, as that is how it could be landing....:) I would put it right on the CG with gear down and empty tanks and let it be a little noseheavy when the gear is up and there is fuel in the tanks.

CCFPILOT 01-14-2009 09:22 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
If you can, mount the battery under the nose gunner as per the manual. I have a 4200 mA battery mounted there and it balances with no extra weight.

jdhughen 01-15-2009 02:43 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 


ORIGINAL: harleydoberman

Tim

I have assembled the b-25 as per instructions with two OS 81 engines and robart retracts. When I balance at the 5" cg point with retracts down I am still slightly tail heavy with 3 oz of lead in the nose, but with the retracts up up the plane goes nose down very slightly. As I am new to planes of this size with retracts could you tell me if this is normal. I have a 4700 suc c NIMH battery in the cockpit behind the piolt seats. I would be greatful for any info.

Tony
I'm not understanding this situation... I'm completly the opposite. Gear down brings weight forward and makes the nose heavier not lighter ( I'm using robarts with scale dubro tires/wheels) . I went with Norman's suggestion and balanced with gear up and let it go nose heavy with gear down. The last thing i want is a tail heavy aircraft. ??? that fuel tank location puts most of the fuel on the CG so it's a non comcern. My $.02

Joel

harleydoberman 01-15-2009 11:21 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Joel

If I explained it right you might understand better. I wrote it the opposite. I balanced it with gear down (as per the instructions) and it is still slighlty nose heavy because when the gear goes up up it becomes slightly tail heavy. If I balance it level with gear up it wants to take a nosel dive with the gear down. I hope that explains it better. Is that normal and should it bal perfect with gear up or down? I would think that I would want to be balanced in the flying mode (gear UP) but that means a mushy aircraft nose heavy with gear down. Will the flaps comensate for this? Any thoughts would be helpful.

Tony


PS
I hope I explained it right this time!

krproton 01-15-2009 07:34 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 


ORIGINAL: harleydoberman

Tim

I have assembled the b-25 as per instructions with two OS 81 engines and robart retracts. When I balance at the 5" cg point with retracts down I am still slightly tail heavy with 3 oz of lead in the nose, but with the retracts up up the plane goes nose down very slightly. As I am new to planes of this size with retracts could you tell me if this is normal. I have a 4700 suc c NIMH battery in the cockpit behind the piolt seats. I would be greatful for any info.

Tony
Hi Tony. I wrote a detailed explanation about this before. You can find it in an earlier post. In short, yes, the C.G. will shift from where it is when the gear is extended to where it will be when the gear is retracted. However, we have accounted for this in our testing and in the specifications of the C.G. location in the instruction manual. We could have told you to balance the model with the gear retracted, but then we would have moved the recommended C.G. location aft accordingly. Balance it with the gear down as instructed in the manual.

Good luck with your plane and keep us updated on how it is going. Shoot us some pics too![sm=thumbup.gif]

Tim

harleydoberman 01-15-2009 09:12 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Tim

Thank you for reitterating what you already posted. I looked to find info about cg but it is a large post. I have moved the battery to the front of the fuse and removed the nose weight, so now I need a little tail weight. I will balance the model level with the gear down and when the gear goes up it will appear to be tail heavy but that is okay. I hope I have understood this correctly.

Thanks for the help

Tony

krproton 01-15-2009 10:55 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
No sweat Tony.

Actually, I looked for the post too, but after going through about ten pages I gave up. I did a write up about it for a customer back at work a few months ago. If I remember, I'll dig it up and post it tomorrow.

As I recall, most of the prototypes I worked on, and my own personal B-25 I got from production stock also required a few ounces of tail weight, so I think you're right in there.

Yes, you have understood it correctly. Again, we could have specified balancing the model with the gear up, but then we would have moved the C.G. back accordingly. If, for example, the C.G. shifts 1/2" aft when you retract the gear, we would simply have recommended a C.G. 1/2" farther aft then it is now. And again, we test fly the model in all imagineable configurations - gear up, down, full fuel tanks, near-empty fuel tanks, etc. Before we even test fly a model, we note on the workbench how much weight it takes to shift the C.G. to predetermined locationsus -ually in 1/4" incriments. At the field, we then find the outer limits of the C.G. by flying the model at each of those locations until it performs adversely, thus establishing the forward and aft limits (of course, control throw comes into play as well).

Best of luck! ;)

Tim

camdyson 01-16-2009 06:43 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Look around post #:425 for CG discussion.

Mirco 01-16-2009 11:15 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
Hi

Pilots and tail gunner are ready for start up the Saito 82 GK:D

regards

Mirco

nenne 01-16-2009 04:09 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Hello everybody
I am a 50+ man from Sweden and have got my TF B25 for a month ago and it looks good.
I have followed this forum for a couple of month and it is really interesting.
The question i need a little help with is what kind of engines a must use.
YS 63 or OS FL [email protected] ?
Is there anybody who has tried this engines?

kenneth

harleydoberman 01-16-2009 04:43 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 


ORIGINAL: nenne

Hello everybody
I am a 50+ man from Sweden and have got my TF B25 for a month ago and it looks good.
I have followed this forum for a couple of month and it is really interesting.
The question i need a little help with is what kind of engines a must use.
YS 63 or OS FL [email protected] ?
Is there anybody who has tried this engines?

kenneth
Kenneth

I have the os 81'S bolted up to my b-25, while I have not flown the engines on the b-25 I mounted them one at a time this summer on a hanger nine ultra stick to break them in. I flew a gallon of cool power 15% thru each with not even a glitch. I start them off on the ground for a rich, fat tank, leaning them out every few minutes, then into the air on a fat mixture. After a 1/2 gallon start to lean them a little. They run great I highly recommend them. I had a OS 70 on the ultra stick that flew it ok but the OS 81 was like turbo charging it.

Tony

norm 01-16-2009 04:56 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
Hello nenne

I have a pair of YS 63's on a A-26 and nothing but headhaches, when you got them running they are highly performant but not on the B-25. I woul recomend the OS81's or the Saito 82's. I was in Stocholm from oct 31 to nov 2 playing hockey a few weeks back. I saw the hobby store but did not have time to enter ansd see it. Visited the museum of the boat (preserved), very impressive...

Good luck with your B-25 and stay tuned


Normand

nenne 01-16-2009 05:26 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Hello Normand
Also thanks to Tony

Ok I have doughter who livs in Stockholm, my self live in the south of Sweden.
If you for any reason will come to Sweden don´t hesitate to give me a mail.

I have both types of engines in my hobbyroom, and I also think that the YS is an engine for an another type of airplane.
I have used YS for a couple of years but can not say that I have had any problem with them.
OS is not so complicated, I will go for the OS
kenneth

Hellcat716 01-16-2009 09:21 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
You just have to know how to set them up. I have had the YS 63's on my B-25 for a year without a single problem. The best choice for the B-25 in my opinion. Ton's of power.

Mirco 01-17-2009 04:18 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
Hi

Just finished my B25. Balanced the B 25 at the mentioned CG location of 127mm with gear down and fuel tanks empty a little bit nose haevy. With gear up the CG location is 131,5 mm.
So the CG is within the recommended range from 114 mm till 140 mm.

regards

Mirco

djstar39 01-18-2009 11:33 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Norman,

Hope the winter weather is treating you well! I'm in Indiana and am VERY tired of the cold and snow already!

I have a question for you on your wheels and brakes. I bought the Robart brake kit (140SET) and the Robart Aluminum 10 spoke brake hub with 4" tire (13840A2). Just put the axle through them from the TFB25 retracts from Robart and the axles appear to be too small (or the wheel openings are too big). I didn't see any collar inserts in the kits so now I have this sinking feeling that I ordered the wrong wheels and brakes.

I believe you're using this same setup so could you tell me if these Robart part numbers are the same as yours or is there something I'm missing?

Thanks!

Dave

ScaleAero 01-18-2009 01:20 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

ORIGINAL: djstar39 Norman, Just put the axle through them from the TFB25 retracts from Robart and the axles appear to be too small (or the wheel openings are too big). I didn't see any collar inserts in the kits so now I have this sinking feeling that I ordered the wrong wheels and brakes. Dave
Believe you'll find you need to sleeve the axle with brass tubing...one within another to achieve the axle diameter to match the wheel(s).

Just a thought... : )

norm 01-18-2009 01:30 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
Dave,

you got to insert 2 K&S brass tubes through it. I di not remenber the size but bring it to your local store and get the proper size. They fit perfectly over the axle and the wheel hub. Do not enlarge the oleo hole as you will weaken it. The smaller brass tube insert in a larger one (next size up) for a perfect fit. The tubes cost next to nothing be certain to buy the brass tube. Once the wheels are set you will have another challenge inserting the brake "caliper". To fix that problem you will have to lightly grind off some of the weldment in front of the oleo until it fits perfecty. Do not try to grind before you get the tubes.

Also the air tubes need to be held in place securely to avoid pinching when they go down and up. The pinch when gears are down will occur in front od the leg between the nacelle and the oleo and when retracted avoid having the tube on the side as it will wedge itself between the retract unit and the oleo pinching it again. you need to have it in front of the oleo at this location. small tie wraps will do the trick. You will understand when you get there. I attached some pictures showing the twist around the oleo to avoid the tube to be pinched. Unfortunately the pictures dont show the twist of the air tube to the front of the oleo inside but I assume you can figure it out. You will love those brakes. Hope this help.

Normand


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