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

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Old 01-13-2012, 06:58 PM
  #2926
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Agree with Ron... needed a lot of right aileron. So much so that others commented that I must have my ailerons screwed up because there was so much right aileron trimmed in. Doesn't seem to bother it though. Flys like a dream! Use a checklist for pre-flight!!!! Those wing screws in the oil coolers are easy to forget to tighten.

Dave
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Old 01-13-2012, 07:45 PM
  #2927
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)


Quote:
ORIGINAL: JBoyd58

Before I make a maiden on my B-25 (still putting it together). I'd like some input from you B-25 owners and flyers.
Based on your first flight, did you have to add none, some or a lot of elev. down trim for level flight?
Would it be wise to set some down elevator (by trim or linkage) for the first flight. If so how much? Seems some
maiden flights need a fair amount of elev. down trim. Thanks!
I added about an 1/8" down elevator to mine. Ill take a photo tomorrow.

I too added quite a bit of right aileron. I took it out an mixed right rudder with my engines throttle. Flys much better when landing and at high speed. At landing I found that the right wing dropped and the plane tracked to the right because there was no engine torque. Its the engines yaw that your fighting not balance. That's rudder. At first I tried mixing the ailerons to the throttles. VERY BAD IDEAL!!!!! ALMOST CRASHED OVER AND OVER AGAIN before she got to the ground. If you try this, make sure to put it on a switch to be able to turn off the mixing at first to tune the mix. Its really nice once you find the sweet spot.

SR
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Old 01-13-2012, 08:15 PM
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

JBoyd58,

I had to put in two clicks down upon my first flight and had to add six clicks of right aileron. Well I added 4 ounces of lead in the right wing and that helped but still needed four clicks of right aileron. I did program my full flaps with down trim on my elevators and mixed in 75 down on my mix, I also added more flap travel since the TF B-25 does come in a little hot when flying at around 22 pounds. Good luck on your maiden.
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Old 01-14-2012, 06:26 AM
  #2929
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Well.... score one for PM! I decided to tear down the nacelles 'just to look around' and make sure everything looked good. The nylon bolts holding the nacelle to the wing were a little loose allowing the engine to move just a little bit laterally. But when I took out the starboard fuel tank to get to the nylon bolts, I noticed that the clunk in the tank seemed to be rolling all over. Pulled the stopper and indeed the fuel pickup clunk was loose inside the tank with the fuel line split at the end. Replaced the fuel tubing. Also noticed that the top engine mount bolts had started to gouge a little into the fuel tank (just enough to scratch it). Shortened those bolts

The clunk off could have easily led to the dreaded engine out / death sprial and the loss of the plane. Just glad I found it before that. Not sure how you would ever know this occurred without tearing it down and looking.

Keep doing the PM folks! Will lead to a long satisfying relationship with this bird. Only hope I can approach Speed's 400 flights!!!

Dave

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Old 01-14-2012, 02:57 PM
  #2930
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Wow - glad you caught that Dave.

Definitely a testament to the value of regular maintenance, even when, perhaps especially when, it is a pain to do. I have had clunks slip off several times. There always seems to be a delicate balance between securing them adequately and risking severing the line under vibration. I'm currently having best success with the black 'Hayes' neoprine line for use inside the tank, secured by very small zip ties. I try to swage the end of the copper feed through pipe (a little)at the stopper end to give the zip tie something to hold against, the clunk itself usually has a lip on it.

If you haven't used the Hayes stuff before it is great because it holds up well and is super flexible after it has been in the fuel for a little while. However, for the same reason it is a good idea to soak it in some fuel for about 24 hours before installingas it does tend to stretch and become super slippery.

Ron.
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Old 01-14-2012, 05:34 PM
  #2931
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Dave, also glad the PM reveald the problems before you got bit! Last years PM on my 50cc MX2, Revealed the clunk off the fuel line.
That's when I started using zip ties on the fuel lines. It pays to PM your birds!
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Old 01-14-2012, 08:07 PM
  #2932
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Quote:
ORIGINAL: djstar39

Well.... score one for PM! I decided to tear down the nacelles 'just to look around' and make sure everything looked good. The nylon bolts holding the nacelle to the wing were a little loose allowing the engine to move just a little bit laterally. But when I took out the starboard fuel tank to get to the nylon bolts, I noticed that the clunk in the tank seemed to be rolling all over. Pulled the stopper and indeed the fuel pickup clunk was loose inside the tank with the fuel line split at the end. Replaced the fuel tubing. Also noticed that the top engine mount bolts had started to gouge a little into the fuel tank (just enough to scratch it). Shortened those bolts

The clunk off could have easily led to the dreaded engine out / death sprial and the loss of the plane. Just glad I found it before that. Not sure how you would ever know this occurred without tearing it down and looking.

Keep doing the PM folks! Will lead to a long satisfying relationship with this bird. Only hope I can approach Speed's 400 flights!!!

Dave

Ditto.......remember this?

http://www.rcuniverse.com/forum/m_64...9/key_/tm.htm#

Post 2466

SR






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Old 01-14-2012, 08:26 PM
  #2933
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)


Quote:
ORIGINAL: Speedracer2112


Quote:
ORIGINAL: JBoyd58

Before I make a maiden on my B-25 (still putting it together). I'd like some input from you B-25 owners and flyers.
Based on your first flight, did you have to add none, some or a lot of elev. down trim for level flight?
Would it be wise to set some down elevator (by trim or linkage) for the first flight. If so how much? Seems some
maiden flights need a fair amount of elev. down trim. Thanks!
I added about an 1/8'' down elevator to mine. Ill take a photo tomorrow.

SR
I needed a lot of down. A photo is better than "clicks". Everyone has different radios and a click is different for each. Futaba 14s can adjust the throw of a click. Same with the planes, all the same yet different. But it is helpful to know you will need to expect down elevator. I asked the same question of the group a few years ago LOL! I've learned a bit since then.

God speed.

SR


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Old 01-16-2012, 07:18 AM
  #2934
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

I've read about people using the Saito 90TS Flat Twin engines but has somebody used the three (3) cylinder radial 90 Saito ? Would it be too big to install ? The only problem could be how to install the exhausts...
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Old 02-23-2012, 06:38 PM
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

HI GUYS
IM TRYING TO POST SOME PHOTOS OF MY B25.IT TELLS ME THAT THEY ARE SUCCESSFULLY UPLOADED BUT THEY DONT APPEAR ANYWHERE.
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Old 02-26-2012, 06:33 AM
  #2936
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Let me try. I don't think I've post to the forum yet.
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Old 02-27-2012, 01:27 AM
  #2937
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Gonzalo,

the saito 90 3 cylinder is really too weak of an engine to power this plane. In reality the "90" means nothing but the size of displacement and it is 3 "30's" fighting each other. there is a great loss of power and the engine is somehow comparable to a 45 - 4 stroke which i think would be even stronger.

I have the 3 cylinder Saito 90, the 450 and the 170, they all are great looking, "pieces of jewelry" good to look at, but wont deliver power. Too much mechanicc to move around in this size engine.

Normand
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Old 03-06-2012, 04:29 AM
  #2938
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)


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Old 03-06-2012, 04:34 AM
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

I AM GOB SMACKED I ACTULLY UPLOADED A PHOTO OF THE COCKPIT OF MY B25.ITS NEVER WORKED BEFORE SO ILL TAKE THIS ONE.ILL PUSH MY LUCK AND DO ACOUPLE MORE TOMORROW
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Old 03-06-2012, 04:36 AM
  #2940
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

THAT PHOTO IS MK1 NEXT ONE IS I THINK BETTER.

RAAF
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Old 03-08-2012, 03:51 AM
  #2941
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

hi guys.
Well the time has come for the maiden flight.ive done a series of grond runs and all is well i just hope i havnt missed anything.I've also put 3 tanks of fuel through each motor which i bought when the b25s came out [big mistake] after reading some of the suggestions on this thread.
The motors run sweetly and havnt flamed out during static testing so no excuses
AUW is 19lbs with all the bling even electric retracts, not to heavy i think.
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Old 03-08-2012, 06:04 PM
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)


Quote:
ORIGINAL: raaf

hi guys.
Well the time has come for the maiden flight.ive done a series of grond runs and all is well i just hope i havnt missed anything.I've also put 3 tanks of fuel through each motor which i bought when the b25s came out [big mistake] after reading some of the suggestions on this thread.
The motors run sweetly and havnt flamed out during static testing so no excuses
AUW is 19lbs with all the bling even electric retracts, not to heavy i think.
Good luck and keep us posted.
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Old 03-14-2012, 11:10 AM
  #2943
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Can anyone with experience on this plane comment on whether a pair of thunder tiger 91 four stroke engines would be to much? I've got an offer for a package deal with those motors but I'm concerned the added 10 ounces per motor and larger size may cause issues in terms of fitting inside the canopy and causing me to add tail weight to an already heavy plane.

Also, has anyone compared the flight of this plane to the hangar 9 twin otter? The twotter can handle a single engine failure without a huge cause for panic, but other than that, I wonder if the feel of flight will be similar?
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Old 03-14-2012, 11:40 AM
  #2944
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

I do not see any problem with these engines, you need only coordinate their installation ,that it all, I am flying with two engines RCV91-CD and it work wonderful , was a bit of work to match them but not something special, he flies very well on one engine to . i use 2 APC 3 blade 13/8
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Old 03-14-2012, 05:17 PM
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)


Quote:
ORIGINAL: Fidelity101

Can anyone with experience on this plane comment on whether a pair of thunder tiger 91 four stroke engines would be to much? I've got an offer for a package deal with those motors but I'm concerned the added 10 ounces per motor and larger size may cause issues in terms of fitting inside the canopy and causing me to add tail weight to an already heavy plane.
The question is the total weight of the engine since we don't know what the reference engine is. 10 more ounces than what?

You really want a light plane. Nothing flys worse than a brick. It takes all the fun right out of it.


SR
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Old 03-15-2012, 09:38 AM
  #2946
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

http://www3.towerhobbies.com/cgi-bin...&I=LXAHTS&P=ML
This is my curret engine.

The extra 10 ounces was compared to a similar 72 size...but I agree that I need to compare it to the stock motor which is no longer sold. Here are the weight and measurements.

Thunder Tiger .91 FS
SPECS: Displacement: .91 cu in (14.97cc)
Bore: 1.114" (28.3mm)
Stroke: 0.937" (23.8mm)
Practical RPM: 1,800 - 12,000
Output: 1.6 HP @ 11,000 rpm
Weight: 26.20oz (742.8g) without muffler
Crankshaft Size: 5/16-24
Height from Mounting Tab Bottom to Top of Rocker Arm: 3.77" (95.7mm)
Height from Crankcase Bottom to Top of Rocker Arm: 4.63" (117.7mm)
Width at Mounting Tabs: 2.36" (60mm)
Width of Crankcase below Mounting Tabs: 1.69" (43mm)
Center of Mounting Holes Same Side: 0.98" (25mm)
Center of Mounting Holes Opposite Side: 2.05" (52mm)
Center of Crankcase to Drive Washer: 2.62" (66.5mm)
Distance from Backplate Screw to Drive Washer: 3.64" (92.5mm)

Stock recommendation: OS FL-70
- 1 cylinder
- Displacement: 0.699 cubic inches
- Bore: 1.091 (in.)
- Stroke In: 0.748 (in.)
- Low RPM: 2300
- High RPM: 12000
- 1.100 bhp @ 11000 RPM
- Weight (no muffler): 16.50 oz.
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Old 03-15-2012, 10:16 AM
  #2947
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Fidelity:

Use em. Just break em in real good, make sure they both have a reliable idle (at least 3 minutes without loading up- this means adjusting the low end mixture), around 21-2300RPM (USE A TACH), make sure they both have a 1-200 rpm "bump" on a pinch test at WOT (USE A TACH) and make sure you're synchronized on the ground. Contrary to a lot of the info floating around, it is perfectly acceptable to get the final synch by leaning one engine slightly, but always pinch test at WOT afterward. (You also want to make sure the throttle servo linkages are as geometrically identical as you can.)

I used a pair of 55 2S, and I'm betting your 91 FS will put out about the same power or slightly more. The extra weight will help- I had to use Higley heavy brass prop nuts on mine to get the CG.
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Old 03-15-2012, 11:52 AM
  #2948
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

The things you should consider.

1. Do you love Thunder Tiger motors?
2. Are they ultra dependable?
3. Are they worth the extra weight?
4. You you want or need the extra HP?
5. Are they new?
6. Can you sell them and get what you want?

Don't use them just because they came with the plane. Go with what you know and like on a twin.

SR
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Old 03-19-2012, 05:50 AM
  #2949
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

My 2 bobs worth.I got 2 of the 70s on mine and they work great.no trouble with idle no flame outs just reliabilty.
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Old 03-19-2012, 07:03 AM
  #2950
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Default RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)

Thanks for the information. The two 91s I have are the older style but brand new in box. I've heard they are very reliable but I think I'll run them for a while on te bench before making a decision.

I was also thinking of selling them (for sale on Rcgroups) but I'm not sure of the newer version is better or if parts are available for the older version I have. Mine goes not have anodized parts.
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