twin 25s onto a Ultra Sport 40
05-04-2013, 03:52 AM
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RE: twin 25s onto a Ultra Sport 40
Probably a real good idea. I have done three similar conversions. First was an old Midwest Strikemaster. After flying a lot as a single engine I converted it to a twin. It was intended for the same power as your US40. I put two Super Tigre 35's on it. Also did a Super Kaos with two 45's and a Direct Connection sea Fury with two OS .52 four strokes. In each case I added about 12 to 16" of constant chord center section to the wing to help carry the extra weight. All were great models and I still have the Sea Fury. Only caveat I can offer is to make sure you do not compromise the spar structure through the nacelles. I did on the Strikemaster to fit fuel tanks and folded the wing in a sharp pullout from a terminal velocity dive. (that was on purpose to see if it would break)
Chuck
Chuck
05-16-2013, 12:09 PM
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RE: twin 25s onto a Ultra Sport 40
I have UltraSport 40 as a twin. Two 30 Magnums 4-strks produce enough power for simple pattern. You can find two photos and two videos on link [link=http://rc-twin.ru/ult.php]UltraSport40twin[/link]. Two 25's 2-strks is a good choice for this model.
06-10-2013, 10:07 AM
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RE: twin 25s onto a Ultra Sport 40
I know it is not the same kind of plane but I have a twin seamaster 40 size that I built and it came out just over 7 lbs and two magnum 25 two strokes handled it just fine. One engine was enough to gain altitude and come around for a landing when the other died during take off.
06-11-2013, 03:31 PM
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RE: twin 25s onto a Ultra Sport 40
A couple years ago I did a ultra-sport 60 twin. I increased the wing about 6 in. & use 2 O.S. 46's in it. She will climb good, but not unlimited vertical. Made twin rudders to sit behind the engines for alittle better rudder authority in case of an engine out landing. Has not happened so far, but ya never know. Really nice hearing the twins singing along on a flyby. I will post some pics when I get my camara working tonight or tomorrow.
06-12-2013, 11:17 AM
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RE: twin 25s onto a Ultra Sport 40
I have flown many twins and from my experience, two .25s will work fine. I would say to use the more powerful, ball bearing .25s. Two OS .25LAs might be on the low side for power. If you want to use the lower power, plain bearing engines, use 2 of the .40 sized ones. A .25FX and the older .40 LA were not very far apart in power.
Use a good, powerful, rudder servo. I also recommend pull-pull to eliminate pushrod flex.
Use a good, powerful, rudder servo. I also recommend pull-pull to eliminate pushrod flex.
