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twin engine size????

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Old 12-05-2011, 09:15 AM
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rinnander
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Default twin engine size????

Hello,

I am building a 81" OV-10 bronco Hobby Hanger ARF. I have glassed the whole plane putting in robart retracts, scale cockpit with pilots, and I hope nice aluminum wheels to be painted white to match the Shinden struts I want. I have put body lines and rivets on the wing still need to do the fuse and tail booms. Anyway the question I have is: will DLE 20's be enough power for my plane I think it might be a tad heavy? Thanks for any help you can give me.

Paul
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Old 12-05-2011, 09:57 AM
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Default RE: twin engine size????

Well, it's designed for two 90 4-strokes, so I would say that two, 20cc gassers will be plenty.
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Old 12-05-2011, 11:40 AM
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Default RE: twin engine size????

Welcome to the forum Paul and to Multi Madness if this is your first one.

The nacelles for that eighty inch scale airplane and relitively small. It for this reason I would stay away from the even the small gassers. Also the booms may be a bit restrictive for sufficient fuel for the small gasser.

I am sorry but going aginst the grain I suppose I by far prefer two stroke glow engines and certainly much prefer the sound of the two stroke glow engines. I have also found folks at least all who I have mentored all have far more success with glow powered multi's.

That airplane is a beaut and having tested the small Urivitch OV-10 with twenty fives for someone, Your largr ship seems to be crying out for a pair of OS-75AX's or perhaps 95AX's.


John
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Old 12-05-2011, 11:49 AM
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Default RE: twin engine size????

John,

I did not think about the small stuff like fuel duh!! I wanted to use large 3 blade props. I have 2 RCV .91 4 stroke that I bought for this plane, for some reason I do not like the nitro type engines. I put one of the RCV in a F4U CMP model it works well but messy with the excess oil. I thought a gasser would be nicer to work with? How much fuel do they need?? Thanks paul
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Old 12-05-2011, 11:53 AM
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Default RE: twin engine size????

I would go with two OS 91 surpass 4-strokes. They hardly spit any excess residue at all.
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Old 12-05-2011, 01:05 PM
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Default RE: twin engine size????


ORIGINAL: MinnFlyer

I would go with two OS 91 surpass 4-strokes. They hardly spit any excess residue at all.
I agree plus the sound of it is a sweet bonus.
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Old 12-05-2011, 01:13 PM
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Default RE: twin engine size????

The 91 fours strokes would be the most I would put in that airplane. But my choices would be two stroke glow.

I am a sound purest and for the precise reason eveyone always wants fourstrokes (sound) I do not. Fourstokes sound even less like scale than two strokes in my opinion and the point is nothing (At least nothing that I can afford anyway) is going to be even close to the real sound.

The sound of multi two stroke glows is something I truly relish and they always turn heads where the fourstroke may not as much anyway. The sound of my Quad Kaydet with four twentyfives always steals the show and I wont even talk about my Six Pack with 6 twentyfives, A sound you very well may never hear.

So the cleaning choirs I learned long ago to actually relish at the field as enjoyable time to talk with the buds while spending quality time with the airplane and actually accomplish a preflight inspection for the next outing.

I don,t know anything about your english horizontal engine but did watch some the fellows recently fly one and it seems that too may be a resonable engine for your airplane.

If this is your first multi it is likely to be fairly rapid with a higher wing loading So if that is the case then perhaps getting some time in with something like a twinstar would be wise, especially so if you can find someone who understands how to fly a multi on one engine and is capable of buddy boxing you through engine outs via short tanking or a capable radio would be most wise.

Anyway its a wonderful project and I enjoyed the little Urivitch ship.

John[8D]
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Old 12-05-2011, 01:20 PM
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Default RE: twin engine size????

Well I rarely disagree with John, but I'll take the throatty sound of a 4-stroke over the annoying, high-pitched sound of a 2-stroke anyday. Single OR twin!
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Old 12-05-2011, 02:11 PM
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Default RE: twin engine size????

Well shoot, Mike wouldn,t life be so boring if everone agreed
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Old 12-05-2011, 04:29 PM
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Default RE: twin engine size????

Thanks Mike and John,

I have to agree with Mike I do like the sound of a 4 stroke and I do want a 3 blade prop that was one reason for the RCV, but they are messy. The OS 91 surpass 4 stroke might be the answer. I think this plane might weigh in at 25 lbs or more loaded with fuel can the OS 91 handle that much weight? I have a smaller OV-10 electric model from nitro planes that I fly, I will have to become a member of my local field to fly this plane. Someone out there may have the twin experience to help with a flame out with one engine. I do know that you need to pull back the power turn into the running engine and then bring the power up slowly. Easy to say with a key board, no so much with two sticks and nerves on a maiden flight right.

Thank you guys for the advice and any other knowledge you would like to share.

Paul
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Old 12-05-2011, 07:44 PM
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Default RE: twin engine size????


ORIGINAL: MinnFlyer

Well I rarely disagree with John, but I'll take the throatty sound of a 4-stroke over the annoying, high-pitched sound of a 2-stroke anyday. Single OR twin!
The OV-10 Bronco had turboprops....I built the 52 inch Uravitch from plans and powered it with two OS 25FX engines running macs minipipes. To me that was a better sound match for the turboprops than any four stroke.
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Old 12-05-2011, 09:07 PM
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Default RE: twin engine size????


ORIGINAL: rinnander

John,

I have 2 RCV .91 4 stroke that I bought for this plane, for some reason I do not like the nitro type engines. I put one of the RCV in a F4U CMP model it works well but messy with the excess oil.
Are you running the proper amount of lubricant with your RCV?

One of the guys at my local field flies a .91 RCV and I notice it runs pretty clean.

I think he's running about 15% synthetic lube with very little castor blend.

I think they are interesting engines, all the advantages of a four stroke with no valves
to bother with and the external dimensions of a two stroke.


Happy flyin', Oscar
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Old 12-06-2011, 06:39 AM
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Default RE: twin engine size????

Oscar,

I am running 15% fuel from my local hobby store with no additives. I may not be a lot of excess, it is my first 4 stroke. It just seems messy, I did bend a tube and vent the oil out of the bottom of my plane. I called and spoke with Pete the guy who makes the engines in England and he explained how to go about it. Maybe I will get one more and put them on this OV-10, I thought gassers would be easier, more cost effective, and less messy.

Thank for the advice,

Paul
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Old 12-06-2011, 08:08 AM
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Default RE: twin engine size????


ORIGINAL: rinnander


Someone out there may have the twin experience to help with a flame out with one engine. I do know that you need to pull back the power turn into the running engine and then bring the power up slowly. Easy to say with a key board, no so much with two sticks and nerves on a maiden flight right.

Thank you guys for the advice and any other knowledge you would like to share.

Paul


Paul I always loose the argument over 2 versus 4 strokes on the grounds of sound and thats fine but where the big advantage becomes evident is when tuning and setting up the engines for multis the fellows tends to be more experianced with the two strokes and the two strokes are far more obvious durning tunning as to what is needed, especially if pinch tuning is used.

If this is your first multi using an unfamiliar type of engine is a big mistake, this contributes to the high rate of failure with first mults.

OK I am off the 2/4 thing and I apolligize for seeming to be argumenitive, its not intended that way.


What I do want to address is what you outlined above for the steps during an engine loss. You left out one of the most important things and that is the use of the rudder.

First order of business is to identify, next is rudder into the good engine (not aileron this is what always kills the airplane) Then power adjustment as needed.

What kills multis is failure to uss that rudder instead of the aileron. Because the rudder must be held in there while the good engine is producing power actually you will be using opposite aileron.

John
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Old 12-06-2011, 09:03 AM
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Default RE: twin engine size????

Hi!
20cc gas engines is way to big!
I would use either 10 or 15cc two strokes (.61 or .91)! Four strokes doesn't sound right on a plane like that!
Also forget 3-blade props! They would be too small, not scale like anyway, if using 10-15cc engines! Go with AP or RAM props! 2-blades for best performance!
12x6 , 13x4 or 13x5 is using 10cc engines and 14x6 or 15x4 if using 15cc two strokes (at sea level).
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Old 12-06-2011, 11:50 AM
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Default RE: twin engine size????

Gas is easier, cheaper to buy and operate plus a bunch cleaner. I won't get into what would be better for this plane, I have never built one and I'm not a twin guy. Sounds like a pilots choice thing to me.
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Old 12-06-2011, 04:36 PM
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Default RE: twin engine size????

Jaka,

20cc way to big? Do you mean weight? torque? HP? or like putting a heli jet engine in a motorcycle dumb too big? I have look at a few gassers and a 15cc and 20cc are about the same size? Maybe the RCV .91sp, which was my first choice with a 3 blade prop will have to be the one I go with. Thanks for the advice.

Paul
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Old 12-06-2011, 04:42 PM
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Default RE: twin engine size????

John,

2/4 stroke either one will get the job done. I just wanted a gasser for the ease and cost of fuel. You are right you need to correct the yaw with the rudder if you have enough time you can trim the rudder to bring her home safely. This is my first twin nitro/gas plane, my electric fly's so nice almost like a trainer I thought a nitro/gas would be about the same? Any advice still will be much appreciated.

Paul
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Old 12-07-2011, 07:06 AM
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Default RE: twin engine size????

Hi!
A glow engine is much lighter! Gives Less vibration! Which means you don't have to build as strong and heavy as with using a gas engine.
The only thing better with a gas engine is that it requiers less fuel which means smaller tank and less weight.
But I would still recommend using two two-stroke glow engines because they weight less and low weight is very important in any plane and more so in a twin.
The RCW .90 is not suitable for your plane as it needs lots of cooling air to function well!
...So forget about any three blade props and go with two good .61 two-strokes (i.e Kyosho GX.61 or OS.61) 13x5 or 13x6 APC and RAM props!
12 oz tank, preferable set up with two clunks (Uni-flow set up) or better still (But not needed) a Tettra "Bubbleless" tank!
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