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Prop Size on Stihl 76cc Conversion

Old 02-26-2007, 02:03 AM
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Rcpilot
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Default Prop Size on Stihl 76cc Conversion

I bought a conversion engine on RCU recently. It's got a brand new cylinder and piston. Ralph did the work, but I didn't buy it from him. It's very nice, and lighter than I expected. I think the only time it's been run since the new piston and cylinder is when Ralph set it up in his shop. It looks like a brand new engine.

I'm wondering about the prop size for it. I would think it should turn a 24-10 up in the 7000RPM range. I hate to buy a bunch of props to experiment. I've already been through that with the 50cc and 60cc engines. It gets expensive. VERY expensive.

The plane is an aerobatic model. Extra 330L with 90" wingspan. 1482 sq.in. It should weigh about 17--18 pounds RTF.

What would you buy? 23-10 or 24-10 or 25-10? I like NX, MSC or MenzS props.
Old 02-26-2007, 08:33 AM
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tim220225
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Default RE: Prop Size on Stihl 76cc Conversion

My 61cc Echo twin will turn a 24/8 Menz about 6700 max. 76cc sounds a little big for the plane to me. I have a 50cc Echo in a Wildhare Extra 300 and it weighs just under 17 pounds and has more than enough power. Don't shake it apart. I have a 72cc Husky saw here to convert and it too is very light already with nothing removed yet.
Old 02-26-2007, 12:41 PM
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Rcpilot
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Default RE: Prop Size on Stihl 76cc Conversion

I'm just wondering about prop size for the engine.

Trust me--a 60cc engine ain't gonna do much with an 18 pound plane at 5973' above sea level. [] The 76cc Husky is fine. I just need to know what kind of power it has. Ralph told me it should run like a Q75. Thats helpful, but most guys using the Q75 have it in a 45 pound warbird with a little bitty prop and massive pitch. Like a 22-14 or something crazy like that. I need a prop for an IMAC plane. I'm thinking 24-10, but just not sure if the motor can turn it. It's a chainsaw engine, so it's gotta run up in the 7000RPM range or it's gonna be a turd.
Old 02-26-2007, 04:37 PM
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davewallace
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Default RE: Prop Size on Stihl 76cc Conversion

Rcpiet,
A menz 24x10 should get about mid 6,000 range. A 24x8 should get into the 7K range. A ZDZ80 only gets very low 7K range with a 24x10. A big engine doesn't to turn as fast as a 50cc. If it is no EI it will be a good runner.

Dave
Old 02-26-2007, 06:03 PM
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Rcpilot
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Default RE: Prop Size on Stihl 76cc Conversion

It's got the electronic ignition with snychrospark advance. Some really nice work by Ralph. I'm just amazed at how light it is. I haven't stuck it on a scale, but I'd bet money it's as light as a bone stock G-62

I'll buy a 24-8 and a 24-10 to see how it does.

Here's a couple pics:
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Old 02-27-2007, 12:20 AM
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davewallace
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Default RE: Prop Size on Stihl 76cc Conversion

Rcpilet,
Beautiful engine.

Dave
Old 02-27-2007, 01:40 AM
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Rcpilot
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Default RE: Prop Size on Stihl 76cc Conversion

Shoot, all I did was buy it from a guy. [sm=red_smile.gif]

Ralph did the work. [sm=thumbs_up.gif]

I wish I had the shop, tools and knowledge to do something 1/2 as good. I'd be proud as pie if I could accomplish that.

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