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. :eek: 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.

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.

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. [:o] 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.

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

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:

RE: Prop Size on Stihl 76cc Conversion
 

Rcpilet,
Beautiful engine.

Dave

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.