Model 2 Prop

[Allen Sutphin 705]

For you guys running a 2 stroke on your 1, 2, or 3, what is your prop length?  I understand a lot has to do with what engine but, I am considering the ground clearance in a level attitude. I was thinking along the thought of a 68". The original Subaru had a 70" and ground clearance was at a min.  I am running the standard gear and know many are using the higher bush gear which adds a bit more length to overall height.

[1avidflyer 1983]

I had plenty of clearance with a 70" on a Kitfox 1 with a 582.  JImChuk

[Allen Sutphin 705]

Thanks, I don't know if this 55 HP will handle a 70" or not. I know it flys with a 68". But then a Kitfox has a big frontal area cowling. Actually too big, bigger than Hoot Gibson's boot.

[NorthIdahoAvidflyer 374]

When I bought my Avid Mark IV it came with a GSC three blade 64 inch prop. Great prop but as far as I’m concerned a little on the short side for the 582. This prop would really be perfect on a 503. The only thing about it on the 582 is that it unloads a bit to much in cruise. Other than that it pulls hard and is smooth. 

I’ve asked the same question you have and talked to a few other local guys and the 68” seems to be a good length for the standard early Avid/Fox configuration. 

I will be selling this GSC in the next month because I bought a Warp hub and blades. Once I get it installed I’ll get rid of the GSC. Right now the GSC is pulling the Mountain Avid through the air every chance it gets.

 

[Good old number 29 158]

My Model 1 had 66” three blade GSC props when I bought it. No clearance issues with using a bigger prop. I have a 503 with the B gearbox, so the bigger concern, justified or not, was spinning too much weight with it. Of course, going to a two blade would fix that, but then there’s more vibration, I’m told. Since the GSC props were out of date, and questionable for service, I went with Powerfin’s recommended 66” x 3, with their B blades. That keeps me under the lawyer-safe low moment of inertia recommended for people who aren’t careful with the throttle. 

Edited 2 Jan 2019 by Good old number 29

[Allen Sutphin 705]

Thanks, Guys! I am going to try to use a 68 or 70" 2 blade on my Hirth 3202. May have to use a 3 blade.

[Good old number 29 158]

I think that’s a great choice. I’m looking forward to your report on the Hirth. I’ve been scoping them out, online. I’m not in the market, but when that time comes, I’m thinking about going that route. Maybe the F23, maybe a 3202 or 3202. Looking at the intake runners, I think you’d want carb heat if you didn’t use the injection. 

[1avidflyer 1983]

Here is an old never run Hirth 55 HP on craigslist.  JImChuk

https://york.craigslist.org/avo/d/new-hirth-2-stroke-aircraft/6756345566.html

[Cloud Dancer 69]

It may be easier to turn a 70" prop into a 68" prop if needed as prop stretchers are in short supply. Depending on the make and model; you might be able to shorten a prop down the road. Just something to think about before forking out huge chunks of cash on something that probably cannot be returned for a refund.