M

MarkSchmitz

Member
Has anyone used a 76" diameter prop on their RV-8? I have a Hartzell that's 76" diameter. Looks like I'd have a little less than 12" ground clearance. Trying to decide whether to sell/trade or maybe use it. Haven't talked to Van's yet. I'm quite a way off from installation but thought I'd solicit VAF input.

Thanks,

Mark
RV-8, QB Fuse
 
I have a 76. No clearance issues. I do many rough, soft, crappy fields and I stand the tail up pretty high to stop.
Works for me.
 
The 76" prop is not a proplem with the RV-8. In fact I remember a discussion with Vans once and they said the -8 is the only RV they would feel comfortable with having a longer prop due to the taller gear. Since the -8 is the only one that could use a longer prop they don't sell sell it.

Now part 2. While the prop may be compatible with the airframe, it may not be compatible with the engine. You need to look at the prop type certificate data sheet. I had a 76" prop that I acquired from a friend and had it cut down to 74" becuase I have an IO-360A1A (200 hp) and the 76" prop was not approved with this engine. While it's true that we're experimental and can do what we want, I was not willing to take the risk.

Jerry
 
I know Dick Martin has used 76" props, and I believe some other people have used 76" props on RV-8s too.

Just for reference, if this was a type-certificated aircraft, FAR 23.925 would require at least 9" of prop clearance, with the fuselage level, and the landing gear deflection corresponding to 1.5g.
 
Kevin Horton said:
Just for reference, if this was a type-certificated aircraft, FAR 23.925 would require at least 9" of prop clearance, with the fuselage level, and the landing gear deflection corresponding to 1.5g.
Click to expand...

Kevin where do you come up with all this stuff? You all always chiming in with this detailed data that is very helpful. Thanks.

My level of research was, hmm, know of a bunch doing it with no strikes, must work.

Turns out is does. I guess it does right up to the point where it doesn't. Im not at that point yet.
 
Kevin Horton said:
I know Dick Martin has used 76" props, and I believe some other people have used 76" props on RV-8s too.

Just for reference, if this was a type-certificated aircraft, FAR 23.925 would require at least 9" of prop clearance, with the fuselage level, and the landing gear deflection corresponding to 1.5g.
Click to expand...
:confused:

Kevin, I have been told a flat tire was part of the spec...is this just for nosewheels? A collapsed oleo strut?
 
Nuisance said:
:confused:

Kevin, I have been told a flat tire was part of the spec...is this just for nosewheels? A collapsed oleo strut?
Click to expand...
Yeah, there is mention of a flat tire, but strangely enough it is apparently only required to be considered if the landing gear has "struts". I'm not sure how that was really intended to be interpreted.
FAR 23.925 (partial) said:
:
There must be a clearance of at least seven inches (for each airplane with nose wheel landing gear) or nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level, normal takeoff, or taxing attitude, whichever is most critical. In addition, for each airplane with conventional landing gear struts using fluid or mechanical means for absorbing landing shocks, there must be positive clearance between the propeller and the ground in the level takeoff attitude with the critical tire completely deflated and the corresponding landing gear strut bottomed. Positive clearance for airplanes using leaf spring struts is shown with a deflection corresponding to 1.5g.
Click to expand...
 
Kahuna said:
Kevin where do you come up with all this stuff? You all always chiming in with this detailed data that is very helpful.
Click to expand...
My day job requires me to dig into the type-certificated aircraft design requirements on a regular basis, so I have learned how to navigate through them. While there is no regulatory requirement for us to follow FAR 23, it is a useful benchmark.
 
Thanks for the responses! I very much appreciate the insight. I did also talk to Tom at Van's today. He confirmed that 76" may be okay on an RV-8. Although I'll still have to make a final decision, the engine/prop config is approved and I believe the clearance would be fine. Good to have options!

Regards,

Mark
RV-8 QB Fuse
 
Kevin Horton said:
My day job requires me to dig into the type-certificated aircraft design requirements on a regular basis, so I have learned how to navigate through them...
Click to expand...
Hmmm. I would interpret this to mean that Kevin must be a full time professional test pilot dealing with certification testing just about every day; or something like that. Pretty good asset for the site, it seems.

I'm looking forward to his first flight in the 8.
 
Check out Kevin's Web Site!

If you think Kevin has a cool job, wait till you see all the information on his web site for building an -8. And his sections on testing and data collection are outstanding. When I was building, his site was one that I went to every week to see how to do stuff....

Uh...that is, until I out ran him... :p

Of course, I can see why it is taking him so long to build - he's got cool airplanes to fly!

Paul
 
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