RV-7 Constant speed Hartzell vs MT?

[JPalese]

What are the merits of the constant speed Hartzell vs the MT on an O-360 equipped RV-7?

In the Hartzell line would you use the metal or composite prop?

In the MT line, 2 or 3 blades?

[Andy Hill]

There is no right / wrong... If you have answers to the following it may help you decide and/or give advice?

1. Weight Priority [Composite] (include CG aspects v RV-7)
2. Cost Priority [Hartzell BA]
3. Rock solid reliability / durability [Hartzell, metal]
4. Climb Perf [3 blade / Hartzell 7605] v Top Speed Perf [2 blade / Hartzell BA]
5. Low vibration [Composite]
6. Looks [personal choice, but tends to bias to 3 blade]
7. Supplied v builder finished Spinner [MT]
8. Ease of Cowl removal/refitting [2 blade]
9. Will RV be kept in a cramped hangar? [2 blade]

I am sure someone will come along to advocate the Whirlwind props as well... not an (easy) option for us over here since not certified.

[Kahuna]

I think Andy made a very good list. Id add.

Service and Support. (Hartzell)
Supporting YOU. (Hartzell). Hartzell supports many activities that you are interested in. This site, RV teams etc. All things being equal, you should support those businesses that support the causes you appreciate and take advantage of.

[JPalese]

Mike:

I appreciate the addition to Andy's list.

On an RV-7 with an O-360 would you use the metal or composite Hartzell?

Does the composite Hartzell have the same restricted RPM operating range of the metal prop.

Both the metal and composite props are blended airfoil, correct?

Thanks!

[Kahuna]

Originally Posted by JPalese

Mike:

I appreciate the addition to Andy's list.

On an RV-7 with an O-360 would you use the metal or composite Hartzell?

Does the composite Hartzell have the same restricted RPM operating range of the metal prop.

Both the metal and composite props are blended airfoil, correct?

Thanks!

There are not any RPM restrictions on either of these for your configuration that Im aware.
The choice between metal and composite for Hartzell comes down to a tradeoff in performance and price and a couple of other things.
The metal prop is heavier and life limited.
The composite is lighter and unlimited service life. Lighter provides a host of performance advantages air born. It also has more static thrust which lends itself to additional performance advantages like take off distances and the like.
The composite is smoother by a lot.
Cruise and top end are equal within a knot or 2 across our fleet.
So if you pay the premium for composite, you get weight savings, smoothness, static thrust, and service life. If none of those appeal to you, then the metal is less expensive while still providing excellent performance.

[gereed75]

I'll add one additional emphasis - CG concerns.

Tailwheel 7's (and 6's) can tend toward aft CG, especially with lighter (composite) props.

Aft CG's (even within the allowable range) will effect control feel and response (particularly in landing), exasperate the bounce tendency, and limit weight hauling capacity.

It is possible to get the empty weight CG forward in the range (where you want it) in a 7 with a light prop, but you need to plan for it in the build (prop extension, everything placed forward that you can etc.).

I originally had an RV 200 in my 6 with a resultant more aft than average empty weight CG. Loved the prop but definately felt the issues when CG's shifted aft (low fuel, two aboard, any baggage). After considering many options, I switched to Hartzell BA.

It is a much happier airplane with a more forward CG. The nose feels more "stable" and I like the more balanced control response. Way less tendency to bounce during landings. Less weight on tailwheel during taxi. Full baggage capacity.

As far as the other issues - Vibration is about the same (in my case the Hartzell "feels" smoother, but neither prop was dynamically balanced). Engine response is more damped with Hartzell (kinda like a four stroke compared to a two stroke). Airplane is about 1.5 KIAS slower with Hartzell. Can't discern a climb difference. Don't do a ton of acro so can't make a direct comparo there like Kahuna can, but for gentlemen acro it is fine.

These effects are a combined function of prop difference and also a CG shift.

Best of both worlds?? - a slightly faster composite prop with an overall lighter airplane and a forward empty weight CG. It can be done but you gotta plan for it.

By the way, RV-200 (250 hours) available at a good price!! See the Classified FS thread.

[JPalese]

I agree with Kahuna about supporting RV friendly sponsors when possible.

Here are some more questions:

1) I did not find the weight difference between the 72" BA Hartzell metal and composite props listed on either the Vans or Hartzell web sites. Anyone know?

1a) It also appears that while the Hartzell Composite is made in both 72" and 74" inches, the only model sold through Vans is 74". Is that correct? Is a 74" diameter prop too large for an RV-7?

2) Never having flown behind a composite prop, what is (are) the payback(s) for the considerable extra up-front cost? . . . . According to Kahuna, "So if you pay the premium for composite, you get weight savings, smoothness, static thrust, and service life. If none of those appeal to you, then the metal is less expensive while still providing excellent performance."

Can the longer service life of a composite prop vice the metal prop be translated into dollars and cents?

2a) Any downside(s) to composite vs metal props? Is a composite prop more easily damaged by FOD (sand, and debris) during ground operation? Can the composite prop be field repaired by filing like a metal prop?

3) According to Vans, an MT Governor can control a Hartzell Prop and vice versa. Anyone have any words of wisdom on the MT vs Hartzell prop governors?

4) What can be done during construction to offset the lighter weight of a composite prop so as not to adversely affect CG and load carrying capacity?

Anything I did not ask, but should have?

Thanks guys!!

[JPalese]

I agree with Kahuna about supporting RV friendly sponsors when possible.

Here are some more questions:

1) I did not find the weight difference between the 72" BA Hartzell metal and composite props listed on either the Vans or Hartzell web sites. Anyone know?

1a) It also appears that while the Hartzell Composite is made in both 72" and 74" inches, the only model sold through Vans is 74". Is that correct? Is a 74" diameter prop too large for an RV-7?

2) Never having flown behind a composite prop, what is (are) the payback(s) for the considerable extra up-front cost?

2a) Any downside(s) to composite vs metal props?

3) According to Vans, an MT Governor can control a Hartzell Prop and vice versa. Anyone have any words of wisdom on the MT vs Hartzell prop governors?

4) What can be done during construction to offset the lighter weight of a composite prop so as not to adversely affect CG and load carrying capacity?

Anything I did not ask, but should have?

Thanks guys!!

[Kahuna]

Originally Posted by JPalese

I agree with Kahuna about supporting RV friendly sponsors when possible.

Here are some more questions:

1) I did not find the weight difference between the 72" BA Hartzell metal and composite props listed on either the Vans or Hartzell web sites. Anyone know?

1a) It also appears that while the Hartzell Composite is made in both 72" and 74" inches, the only model sold through Vans is 74". Is that correct? Is a 74" diameter prop too large for an RV-7?

2) Never having flown behind a composite prop, what is (are) the payback(s) for the considerable extra up-front cost? . . . . According to Kahuna, "So if you pay the premium for composite, you get weight savings, smoothness, static thrust, and service life. If none of those appeal to you, then the metal is less expensive while still providing excellent performance."

Can the longer service life of a composite prop vice the metal prop be translated into dollars and cents?

2a) Any downside(s) to composite vs metal props? Is a composite prop more easily damaged by FOD (sand, and debris) during ground operation? Can the composite prop be field repaired by filing like a metal prop?

3) According to Vans, an MT Governor can control a Hartzell Prop and vice versa. Anyone have any words of wisdom on the MT vs Hartzell prop governors?

4) What can be done during construction to offset the lighter weight of a composite prop so as not to adversely affect CG and load carrying capacity?

Anything I did not ask, but should have?

Thanks guys!!

I can answer a few of those.
1a. We chose at Hartzell recommendation the 76" for all of our fleet with the exception of the RV-4, where we chose, at our decision not Hartzells, the 74" since we have a short legged R-4. We don't have a 7, but our RV6 is running 76". Heck I run 80" on my 8. No problem.
2a. Our experience is that the nickel edge of the composite prop is much more capable of maintaining its edge than its aluminum counterpart. So from a wear and nick point of view, composite prop wins. And as for repair, again the composite wins hands down. Certified unlimited service life is all about no(or perhaps very tiny) material fatigue and serviceability of the leading edge and composite materials. You would be shocked at the amount of damage a composite blade can withstand and still be repairable by Hartzell. Ive seen some in their plant. Its quite amazing.
3. We found both those governors and others, functioned the same.
4. Not unlike what you see in weight build distribution of other RV's, the battery is the easiest move up to the FW. There are of course other options as well.

Ill see if I cant get the weight diff #'s on the 2 props for you and report back.

[Kahuna]

Originally Posted by JPalese

I agree with Kahuna about supporting RV friendly sponsors when possible.

Here are some more questions:

1) I did not find the weight difference between the 72" BA Hartzell metal and composite props listed on either the Vans or Hartzell web sites. Anyone know?


Thanks guys!!

And from Hartzell....

The metal C2YR-1BFP/F7497 weight is 58 lbs (prop only, no spinner)

The composite C2YR-1N/N7605-2 weight is 41 lbs (prop only, no spinner)