F

fstringham7a

Well Known Member
Prop decision!!!!!

Hi to all

Will folks it is now time to bite the $$$$$$$$$ bullet and buy the the big ticket items. Engine/Instruments/Prop. Pretty much made the decision on everything but the prop. After discussing the prop purchase choice with a very knowledgeable plane builder/engine builder/all around great pilot the choices have been narrowed to the 72" 200 horse hartzell blended air foil or the 200rv whirlwind 72 inch two blade prop. My mentor is very high on the 200rv!

With that said, what are the views of the group, especially those of you that are flying behind a whirlwind prop.

200rv light but expensive...and gets about 5 plus mph more speed than the Hartzell.....based on one eye witness account that has flown behind both props. TBO @ 500 hours @ a cost of around $500. No problems with engine harmonic issues at various rpm positions.

Hartzell heavy but less expensive by $1700. TBO at 2000 hours at a cost of $2000. Engine harmonic warnings at various RPM.

So what say you? :confused: Decision will be made by Friday....I want to be done and flying asap!


Frank @ sgu RV7A "NDY"
 
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Hi Again

116 hits and no comment! What to do? If I am reading this correctly or not reading any comments it really doesn't matter either way according to you folks. One prop will be as good as the other! Weight/$$$$$/supposed performance of the 200rv as compared to the hartzell. Flip a coin is maybe the way I should make this decision.

Thanks for the help in this matter. No Really.....I mean thanks for the help, as I believe that no comment sometimes can read as long as a novel.

Frank @ SGU RV7A "NDY"
 
There's a whole section on this forum dedicated to props. I'm sure you will find your answers there.
 
fstringham7a said:
Hi to all


No problems with engine harmonic issues at various rpm positions.


Frank @ sgu RV7A "NDY"
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I can't comment on your other questions, but I am wondering about the above statement. Have they done testing to verify this?

My understanding was that they have not.

It is a common misconception that since it is not a metal blade that there is no reason to be concerned about it, but from talking to the Hartzel test engineers (they have there own composite propellers) this is totally untrue.

Even MT specifies limitations on some engine/prop combinations.
 
Van's did a prop comparison in the RVator

I think George posted an image of it in the other thread. IIRC, the Hartzell blended airfoil was the faster of the 2 props, in fact it was the fastest period. (except for some theoretical calculation they did on a FP Sensensich at 2730 rpm or something like that).

I think this is the image

my.php
 
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Kevin

I did read the threads from the past ...was just looking for some up to date info and to be honest was also looking for someone to verify my understanding of the differences between the two props. Thanks for you help I appreciate the heads up anyway.

Scott it is true that I did get some info from Whrilwind on the harmonics issue but they seemed to down play it as not as big a factor as with the metal props.

So back to my question......What should I buy........I guess I am looking for someone to act as a parent ...or better yet a spouse to blame if the decision made goes south in the future?

Thanks for the help.

Frank @ SGU RV7A "NDY"
 
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fstringham7a said:
....... Flip a coin is maybe the way I should make this decision.
......Frank @ SGU RV7A "NDY"
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occasionally, there is more than 2 choices, SO I prefer:

Hanging all choices on the dartboard, install blindfold and fire away. :D
 
fstringham7a said:
116 hits and no comment! What to do?
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Yeah, but are those 116 hits from people who have flown both of your finalists? Many of us (or at least myself) have experience with only one of the props, so a comparison based on personal experience is impossible. Why then, did I choose my Hartzell? I read every thread that I could find (both here and on the old Yahoo groups), as well as reading some really great articles on Randy Lervold's site and an issue of the RVator that did direct prop comparisons. For my -8, the answer for me came out the BA Hartzell. Don't know if you'll come up with the same answer for a -7, but there are a tons of opinions already captured in the archives....

If there was a clear "winner", there wouldn't be several props to choose from! :p
 
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Frank 2

Frank 1 here,

As you will remember I have the blended airforil 72 HartzHell prop...I also have it hanging out on a 2.25 inch prop extension.

From this you can deduce there are no W&B issues with the heavy prop even on an exension.

When I bought mine it was a slam dunk, Van's had done speed testing and found the Hartz to be the fastest, its definatly the cheapest and has the longets TBO (I actually thought it was longer than 2000 hours but oh well)

So for me the choice was obvious...even if the Whirlwind was 5 mph faster, the lower cost and much longer TBO would still make this an easy choice for me.

With the paralell motors (never could spell that word) there will be harmonic issues, I believe its only the counterweighted crank engines that you can run them where you like. To be honest my "avoid 2350RPM or less above 22"mp" limit is not an issue in the real world.

Frank 1
 
robertahegy said:
If you are going Hartzell BA on a 7A you should do a 74" prop.

Roberta
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Hi Roberta, the 72'' vs 74" debate is an interesting one. You seem to be in the camp that believes that a couple of extra inches in length is better. ;)

In reality the longer prop climbs better but cruises slower so from a performance perspective there is nothing between them.

On reading the archives the ONLY advantage I can see being put forward for the longer prop is that you have some extra metal you can take off if you have a prop strike. But that argument is a catch 22 situation because with the longer prop you're an inch closer to the ground and therefore considerably more likely to HAVE a prop strike in the first place.
 
After reading and looking at everything I could find relative to this issue I put MT composites on both my planes.

Why??

Because they looked the sexiest of all the options.

I could not find one good scientific or mechanical or physical reason to select one prop over the other.

If I were you unless someone could prove to me that the Hartzell SERIOUSLY degrades performance I would go with the Hartzell for financial reasons.
A 5mph gain on a 350 mile cross country calculates out to be a 12 minute difference in arrival time assuming cruise speed from parking place to parking place. In reality block time would change by no more than 3-5 minutes if that much.

These planes perform so well that ,in my opinion, the prop manufacturer is not a significant issue.

Aesthetics and economics are.
 
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WW 200RV

Frank,

You won't go wrong with the 200RV. I have it on my 7 and the preformance is great.

Robbie Attaway of Attawayair.com recently purchased one. He had a Hartzell and went to an Aerocomposites. He had over $12K in that prop and it cracked twice on him with very few hours.

A another local builder had a 200 RV that he was not ready for so he tried it for a few hours. He said the performance was incredible and he gained lots of speed. He ordered one and is now flying it.

There were some initial problems with the spinner backplate but those issues have been corrected.

Buy and use with confidence.
 
<<I could not find one good scientific or mechanical or physical reason to select one prop over the other.>>

Has Whirlwind actually strain-gauged any specific engine/200RV combinations for a vibration survey?
 
Check w/WW

DanH said:
<<I could not find one good scientific or mechanical or physical reason to select one prop over the other.>>

Has Whirlwind actually strain-gauged any specific engine/200RV combinations for a vibration survey?
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Don't know. I know the prop was designed specifically for the RV airframe, but what was involved in that I don't know. Our local guy that dynamically balances props says he can get these balanced closer than any other.

There is another 7 on our field. Same engine and similar avionics. He is 60lbs lighter. Throw in pilot weight difference and he is 100lbs lighter than me. The only real difference is the prop. He has a Hartzell blended airfoil and I have the WW 200RV. I can walk away from him at equal power settings.

I know of know blade issues with the WW. As noted, the only issue was with the early spinner backplate brackets.

I'd certainly buy a WW if doing it again.
 
RV7Guy said:
Don't know. I know the prop was designed specifically for the RV airframe, but what was involved in that I don't know. Our local guy that dynamically balances props says he can get these balanced closer than any other.

There is another 7 on our field. Same engine and similar avionics. He is 60lbs lighter. Throw in pilot weight difference and he is 100lbs lighter than me. The only real difference is the prop. He has a Hartzell blended airfoil and I have the WW 200RV. I can walk away from him at equal power settings.

I know of know blade issues with the WW. As noted, the only issue was with the early spinner backplate brackets.

I'd certainly buy a WW if doing it again.
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Man, I look at the cost difference, and can't justify the WW. I don't understand how a prop that HASN'T been certified on anything could cost as much as props that have.
 
RV7Guy said:
Our local guy that dynamically balances props says he can get these balanced closer than any other.

There is another 7 on our field. Same engine and similar avionics. He is 60lbs lighter. Throw in pilot weight difference and he is 100lbs lighter than me. The only real difference is the prop. He has a Hartzell blended airfoil and I have the WW 200RV. I can walk away from him at equal power settings.
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The level of dynamic prop balance has no correlation to propeller-crankshaft interaction issues. It is a whole different issue. If not, props with RPM limitations could have the limitations removed if they are successfully balanced dynamically.

As for comparing performance...the only way to get real #'s that mean anything would be to test both props on the same airframe.

I have seen big performance differences between RV's of the same model that were virtually identical...engine, weight, and propeller.

There are far too many factors involved for us to generalize performance comparisons between one airplane and another.
 
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