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-   -   For the aero engineers and wanna bes (https://vansairforce.net/community/showthread.php?t=140101)

Guy Prevost 07-21-2016 11:22 AM

Quote:

Originally Posted by Christopher Murphy (Post 1097164)
Is this some competitive trash talk? Lol Umm ive won this class 4 times and set the class speed record of 214mph in 2010 flying much of the race at reduced power..

Since im based at 5100 msl. The only testing i can do is on the flight into KMHE. Im thinking the increase in hp will be offset by the more dense air but my gut tells me i will need more pitch..
Cm

I think he's just pointing out that at 1000'DA in summer you will be underground even in the midwest...

Christopher Murphy 07-21-2016 11:29 AM

1000ft da
 
Quote:

Originally Posted by rv7charlie (Post 1097162)
If it's a ground adjustable composite Sensenich, the reason it doesn't perform above 2700 is likely more about airspeed than rpm. According to Sensenich, they don't make blades for the ground adjustable hub that are twisted for RV speeds (excepting the -12). You'll hit a 'wall' much earlier, when the inner portion of the blade doesn't have enough pitch & starts blocking airflow, instead of contributing thrust.

Call Sensenich & ask them about it; I did when I was considering a prop using their blades.

Charlie
(Hate to repeat myself, but please don't try to fly that race at 1000' DA.)
:-)

Charlie. The 1000 ft da was just an arbitrary number. Most of the course is above 1000msl. It is my hope that i can get a big tailwind higher up but sometimes the fastest altitudes are lower. If I were very serious about winning the race the catto prop would be installed. Im just very curious about how this prop will perform at lower da's

Ive been talking to sensenich since the day they first showed this prop. Ive tried to get them to offer a heavier spacer and the prop has been back to them for some tweaking of the index pins.

It performs very similar to the metal prop without the rpm restriction and it seems very smooth. It has much better acceleration on take off too.

Cm

rv7charlie 07-21-2016 11:51 AM

Interesting. We must be talking to different people.

About a month ago, I asked about performance on a ~180HP -7 using the GA blades, and the guy I spoke with was very specific in saying that the blades are intended for Light Sport speeds, and would be sub optimal for faster RV's because of inadequate twist. (He said that it isn't power issue; the prop I was looking at had 3 blades & could absorb the power.)

I also asked specifically about whether they had considered making blades optimized for the 3/4/6/8 speeds, and he said that they'd discussed it but nothing was actually in the works.

Charlie

Christopher Murphy 07-21-2016 12:39 PM

Interesting
 
This prop was made especially for faster RV types

Here is a link to their site concerning this propellor

http://www.sensenich.com/products/item/92

It is a very light prop and for the rv4 thats a problem. I had sabre make me an 11lb spacer to help the cg.

So far I am very happy with the prop. I have flown much acro, formation, and several airshows with it. I dont think too many rv4s are using this prop and the issue i had was not enough pitch available so we re indexed the pins.

Cm

Saber25 07-21-2016 05:06 PM

Chris,

Come down to visit and we'll do a side by side speed and climb comparison. I'm really curious about how that prop compares to mine, I'll buy lunch at PUB.

On the other hand, I could meet you at KBJC and you buy lunch. I only have several more years to fly in that airspace before the ADS-B---stuff kicks in.

Cheers, Hans

Christopher Murphy 07-21-2016 09:33 PM

We should
 
Hans

We need to fly together again. Ive been so busy the airplane has been sitting in the hangar too much.

Twister

rv7charlie 07-22-2016 07:07 AM

Quote:

Originally Posted by Christopher Murphy (Post 1097201)
This prop was made especially for faster RV types

Here is a link to their site concerning this propellor

http://www.sensenich.com/products/item/92

It is a very light prop and for the rv4 thats a problem. I had sabre make me an 11lb spacer to help the cg.

So far I am very happy with the prop. I have flown much acro, formation, and several airshows with it. I dont think too many rv4s are using this prop and the issue i had was not enough pitch available so we re indexed the pins.

Cm

Thanks for the link; that's very good news to see a Sensenich adjustable composite prop for RVs. I can't imagine why the guy I spoke with didn't tell me about this prop, because I specifically asked him about composite blades for RVs.

Charlie

Christopher Murphy 07-28-2016 10:31 PM

Here is what I observed
 
I ran the AVC race. First leg 208mph second leg 204mph. Ended up flying at 9500/7500 msl at 2650 rpm. Not full power. I found I could get about 2850 rpm at 2000ft msl with the prop pitched the way I had it for higher altitude.

I got second place by .11mph...

Cm


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