islandmonkey

islandmonkey

Well Known Member
I have flown a number different types of aircraft with VP propellers that were turned either by carbureted or injected engines. However, I have never flown behind an injected engine turning a fixed pitch propeller. Is there any reason why fixed pitched propellers and injected engines are not mated together more often. I have searched through the forums to try and answer this conundrum but have come up with no answers.
 
islandmonkey said:
I have flown a number different types of aircraft with VP propellers that were turned either by carbureted or injected engines. However, I have never flown behind an injected engine turning a fixed pitch propeller. Is there any reason why fixed pitched propellers and injected engines are not mated together more often. I have searched through the forums to try and answer this conundrum but have come up with no answers.
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Anthony,

I suspect the reason you see more injected engines with CS props is due to the builder wanting to extract maximum performance from his expensive engine. There is no reason why a FP prop won't work fine on any of our RV engines, and they have been installed on every model of RV many times regardless of engine used.

It really comes down to which has higher priority, max climb performance or minimal periodic maintenance and lowest possible cost.

P.S. I edited the title of your thread so it will be more descriptive for the search engine.
 
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Sam Buchanan said:
Anthony,

I suspect the reason you see more injected engines with CS props is due to the builder wanting to extract maximum performance from his expensive engine. There is no reason why a FP prop won't work fine on any of our RV engines, and they have been installed on every model of RV many times regardless of engine used.

It really comes down to which has higher priority, max climb performance or minimal periodic maintenance and lowest possible cost.

P.S. I edited the title of your thread so it will be more descriptive for the search engine.
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As usual, we talked about C/S versus F/P quite extensively yesterday, as three of us C/S pilots went to help an RV builder who was contemplating a fixed pitch on his 9A. It came down to this.............

We fly in a mountainous region. Our airports are at 4000'+ msl, and the mountains head quickly up to 11,000+ just a few miles away. For us, takeoff performance, and even descent performance, that you can get from a constant speed, means quite a bit. For those who live and fly closer to sea-level altitudes, it's not going to matter as much............I suppose..

L.Adamson --- RV6A
 
Thanks Sam for editing the title. Thanks also to everyone else who replied.

I am interested in keeping things as light as possible. That was my main reason for asking. Going for fuel injection will have a slight weight penalty but that is more than compensated by the better fuel distribution between cylinders, therefore allowing lean of peak operation. I would love the flexibility of a VP prop but the weight penalty I feel will be to great. I am limited to 1175lbs max weight with no option to increase. So I will be aiming for an empty weight of around 765lbs. This will enable me to fly with full fuel and 50lbs of baggage. However to achieve this I must loose 20lbs but that is another story.
 
Anthony,

A Sensenich FP and an MT c/s weigh about the same for an O-320, when prop bolts, spacers, spinners as well as the prop, are taken into account (around 40lb). The lightest FP prop would be around 20lb installed. By using the lightest starter, a B&C SD-8 alternator, and a pair of P-mags you would be half way toward saving the other 20lb. So the c/s penalty is only 10lb.

Pete
 
Hi Pete,

Here is a link to my build site:

http://www.inselaffe.com/rv3/wordpress/?p=69

As you can see I have and will continue to consider all of the points you have mentioned. I have heard good reports about Catto propellers and an email to Craig Catto received this response:

Hello,
The 2 bladed propeller for this is 12.5 pounds.

You will also need the 4" extension I believe from Saber mnfg. The weight of this is 5.62 pounds.
The 7" diameter x 3/8" thick crush plate you need is 1.2 pounds
They have good weights on their parts if you wish to contact them directly. www.sabermfg.com

The Vans 13" spinner kit weight is 3.3 pounds with bulkheads and hardware.

Hope this helps.
Regards,
Craig Catto

This adds up to a total weight including the spinner of around 23lbs. I shall certainly be keeping an eye on MT propellers as these are manufactured this side of the Atlantic.

On another note, next time your at North Weald, give Alan, The Fat Controller at the Squadron and John the refueller my best regards. North Weald was my base when I lived in the UK.
 
penguin said:
Anthony,

A Sensenich FP and an MT c/s weigh about the same for an O-320, when prop bolts, spacers, spinners as well as the prop, are taken into account (around 40lb). The lightest FP prop would be around 20lb installed. By using the lightest starter, a B&C SD-8 alternator, and a pair of P-mags you would be half way toward saving the other 20lb. So the c/s penalty is only 10lb.

Pete
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is there anything that says he can't put the lightweight accessories on the heavier engine/prop combo also so the comparison is a wash?
 
penguin said:
Anthony,

A Sensenich FP and an MT c/s weigh about the same for an O-320, when prop bolts, spacers, spinners as well as the prop, are taken into account (around 40lb). The lightest FP prop would be around 20lb installed. By using the lightest starter, a B&C SD-8 alternator, and a pair of P-mags you would be half way toward saving the other 20lb. So the c/s penalty is only 10lb.

Pete
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FYI - The Catto I had on my O-290-D2 was only 9 lbs. The new prop for the new O-360 just came on Thursday and I haven't weighed it yet but it feels a little bit heavier than the old prop. Still less than 20 lbs but though.
 
islandmonkey said:
I would love the flexibility of a VP prop but the weight penalty I feel will be to great. I am limited to 1175lbs max weight with no option to increase.
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There are composite constant-speed props available as well, that will keep the weight down - such as the Whirlwind props (and others).
 
My real point was the installed weight of the various props - as Craig Catto pointed out, all the attachment 'stuff' often weighs as much as 10lb - which is included in the weight of an MT c/s prop (and may be others as well). Whirlwind props seem great, but are not yet cleared in the UK - so using one is a risk as getting UK approval is far from a walk in the park.

Its always a question of compromise and performance goals. How much will the basic airframe weigh? Who knows until its nearly finished! Might be a case of waiting until the very end of the project until making a prop decision? If you have enough weight to spare then go the c/s route; if weight saving is key then use a fp.

I'll certainly pass on your regards to the NW crew.

Pete
 
spec

Dan, could you comment on takeoff distance, cruise speed, rpm etc with the 3 blade Catto?

Thanks

Bevan
 
Bevan said:
Dan, could you comment on takeoff distance, cruise speed, rpm etc with the 3 blade Catto?

Thanks

Bevan
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I don't have the exact numbers in front of me.
My prop pitch is 76".
My home airport elevation=76 feet
Takeoff distance, don't have the exact number but do get off very quick, about 4-5 secs.
I'll accelerate to 125mph, pull & climb. I'm seeing 1800-2300 vsi.
My wot rpm=2680-2700.
Cruise, ~195rpm.
 
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