Restoring an RV6

IO390 wrote:

Well, performance improvements from a constant speed prop in both takeoff/climb and cruise are considerable on an RV, given the large speed range.

sure thing, but the RV6 is a decent performer with a modest engine. I’m not saying it’s a bad idea, but would certainly look at a better / different wooden prop first.

Dan wrote:

No less than 2 RV-7s have converted from FP to CSP this year, both of them stating: now it’s a different animal

no question about that, it’s a different animal for sure, but is it better?

There is this old story circulating on vansairforce about a buch of guys flying F16s in their day jobs. Having nothin serious to do they started dogfighting in RV4s and RV8s. Then they started switching airplanes. No matter who was at the controls one airplane came always on top. That was a light RV4 with O320 and a wooden prop. It would outrun and outturn everything else.

Silvaire wrote:

CS is also helpful for formation flying, because if you pull power the plane ‘goes backwards’ more readily.

Peter wrote:

Much better pitch stability with a CS prop. Plane is easier to fly.

I’m not sure I’m following you Peter, how would a CS prop influence pitch stability?

Quote dogfighting

Is your daily routine flying mission (I love this word ) dogfighting … really?
Well, sure ain’t mine. Maybe we gotta ask the OP, @IO390 is dogfighting in your present, or future mission profile? Then @RV14 would have a point in this debate.
OTOH if @IO390 wants optimum Total Performance, such as short TO & LD performance, superior ROC, good efficient and quiet cruise performance, he’ll probably choose a CSP.

Back to my question, 2nd or 3rd gear on the road?

how would a CS prop influence pitch stability?

A fixed prop speeds up the engine if you pitch down, which increases engine power (because it is sucking more air in – same as if you opened the throttle a bit more).

A CS prop runs at the same rpm and the governor varies the blade pitch to consume the (constant) power the engine is delivering. So the engine power does not increase if you pitch down.

Dan wrote:

short TO & LD performance, superior ROC, good efficient and quiet cruise performance, he’ll probably choose a CSP.

Total Performance is not (only) about getting from point A to point B, but it’s also about doing a bunch of different things where more weight on the nose and less power are not desired. I could get from point A to point B in a SR22 as fast as in my airplane and admittedly in more comfortable surroundings. The reason why I’m flying an RV is because my mission profile does also include dogfighting Couldn’t do that in a Cirrus.

where more weight on the nose

We could probably argue thru the nite… you obviously don’t have the W&B of a typical RV-6… which I happen to have
Believe me, or probably believe me not, but a typical-6, as originally designed, will be tail heavy with its wooden prop and O-320. Adding weight up front (maybe installing a CSP) will permit a MTOM operation which would in most other cases not be possible as the rear CG would be compromised before.

less power are not desired

Say what? I’d rather say a CSP will offer an « increase in power », at all levels and airspeeds. With a CSP you will be able to get rated power at any altitude or temperature, which one definitely does not get with a FP.

Dan wrote:

you obviously don’t have the W&B of a typical RV-6

Of course I’m not gonna debate you on a “typical” RV6. It’s super easy to build an overweight aircraft and even easier to add kilograms over the years.

Dan wrote:

I’d rather say a CSP will offer an « increase in power », at all levels and airspeeds. With a CSP you will be able to get rated power at any altitude or temperature, which one definitely does not get with a FP.

Governor would consume power and add weight, that means less power and more drag, because aircraft will be flying at a higher angel of attack
CS Prop will always be heavier than an equivalent FP one, therefore again more drag

And please allow me to correct you on this one:
Dan wrote:

CSP will offer an « increase in power », at all levels and airspeeds

FP prop would / might outperform CS prop at one specific condition

at one specific condition

Absolutely.
One specific condition… of which there are hundreds, thousands, millions on each and every flight?
Next question would be, why has the CSP ever been conceived, and is being applied (as installed and used) in a majority of RVs, as well as SEPs?
And the still non-answered basic query, are u driving in 2nd or 3rd gear drive on your car?

PS
That will be my last take on this one @RV14. Feel free to open a new thread on FP vs CSP, pros and cons, good luck

Dan wrote:

Next question would be, why has the CSP ever been conceived, and is being applied (as installed and used) in a majority of RVs

correct me if I’m wrong, but according to my memory, the factory build RV10 prototype was the first one which flew with a constant speed prop. RV6 was certainly engineered with a FP prop

Dan wrote:

One specific condition… of which there are hundreds, thousands, millions on each and every flight?

Sorry, I wasn’t clear enough, let me rephrase my statement:
If someone wants the fastest RV6, then FP prop would be the way to go, of course performance at other speeds will suffer
if the goal is to achieve the shortest takes take off, then again get a fixed pitch propeller
if one wants to win every single dogfight, than FP prop is a must have it would not be the fasted AND shortest take off airplane at the same time though

The point I’m trying to make is trivial: there are trade offs to every configuration. Good idea to point them out