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Prop extension cost

cjensen

cjensen

Well Known Member
If I go with a James cowl and a Catto prop, I'll need a 4" extension, according to James' website. I can't find any info on where to buy one (other than AS&S, and they don't come right out and say how much), or how much these dudes cost.

How much have you paid? :confused:
 
Check out Sabre Manufacturing

cjensen said:
If I go with a James cowl and a Catto prop, I'll need a 4" extension, according to James' website. I can't find any info on where to buy one (other than AS&S, and they don't come right out and say how much), or how much these dudes cost.

How much have you paid? :confused:
Click to expand...
Hi Chad,
If its for a wood prop, Its a special order from Vans. I believe they still get them from Sabre Manu.
You can get in touch with Sabre direct [size=+1]at (817) 326 - 6293[/size]. Their website is: http://www.geocities.com/sabermfg

Here is their prices from the website.
[size=+1]
PROP EXTENSIONS 7" DIAMETER - 7" dia. prop end, 6" dia. engine end
Standard lengths: 4"x 7-- $355 6"x 7-- $504 8"x 7-- $653

CRUSH PLATES - 6" dia. x 3/8" thick-- $45 7x3/8-- $55 7x1/2-- $65[/size]
 
Chad,
Without arguing any actual or perceived beneficial differences between the two available SJ cowls, I'll just point out that you don't have to use the extended cowl.

I feel that the greatest benefit comes from using a tight plenum (SJ) which allows the smaller intakes of the SJ cowl to do a better job of cooling but with less drag.

So in my case, I'm using the standard length SJ cowl (same length as Van's) and the SJ plenum with my TMX IO-360 and Catto 3-blade prop. For that installation, all you need is a thicker crush plate, and I bought the heaviest one available (from Sabre) to overcome the inherent aft CG issues that the '7's have when using light props.

Just throwin' that out there...
 
Last edited:
Well, disregard my first post then...I didn't know there were two sizes of SJ cowls. From reading their website, I gathered that there was one size, and it required an extension.

Problem solved. If I go SJ, I'll use the standard length.

Thanks Vern! :D
 
I am pursuing the same setup on my RV7. One comment is the prop extension will move the CG forward. The trade off having to use the 4" prop extension.
I have not run the calcs to see if 4" has much effect on the CG.
 
It would affect the CG, if your going with a FP prop, I don't see why you WOULDN'T go with the long cowl, inversely, if going CS, I don't see why anyone WOULD go with the long...

The -7 with a light prop would benefit from moving it fwd a few inches, AND the extra nose weight of the long cowl.
 
Researching for future choice...

I too, am interested in the James cowl. Reading on the site, I've found the following...

"Available for RV-6, RV-7, RV-8, RV-9 and the Mustang II in fuel injected or carbureted versions. Uses a prop extension. A shorter length, carbureted version of the RV-6, 7, & 9 is available for use without a prop extension."

The question I have is, does this mean that you can use the shorter version for carb setups, but MUST use the extended cowl for FI engines (don't know why, but I guess maybe room underneath for everything)?

One other question, what is the differential cost? I can see the price for the James cowl, but can't find anywhere on Van's site what I'd save by excluding their cowl from the finish kit (which I've yet to buy).
 
The cost differential is not huge. Around 200 bucks (give or take a few pennies). Vans credit was 850 for their cowl..

PS. If you were to go with Sensenich metal prop, you can order it with 4" extension at no additional cost.. :)
 
I have a long SJ cowl

IF you have a FF sump it is highly unlikely in my estimation that the standard length cowl will work...IT certainly WON'T work with an AFP FI system....Just not enough room.

I ended up with a HArtz C/S prop, a 2.25" extension (it should be 2 and 5/8ths but that is what they had in stock).

Absolutley no problem with moving the CG forward on a parallel valve engine anyway.

Frank 7a, SJ cowl, AFP
 
frankh said:
IF you have a FF sump it is highly unlikely in my estimation that the standard length cowl will work...
Click to expand...
...and even if you could get the FI components to fit, you'd have to get very creative with the intake, since it would be tough to do via snorkel from the round cowl holes.

The reason I ask long vs. short is because I like the combination of FI, the speedier cowl and ability to do aerobatics, but I've also read that aero is somewhat of a no-no with the prop extension. Is this urban myth or real (i.e. I can have any two of the three, but not all three)?
 
Propellor Bolts

I believe Sensinich will also provide you with the proper bolts.

They may look like AN bolts, but they are not.

The thread length is extended to work with the bushings that go in the crankshaft flange. AN Bolts have a shorter thread made to work with full height locknuts or shorter nuts depending on your application.

If you are buying an extension kit or even a new FP prop, make sure it comes with the proper fasteners. They are NOT cheap :eek: or easily obtainable.

BTW I do not sell 'Prop Bolts" those should be obtained from the propeller manufacturer.

I do sell AN bolts that will hold props on, but you would have to use locknuts and special bushings for the Crank Flange from Lycoming that have NO THREADS.
 
java said:
...and even if you could get the FI components to fit, you'd have to get very creative with the intake, since it would be tough to do via snorkel from the round cowl holes.

The reason I ask long vs. short is because I like the combination of FI, the speedier cowl and ability to do aerobatics, but I've also read that aero is somewhat of a no-no with the prop extension. Is this urban myth or real (i.e. I can have any two of the three, but not all three)?
Click to expand...

Urban Myth!...Remember the recent airplane with an 8"...Yes that 8 inch prop extension, C/S prop and rated to +16G's......Wow!

Yes I researched this at length and came to the conclusion it was fine.

Remember the RV is not a Pitts, the guyroscpic forces are simply not going to be like on a hard aerobatic machine, the RV is for sport aerobatics. Not an issue.

Eh? snorkel?....There is a ram air intake, no connection to the cooling inlet holes and would be impossible to do i think.

Frank
 
I recently installed a short SJ cowl on a -7 with a Hartzell C/S for someone else.

The only thing I can add is that the SJ cowl is really made for the 4 inch extension, by Sam James' own admission. It does work with both 2 1/4 and 4 , but the 4 inch extension will provide you with a better transition from the plenum to the intake rings on the cowl. The longer cowl will give you a better appearance IMO. This also applies to the transition of the air intake for carbureted engines to the small intake ring. The more flexibility in the take transition tube makes cowl installation easier.

JT
 
Subaru?

Hi Chad,
Your signature says E6 Subaru. If that is what you're putting in the 7, then the openings may well be too small for the two radiators that sit behind them. Be careful with this issue. A friend has the 4 cyl Sube in his 7 and it runs hot.

Are the radiators still behind the cowl openings on the E6?

Regards,
 
4" too long

with the c/s prop...its 2 and 5/8ths....The 4" was for FP props I believe.

With the 2.25" extension I only had about 1/2" or so to trim off the back edge.

The cowl was designed to fit the Hartzell extended hub with no extension...The differenece between the extended (M hub) and compact (C hub) is 2 aand 5/8ths

Frank
 
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