Prop extension cost
 

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
 

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 directat (817) 326 - 6293. Their website is: http://www.geocities.com/sabermfg

Here is their prices from the website.

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

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...

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

...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)?