Puzzled in Prescott

From the immortal words of Ricky Ricardo--"Splain this to me Lucy!"!

The request for an "explanation" is due to the fact that I am considering the move from my fixed pitch propeller to a Whirlwind RV200 c.s. unit. The complicating factor is that I have a "long" Sam James cowl which, with my fp propeller, requires a 4" vs a 2 1/4" propeller extension. So--my cowl is 1 3/4" longer than the current stock Van's cowl. Now, when I call Saber Manufacturing (who made my extension and hundreds for the folks on this forum) they tell me that I need a 2 1/4" by 6" prop extension for the cs Whirlwind----huh??? Why would I need a 2 1/4" extension when my cowl is only 1 3/4" longer than stock and when no extension is necessary when going to the cs prop when equipped with a stock Vans cowl?. Response, that is the way it works out given the hub shape.

Now, I do not doubt this to be true as Saber has been making extensions for a very long time--I just do not understand why I would not need a
1 3/4" extension vs a 2 1/4" extension.

Can anyone "splain" this to me??????

Puzzled in Prescott,

Cheers,

db

Not sure of your entire situation, but I've got an IO360 on my 9A with the long James Cowl, and used the 2.25"x6" saber extension with my Whirlwind CS prop, fit like a glove.

Prop

I didn't build my 7 but same. 2.25 extension with James cowl. Absolutely perfect fit.

Thanks

Thanks for the info guys.

I built my plane originally with the long James cowl/4"extension/fp Catto prop. I made the space between the spinner and cowl what I wanted with those components. What puzzled me was the fact that my spacer is 1 3/4" longer than the 2 1/4" extension used on a standard Vans cowl with a fixed pitch prop --which uses no extension with a cs prop. I therefore concluded that with a cs prop I need a 1 3/4" extension--not a 2 1/4" extension as was suggested!!? Puzzling to say the least!! I think I will NOT order the extension until I get the prop and can measure exactly what my airframe needs in order to maintain the appropriate spinner to cowl spacing.

Am I missing something here??

Cheers,

db

I have a 7A, same fuse, the SJ long cowl, 3" saber and Hz CS,

WW 200RV

I suspect is because of the way the spinner/backplate assembly is mounted. You won't be disappointed with the WW!!!