MT Prop Extension For RV=9A Standard Cowl

[9GT]

What are folks using for the MT propeller extension for the standard Vans cowl? I am assuming that I need a 2.250? spacer since that is what came with my kit with the FP Sensenich I sold for CS MT. My cowling was already rough cut and fit for the Sensenich from the previous builder and I don?t want to buy a new one unless I have to or there is a compelling reason to go further out with the prop. Sabre the recommended manufacturer source for the extension?

[rvbuilder2002]

Originally Posted by 9GT

What are folks using for the MT propeller extension for the standard Vans cowl? I am assuming that I need a 2.250? spacer since that is what came with my kit with the FP Sensenich I sold for CS MT. My cowling was already rough cut and fit for the Sensenich from the previous builder and I don?t want to buy a new one unless I have to or there is a compelling reason to go further out with the prop. Sabre the recommended manufacturer source for the extension?

A prop extension isn?t used with a standard cs prop.
It is only used with a fixed pitch to make it mimic the same spacing as a cs.

[DennisRhodes]

Dont think you would use a prop extension with a CS prop.

[airguy]

Originally Posted by rvbuilder2002

A prop extension isn’t used with a standard cs prop.
It is only used with a fixed pitch to make it mimic the same spacing as a cs.

The Whirlwind uses a 2.250" extended hub. Are you considering them a "non-standard" CS prop?

[rvbuilder2002]

Originally Posted by airguy

The Whirlwind uses a 2.50" extended hub. Are you considering them a "non-standard" CS prop?

But it is an integral part of the propeller hub. Correct?

By definition, a prop extension is usually something you are adding to a propeller to move it fwd of where it would be if you just bolted it directly to the fron of the engine ( like is often done on certificates aircraft).
The 2.25" extension we use on fixed pitch propellers is used to move the blades fed to the same position they would be with a compact hub Hartzell constant speed. I think the standard MT props use the same dimension. If WW uses 2.5", I would say that is non standard, but you still wouldn't add an additional extension when installing it.

[9GT]

Originally Posted by rvbuilder2002

A prop extension isn?t used with a standard cs prop.
It is only used with a fixed pitch to make it mimic the same spacing as a cs.

That was what I thought also. Something is amiss here then. I am using the 3 blade MT prop recommended by Vans for the IO-320: O-320, 71", 3 Blade, hydraulic pitch change
Part Number = PROP MTV12C/180-57. I have it mounted up to start the finish fit of the cowl that was previously fitted with the Sensenich FP with spacer and the cowling is definitely a couple inches too long. I'll be into the honeycomb by at least an inch to try and make it fit and won't have clearance for the alternator for sure. I'll get a couple pics at the hanger later today. The hub on this MT is definitely shorter than the MT hub on my buddies IO-360.

[9GT]

Never mind. After some more finagling it fits💪

[airguy]

Originally Posted by rvbuilder2002

But it is an integral part of the propeller hub. Correct?

By definition, a prop extension is usually something you are adding to a propeller to move it fwd of where it would be if you just bolted it directly to the fron of the engine ( like is often done on certificates aircraft).
The 2.25" extension we use on fixed pitch propellers is used to move the blades fed to the same position they would be with a compact hub Hartzell constant speed. I think the standard MT props use the same dimension. If WW uses 2.5", I would say that is non standard, but you still wouldn't add an additional extension when installing it.

Negative.

The Whirlwind RV200 prop uses the Saber 2.25" extension, separate from the prop hub, when installed on a 360 with the James extended cowl for an RV 9A. It may or may not be needed with the Vans standard cowl, but it is needed with the James long cowl.

http://websites.expercraft.com/airgu...y&log_id=79210

[rvbuilder2002]

Originally Posted by airguy

Negative.

The Whirlwind RV200 prop uses the Saber 2.25" extension, separate from the prop hub, when installed on a 360 with the James extended cowl for an RV 9A. It may or may not be needed with the Vans standard cowl, but it is needed with the James long cowl.

That is because it is an "extended cowl"

The conversation is/was about a standard van's cowl which is designed around "standard" propellers, which from what I understand the WW dimensions are also (though I have never personally installed one so don't know for sure).

So for "standard" propeller installations, an extension would / should not ever be needed for a constant speed propeller installation.

[ssturges]

My story,

I used an RV200 CS prop(non standard). The problem with the prop is they provide you with a spinner solution but the spinner solution backing plate interferes with the flange on the Van cowl opening, they are different shapes and the spinner backer is two piece and thick. This requires to move the cowl back or prop forward or severely modify the flange on the cowl.

I also used skybolts on the cowl which require a sizable distance of fiberglass on the back of the cowl before the honeycomb material. This made it unable to make the cowl short enough to avoid the conflict with the front flange and the prop. I decided to spend my way out of this as I getting burned out on the last 10% of the project and bought a 1.25" CS prop extension from Saber(They were very helpful). People who have retro the RV200 prop in that past have done this. The 1.25" was not undesirable as it helped with W&B. Don't care for the extra .25 gap between the prop and cowl, but rather that vs a major fiberglass project and giving up skybolts.

Any time you deviate from stock you are going to pay a price. I am sure people here solved this problem 10 different ways.