Move prop forward

[uk_figs]

When I built my RV-7 I positioned the cowl close to the rear of the spinner (about 3/16 inch gap). Now the engine has dropped a little such that the gap is about 1/8 which is no big deal except when I have to remove the lower cowling with the 3 blade Catto prop. Removing the cowling is a real PIA in particular trying the drop the front (with the inlet intake and carb intake seals) without scratching the cowl or the spinner.

In my configuration I have the Sabre prop extension bolted to the crankshaft and the mounting bolts protrude about 1/8 in through the back of the crankshaft mounting plate so my question is whether it would be acceptable to add a 1/8 plate to the sabre extension to increase the cowl to spinner distance to about 1/4 inch.

Figs

[scard]

Figs,
You of all people should NOT move the prop any further forward!!

Sorry, just couldn't resist.

[Carl Froehlich]

Another approach is to fix the sag. Put an additional washer on each of the two lower engine mounts between the engine and the mount.

Carl

[uk_figs]

Even if I fix the sag I still think it would be better if the prop was a little further forward.

Scott
I just hope you, Jerry and Dan never get together

[vfrazier]

Add an appropriately sized washer behind each firewall/engine mount pad. Use your good judgement.... a stack of 23 washers is too much..... but one washer or judiciously sized spacer under each pad should be OK.

Buy new EM bolts if necessary.

[agirard7a]

I had a similar problem when I converted from a 9a to a 9.
The spinner was hitting the cowling. The engine was 1/4" aft from the 9a mount position. I checked in with Vans and confirmed a fix
By adding both an 1/8" prop spacer between the spinner and 2 1/4 prop spacer and also added 3, 3/8" stainless washers behind each bolt mounted to fire wall. I replaced the 3/8" bolts with ones 1/4" longer. The prop bolts still had 3 threads showing aft of the crank flange.

[uk_figs]

I checked that I had enough threads showing behind the prop flange to accommodate a 1/8 inch spacer which seemed the way to go but after a discussion with Sam Tilton of Sabre I think the best solution is probably to order a longer prop extension. The reason for this is a spacer either before or after the prop extension will reduce the amount of penetration of the shear lugs that are in the prop flange for the prop extension and in the prop extension to engage the Catto prop. The lugs can be replaced with longer versions but seems like a lot of effort for not much less $$.

Sam can make a custom length extension and I can also get a heavier (larger diameter) spinner spacer which will further help my CG when loaded.

Thanks for the tips, I will probably have a 2 1/4" 0-360 prop extension for sale for a good price in the near future