cowl to spinner height

prkaye · #1 01-20-2009, 02:55 PM

This is the first place I've come across where the Orndoff video says something that is really at-odds with what the plans say.
In the video, when George is fitting the upper cowl, he drills some temporary alum strips and uses spacers so the front edge of the cowl is sitting 1/8" above the rear spinner plate. I quote: "...this held the cowling an eighth of an inch higher than the spinner plate".
Now, the plans definately say "Block the forward end up to be 1/8" to 3/16" BELOW the spinner to allow for future engine sag" (I added the capital letters for emphasis).
The only way both of these can be correct is if the spinner is 1/4" thick (so 1/8" above the spinner plate is the same as 1/8" below the surface of the spinner). The spinner is less than 1/8" thick.
Ordinarily I'd just follow the plans without question, but other have testified, and I've found, that the methods in the Orndoff videos are never wrong.
What's the deal here? Has the cowling design changed since the orndoff video was made? Should the top forward edge of my cowl be above, below, or flush with the outside surface of my spinner?

yakdriver · #2 01-20-2009, 10:55 PM

Set my spinner 3/16 above the cowl and after 100 hours it is exactly level with the cowl. Don

erich weaver · #3 01-21-2009, 11:11 AM

Ditto on Yakdriver's response

erich

rv8bldr · #4 01-21-2009, 11:27 AM

Yep, me three

alpinelakespilot2000 · #5 01-21-2009, 12:14 PM

There are a ton of threads on this issue re: engine sag. The long and short of these threads is that it depends on whether you have a conical or dynafocal mount and whether you are using the cheap Van's isolators or good Lord isolators. Different combinations of the above will result in a lot of sag on one hand or little to no sag on the other hand. Good luck.

aerolite · #6 01-26-2009, 06:35 AM

Phil,

As Steve M. said in last post there has been a ton of discussion on this. I made my decision based on mounts. I used Lord mounts which have a history of the least amount of sag and went with a difference of 1/8".

Steve

prkaye · #7 01-26-2009, 08:38 AM

OK, thanks guys... I used Vans' mounts, and have set my cowl 1/8" higher than spinner to compensate for future sag.
Cowling fitting is a long and big job, but it seems to be going well. All the firewall hinges are done, now just those long side seams to finish. Then it's on to baffling!

Norman CYYJ · #8 01-26-2009, 08:47 AM

You want the cowling below the spinner NOT above. I think that is what you meant.

prkaye · #9 01-26-2009, 02:19 PM

Yep, sorry that's what I meant.