What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Thrust offset and front of cowl

FinnFlyer

Well Known Member
According to dwg 33, the engine is supposed to have 1.25 degree offset.
That translates to a bit more that 1/4" across the 13" spinner plate.

Looks like that is not built into the cowling. Mine is greenish fiberglass with visible honeycomb and no visible scribe lines.

So it looks like I need to build out the right side of the front of the cowling.

Which brings me to this question: What is the minimum distance between cowl and spinner you successfully have that still allows removal of cowling?

(Plans calls for 1/4", but I'd like to make that smaller.)

Finn
 
I have built 2 RV6 James cowlings.
The offset is designed into the the engine mount.
Once you have the engine and prop/spinner mounted, you fit the cowling to it! Yes it is offset but only you will know it.
The offset is right and down a bit as well.
I tried for 1/8" space but it is tight...3/16 will work, 1/4 is ok too.
Fitting the cowl...I started tight to the spinner then as I tweeked the firewall fit, the gap appeared.
Best of luck. Messy work but rewarding.
 
Spinner / Cowl clearance

I used 1/4? per plans on my 3 and the spinner and cowl are scratched up with a 2 blade prop 😒
So, the 4 I am finishing with SJ cowl and 3 blade prop has generous gap. The lower cowl leakage is contained with Dave Anders style wool felt seal on the crank to prop Saber extension. Just food for thought.
 
A couple things..

I built my -4, and had the second generation blue/green cowling with honeycomb core. I believe third generation are all pink now. Mine definitely had offset built in it, which is easy to see when you stand it on end and look at it from several feet away. It all worked out perfect with the dynafocal 1 engine mount. I would not advise going less than the 1/4" space, as removal of the lower cowling is not easy. Take my word of advise, and keep these things in mind to get it just right. 1) The back edge of the spinner can be left long and trimmed to get the gap fine tuned. 2) Make sure you have your gear leg fairings installed before you final fit your cowling, as the shape of the trim-out at the gear intersection will be the biggest factor in how easy your lower cowling can be removed. The gear leg fairings will need to be cut/angled slightly so the cowl drops past them. I made all my trim-outs so the upper gear fairing (you have to custom make it),has minimal edge coverage giving the most cowl clearance I could get. The fit of the snorkle to the FAB will also be a factor in things, and I recommend your flex boot allows you to pull straight down with no forward movement required. I still use protective tape on my lower cowling in the areas behind the spinner during remove/install as slight contact is imminent. Take your time, and it keep these things in mind. The cowling fit/finish is one of those things you want to be good looking, but also easy to get open/closed on a regular basis.
 
Slip a micro fiber cloth between the spinner and cowlings during removal and installation, it will prevent scratching.
 
Back
Top