Your rear end is too heavy

I’ve seen many threads exploring ways to cope with w&b issues ensuing from the use of a light engine and prop combination (320 or 360 with a Catto, for example) on an RV-7. It got me to wondering about the relative weights of the fiberglass bits of the empennage. Could their be useful weigh savings by substituting hydroformed aluminum pieces in their place? If anyone has an as yet unassembled -7 empennage kit and would be willing to weight the fiberglass parts it could lead at least to an interesting discussion.

Jim

-6

Jim, I’ll weight my -6 parts today. Maybe close enough?

3' x 3' .024 aluminum with blue wrap on it = about 2 lbs on my scale.
stock glass intersection fairing with paint = 1 lb
Horiz, vert, rudder & elevator fairings = about 2 lb (old gel coated type fairings, no paint)

So, if in the end you chew up about 2 sq yards of aluminum material into small pieces, you save 1 lb - but you get tips like a P-51 & and add countless hours to your build.

Better to use a few hours of planning & pick your equipment options to meet your desired CG results.

Thanks Ralph. No need to get out the scale.

Thanks. Just what I needed.

Jim

Aft CG...

I have and RV7A, IO-360 and Catto Prop. I too have noticed the CG going back in lower fuel states. One time I was fully loaded with a big guy in the right seat and the baggage compartment full. Landing with about 7 gallons of fuel, I thought my trim motor had stopped functioning. It was not trim motor, It got my attention and I was now cautious in low fuel states. I had a few failures of Prestolite Starters. I think the builder must have put it on because it was heavy. Not a great starter in my opinion. I decided to try a Skytec high torque starter. It is 7 lbs lighter than the Prestolite. Not helpful to my CG situation in low fuel states. I decided to mount 10 lbs of Ballast at the same station as the starter. The Sam James cowling would not fit back on with the full 10 lbs the way I had it mounted, so I cut off about 1 lbs. That gives me about 2 more pounds on the nose and I can tell a positive difference in the handling in lower fuel states....

Inlet rubber connector

Jeff

Looking at your photo above I note that the rubber connector between the filter air box and cowl looks very stiff.
If you look at Vans FAB update they now use a much softer silicone to allow for the movement of the engine.
I appreciate yours is different but you still need to allow for the movement.


Regards

Peter

inlet

kiwipete said:

Jeff

Looking at your photo above I note that the rubber connector between the filter air box and cowl looks very stiff.
If you look at Vans FAB update they now use a much softer silicone to allow for the movement of the engine.
I appreciate yours is different but you still need to allow for the movement.


Regards

Peter

Click to expand...

Peter,

I gives a little. I will look to see what you are talking about. I have a Sam James aftermarket cowl. Do you have a picture of yours?

Jeff

Jeff

Link to vans updated instructions which details the connector

https://www.vansaircraft.com/wp-content/uploads/2021/06/FAB-320-360-540-Air-Box.pdf

As for mine it’s what I’m currently working on the FAB. I’m finalising wether to use soft silicone (Vans lastest instructions) or as Sam James cowls use neoprene. If neoprene I need to find out how thick.

Just a observation when I saw your photo.

Regards

Peter

PS sorry to original poster I’ve started a thread drift