Electric trim retrofit RV8a

[Majorpayne317641]

Hi,

I am trying to figure out if the lead counterweights in the elevator can be removed without drilling out rivets on the skin? When I do the swap I am going to check the balance of the elevator and I’m afraid I will need to put new lead weights to start the balancing from scratch. Anyone else done this? Thanks.

 

[Jonnyb]

Depends how old your kit is, but on the -8 the counterbalance weights are secured with a nut and screw. You will have to remove the fibreglass tip to get to them though.

 

[Majorpayne317641]

Thank you, mine is according to the plans as far as I can tell. I was afraid that there is an additional nut and screw behind the rib. The tip shouldn’t be too hard to remove.

 

[Mikeyb]

I happened to have one of those kits in a box. It only weighs 5 ounces. It’s right near the hinge line. The counterweight arm is 4 times further back from the hinge line which implies you could balance it with 1.3 ounces of added weight on the inboard side without messing with the fiberglass. A lot of builders use a weight attached with a bolt near the tooling hole in the counterweight arm as trim weight after the part is painted.

There is some debate about how well the elevators have to be balanced. It’s probably worth asking Vans support
Mike

 

[Majorpayne317641]

When I spoke to builder support they were a little perplexed as to why I wanted to have new lead weights on hand. The tech said it’s pretty much the same weight. When I asked again, but shouldn’t I check the balance and adjust if not in balance? They said well yeah, but it will be about the same. Not sure if that was the specific tech saying it’s fine or if that’s the real answer. No way to know unless you flutter test with elevators that are slightly out of balance…

I realize in engineering it is or it isn’t but when you reach that point of it isn’t and it happens to result in severe consequences, I don’t push those limits. We used to say measure with a micrometer and cut with an axe back in my ME undergrad days.

Oh and one last note…I GUARANTEE that with the cheap paint job they threw on my aircraft from the second owner I bought it from…the elevators were not checked for balance.

I happened to have one of those kits in a box. It only weighs 5 ounces. It’s right near the hinge line. The counterweight arm is 4 times further back from the hinge line which implies you could balance it with 1.3 ounces of added weight on the inboard side without messing with the fiberglass. A lot of builders use a weight attached with a bolt near the tooling hole in the counterweight arm as trim weight after the part is painted.

There is some debate about how well the elevators have to be balanced. It’s probably worth asking Vans support
Mike

 

[Mikeyb]

My hunch is it won’t take much to get them to balance. No way are you going to have to replace the weights. If you have to remove some weight you can just drill through the glass into the lead. Do it on the bottom side and fill it after. Adding weight to the inside of the rib with screws is done all the time.