What's new
Van's Air Force

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

Removable rudder tip for RV-7

idubrov

Well Known Member
I am currently building an RV-7 rudder, and I am considering changing the plan to make rudder top tip removable.

I have already drilled and dimpled the last three holes on the trailing edge on both of the skins (as per plans, since the space is "tight" there, they suggest you to dimple it before the skins are riveted).

Now the problem is that dimples are for the CS4-4 rivet, which uses -4 dimples. The #4 screw would fit the dimple, but the hole is too big for it. #6 screw requires a slightly deeper dimple, but the hole size is about right for it.

Also, the edge distance from the hole is 1/4", which is both defined by the tip rib (because of its flanges facing up) and also it is the minimum edge distance on the fiberglass as per plans (however, this distance is given assuming the CS4-4 rivet).

Here is what I am thinking:

1. Go with #6 screw as the three trailing holes are almost dimpled for #6 already.
2. Unrelated, but trim the fairing so it sits deeper (see the first attachment, currently it hits the tip rib flanges too early so there is a big gap). Or should I just epoxy that gap, as per Section 5.18 (currently the gap is ~1/8").
3. Epoxy a backing plate of aluminum (can I use T-88 epoxy here, since I have it already?) to the fiberglass rudder tip so it adds a bit of the strength. I don't think this is strictly necessary, but aluminum backing strip should remove any concerns about the edge distance. Right?
4. Install K1000-06 nutplates on the fiberglass / aluminum backing plate, countersink fiberglass as necessary to take #6 dimple.
5. See how well it would fit, attaching it to via the three (six) existing holes (without re-dimpling them for #6 yet). In the worst case, I would reorder R-909 and go with the original plan to use CS4-4
6. If everything goes well, re-dimple the holes to #6 (any concerns with that? like metal fatigue on the skin?), drill the remaining holes and dimple them for #6. For re-dimpling I would make female dimple for #6 on a steel plate and drive the male #6 dimple with the rivet gun.

Does that sound like a reasonable plan? Never worked with fiberglass before.
 

Attachments

  • IMG_5467.jpeg
    IMG_5467.jpeg
    221.2 KB · Views: 168
  • IMG_5468.jpeg
    IMG_5468.jpeg
    172.1 KB · Views: 217
  • IMG_5469.jpeg
    IMG_5469.jpeg
    192.3 KB · Views: 150
Last edited:
Thoughts

Point no. 2 to trim the fairing to eliminate interference with the rib flange sounds reasonable. Otherwise, it's not clear why you want to make the tip removable? The standard method of fixing per the plans is sound. If there is ever a need to remove the tip (rare and probably never) then the rivets can be drilled out and replaced with new ones.
 
Rudder tip

Not sure why you want it removeable but it's Expiremental so go for it. I bonded and riveted mine. It's very permanent.

1. Might ask Vans to be certain.
2. Trim the flange so the cap fits. You'll have to do it in other places too.
3. I did. Thin stuff. Helps provide some structure fir fasteners.
4. If I did nutplates, that's how I would do it.
5. Three might be too few and no need to buy a new cap. It's fiberglass. Just repair it.
6. That's one way. Better make sure nutplates will fit inbthe space too.
7. Suggest playing with some fiberglass first. It's easy but easier when you have a little experience. Also look at how the cap matches the VS cap. Mine was pretty bad. Easiest method is to mount the rudder and treat both caps as a single unit then cut the gap and clean up.
 
I guess, you are right. Maybe, I don't need them removable after all.

Thanks!

I wish the -4 had a removable tip.. I want to add a red beacon but the builder riveted and filled the seam.. I don’t want to have to grind out the filler for it.
 
It's helpful to make the bottom tip removable if you mount a tail light into the aft end of the rudder. Easier access to the wiring.
 
A bit of a PITA but can be done.

My upper tip(s) is are removable. Same as other tips, just less space to do it. I used #4 screws. I suggest if you do that, wait until it is finished to use stainless screws as they are weaker and more prone to driver damage. #4 nut plates etc are (were?) a bit more difficult to find, especially floaters.

I can not address the pros/cons of doing so, just that it can be done.

There is some experimentation (maybe debate and personal preference) on making dimples vs countersinks as it can be hard to remove with all the "teeth" of dimples holding it in place.
 
Back
Top