Empennage Fibreglass tips

[Glingerburner]

Hi, this is my first posting so you'll have to bear with my ignorance.

I'm just about to complete the empennage on an RV9A and while I'm waiting for the wings to arrive, I thought I'd have a go at the fibreglass work. The tips I have been sent for the HS are about 2 inches too long ( front to back) What is the best way of marking these to cut them down. Do I cut them square at the junction of the HS front sapr and the nose rib or Do I temporarily mount the tips and then draw lines where the elevator tips meet them, if so what is the maximum and minimum clearance between elevator tips and HS tips? What is the best tool to cut fibreglass?

Secondly, the rudder bottom has a line scribed into it which will allow the rudder horn to seat correctly, is this the correct cutting line to follow all around?

I'd be grateful for guidance since the instructions are short of advice and there isn't much about installing tips (apart from reinforcing) on the forums around the world.

 

[TSwezey]

There are many posts throughout the website on this issue. Someone will probably reply that can tell you quickly but the quickest way for you to get the info would be doing a search on it. Quick answer ..Mount the elevators and leave atleast 1/8" gap between elevator tips and the HS tips. I used a cutoff wheel to cut the fiberglass..You can use a dremel cutoff wheel if you have one. Remember you can always cut more off but it is hard to add on!
If the rudder line is about a half inch above the indentation then that should be the correct line.
Good Luck!

 

[Robert M]

Hi Glingerburner, welcome to the forum.

What I did was mount the HS tips without cutting any length off, got 'em where I wanted them, drilled them and clecoed as I went, then I removed them. Then I mounted the elevator tips the same way - got 'em where I wanted them and drilled/clecoed. Now, with the elevator tips swung out of the way, (up or down), I replaced the HS tips. I rotated the elevator tip until it was against the tip of the HS and marked a line along the shape of the elevator tip onto the HS tip. I did this for both sides - top and bottom. After the lines were marked, I removed the HS tips and used the dremel heavy duty cutting wheel to cut along the line. Then I used a dremel sanding disk to shape the HS tips to fit the elevator tip contour to the 1/8" +/- gap.

As for the rudder bottom piece, most builders have said .."wait until you have the HS and rudder mounted on the fuselage before cutting and shaping". You can get a beter alignment that way, or so I'm told. I recently found out that it's even more critical on the -9's as the bottom rudder fiberglass can interfere wit the tail wheel cables and springs.


I hope this helps.

 

[scard]

Trim & fit, trim & fit, ...
I wouldn't advise to ever fully commit to a scribe line on the fiberglass parts from Vans as a trim line. I would almost ignore it and trim to an edge that works for you.

 

[Greg Arehart]

Belt sander technique

For my fiberglas work, I have used a hand saw (dedicated to fiberglas after the first stroke because it gets too dull for anything else very rapidly) to rough out the line/curve I want. I bolted a belt sander (hand one, not a benchtop one) to my workbench so it hangs off the side just a bit, and use the belt (I'm using 100-grit) to gradually take down the edge. For straight edges, I use the bottom of the belt where it is flat; for curved parts, I (CAREFULLY) use the roller on the front of the sander. But be careful, one can easily sand away too much too fast. As noted by Scott, trim and fit, trim and fit.

For my HS tips, I did similar to Robert and left about a 5-7 mm gap. I ended up then fabricating an Al rib to attach to the tip. I used a couple of bits of epoxy to tack this to the fiberglas, and then laid up a layer of fiberglass cloth on the inside of the rib overlapping the HS. If your rib fits very well, this is easy. If, like me, you end up with a less than perfect fit, it helps to put some paper tape on the outside of the rib/tip assembly to keep the epoxy from drooling out of the fabrication before it sets up (I'm certainly not much of a fiberglas worker - one good reason for an Al airplane!). Because there was a slight bit of a curve to the HS tip and the rib was basically straight, I then added some lightweight filler material to the outside (aft) part of the fabrication so it looks nicer (my fiberglas work on the inside looks, shall we say, "less than attractive").

For the rudder, I found that the faint line worked about right for the cut there.

Hope this helps.

greg

 

[Glingerburner]

Thanks Guys. I've done a lot of searching for that information, but for some reason I'm not getting answers. Besides,I think it is useful to get as much as possible onto the specific RV-9 forum and it would be easy to miss the point about mounting the rudder bottom after fuselage attachment on a general RV forum.

This is all really useful and delivered with such speed and from so far away! Happy Christmas.

Richard