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Tips on elevator tips!

C

crabandy

Well Known Member
How did most people glass/fair-in the elevator tips to the front of the lead counterweight on the 7? I want to keep it as simple as possible and not fiberglass the tip to aluminum gap. I'm debating on laying glass over the entire front if the elevator horn (covering lead and 2 counterweight screws). In order to do this I think I need to cut the vans tips 1/4-1/2 inch back from the front face of the counterweight to form a scarf joint and build up the top and bottom radius of the horn (inboard of the tip) with flox to match the shape of the elevator-tip and lay glass over this. Any ideas?
Thanks,
Andy
 
crabandy said:
How did most people glass/fair-in the elevator tips.....
Click to expand...
Andy,

I'm not most people and my solution may be a bit unconventional, but here's what I did: Using a heavy pair of scissors, I cut out pieces of .025 aluminum stock, trimmed and sanded to fit, then bonded in place using proseal. I don't know how you can get much simpler than that.

30bmcqo.jpg
 
Try this

Some has been written before on this (check out DanH posts...fiberglass guru).

Here's what I did:

1. Create a scarf joint on the existing tip... as much as possible.

2. Cover the lead/screw area with packing tape.

3. Lay up a couple of plies of fiberglass cloth over the tip. If you have peel ply it will probably save you time later because...

4. You then sand everything smooth and blend it in.

5. If you have a large gap to fill up you may need to lay up some cloth and then flox over it, then cloth on top of that. Mine have a little "arc" in them to match the horizontal stab tip.


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Don
 
Thanks for both of your replies! I've looked at "hours" of fiberglass on the threads and they've helped a lot, especially Dan H's.

Cfiidon those were the exact photos I was looking for and what I had in mind. Did you flox/epoxy between the outer surface of the lead and the inside of the tip to glue it on? My tips have a slight gap 1/16-1/8 to no gap around the counterweight I was going to paint the outside of the counterweight with 1/8th inch of flox, install the elevator tip and squeeze/clean up excess flox, let it cure to a gel state than glass over as in your photos.

Rick, do you have any pics from the front how the aluminum fits/looks?

Thanks,
Andy
 
I don't know if this is important to you but ...

I don't know if this is important to you but the recessed area at the ends of the horizontal stabilizer and the elevators (primarily the elevators I think) are a significant source of drag. If you look at them and imagine the 200 mph airflow entering there and traveling along behind the leading edge of the elevator I think you can see why. I filled and glassed these and picked up on the order of 3 kts (that is MAJOR increase in speed). I got no such increase from filling the ends of the ailerons or flaps. My RV-6A rudder has no "horn" so I have not tested this area,

Bob Axsom
 
Thanks Bob,

It is!

So far my plan is to attatch/fair out the elevator/rudder tips to their final shape prior to cutting and filling in the stabilizer tips so hopefully I can make an even gap of 1/8 inch between the two with a radius to match the arc of the counterweight horn on the inside of the stabilizer tip.
 
What about expanding foam?

Any thought to using spray-in expanding styrofoam (cans are sold at HD and Lowes)? Seems like you could spray it into the tip, let it expand/fill, then trim it off flush at the opening once it has set up.

I'm approaching that point so the timing for this thread is perfect.
 
Glassing in tips

What worked for me was to buy blue foam. Then cut into shape and recess about 1/8 in from the end of the tip. Lay in a couple layers of glass, just enought to create a stiff layer. Then put gasoline on the blue foam and it will be eaten away. Then a couple of more layers from the inside. I then mixed microballoons and epoxy resin to fill in the outside of the tip. Shape and sand to your liking.
 
Hi Bob,
Can you explain further please ?
Are you saying you filled and smoothed the existing gaps ?
Did you modify the shape or radius of the elevator balance horn ?
Thanks much
Mike
 
I did it this way. Spray-in foam slightly recessed...carve out a small chamfer in the corners...fill these corners with flox...then glass over the top of the foam...finishing up with filler/sanding for cosmetics.

But two things I considered. One, get a product that claims it wont retain water and test it. Two, I primed all parts before adding foam...just in case moisture gets trapped inside at least I have a backup for corrosion.

Disclaimer...my plane is not flying so results are inconclusive...wil it crack in five yrs? dunno? But I will say Rosie did it this way I believe and when I seen his plane over the summer...no cracks and still looks great and lots 'o hours on his airframe. It sure does look nice and as Bob said in another post, should help with speed [Edit: I was referring to the HS and elevator ends, which I also did].

Keep in mind, its a fair amount of work to get it looking nice if you arent used to doing it.

scrollF4 said:
Any thought to using spray-in expanding styrofoam (cans are sold at HD and Lowes)? Seems like you could spray it into the tip, let it expand/fill, then trim it off flush at the opening once it has set up.

I'm approaching that point so the timing for this thread is perfect.
Click to expand...

From Rosie: Ron is absolutely correct - exactly as he described (flox and such) with no cracking after ~3300hrs ;-)

Elevator_Tip_using_flox.jpg
 
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Tip caps

Actually,
I'm now leaning toward Rick Galati's approach, because I'm all about the "KISS" factor. Rick, how did you get the .025 "plates" to set in flush so nicely? And how long have you been flying those tips (indication of your handywork's durability)?
 
scrollF4 said:
Actually,
I'm now leaning toward Rick Galati's approach, because I'm all about the "KISS" factor. Rick, how did you get the .025 "plates" to set in flush so nicely? And how long have you been flying those tips (indication of your handywork's durability)?
Click to expand...
Nothing to it really. I traced the pattern outline of whatever tip I was working with onto .025 aluminum sheet with a Sharpie, cut the pattern out with scissors, then fine shaped the "plate" on my bench sander so that it sit nice and flush inside the tip. Inside the (removable) tips themselves, I ran a bead of proseal (or as in the case of my -8 shown below, used cotton flox and epoxy) to make that bond. As most people know, proseal or epoxy accept paint real well. My -6A has been flying since 2005 and I can happily report no degradation of the work has occurred whatsoever. Naturally, I anticipate the same long term result with the -8.

1e4ep2.jpg
 
Be very, very sure of whatever methods you choose. This is one of those places where simple things can bite. Loose bits in the stabilizer-elevator interface can cause a locked elevator, and that can make you dead as a canned ham.
 
Smilin' Jack said:
.....what is cotton flox?.....proseal is the same stuff they use on the tanks?....
Click to expand...
Jack,

Proseal as described in my previous post is the same stuff we use in fuel tank construction. Cotton flox, available from a variety of sources is finely chopped up.....cotton:

http://www.aircraftspruce.com/catalog/cmpages/flockedcotton.php

Typically, I stir the flox into a cup of West System epoxy until the mixture achieves a "peanut butter" like consistency. I'm sure others can tell you more about the technical aspects of what goes on when you do that but I can you tell from a practical standpoint and longtime experience that it strengthens the epoxy dramatically. I've long used cotton flox and epoxy as a structural "liquid shim" in a variety of situations and outlined many of the possibilities here:
http://www.vansairforce.com/community/showthread.php?t=6750&highlight=Liquid+Shim

Hope this helps.
 
Before I filled mine I had "fiberglass never done it before syndrome" so I bought some glass supplies including cloth, flox, micro balloons, and the chopped glass stuff ( I cannot remember the name of it right now). Then I went around the barn and applied some to all kinds of things to test the adhesion, crack filling ability, etc. I fixed a hole in my bush hog, stuck some on a rusty old trailer frame and played with some old fiberglass junk to kind of get a feel for it. I found that wax paper and saran wrap are valuable tools as well. This got me over being afraid of it and I even got to where I kind of liked working with the stuff. Yes, the bush hog is holding up fine as well.
Good luck and let us know how it turns out for you!
 
OK Will Do

mvs163 said:
Hi Bob,
Can you explain further please ?
Are you saying you filled and smoothed the existing gaps ?
Did you modify the shape or radius of the elevator balance horn ?
Thanks much
Mike
Click to expand...

I did the closure of the fiberglass tip opening with blue foam and fiberglass as usual and it came out well but I left the recessed area at the ends of the horizontal stabilizer and elevator as designed - about a 3/4" deep semi-rectangular shaped pocket. In looking at the airplane (RV-6A short tail 6 no rudder horn) in my personal quest for speed I saw the way that Van designed these and the other control surfaces for ease of closure riveting with solid rivets. I said to myself if I fill all of these pockets the drag will go down. So I progressively did it with balsa wood and a flathead sheet metal screw and dimple washer. The only place it made a positive difference was in the stab/elevator interface and there it was a significant gain in speed. On the elevator this is the area aft of the counterbalance weight.

Bob Axsom
 
scrollF4 said:
Hey Rick, why did you chose to make your tips removable? For inspection purposes?
Click to expand...
Sid,

Personal preference drove me make the tips removable, nothing more. My background is military aircraft production work. Part of the design philosophy in that environment is that nothing.....but nothing is ever permanently covered in a military aircraft, at least not on any of the combat aircraft I ever worked on. Also, budget minded as I am, having the tips removable has given me the flexibility to remove them on a whim, take em home and paint the tips at my own convenience. Removing and reinstalling them takes only minutes, something I've already done a few times now. Once, I even uncovered a mud dauber home firmly attached to the horizontal stab. structure. Were it not for removable tips, it would have remained unseen and the mud still be in there. Finally, drilling out and then replacing pop rivets just seems a hokey, low rent alternative to me. Like I said, personal preference. As a builder, having that option is a major part of what drove me to build an airplane in the first place.
 
RV7Ron and Rosie,

When you glassed over the top of your slightly recessed foam, what weight of glass did you use, how many layers, and how far did you extend these layers on the horizontal surfaces of the stabilizer and elevator?
Currently I only have the ACS #7781 8.92 oz/sq yd crowfoot weave, would this be a good cloth to glass this in with, or should I get some thinner/light weight stuff so it's easier to fair it into the horizontal surfaces of the stabilizer and elevator?

Thanks,
Andy

From Rosie: I used the lightest stuff out there and used several layers to build up the part that was left recessed. There is no need to overlap to the top or bottom of the control surface if you used flox around the edges; you just have to overlap the glass onto the flox. When you then sand, the cloth will fall off when the sanding block hits the flox. The recessed glass is then flush with the flox (thus the need to have the glass recessed else you'd hit foam when you hit flox). Will try to find another picture if that would help.
 
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