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Balsa Wood swelling up in HS tip

tom paul

Active Member
I had to leave the plane outside a little while back when visiting my parents in Rochester. The local FBO wanted $175/night for hanger space, so I went for the $15 tie down. It rained a lot that night. The when I departed a couple of days later, I noticed the elevator counterweight was slightly contacting the tip of the HS. It wasn't much, just a little kiss as it moved through neutral. After a few days without moisture, it went back to normal. I do see some slight cracking in the paint around there, and there is ever so slight movement to the tip of the HS if I tug on it. I did not build this plane. I have heard that the tip is Balsa wood, but I don't know that for sure. I suppose putting a coat of sealer over the cracks would help keep it dry in there, in case I need to tie down in the rain again.
Has anyone else had this issue? And, do any builders have any advice for me?
Thanks,
Tom
 
I had to leave the plane outside a little while back when visiting my parents in Rochester. The local FBO wanted $175/night for hanger space, so I went for the $15 tie down. It rained a lot that night. The when I departed a couple of days later, I noticed the elevator counterweight was slightly contacting the tip of the HS. It wasn't much, just a little kiss as it moved through neutral. After a few days without moisture, it went back to normal. I do see some slight cracking in the paint around there, and there is ever so slight movement to the tip of the HS if I tug on it. I did not build this plane. I have heard that the tip is Balsa wood, but I don't know that for sure. I suppose putting a coat of sealer over the cracks would help keep it dry in there, in case I need to tie down in the rain again.
Has anyone else had this issue? And, do any builders have any advice for me?
Thanks,
Tom

Did you wrap the balsa in fiberglass cloth? I used balsa in mine as well, but is completely encapsulated.
 
Tom, the shells of all the empennage tips are fiberglass, but the ends of the shells are typically filled by the builder. The usual method is to tack in some kind of bulkhead, then glass over it. Here it sounds like your builder used a bulkhead material which swells with moisture, quite possibly balsa.

Given control jam is serious issue, I'd recommend a rework of those bulkheads.
 

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I agree completely with Dan - you need to rework those to prevent a possible control jam. Back when I built my -8, it was common (maybe in the instructions, or just passed on from other builders) to use a piece of balsa in there, then fill with micro to shape. I think I used a balboa plug, made a fiberglass bulkhead, then chipped out he also, then finished with micro. Lots of ways to do it, so long as you don’t ever get zero clearance to the elevator horn….
 
I'm in complete agreement with the need to rework the area.
Drill a small hole in one and then examine the wood/filler with a magnifying glass to see what it is.
I'm in agreement that it is probably wood.
I used a thin piece of extruded poly urethane (blue or pink board used in construction) tucked in to hold the fiberglass work smooth. It will not expand. I just happen to have gobs of it being in the home building business.
Art
 
End plug

Mine is a piece of fiberglass. I layed up 4 layers between two sheets of 4mil plastic. That was cut for the tip bulkheads.
Cut to fit inside. Flox it inside flush to the outer edge.
Cover the outside with a single layer of glass or just micro over it and finish.
 
The instructions for the RV-14 are easy to follow. You can take a spare scrap of aluminum sheet, make the slight bend to follow the elevator counterbalance tip shape, then lay down several layers of fiberglass on that (be sure to wax the aluminum so it will pop off easily).

Once the fiberglass hardens, you can cut and sand it to fit inside the HS tip end. You can mix up some 5-minute epoxy to tack it in place, then put another layer of fiberglass inside to hold it in place permanently. Fill/sand as needed. I set back the fiberglass about 1/16" inside the fairing, then filled with micro and sanded to a concave shape to keep the clearance constant with the counterbalance arm.

IMG_3051-M.jpg


IMG_3058-M.jpg
 
No Balsa!!

Yeah, whoever built it should not have used balsa. It swells considerably. Might have rework as Dan mentioned. Not a huge job but your paint will be messed up. There are a few options there.
 
Balsa is in the Build Manual for the RV-6

Yeah, whoever built it should not have used balsa. It swells considerably. Might have rework as Dan mentioned. Not a huge job but your paint will be messed up. There are a few options there.

The build manual for my RV-6 shows balsa as one of the acceptable options for closing the elevator tip. That's what I used in 1997 and it still looks as good now as it did then. It is encapsulated with a coat of resin for moisture resistance.
 
thanks guys!

Sounds like I have some work to do. I didn't build this, or any other airplane, and I am not an experienced fiberglass guy, but i can figure it out. I am not clear on exactly what to do, or where to start. How much am I to disassemble, for example.
The front of the tip is showing signs of having had a few hangar bumps, and a poor color matched touch up, so if I am going in and matching paint, I should address this as well. Any advice would be appreciated.
Here are some pictures. the paint on the tip bulkhead is very cracked.
https://photos.google.com/photo/AF1QipNnZcxUQBnhfu0AwpeP4G4GIB0rW6pYSBcfP1r8

https://photos.google.com/photo/AF1QipNBU2zkrJ6IttmlEioJDp4VH276MLWTDsRM2f-E

https://photos.google.com/photo/AF1QipO62qnHogvFhnO6m-gm44ArneCkVT9dMWxoNsc1
 
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The build manual for my RV-6 shows balsa as one of the acceptable options for closing the elevator tip. That's what I used in 1997 and it still looks as good now as it did then. It is encapsulated with a coat of resin for moisture resistance.

Yellow pine for me in 1997, 1998. It was there and relatively light. Sealing it is the key. Otherwise, any wood would swell.
 
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Thanks. I see them but not sure if anyone else can

The pictures on google are not viewable, error message 404. If the pictures are uploaded to VAF instead (click on the paper clip to do it) then we should all be able to see them.
 
Hopefully these pics work
 

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This is what it looked
Like when it was
Swollen and rubbing. It has since shrunk back and is not touching.
 

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elevator tip rubbing

Hmmm. The paint cracks on the front side of the stabilizer tip look like they could be from "hangar rash" type event. Looks to be an impact on the left most crack on the front view photo. The back side cracks on the horizontal stab tip could well be from the underlying filler (balsa?) expanding and contracting with moisture.

The underlying filler in the back side of the stab tip needs to be dealt with, as in removed and replaced with a more moisture stable material. I would also want to see more of a gap between the stab tip and the elevator tip corners...something around 1/8" as the elevator tip swings through. Control surfaces rubbing is NOT something to tolerate. It has the potential to jam, and end badly.

That said, all this is relatively easy to fix with some fiberglass and paint work. Lots of folks around here can help with those things. Good luck with the repairs.
 
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That said, all this is relatively easy to fix with some fiberglass and paint work. Lots of folks around here can help with those things. Good luck with the repairs.

Thanks Steve!
Regarding fixing it, I would like to fix the hangar rash result as well. It was like that when I bought the plane. I'm wondering where to find info about how to proceed. I'm not afraid of learning to fiberglass, but I need to know where to dive in, of I want to fix the front of the HS tip as well. I don't want to just start sanding and grinding and not know anything about the underlying structure. Builders may be chuckling at my lack of knowledge about this, but any tips will be appreciated.
 
No worries. We all started from zero at some time. (My rv was my first experience with aircraft sheet metal and fiberglass.)

I can PM you some suggestions on how to proceed, along with some photos of mine….but it will take me a couple days to pull it together.
 
Fiberglass

Thanks Steve!
Regarding fixing it, I would like to fix the hangar rash result as well. It was like that when I bought the plane. I'm wondering where to find info about how to proceed. I'm not afraid of learning to fiberglass, but I need to know where to dive in, of I want to fix the front of the HS tip as well. I don't want to just start sanding and grinding and not know anything about the underlying structure. Builders may be chuckling at my lack of knowledge about this, but any tips will be appreciated.

Tom
Fiberglass is pretty easy. The Bodisatva is Dan Horton. He posted a "Sticky" in the Fiberglass section we all use as a reference. I've used his techniques on my bird. Feel free to browse my blog (below). The three Kitplanes canopy articles cover fiberglass from layup to paint. Happy to help by phone as well. Shoot me an e-mail (below) for contact info.
 
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