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RTV question

D

dwilson

Well Known Member
I am ready to rivet the trailing edges of my elevators and glue in the foam ribs on the trim tab.

Another thread mentioned RTV instead of ProSeal. Said to "be sure and get acid free"

Went to the automotive store today and looked for "acid free" RTV. The guy looked at me like I was from New Orleans. He sold me a tube of RTV.

I plan to use this on the trailing edges tonight. Can I use it on the foam ribs too, or will it melt them?????

Thanks,
Duane
 
Wouldn't use it

I wouldn't use RTV. Unless you plan to leave the plane bare aluminum you'll play hell painting the rudder. Where ever the RTV is the paint is not going to stick.

If you don't want to use Proseal, consider epoxy and micro balloons. Slow cure epoxy will give you plenty of working time. When it cures you can block sand the TE to clean it up. Not nearly as messy as proseal with the same results.

Darwin N. Barrie
Chandler AZ
 
Use a piece of smooth steel angle, drill the holes to match the rivet pattern, and hold the pieces that way. just drill every other hole. You won't need glue then. Hold the parts with clecoes and place a rivet in the other holes and shoot them down partially. Remove the piece from the angle and finish on your back rivet plate.

Worked for me,

Roberta
 
Pep Boys?

I got some from Pep Boys - Ultra black permatex, it said low acid or no acid (can't remember) on the cardboard carrier.

Pete
 
A repeat offender advised me to use Marine West Epoxy mixed with cotton flox and it worked fine.
 
Duane,
There's a lot going on in your message. Maybe I can help.
dwilson said:
I am ready to rivet the trailing edges of my elevators and glue in the foam ribs on the trim tab.
Click to expand...
Why use foam? I would install small aluminum ribs. It's probably more work to make, but less work to finish and it will last forever. Whatever you stuff over the foam (slurry or flox) will eventually crack and the paint will chip. Aluminum and fiberglass have different coefficients of expansion and cracks are inevitable.

dwilson said:
Another thread mentioned RTV instead of ProSeal. Said to "be sure and get acid free"
Click to expand...
Three things here. First, I would never put RTV where you want to paint. Paint just won't stick to it and even if it does, it won't stay there for long. Two, RTV will not hold as well as ProSeal and is generally, not that good of an adhesive in this situation. The RTV will allow the part ot move just slightly, thus assisting in the aforementioned cracking. Third, acid-eating RTV is an urban legend. When the RTV sets, it is basically inert and no threat to "eat a hole in your aluminum" as the legend goes.

dwilson said:
Went to the automotive store today and looked for "acid free" RTV. The guy looked at me like I was from New Orleans. He sold me a tube of RTV. I plan to use this on the trailing edges tonight. Can I use it on the foam ribs too, or will it melt them?????
Click to expand...
Yes, RTV will dissolve certain foams. It all depends on what you are using. All round, I don't think you'll be happy with foam ribs but it's your rig, do what you'd like. A previous poster mentioned using flox as a cover. You can do that but that stuff is a real bear to sand and that's not really the intent of flox. What you really want is a dry mix of slurry (microballons). I would cover it with one layer of glass cloth first before applying any surfacer as this aids adhesion.

(Graduate of the Rutan School of Fiberglassing)
 
arffguy said:
These are the interior parts, right? What is the worry about painting over it????????
Click to expand...

The foam ribs are inside the trim tab just to stiffen it a little bit. They are what Vans calls for in their plans.

I appreciate all your input. I will use ProSeal and finish these parts up this weekend!

Thanks
Duane
 
Last edited:
Dumb question

Dumb question from me but what RV is this? I dont recall foam ribs for the elevator trim tab when I did my elevator (RV-7) did I miss something on the plans? The only riveted trailing edge was the rudder where I used the tecnique outlined by Roberta with the aluminum angle and proseal which worked very well and produced a very straight edge. :confused:
 
uk_figs said:
Dumb question from me but what RV is this? I dont recall foam ribs for the elevator trim tab when I did my elevator (RV-7) did I miss something on the plans? The only riveted trailing edge was the rudder where I used the tecnique outlined by Roberta with the aluminum angle and proseal which worked very well and produced a very straight edge. :confused:
Click to expand...

Building an RV9A quick build. The trim tab that hangs off of the back of the L. elevator has two little foam "ribs" that get glued into place before closing the trim tab. The instructions suggest glueing them in with ProSeal.
The trailing edges that get glued are the rudder and the elevators. I think the ailerons and flaps may also have glued/riveted trailing edges, but not sure without the plans in front of me.
I wanted to do the elevator and trim tab glueing all at the same time so that I only had to mix one batch of ProSeal.

Duane
 
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