Sealing the fuselage tubing against internal corrosion (merged)

[Winston L.]

Re: Price and availability of wing lift struts

Winston, thanks but I am not following this part;

"When it is welded you can't see the holes they are to give a passage way for the oil to flow down the tailpost and into the longerons etc."

Does "it" refer to the fuselage or the hole in the bottom of the tailpost?

Do you have this drain hole at the tail post bottom like I do?

Dave

My understanding is that they drill each tube so that they are open to one another so that the inside of the tubes will not be isolated from eachother.

That way the oil has access to the entire interior of the tubing structure.

It also sounds like there is a weep hole so the excess oil may be drained.

[1938BF50]

Re: Sealing the fuselage tubing against internal corrosion

Here in the bike business we do the same for quenching during heat treat. We have to locate vent holes so quench media can completely fill the tubes in the bike frame and allow steam to escape. Where a tubing/weld cluster happens you need to "vent" the blind end of the tubing joining another. In the case of the aircraft frame, it is my GUESS that the longerons were either opened up via drilling or even "punched" with the torch while fitting up and preheating that cluster. Hope this helps to clarify?

[crispy critter]

Re: Price and availability of wing lift struts

Winston, thanks but I am not following this part;

"When it is welded you can't see the holes they are to give a passage way for the oil to flow down the tailpost and into the longerons etc."

Does "it" refer to the fuselage or the hole in the bottom of the tailpost?

Do you have this drain hole at the tail post bottom like I do?

Dave

Dave and others,
The factory SEAPLANE (BCS12D or any other BCS #'s)fuslage is the only ones that had this done.They would put a hole in every straight passing tube so when the brace tubes or what ever was welded the end of said tube was welded with the hole in the straight thru tube in the center of the welded end. In short...all the tubing intersections and joints have passege ways for oil to pass thru to every tube. Once the fuslage tubing was filled with X amount of preservative(i.e. lionoil,tube seal,creeping oil,etc) then the hole in the top of the tail post was corked before installing the vertical stablizer. The oil was poored directly down the tail post with the tail high and the nose low. Also the small hole that is located at the bottom of the tail post(like Dave is talking about) should have already been sealed before injecting the oil.You can seal the small hole at the bottom of the tail post with a spot weld,a drive rivit,or I have seen a screew used but the best recommended way is with a spot weld or drive rivit. Remember this only works on the factory seaplanes, if you want to put this stuff in the non-seaplane fuslages you have to drill and fill each tube by itself. The longerons(if in original configuration) should only be drilled an inch or so from the tail post and another at the far end so air can escape as the oil runs down.Once oil starts out the other end of the longeron then you can easily seal it with a drive rivit at both ends leaving most of the oil still inside the tube.

To make it simple to understand...the tubing should have some kind of preservative inside it and NO holes in any of the tubing anywhere.

[Guest]

Re: Price and availability of wing lift struts

Dave and others,
The factory SEAPLANE (BCS12D or any other BCS #'s)fuslage is the only ones that had this done.They would put a hole in every straight passing tube so when the brace tubes or what ever was welded the end of said tube was welded with the hole in the straight thru tube in the center of the welded end. In short...all the tubing intersections and joints have passege ways for oil to pass thru to every tube. Once the fuslage tubing was filled with X amount of preservative(i.e. lionoil,tube seal,creeping oil,etc) then the hole in the top of the tail post was corked before installing the vertical stablizer. The oil was poored directly down the tail post with the tail high and the nose low. Also the small hole that is located at the bottom of the tail post(like Dave is talking about) should have already been sealed before injecting the oil.You can seal the small hole at the bottom of the tail post with a spot weld,a drive rivit,or I have seen a screew used but the best recommended way is with a spot weld or drive rivit. Remember this only works on the factory seaplanes, if you want to put this stuff in the non-seaplane fuslages you have to drill and fill each tube by itself. The longerons(if in original configuration) should only be drilled an inch or so from the tail post and another at the far end so air can escape as the oil runs down.Once oil starts out the other end of the longeron then you can easily seal it with a drive rivit at both ends leaving most of the oil still inside the tube.

To make it simple to understand...the tubing should have some kind of preservative inside it and NO holes in any of the tubing anywhere.

Thanks Kevin,

Help me with this and maybe you don't either.

Why would the factory drill that hole (in blue above) if it has to be plugged prior to pouring the oil in teh top of the tail post?

Why bother to make it?

Thanks again, Dave.

[Winston L.]

Re: Sealing the fuselage tubing against internal corrosion

I see what you are saying, you could just turn the fuselage over and drain the excess oil from the top of the tailpost.

[Guest]

Re: Sealing the fuselage tubing against internal corrosion

I see what you are saying, you could just turn the fuselage over and drain the excess oil from the top of the tailpost.

Additionally if the hole is sealed before pouring in the oil then you must turn the fuselage over and drain the excess oil.

I don't follow why the hole was ever made.

[crispy critter]

Re: Sealing the fuselage tubing against internal corrosion

I don't know why the hole is in the tail post unless it is there to let water out of the tail post if it ever got wet....I really don't know. I just know it is supposed to be sealed. As for the oil in the tubing. You are supposes to put enough in to cover the entirity of the tube and sealed. You are not supposed to let it all drain out. If you have a standard fuslage and drill both ends of a tube,I was taught to inject oil in the high hole until you see it start to come out the low hole then plug the holes with the oil left inside the tubing. With the seaplanes they inject a select amount of oil(measured in cc's) into the tail post and seal it up with the oil inside. The oil preserves the tubing forever if done correct.

[mhorowit]

Re: Sealing the fuselage tubing against internal corrosion

I was under the impression you coated the insides of the tubing and then let the oil drain. Apparently there is a difference of opinion?

Second - in a standard fuselage, the tubing isn't interconnected. Since oil can not pass from one tube into another, how many holes does one have to drill in order to properly treat the fuselage? - MikeH

[mhorowit]

Re: Sealing the fuselage tubing against internal corrosion

Now, courtesy of Forrest, we see Ms Ferris's letter, especially page 2. Notice all the places tubing is vented to the atmosphere! Contrast that with the discussion of filling the fuselage tubing with oil and sealing it. Seems like a contradiction to me and seems to add weight to coating the inside, draining the oil and leaving the tube open to the atmosphere. - MikeH

[mhorowit]

Coating insides and sealing tubing

Let's talk about linseed oil and coating the insides of tubing; especially since some folks seem to indicate they are filling their tubing with oil, NOT draining it, but rather sealing the tubing, apparently nearly filled. I was under the impression one filled the tubes with oil, sloshed it around and allowed it to drain. Leave the drain hole open. End.

It seems to me to be a contradiction in logic that in some cases we seal a tube and in others we don't.

What I see is a weep hole at the bottom of each of the lift struts, at the bottom of the landing gear, fuselage drain, Horizontal stabilizers and elevators, trim tab, rudder.

Does anyone elses see sealing any tubing to not follow logic? - MikeH

[Len Petterson]

Re: Coating insides and sealing tubing

Fill and move the part all around so the oil contacts all internal surfases and Drain.
So I am told long ago. To leave the drain hole open or not? I dont know.
Len

[N96337]

Re: Coating insides and sealing tubing

I used to use linseed oil..then tried Polyfiber's Tube Seal..that stuff is awesome!! You can set a drop of it on one side of the shop and by morning, it's spread all the way across to the other side!!! Well, not quite that bad, but it really "climbs" and "creeps". They have a formula in their manual that tells how much to put in a tube of a given size and length, and I usually just inject it with a small syringe, being careful to keep the oil from the edges of the hole, then I weld up the hole. They say to close up the hole with a pop rivet, but I prefer the welding or even a drive screw.
I've had a quart here for a long time, so it doesn't take much to do a fuselage. If it leaks out, (don't ask) it will form a "seal" unless the hole is of a pretty good size.
JH

[Guest]

Re: Coating insides and sealing tubing

I have most recently used The poly fiber tube seal like JH and using the amount prescribed in their data based on tubing size and length.

Prior to that used the fill with hot linseed oil until no more fits in and then drain the oil by making a hole or holes somewhere.

In each case above I often but not always had to make a hole to use as an oil fill hole.

But I always have plugged all the fill hole(s) and drain hole(s) that I made for the purpose of filling or draining the oil.

I have never plugged an existing (or pre-existing may be a better description) drain or weep hole as it is also called.

For a long time I thought using boiled linseed oil meant that I must apply it hot after boiling it. It's not so. You can use linseed oil hot or cold. Boiling refers to teh processing the oil goes through.

While there is a good reason to apply it hot like you can sense where the oil is and do not intend to discredit that in any way.

You can buy boiled linseed oil or raw linseed oil.

Boiled oil polymerizes faster, ie sets or dries faster and may last longer too as I recall, So you could use boiled linseed oil cold to fill a strut and drain it since you would easily know where the oil goes in a single element like that which is easy to fill and then to tell when its filled compared to pumping oil in to fuselage tubes.

The raw oil does not behave or last as well and should be boiled before use as a preservative. I had not recognized that this was the difference that was being pointed out to me and had though for a while that it might only be used after boiing my me. ie purchase boiled oil and you can use it cold when you want or need to.

Linseed oil comes from flax seeds. When I first started taking flax seed oil I was surprized how much it smelled like the linseed oil I used in the shop! They are one in the same in terms of their origin but under go different processing. Don't try eating linseed oil from your hardware store.


Dave

[mhorowit]

Re: Coating insides and sealing tubing

Dave - in your experience, what tubing is interconnected so that oil will flow between them? - MikeH

[Guest]

Re: Coating insides and sealing tubing

Hi Mike, I only recall at longerons at tailpost and longerons up near cabin section vertical risers by doors.

In hindsight I bet I just described clusters where there is a fitting and all tubes that exist there are tube ends????

Dave