NOT recommended: foam in gear leg fairings...

[Scott Will]

The past week I had reason to remove the gear leg fairings to gain access to the hydraulic brake lines. When installing the main gear leg fairings for what I thought was the last time, I used the Great Stuff expanding foam from the aviation aisle at the Depot.

Here to say that I wish I didn't do that. Why? Well it makes for removing the gear leg fairing a huge ordeal that almost resorted to me cutting the fairing off. I could not pull the hinge pin out at all!! I ended up using a pair of small vice grips and banging on it with a hammer... til the end of the hinge pin fell off! I was able to dremel away a small amount and get a fresh piece of hinge pin and use the vice grips with moderate success. I destroyed the hinge pin getting it out.

When the foam cures, it leaves behind a very tough glue ... I originally thought, "hey, I'd just throw some acetone in there and eat the foam away". Boy was I wrong. The glue managed to get in the hinge pin... ughhh.

After I managed to get the fairing off, I spent a while cleaning up the gear leg and inside of the fairing. Acetone would eat the foam but nothing I found cleaned off the glue. Now my gear leg fairings are showing the rivets popping thru the paint after working the fairings quite a bit.

Turns out I have to do the other side as well. Not looking forward to it. The good news is the new hinge pin went in a lot easier than the other came out. Now tomorrow I have to do the other side and hope I don't destroy the hinge pin.

Would I put foam in the fairings again? Not.

 

[MSFT-1]

Boy, do I ever know what you mean

I got some of that stuff on my hands and wiped it off with a dry rag. About an hour later I realized the back of my hand was sticky to the touch. I tried water. I tried soap. I tried paint thinner. I tried Avgas. It would seem like it was gone until it dried then my hands were as sticky as ever. Multiple tries with paint thinner (and lots of cursing) later I got my hands "acceptably" clean but it was the better part of a day before they truly weren't sticky anymore.

 

[rv6rick]

Hello??

Yo' Scott...what you do is, apply a layer of clear packing tape to the inside of the fairing BEFORE you spray in the 'Great Stuff'....and go right over the hinges when you do it. You might wear some disposable rubber gloves as well...only a couple bucks for each item at Kroger or WalMart.

If you like...you can remove the fairings a day or two after the 'Great Stuff' has cured. Then....you take half of a hacksaw blade (or whatever) and cut off the 'bulges' from the top, bottom, and insides. After that you can lay on a thin layer of epoxy....this way the foam won't get wet and it even looks real nice the next time you want to change your brake line .

The fact that it IS real sticky is what makes it 'Great Stuff'.....you just need to do the above so it only sticks where you want it to.

I just did this to my Rocket yesterday.

No charge for this one .

The past week I had reason to remove the gear leg fairings to gain access to the hydraulic brake lines. When installing the main gear leg fairings for what I thought was the last time, I used the Great Stuff expanding foam from the aviation aisle at the Depot.

Here to say that I wish I didn't do that. Why? Well it makes for removing the gear leg fairing a huge ordeal that almost resorted to me cutting the fairing off. I could not pull the hinge pin out at all!! I ended up using a pair of small vice grips and banging on it with a hammer... til the end of the hinge pin fell off! I was able to dremel away a small amount and get a fresh piece of hinge pin and use the vice grips with moderate success. I destroyed the hinge pin getting it out.

When the foam cures, it leaves behind a very tough glue ... I originally thought, "hey, I'd just throw some acetone in there and eat the foam away". Boy was I wrong. The glue managed to get in the hinge pin... ughhh.

After I managed to get the fairing off, I spent a while cleaning up the gear leg and inside of the fairing. Acetone would eat the foam but nothing I found cleaned off the glue. Now my gear leg fairings are showing the rivets popping thru the paint after working the fairings quite a bit.

Turns out I have to do the other side as well. Not looking forward to it. The good news is the new hinge pin went in a lot easier than the other came out. Now tomorrow I have to do the other side and hope I don't destroy the hinge pin.

Would I put foam in the fairings again? Not.

 

[N941WR]

The other problem with Great Stuff is that you don't want to use it where it can get wet. This is because the stuff will retain water and cause corrosion.

By itself, w/o the water, this is not a problem. I've used it to hold the fuel line in place as it runs between the fuel valve and boost pump w/o any problem. Oh, and before I used it there I tried to see what chemicals would impact it, nothing in my shop, including 100LL even touched that stuff.

 

[dhall_polo]

Are you saying that you taped the gear leg and brake line and the inside surface of the fairing itself? Not quite getting the picture - sorry. This step is not too distant future, so I'm following this thread with some interest.

Don Hall
N517DG - wiring

 

[Brantel]

Scott,

Thanks for sharing the results...

Curious though, why are you going after the brake hoses?

 

[rv6rick]

Hi Don,
No....just tape the inside of the fairing where you don't want the 'GS' to stick. You DO want the 'GS' to stick to the gear leg (and stiffener if installed)....unfortunately it will stick to the brake line as well (which is OK). 'If' you need to work on a brake line down the road you'll have no trouble removing the fairing. That said...you will have to bust off the 'GS' and shoot in some new stuff after you're done in there.

This approach will:
-allow you to remove the fairing without breaking it OR the ruining your paint
-keep water out (by adding a layer of epoxy)
-set the angle of the fairing
-hold the fairing in place

Savvy??

Are you saying that you taped the gear leg and brake line and the inside surface of the fairing itself? Not quite getting the picture - sorry. This step is not too distant future, so I'm following this thread with some interest.

Don Hall
N517DG - wiring

 

[gmcjetpilot]

Yep old lesson re learned

People used expanding foam on gear legs back quite a bit in the 80's. What people found was gear leg would corrode after time. This was before the gear legs came powder coated as well (they came bear metal in the old days). Even if builder primed the gear legs would corrode. Regardless the word went out in the RVator don't use expanding foam on gear legs was not a desirable plan, about 10-15 yrs ago. Not sure if the compendium of RVator back issues (20 years of 25 years of.... RVator) has it included in there compulation editions. I have almost all the original RVators since about 86 or 88.