Loose frame bolts and deterioration of floor.

[Ak Ron]

Thanks for the nice diagram, Andrew. I am having trouble visualizing this, especially the part from below. My belly at the frame is intact so I am thinking I just need to fiberglass over the top(inside), as well as bond the wood to both the belly and the top so it becomes part of the structure. Were you thinking I had a hole clear through the bottom also?

[LeonardS]

are you sure you want to use stainless steel for the bolt? While it is true that the stainless steel bolt won't rust, it can make the material around it rust, makes everything connected to it a sacrificial anode...in your case the frame.

[Andrew Gibbens]

Ron if the bottom skin is undamaged then that doesn't need any work - that's good, as it avoids overhead work!

So, yes, add a new patch of plywood, bonding it both to the bottom skin and to the original wood core alongside. Epoxy with sufficient filler added to make a paste would be the best choice for this, but personally I would be equally happy using Bondo as both adhesive and filler.

Then a layer of fibreglass laminated over the top (like the bottom sketch) would complete the job.

Which, I think, is exactly what you said!

[Ak Ron]

LeonardS: I didn't realize there was a galvanic reaction between steel and stainless. Would hot-dipped galvanized be any better?

Andrew: Thanks. That clarifies it. I am thinking since the wood is pretty wet that I may just put the wood in, bolt it, and leave it open for the summer to dry out, then epoxy it all later.

Another comment from Outback: "... inject silicone in the bolt
hole when installing the new bolt."

[Donna D.]

Originally Posted by Ak Ron

Another comment from Outback: "... inject silicone in the bolt
hole when installing the new bolt."

and have it fail in a couple of years. There are BETTER caulks.

[Thomas G.]

Originally Posted by Ak Ron

LeonardS: I didn't realize there was a galvanic reaction between steel and stainless. Would hot-dipped galvanized be any better?.........

Galvanic action occurs when two metals with different electrode potentials are in contact in the presence of an electrolyte (like salt water). This is a problem with boats, not so much FG trailers. In FG trailers the mild steel bolts tend to rust through, so I think that using a stainless bolt would be a good idea.

[Raz]

Originally Posted by LeonardS

are you sure you want to use stainless steel for the bolt? While it is true that the stainless steel bolt won't rust, it can make the material around it rust, makes everything connected to it a sacrificial anode...in your case the frame.

Leonard, your comment caught my attention as my Trillium has stainless steel bolts holding the body to the frame. While I have heard of galvanic issues between aluminum and stainless, I have never heard of issues between stainless and regular steel. An internet search found lots of aluminum/ stainless concerns but nothing about stainless and regular steel.

I was curious so I did some reading (it's been a while). In order for galvanic corrosion to occur three condition must be met. 1)The metals must be different. 2) They must be in electrical contact. 3) An electrolyte ( water, salt water, acid) must be present at the contact point. Since it's common to have dissimilar metals in contact without issue, the speed of the corrosion depends on the two metals in question. Each metal has an Anodic index value. The difference between the two predicts how reactive the contact will be. With stainless steel at 0.6 and ordinary steel at 0.85, a difference 0.25 exists. Since this exceeds the "harsh" environment value of 0.15, corrosion is a possibility. A harsh environment is defined as outdoors, wet, or salty. That said, the tightness of the bolt and paint on the frame have to be in my favor. I suspect a non-conducting washer would be a cure if one is needed. Right now winter has returned. It snowed last night. When it warms up I'll see if it's an issue on my 3 year old trailer. Leonard, if you can add your experience or supply a good reference, it would be welcome. Raz

[LeonardS]

Raz,

I can add my experience. In my youth...(ok I was 30), I rebuilt a wrecked Hobi-cat trailer to be a trailer for my Zodiac inflatable. I had to add crossmembers to the existing crossmembers in order to raise up the rails for the keel of the inflatable. I had decided that since welding galvanized sucks, I would simply bolt it all together. I was using galvanized box steel, as that is what was already there. I had galvanized bolts all ready to go...when I happened upon some stainless bolts that were on sale. Had to be better, right?

Nope. The galvanized steel rusted around the bolts. I had taken the precaution of using galvanized paint (I know, not the same as hot-dipping) where I drilled the holes, etc, but the stainless had just too strong of a cathode action. D'OH! Then I remembered my high school and college and professional training concerning dis-similar metals. Where I had mounted stanchions for my lights, using galvanized hardware, no such problem.

Even though the trailer rarely saw salt water, it did stay out in the rain. Probably just wet enough to "have the presence of electrolite".

If the OP is fixing his trailer so that it stays dry, then likely using stainless won't matter. But...the original bolts got wet somehow, as they rusted. I'd just use a hardened bolt, myself.

Because if you use stainless bolts and the frame rusts and then the egg falls off while driving, you could cause a wreck and your family will dis-own you and your insurance will abandon you and the authorities will find the non-standard bolts and throw you in jail. And your hair will fall out.

[Raz]

Originally Posted by LeonardS

Raz,

I can add my experience. In my youth...(ok I was 30), I rebuilt a wrecked Hobi-cat trailer to be a trailer for my Zodiac inflatable. I had to add crossmembers to the existing crossmembers in order to raise up the rails for the keel of the inflatable. I had decided that since welding galvanized sucks, I would simply bolt it all together. I was using galvanized box steel, as that is what was already there. I had galvanized bolts all ready to go...when I happened upon some stainless bolts that were on sale. Had to be better, right?

Nope. The galvanized steel rusted around the bolts. I had taken the precaution of using galvanized paint (I know, not the same as hot-dipping) where I drilled the holes, etc, but the stainless had just too strong of a cathode action. D'OH! Then I remembered my high school and college and professional training concerning dis-similar metals. Where I had mounted stanchions for my lights, using galvanized hardware, no such problem.

Even though the trailer rarely saw salt water, it did stay out in the rain. Probably just wet enough to "have the presence of electrolite".

If the OP is fixing his trailer so that it stays dry, then likely using stainless won't matter. But...the original bolts got wet somehow, as they rusted. I'd just use a hardened bolt, myself.

Because if you use stainless bolts and the frame rusts and then the egg falls off while driving, you could cause a wreck and your family will dis-own you and your insurance will abandon you and the authorities will find the non-standard bolts and throw you in jail. And your hair will fall out.

Interesting, in your case you used stainless with galvanized (zinc coated) steel. Galvanized steel has an Anodic value of 1.2 and a difference of 0.6. This indicates that corrosion is much more likely. Or more correctly, will happen faster. Thanks for the reply. I'm trying to keep as much hair as I can Raz

[steve dunham]

One problem I"ve encountered is that a lot of the stainless steel bolts , nuts , screws, washers ETC sold in the US are made overseas ( China Indonesia , India) Many of these bolts are ungraded and the quality of the stainless steel is non existent . (Nickel cost $$$)
How many of us have bought a "stainless steel" BBQ grill that rusted away in 2 or 3 years. I have been on jobs where they used galvanized washers with stainless steel bolts and the galvanic action was visible in a very short period of time

[Donna D.]

Stainless steel does not equal rustless. Otherwise it would be called rustless steel instead of stainless steel. Stainless just rusts sloooower but once it gets going it goes just as fast as mild steel.

Stainless steel stove tops and sinks are an example most are familiar with.

[Thomas G.]

It is worth noting that "stainless steel" is a generic term. There are all kinds of stainless steel with different added alloys to change its properties.

I found this wiki informative, including the explanation of galling and seizure issues.

When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off, causing the parts to weld together. When disassembled, the welded material may be torn and pitted, an effect known as galling. This destructive galling can be best avoided by the use of dissimilar materials for the parts forced together, for example bronze and stainless steel, or even different types of stainless steels (martensitic against austenitic), when metal-to-metal wear is a concern.

Stainless steel - Wikipedia, the free encyclopedia

[Ak Ron]

This website is great! Thank you all for your ideas and experiences.
I have been drying the wood for over a week now with a small fan and it is coming along well. I'm in no rush so I'll keep drying it till it is as good as possible and then do the seal up with epoxy and fiberglass. (a new experience for me) I will use a stainless bolt as that seems like the best compromise from what I've heard. And I will caulk the bolt hole well with something other than silicone! Something gooey, tenacious, non-hardening and nasty. (I have used something like this in my house construction...they call it "black death"!) Any other ideas that people have experience with.

[freddo411]

My experience using large stainless steel frame bolts:

http://www.fiberglassrv.com/forums/f...-up-51193.html

In short: don't.

Cheers

[Jared J]

Originally Posted by freddo411

My experience using large stainless steel frame bolts:

http://www.fiberglassrv.com/forums/f...-up-51193.html

In short: don't.

Cheers

My entire camper is stainless fasteners, other than what's holding the axle on. No problems.

[Raz]

Ron, I had a look at my stainless steel bolts and I don't see any signs of corrosion between the steel frame and the stainless bolts. Perhaps in the future it will be an issue.?? Since you have some fiberglass pieces that you cut from the floor, you could make fiberglass washers to separate the two metals if it's a concern. Raz