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Bolt Together Aluminum Trailers. Yes or No? Possible Problems?

Old 10-01-2009, 02:25 PM
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Question Bolt Together Aluminum Trailers. Yes or No? Possible Problems?

Hello all.
I have no personal experience with bolt together aluminum trailers and was hoping to get some feed back. From what I hear, the reason why they bolt aluminum trailers together is because aluminum has a fair amount of flex. If the trailer is welded together these welds can crack. Is this comment true? If you bolt an aluminum trailer together what are the best nuts and bolts to use, stainless steel or galvinized steel. I want a trailer that is almost rust proof so stainless seems the way to go, but I also hear that stainless reacts badly with aluminum. Is this true, does it react that much worse than aluminum does with galvinized steel? Do you definately need to insulate the nuts and bolts from the aluminum frame with some kind of rubber washer. If so what is the best to use? And lastly, do you find that all these nuts and bolts tend to keep vibrating loose leaving you with having to tighten them up every year or so?
Thanks for reading. Any feed back is good!!!
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Old 10-01-2009, 04:35 PM
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Good thing you asked, as you have heard some bad information. Aluminum boat trailers, like steel boat trailers "both" flex, and some flex a lot. To the best of my knowledge, all aluminum trailers are bolted together with either galvanized or stainless steel hardware (at least those boat trailers manufactured in coastal areas), and there are literally tens of thousands of aluminum trailers in use around saltwater today. I have three, and I've been using aluminum boat trailers exclusively for the past 40 some years.

As for galvanic corrosion, unless you leave your aluminum trailer in the water for prolonged periods of time, your aluminum trailer will outlive you, so isolation of the aluminum and galvanized or stainless hardware is a non-issue.

As for nuts and bolts vibrating loose - also a non-issue. If the trailer has galvanized hardware, the galvanizing on the bolt holds well to the galvanized coating on the nut. And similarly, if stainless bolts are used, most trailer manufacturers use nylock nuts or lock washers - nylock nuts have nylon inserts inside of the nut that locks the nut onto the bolt. This is not to say that a wise trailer boater does not have to check his nuts now and then.

Last edited by First Light; 10-01-2009 at 05:07 PM.
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Old 10-01-2009, 06:42 PM
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Thanks for your input first light.
Another question. If the aluminum trailer has stainless nuts and bolts. Even though aluminum doesn't rust, neither does stainless steel. Is it, a case of, if salt gets in between these 2 metals then corrosion begins? If so does that mean that every time you dunk your trailer into salt water do you need to wash with fresh water every nut and stainless nut and bolt thats touching the aluminum?
Thanks again!

Originally Posted by First Light View Post
Good thing you asked, as you have heard some bad information. Aluminum boat trailers, like steel boat trailers "both" flex, and some flex a lot. To the best of my knowledge, all aluminum trailers are bolted together with either galvanized or stainless steel hardware (at least those boat trailers manufactured in coastal areas), and there are literally tens of thousands of aluminum trailers in use around saltwater today. I have three, and I've been using aluminum boat trailers exclusively for the past 40 some years.

As for galvanic corrosion, unless you leave your aluminum trailer in the water for prolonged periods of time, your aluminum trailer will outlive you, so isolation of the aluminum and galvanized or stainless hardware is a non-issue.

As for nuts and bolts vibrating loose - also a non-issue. If the trailer has galvanized hardware, the galvanizing on the bolt holds well to the galvanized coating on the nut. And similarly, if stainless bolts are used, most trailer manufacturers use nylock nuts or lock washers - nylock nuts have nylon inserts inside of the nut that locks the nut onto the bolt. This is not to say that a wise trailer boater does not have to check his nuts now and then.
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Old 10-01-2009, 07:12 PM
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Originally Posted by Saro View Post
Thanks for your input first light.
Another question. If the aluminum trailer has stainless nuts and bolts. Even though aluminum doesn't rust, neither does stainless steel. Is it, a case of, if salt gets in between these 2 metals then corrosion begins? If so does that mean that every time you dunk your trailer into salt water do you need to wash with fresh water every nut and stainless nut and bolt thats touching the aluminum?
Thanks again!
salt water can be a nasty force when it comes in contact with metal. even the aluminum will start to pit and you will develop some surface rust on the stainless. This isn't really enough to do the trailer in or weaken it beyond repair though. Just for safe measures, why not take the extra 2 minutes and rinse the trailer off. you need to rinse the leaf springs and brakes anyhow
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Old 05-26-2015, 10:07 AM
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Originally Posted by First Light View Post
Good thing you asked, as you have heard some bad information. Aluminum boat trailers, like steel boat trailers "both" flex, and some flex a lot. To the best of my knowledge, all aluminum trailers are bolted together with either galvanized or stainless steel hardware (at least those boat trailers manufactured in coastal areas), and there are literally tens of thousands of aluminum trailers in use around saltwater today. I have three, and I've been using aluminum boat trailers exclusively for the past 40 some years.

As for galvanic corrosion, unless you leave your aluminum trailer in the water for prolonged periods of time, your aluminum trailer will outlive you, so isolation of the aluminum and galvanized or stainless hardware is a non-issue.

As for nuts and bolts vibrating loose - also a non-issue. If the trailer has galvanized hardware, the galvanizing on the bolt holds well to the galvanized coating on the nut. And similarly, if stainless bolts are used, most trailer manufacturers use nylock nuts or lock washers - nylock nuts have nylon inserts inside of the nut that locks the nut onto the bolt. This is not to say that a wise trailer boater does not have to check his nuts now and then.
Well I guess your knowledge sucks cause most good companies only weld aluminum trailers just call pacific trailers!!!! They will tell you why not ta waste time with bolt together or better yet buy one an head down I-10 in cali see how long it holds up LOL
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Old 05-26-2015, 10:25 AM
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Originally Posted by First Light View Post

As for galvanic corrosion, unless you leave your aluminum trailer in the water for prolonged periods of time, your aluminum trailer will outlive you, so isolation of the aluminum and galvanized or stainless hardware is a non-issue.
Had a galvanized "U" bolt eat right through one of the aluminum crossmembers of my last trailer after 5.5 years. The rest of the crossmembers were very close to failure when I replaced them. The boat was used once a week and everything was rinsed thoroughly with freshwater afterwards. Now I coat every piece of steel hardware on the trailer including the springs with CorrosionX Heavy Duty twice a year. No more problems with galvanic corrosion on the aluminum or rust on the hardware. Even the five year old bunk brackets, springs and equalizer bars are rust free.

I agree that a welded trailer is definitely better, but the cost was prohibitive when I purchased mine.
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Old 05-26-2015, 11:21 AM
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I deal with structural aluminum quite often.... both welded and bolted. The fail rate for either application is very low. Welded structure always fails at the weld or near the weld.... bolted structures generally crack at the bolts usually from coming lose or the incorrect use of hardware or torqueing. Aluminum Corrosion is common and requires the use of inhibitors. Stainless is the preferred fastener with aircraft locking nuts... or double nuts. The use of Belleville washers would help for applications using fasteners. We hardly ever use lock washers.

I was a certified welder (as a young man) and quality structural aluminum welds take skill. Welding processes have improved but the aluminum is the same.
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Old 05-26-2015, 02:32 PM
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Seen plenty of both bolted and welded aluinum trailers, custom are usually welded and need the boat on site to make, and provide a fit that won't change unless it breaks. Universal trailers are bolted to allow ease of change as far as bunk placement and mass production. The downside is bolts can loosen and move however you can sell a universal trailer easier down the road if needed.

Unless you plan on keeping boat and trailer 10 plus years I think it's a toss up.
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Old 05-26-2015, 04:08 PM
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My 17 year old aluminum trailer has galvanized U bolts and axles and mainly stainless fasteners.

The corrosion problem is biggest where galvanized touches aluminum- the aluminum is sacrificed. I have rebuilt most of the trailer and placed rubber between the galvanized and aluminum components which has slowed the corrosion.
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Old 05-26-2015, 05:44 PM
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Originally Posted by boatexpert View Post
Well I guess your knowledge sucks cause most good companies only weld aluminum trailers just call pacific trailers!!!! They will tell you why not ta waste time with bolt together or better yet buy one an head down I-10 in cali see how long it holds up LOL
I hope your response here was meant to be sarcastic. I drive my bolted together trailers down i10 quite frequently and I assure the bolts far outlast the welds.

Bolts can be replaced quite easily whereas rewelding oxidized aluminum is a temporary fix at best. Also, finding good tig welders is not that easy.

I wouldn't want a welded trailer because aluminum because welds break, are hard to fix properly, and most often cost more.
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Old 05-26-2015, 06:10 PM
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Myco and several others make welded aluminum trailers that are "brick chithouses" however they cost 2-3 times as a bolted together trailer. That said, I've had a number of boats with bolt together aluminum trailers, including a 12,000 cigarette boat. All stainless hardware and never had a problem.
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Old 06-14-2019, 05:45 PM
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Originally Posted by boatexpert View Post
Well I guess your knowledge sucks cause most good companies only weld aluminum trailers just call pacific trailers!!!! They will tell you why not ta waste time with bolt together or better yet buy one an head down I-10 in cali see how long it holds up LOL
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Fyi info, Pacific quotes, builds and sells bolted I beam and Welded Channel AL trailers, along qith painted steel and Galvanized, Welded trailers are more expensive, and as a welding inspector, I will spec bolted, thank you very much.

Bolted allows you to more easily adjust it for your, or other boats if you sell it. I have owned bolted aluminum trailers.

I also live off the I-10 and have never had a problem in over 40 years either.
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Old 06-14-2019, 07:34 PM
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The most prevalent areas I see welded today are for bunks fitted to specific hulls. Rest is pretty much bolted
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Old 06-14-2019, 10:18 PM
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I have used and owned both types of trailers. Both seem to work fine. A bolted trailer will suffer from more galvanic action where bolts and aluminum touch. Most of your custom trailers are welded. A bolted together trailer has much more galvanized parts on it. All those parts will need replacing in 5 to 7 years as the will be very rusted also..A welded trailer has very few galvanized parts on it..
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Old 06-14-2019, 10:32 PM
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Hi DavenFla,

I was just curious about this statement. Why don't you use lock washers? I'm not knowledgeable about these things, but I am assuming Belleville washers are just like the washers in reel drags? Always used lock washers, never thought about large belleville washers. Just curious is all.

"Stainless is the preferred fastener with aircraft locking nuts... or double nuts. The use of Belleville washers would help for applications using fasteners. We hardly ever use lock washers."
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Old 06-15-2019, 07:41 AM
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Originally Posted by cajflynn View Post
I hope your response here was meant to be sarcastic. I drive my bolted together trailers down i10 quite frequently and I assure the bolts ifar outlast the welds.

Bolts can be replaced quite easily whereas rewelding oxidized aluminum is a temporary fix at best. Also, finding good tig welders is not that easy.

I wouldn't want a welded trailer because aluminum because welds break, are hard to fix properly, and most often cost more.
I heard the same story from a trailer repair guy in Marathon. He said he sees a lot of Al welds go bad. If anyone is in a place to see a worse boat trailer environment than in the Keys, I'd like to know.

Plus, you can replace bolted hardware about a 100x easier than fixing welds.
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Old 06-17-2019, 12:02 PM
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Originally Posted by bayrunner16 View Post
Hi DavenFla,

I was just curious about this statement. Why don't you use lock washers? I'm not knowledgeable about these things, but I am assuming Belleville washers are just like the washers in reel drags? Always used lock washers, never thought about large belleville washers. Just curious is all.

"Stainless is the preferred fastener with aircraft locking nuts... or double nuts. The use of Belleville washers would help for applications using fasteners. We hardly ever use lock washers."
Belleville washers can compensate for heat and flexing, a lock washer can not. In addition lock washers often crack. On a trailer... flexing is the issue. The key with belleville washers is not to over torque. (they have a rating).Where temperature and flexing is not an issue, locks are fine.
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Old 06-17-2019, 12:33 PM
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Originally Posted by HullSlap View Post
Had a galvanized "U" bolt eat right through one of the aluminum crossmembers of my last trailer after 5.5 years. .

Hardly any surprise considering your trailer used galvanized fasteners up against aluminum. You have to isolate them or they die fast as you experienced.
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Old 06-17-2019, 01:54 PM
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I use these between SS U bolts and Galv Steel or AL. But, tighten them up; they can slide a bit easier if loose.
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Old 06-20-2019, 05:50 AM
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Ever see anything welded to a truck frame?
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