Aluminum Trailer with I beam cracks?

[O.T.Water]

Hi All, See if I can explain this properly. I have an aluminum I beam trailer that is a float on with 2 bunks that most of the boat rests on. Up front the V of the boat before it curves up to the bow rests on a nylon V brace attached to an alumium cross brace. My cracks are on both sides where the front of the covered beams attach to the outside I beams with 90 degree angle brackets. The bottom of the beam is actually separating away from the upright (I) ever so slightly. Not sure why this happened, the boat is only 16' and dosen't weigh that much. I bought it 6 months ago and it may have been like that when I got it. Thinking of having it welded and reinforcing that area with stainless u-bolts. Anyone ever had this happen? The trailer is only 8 years old. Thanks O.T.

 

[smokeonthewater]

Re: Aluminum Trailer with I beam cracks?

pics are needed..... edit your post to substitute bunks for "covered beams" or you will get all kinds of confused answers...... next I suspect that either your trailer is not up to it's load or has been damaged in the past or more likely this is a case of poor design..... it may be fixable but needs to me inspected very carefully for any other cracks.... Also as I'm sure you realize the cause of the cracking needs to be eliminated..... I suspect it is from localized stress from improper attachment of the bunks

 

[O.T.Water]

Re: Aluminum Trailer with I beam cracks?

Thankyou for the proper terminology, wasn't exactly sure what they were called. The rear bunks attach the same way. When I inspected the trailer for more cracks I was expecting to see cracks there also being at the end of the beams and more weight from the rear of the boat but they were fine. I did notice the upright part of the beam is a thinner aluminum than the upper and lower plates. I was thinking that the boat was slammed or driven hard onto the bunks instead of being floated on? Just a thought. O.T.

 

[jeeperman]

Re: Aluminum Trailer with I beam cracks?

Thankyou for the proper terminology, wasn't exactly sure what they were called. The rear bunks attach the same way. When I inspected the trailer for more cracks I was expecting to see cracks there also being at the end of the beams and more weight from the rear of the boat but they were fine. I did notice the upright part of the beam is a thinner aluminum than the upper and lower plates. I was thinking that the boat was slammed or driven hard onto the bunks instead of being floated on? Just a thought. O.T.

This is typical I-Beam cross section.
Is it cracking near welds or near bolted spots or away from such things?

Structural aluminum shapes do not like vibrations or flexing whereas you can get away with lots of both with steel construction.

But a picture would help a lot.

 

[northernmerc]

Re: Aluminum Trailer with I beam cracks?

As you probably know, welding aluminum is tricky. If you can afford it, take it to a good welder for repair and reinforcement.

 

[O.T.Water]

Re: Aluminum Trailer with I beam cracks?

I'll have to do some photo's but I leave for and return from work in the dark so I'll have to wait till saturday. There are lots of pipe welders around here for aluminum towers so it should be easy to find someone to do it. Then I figure to reinforce it with stainless ubolts or have the welder maybe box the frame in that area. O.T.

 

[Yepblaze]

Re: Aluminum Trailer with I beam cracks?

It's always possible that it has reached the end of it's useful life. And that must be considered against repairs.

If repairs and modifications prolong the SAFE!!! life of the unit that is ultimately up to you.

You obviously are aware that there is an issue that needs addressing, so that puts you one step ahead of the game.

Have it addressed by a processional proficient in aluminum trailer repair.

 

[O.T.Water]

Re: Aluminum Trailer with I beam cracks?

Yep, that sounds like a plan! O.T.

 

[Pez Vela]

Re: Aluminum Trailer with I beam cracks?

In contemplating your next move, you may wish to consider WHY the I-beam frame cracked in the first place. More than you probably want to know can be found in an article discussing the use of cantilevered bunk design to alleviate the stresses in aluminum I-beam boat trailers.

http://www.patentstorm.us/patents/6113124/description.html

 

[O.T.Water]

Re: Aluminum Trailer with I beam cracks?

In contemplating your next move, you may wish to consider WHY the I-beam frame cracked in the first place. More than you probably want to know can be found in an article discussing the use of cantilevered bunk design to alleviate the stresses in aluminum I-beam boat trailers.

http://www.patentstorm.us/patents/6113124/description.html

Very interesting and informative. Will have to read when I can study it more. Maybe as simple as supporting the bunks at more points along the I beam after it's been repaired of course. Thanks for the info. O.T.

 

[Pez Vela]

Re: Aluminum Trailer with I beam cracks?

What I believe the article is discussing is the use of cantilevered bunks that extend well beyond the rear of the trailer frame as shown in this picture ... the idea being to reduce the flexing forces (at the point of your fracture) while driving the rig around. I think the article nicely sums up the advantages and disadvantages inherent in both steel and aluminum construction. Neither is perfect.

 

[mikeneal]

Re: Aluminum Trailer with I beam cracks?

Sounds like a fatigue based crack, pics would help. Why would it crack? That has unlimited possibilities and nobody can answer that intelligently without additional information. One thing for certain is if the trailer fatigue cracked then welding is not the answer. Adding a heat effected zone will only make matters worst. I am a mechanical engineer by trade and have done a fair amount of failure analysis, if the trailer fatigue cracked it is junk, ready to be sold for scrap.