U-bolting on a crossmember - help please!!

[73 Dolphin]

So... took a boat Ive been working on for 6 months to the water this last weekend.
Idea was to pull the boat back on the trailer and also check for leaks at the dock.
Good news - boat didn't leak. Bad news - the rear cross-member part collapsed.
So I went and bought a new 80" 3x3 galvanized cross-member.
Do not want to weld it on. Any good Ideas on how to attach this?
Obviously I'm not keen on the solution so far!!

 

[73 Dolphin]

Should say I cant weld it on ( as its galvanized )....looking to find a smart clamping solution.

 

[GA_Boater]

Galvanized can be welded. It takes special precautions and a pro should able to handle it.

Before doing anything, you had a cross member rust out - Probably more than just the galvanized cross member is in danger of giving up. What does the rest of the trailer look like?

 

[alldodge]

Smaller U-bolts, use 2 on each side and a square 1/4 plate steel

 

[dingbat]

Mine is thru bolted in both directions

 

[73 Dolphin]

GA_Boater - No welding - I don't weld and the mobile welders wont touch a galvanized trailer.. Its a trailer that I bought from one of those rich guys who never cleans his toys.
The frame is completely rust free. The spring hanger bolts and such all need replacing though. He basically never rinsed it off. In other words just the parts that got wet need changing out and not the frame as it's u section.

AllDodge - thanks. That looks like the way to go. I have 1/2 inch aluminum that I can fabricate. I need 2 inch wide u bolts 1/2" threaded and 9" long if I can find them.

 

[73 Dolphin]

Dingbat - I should have said its a u section frame only 1 1/2 inches wide and 4' deep. Not enough meat to bolt through?? Clamping is the way I think I need to go. Thanks for the reply.

 

[bruceb58]

Was the crossmember a closed tube? Is the rest of the trailer the same construction? If so, the rest of the trailer may be in the same shape. Closed tube trailers rust from the inside out.

 

[Bondo]

and not the frame as it's u section.

Ayuh,...... Fairly easy to use 1 bolt, each end,.....

Drill through, 'n use short pipe pieces round the bolt inside the pieces so they don't collapse when ya tighten it,.....

 

[dingbat]

Was the crossmember a closed tube? Is the rest of the trailer the same construction? If so, the rest of the trailer may be in the same shape. Closed tube trailers rust from the inside out.

Pretty common problem.

Ive had to replace my rear axle and rear cross member. Everything else is in pretty decent shape. Only parts that get wet (saltwater) each time I launch and retrieve

 

[fishrdan]

Ends of the old tube look in decent shape, and new tube looks like it "may" telescope inside the old tube.... So how about hacking out the middle section of the old tube, leaving 6-9" of old tube left welded to the frame, then slipping the new tube into the old tube stubs?

Not sure if the tubes are the same angle of bend, and you may have to figure out something for the guides that slip into the old crossmember.

 

[73 Dolphin]

The goal here for me is to get this trailer operational again. The boat is in such a position that i really cant jack it off the bunks and support it and I cant drive the trailer to the water in its condition. Also the mobile trailer repair folks wont weld a galvanised trailer. What I can do ( and have done ) is jack the bunk attached to the collapsed crossmember. Thats why in the original pictures the new cross member is forward on the original. I hope this describes my situation more clearly.

I really dont want to weld or even drill holes.
Either option will expose the frame to rust in no time flat.

Clamping is the way I want to go if possible. I did buy some 1/2" aluminum base plate. Later today I need to go drill some holes for the 1/2" dia clamp threads.
it should look much like the images in AllDodges reply.

The problem i have is, not being welded or drilled and bolted, I'm concerned about the cross member sliding from side to side or front to back.

The other thing is the original cross member had a welded brace to stop the rail from towing in. I need to find a way around that too.

I appreciate all of the suggestions, some which deal with the concerns above. I'll be posting some pictures as I go.

Hopefully this will eventually help someone else in the same situation ( I cant be the only one, right? )
or dissuade someone from trying it!

 

[Silvertip]

Clamping a crosspmember provides "Zero" lateral strength. Bolting or welding is required -- especially at the back of the trailer.

 

[Grub54891]

Bolt it on please. After drilling the holes, spray them with galvanized rattle can. You don't want that piece moving around.

 

[The Force power]

Or weld on (stick welder) & spray paint area to prevent rust

 

[Chris1956]

On my 1500# trailer the cross member is clamped to the main frame. The cross member is first drilled to accept a U-bolt. The U bolt goes over the main frame and thru the holes in the cross-member, and nuts and washers are installed and tightened.

On my 3900# Tandem trailer, the cross member have a U-shaped bracket welded to each end. This is thru bolted to the main frame. I would think you can get such brackets and bolt them to the cross member and then to the main frame.

 

[73 Dolphin]

This is the solution I came up with. 1/2 inch aluminum plate primed and painted.
Clamped to the frame. Then the cross member is clamped to the plate. As far as I can tell this shouldn't be able to move anywhere. Also I left the original cross member on to help with the rigidity.

I hope this helps someone in the same situation.

If anyone wants to say why this wont work please feel free to advise me or others trying to do the same thing.

Thank for all of the advice!

 

[bruceb58]

Can you take a picture further away to give us some context on where this crossmember is on your trailer?

 

[fishrdan]

I don't think it's structurally strong enough for the rear corner of the trailer. At a bare minimum, I would drill through the center of the plate and into the bottom of the new cross member, then install a 1/2" bolt on each side. This will lock the cross member into the plate and keep the cross member from walking around, and keep the aluminum plate from bowing (to some extent).

If you're worried about rust/corrosion, slather the bolt and hole with 3M #3 aviation sealant, so the raw steel edges are coated in sealant.

 

[73 Dolphin]

Can you take a picture further away to give us some context on where this crossmember is on your trailer?

Its right up against the original. Is that what you are asking? I think the pictures show that though?