Galvanized Steel Trailer Conversion from Rollers to Bunks

jhendery · May 17, 2013

Hey Folks,

I am converting my galvanized trailer from rollers to bunks.

The trailer was used originally used with an 18 ft glasser bow rider.

Now the trailer will be used with a 16 ft aluminum runabout.

My thinking was to purchase per-fabricated brackets and bunks. Mount brackets and bunks to the trailer and I should be good to go.

Here is the trailer

So my thinking was to mount the brackets using the starboard and port support beams. I installed the bracket in the picture below to get an idea how things would line up. The bunks would be mounted to the plates found at the top of the support brackets.

Something to know The width of the boat fits inside starboard and port trailer tires. Regardless I was planning to install the brackets 2 or 3 inches taller than the tires.

Would it be better to install the brackets on the inside or outside of the support beams. What width should the bunks be installed to evenly distribute the weight of the boat on the trailer?

The boat can be viewed in my re-build thread here. Thanks in advance!!

http://forums.iboats.com/boat-resto...uminum-mackenzie-runabout-rebuild-558956.html

roscoe · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Click photo.

Bracket should be rotated 90* and mounted to the crossmember as shown in photo.
Swivel mount on top will then conform to the angle of the hull.
A square "u-bolt" is used to hold it in place.

smokeonthewater · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Yep WHS

It won't work the way you have it planned because the bracket will fatigue and break

jhendery · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Thanks Roscoe and SOTW.

Ok that makes sense. Turn the bracket 90 degrees and mount the bracket to the inside of the crossmember using u-bolts.

What length of bunks should I go with 4, 5 or 6 ft lengths? Does it matter?

So that's it for bunks - the starboard and port sides will support the majority of weight at the stern.

At the bow the boat will rest on a single roller where the keel meets the trailer? You can view the single roller in the first trailer pic above.

What height should the brackets be installed? Since the boat will fit between the tires should I be going for the lowest height as possible?

One other thought - I have the original mounting brackets and rollers. I was going to sell them. Should I remove the rollers and use the brackets to mount the bunks instead of the bracket displayed above?

smokeonthewater · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

I'd say the bunks should be close to 2/3 of the overall boat length
My 28' boat (32' overall) has 16' bunks

Don Hansen · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

You make no mention of keel rollers. Your going to need them or the keel under the narrow bow will rub on the cross members before the hull contacts the bunks.

DLH

jhendery · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Thanks SOTW and DLH.

Ok. So here's a mockup of what I think I need to do.

Red indicates rollers. The bow roller is already in place. Not sure about how to install the stern rollers but perhaps the rollers would be mounted to the horizontal cross members.

Light blue indicates where the bunks would be installed onto the brackets.

And yellow indicates where the brackets would be installed. On the inside of the trailer support beams using u-bolts.

Is there anything else missing?

jhendery · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

duplicate

Don Hansen · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Your brackets, marked in yellow, should be mounted on the cross members. That way you will be able to tilt the bunkers so the tops makes the most contact with the boat. You could go either inside or outside the frame rails but I like the the bunkers on the inside as you show it so your nice new boat finish is not damaged by the ends if the frame rails.

DLH

Don Hansen · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Also, I would use square u-bolts to attach the bunker brackets to the cross members. That way you can fine tune the brackets, port to starboard, as needed. From your picture the up-rights for your brackets seem to be made out of flat stock with no angle bends for strength to them. Maybe these would be better.

I edited out my other 2 tries. These are what I meant.

BOLSTER BRACKETS - Tie Down Engineering 81221 - iboats

DLH

colbyt · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

I'm only looking at pictures with no measurements to really work with but if I had a trailer like that and a boat of that apparent size I would simply add a piece of 1x stock to the top of the rails and carpet it. If it needed an angle the table saw would create it. Then add the keel rollers. There are brackets that will do the job.

jhendery · May 17, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Thanks DLH. I will mount the brackets onto the cross member beams on the inside using u-bolts.

The brackets from BPS do have the angle bends.

Have a good weekend eh!

Don Hansen · May 18, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

I was looking at the picture that you marked the locations of the brackets. In that picture you can't really see the angle bend.

I'm curious. In the first picture of your thread showing your progress as you rebuild your boat, it shows your boat setting on the trailer. The transom seems to be sitting a long ways back from any support. Bunkers made to reach that far back would reach out a long ways from the support brackets. Are you planning to move the boat forward on the trailer? Looks like you have the room to do it.

DLH

smokeonthewater · May 18, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

bunkers are holes in the ground

trailers have bunks

just an fyi

Don Hansen · May 18, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

smokeonthewater said:
bunkers are holes in the ground

trailers have bunks

just an fyi

Thanks for the reminder. Don't know why I do that. Sometimes I catch it, sometimes I don't. Another one I do is "you" instead of "your"

DLH

jhendery · May 20, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Don Hansen said:
I was looking at the picture that you marked the locations of the brackets. In that picture you can't really see the angle bend.

I'm curious. In the first picture of your thread showing your progress as you rebuild your boat, it shows your boat setting on the trailer. The transom seems to be sitting a long ways back from any support. Bunkers made to reach that far back would reach out a long ways from the support brackets. Are you planning to move the boat forward on the trailer? Looks like you have the room to do it.

DLH

Thank DLH. You make a good point.

I took measurements and realize I need to re-position the winch post.

LA boat is roughly 14 ft from stern to where the bow will rest at the bow stop. Currently the trailer measures 11 ft from the rail end rail to bow stop. So I think I need to move the winch post roughly 3 feet forward.

This picture displays the position where I will mount the bracket to the horizontal cross member. The width from port to starboard bunk is roughly 32 inches. I think this is good since the hull begins to curve upwards around 35 inches. Notice where the tape begins - I think I will bring the bunks back to this position roughly 1 ft from stern brackets.

Re-position the winch post roughly 3 ft.

Another trailer shot.

I think I only need one stern roller mounted on the cross member closest to stern? Should I have another roller on the second cross member?

Have a good one eh!

Grandad · May 21, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Yes, you need a roller at the second crossmember. Imagine the empty trailer tipped as it sits on the launch ramp as your boat approaches while floating level. Because of the angle difference, the forward part of the keel tight to the stem will float over the submerged tail roller and impact the second crossmember. Additional keel rollers help to distribute the weight anyway, once you're loaded. Win,win. - Grandad

krakatoa · May 21, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Hope this pictures help you in to your conversion...

jhendery · Jun 5, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

Quick update without pics ...

I decided to give BPS brackets and bunks a go. Still need the rollers. Those will come soon.

I also had 8 square u-bolts made up for the 4 brackets. Now I need 8 plates to install the brackets and u-bolts to the cross members.

Perhaps unnecessary but I decided to prime and tremclad the brackets. Can't hurt.

jhendery · Jun 7, 2013

Re: Galvanized Steel Trailer Conversion from Rollers to Bunks

What is the best method to install trailer brackets? As far as I can tell there are two options.

Option 1 - install one square u-bolt through center of bracket

Option 2 - upgrade u-bolt bracket plate and connect bottom and top u-bolts

Option 1

Option 2

Galvanized Steel Trailer Conversion from Rollers to Bunks

Petty Officer 1st Class

Supreme Mariner

Fleet Admiral

Petty Officer 1st Class

Fleet Admiral

Petty Officer 1st Class

Petty Officer 1st Class

Petty Officer 1st Class

Petty Officer 1st Class

Petty Officer 1st Class

Master Chief Petty Officer

Petty Officer 1st Class

Petty Officer 1st Class

Fleet Admiral

Petty Officer 1st Class

Petty Officer 1st Class

Lieutenant Commander

Senior Chief Petty Officer

Petty Officer 1st Class

Petty Officer 1st Class