Need Bunk Replacement Advice

I just bought a trailer for a 1981 Thunderbird Formula. Since the trailer was not originally for this boat, all the parts don't fit.

As it sits, it has two sets of vertical bunks, each about 8 feet long. I want to replace the inner set (they sit directly on the trailer frame) and dispose of the outer set. At the same time I am adding three sets of keel rollers at the first cross member, at center hull, and under the bow section.

My questions are:

• Is there enough support from a pair of paired 2x8x10 bunks and keel rollers
• If not, how do I get the bunks to fit the hull properly - it is easy to get one set to fit the hull, but the second is a little more difficult. Can I put a second set of bunks on with the boat loaded somehow?
• Does the top edge of the bunk need to be cut to match the angle of the hull? The Thunderbird is a deep "V" hull and it seems like the hull will rest on just the edge of the bunk.

Sorry if these are obvious questions - I never trailered a boat before (we dropped our boats in the water for the summer and pulled them for the winter in my younger days) so I am lost. I read through the first ten pages of the forum and used the search function... if I committed a forum faux pas please go easy on me

I am also a bit pressed for time. The person I purchased the boat from needs it moved asap - this weekend! I just got word last night so now I'm in a panic.

Any help would be appreciated - Thanks!

Re: Need Bunk Replacement Advice

Pics woudl be great but ill give it a whirl...

Most convenient way to do this is to lift the boat and support it and then place the bunks to conform to the chines on the hull. Usually you want to have the 2 center bunks down first to support the keel, and most of the weight of the boat. Then you will lower the boat down onto the center bunks and allow them to move under the weight of the boat to conform to the keel angle. Once they have the weight of the boat on them, tighten them down.

Than you want to measure up from the base of the trailer frame to the position you would like to have support under from the outer bunks. Make sure the boat is sitting level when you take this measurement. Get brackets that have the length you need and bolt your bunks to them. Bolt the bunk brackets to the frame and adjust up till the boat is level on the trailer and slightly supported by the outer bunk. Tighten the brackets for that outer bunk and go to the other side and do the same thing. Just make sure you get the boat nice and level and preload the outer bunks a little bit. Most weight should be on the center <keel> bunks. The outers just hold the boat level mostly and take less weight load.

If you cant lift the boat, your other option is jacking the boat up, and iv never done it as i always wench my boat off the trailer from my garage rafters. Tho yes you can jack the boat up with the bunk boards and raise or lower the boat on the trailer or move other bunks around. This method i find more trouble than lifting.

GL
RC

Re: Need Bunk Replacement Advice

Rollers work better than long bunks generally.

It is best to have a lot of contact points for the boat hull bottom.

Best practice is to attempt to have the center of gravity close to or slightly forward of the axle.

One way to set things up is to attempt to locate the approximate center of gravity of the boat when its on the trailer by seeing how heavy the tongue feels and adjusting the boat fore or aft to achieve a slight tongue heavy situation.

Then jack and block the boat slightly higher than the trailer. Adjust the rollers to all touch the boat bottom. Inspect that the boat is level, the ground is level and all rollers are touching. Tighten all roller support clamps. Remove lower the boat onto the trailer and double check your work.

Re: Need Bunk Replacement Advice

Center of gravity could cause a tongue weight overload. The center of gravity really doesnt matter. What does matter is having 10-15% of the total trailered weight on the tongue. Otherwise just set it to fit the boat and tighten it all down.

Re: Need Bunk Replacement Advice

Don't worry about the CG of the boat / trailer setup. As said, you need the proper tongue weight when all set up; about 10 to 15% of the total weight of the trailer. If you stay with bunks, you can get some of the bunk spray. From what I understand, it is some slick stuff and people have lost their boats on a concrete ramp while backing down.

Re: Need Bunk Replacement Advice

I think I may have lucked out.

I measured the boat, and the hull has a pair of flat runners along the length of the hull - at the same points as the bunks.

I am going to use rollers just to be certain that the bow doesn't ram into the cross member going on the trailer, but I think the bunks will be fine as they are and the hull will actually ride just fine. I may have to build the outer bunks up with a 2x4, but that's child's play!

Thanks!

I'll post some pics and maybe get some more advice when I've got the boat on the trailer!