Trailer Bunk Setup

Moderator: GreenLake

Trailer Bunk Setup

Postby James4 » Tue Sep 13, 2022 10:20 pm

I've got a nice galvanized trailer that came with my DS II. The bunks were set as far apart as the trailer allows, which is about 39" from outside to outside. The boat really sways on the trailer, and I notice that the bottom of the boat is deflected slightly by the bunks, which are about 6 feet long. I worry the deflection in the hull will eventually weaken it. I think it would be difficult, but possible, to modify the brackets holding the bunks to space them further apart so that they were supporting the boat closer to the vertical part of the hull. I don't know if making them longer would make them any better. And I've thought of laminating new bunks so they're more willing to conform to the hull shape. I've adjusted the rollers to take more of the weight, but there's still plenty of deflection. If I'm worrying about nothing, that would be fine to hear. Thanks for any thoughts.
James4
 
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Re: Trailer Bunk Setup

Postby GreenLake » Tue Sep 13, 2022 11:54 pm

The first thing to look at might be widening the bunk supports. That increases the surface area and reduces point loads. At the same time, you might look at extending them towards the rear, if there is space. The goal would be to extend the bunks so that they support as much of a the flat areas of the rear half of the hull as is feasible.

Some people use a center bunk (instead of rollers) to support the centerline "V" part of the hull. Again, to spread out the loads.

A disadvantage of the DSII over the DS1 is perhaps the fact that the seat uprights don't connect to the hull and therefore don't act as stiffeners in the same way. Still, a wider support base should help with spreading the load.

Some trailers, as delivered, have criminally narrow bunks; those will eventually damage your hull.

If your bunk supports are nearly 40" apart, that's over half of the DS's beam (and the usable width for support is less, due to the hull's curvature). If you fit bunk boards of 8" or even 12" wide, that should make a big difference.

As far as rollers go, I would set things up so that the bunks are a bit higher in the rear so that the last roller in contact with the hull is no further aft than the aft edge of the CB trunk. Even if a bit lower, those rear rollers will support the front of the boat as it rolls on/off. Only when you fully pull the boat onto the trailer would the bunks take the full weight.
~ green ~ lake ~ ~
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Re: Trailer Bunk Setup

Postby James4 » Wed Sep 14, 2022 1:05 am

Greenlake, thank you for your prompt response. I will immediately look into wider bunks. If I used 1x8's or 1x10's, they would be more flexible and willing to conform than the current 2x4's. The boat and trailer were previously used only with a hoist, and rather than rollers, the trailer had a padded 2x6 for about 10 feet. The big question for me that I'm starting to look into, is what is the weight distribution between the rollers and the bunks. Given that the hull is rather flexible, which in my mind translates into thin and possibly week, I'm wondering if most of the weight should be on the centerline of the boat. Thank you again for the help. This forum is wonderful.
James4
 
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Re: Trailer Bunk Setup

Postby GreenLake » Wed Sep 14, 2022 8:07 pm

Glad you like the forum.

If you look at the rear of the DS hull, you'll notice that it's actually pretty flat. Those are the areas that you want to support with your bunks. You would still space them as widely as you could while not extending into the curved portions.

The "V" in the centerline is pretty stiff, from geometry alone: it's hard to bend a V along the spine. So that part can take some weight, but rollers are also point supports. So I would be a bit careful - that's the reason I set it up so the roller that does touch the center line is not too far behind the CB trunk.

Ideally, when you've set up your new bunks you are able to dial in things to where you don't see visible deflection of the hull.
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