Bunk positioning.

[pman7]

I have a 16' fiberglass, 71 Ouachita boat and I'm changing trailers. The new one has adjustable bunk positioning.

I'm using 2ea 8' long 2x6s with the boat sitting on the flat 6". There are also 3 center rollers plus the roller on the stop bar at the front.

On fiberglass boats should the bunks generally be closer to the outside edge or should they be about halfway out, considering I also have the rollers?

My boat has a ridge about 15-16 inches out, on both sides, from the center line of the boat. My boat is about 48" wide at the bottom rear. Should I place the bunks to the outside of the ridge or the inside of the ridge?

 

[tashasdaddy]

Re: Bunk positioning.

i would place them outside. how many supports do the bunks have? i hope atleast 3 on each side, if you are going flat. you want more weight on the bunks than the rollers.

 

[pman7]

Re: Bunk positioning.

I mis-stated the bunk length. The bunks are about 6'2" long. I had a brain cramp when I wrote that. The boards I bought were 8' boards.

Each bunk has only two supports. I hope that is sufficient for the 6' bunk rather than the 8'.

Although the bunks I'm replacing didn't have extra support, I plan to put a 2x4 support underneath each 2x6, perpendicular edge wise, to the 2x6.. This will add support as well as help prevent the 2x6s from warping. You can pick straight boards out of the stacks from Home Depot or Lowes and a week later they're crooked. I hope the brace will reduce the typical warp.

 

[Mark42]

Re: Bunk positioning.

You may actually want the 2x6 to sag a bit under the weight of the boat so that the bunk doesn't deform the hull of your boat. I would rather have the bunk bend to the shape of the boat rather than the boat bend to the shape of the bunk.

I would also make a point of having the boat rest on the bunks near a ridge in the hull because that is a strong point in the hull. Often having a stringer or similar support on the inside.

Once the boat is on the trailer, you can raise or lower the bunks by using a floor jack and length of 2x4 to support the bunk when the mounts are loosened and moved up or down.

I also lean to having more weight on the bunks than on the keel rollers. My MFG sits on a bunk trailer with keel rollers, but my Bayliner has no keel rollers and the entire weight of the boat is on the bunks. The difference being that the Bayliner trailer is custom built by Bayliner specifically for that model boat. So I trust they know what they are doing. Point being that every boat is different, so use your best judgement based on the shape of your boats hull.

BTW, both trailers bunks are curved under the weight of the boats.

 

[Nova II 260]

Re: Bunk positioning.

You may actually want the 2x6 to sag a bit under the weight of the boat so that the bunk doesn't deform the hull of your boat. I would rather have the bunk bend to the shape of the boat rather than the boat bend to the shape of the bunk.

A 16 footer is not much weight, let the bunks form to the hull. BTW, support your transom. Let the boat sit and fit on the bunks, then bring your rollers up to the keel. The lower it sits on the trailer the easier tow and to load/launch.

 

[srothfuss]

Re: Bunk positioning.

On fiberglass boats should the bunks generally be closer to the outside edge or should they be about halfway out, considering I also have the rollers?

pman in my experience [sailboat trailering] it's very important to support the weight of a fiberglass boat on the keel and use the bunks to stabilize the boat side to side. If you put too much pressure on the sides of the hull via a bunk strip it can compress the hull over time and create a weak spot.

Nova's explaination on setting up the rollers and bunks is the method I've used previously to readjust my current trailer. I would have the bunks above the ridges on your boat to give you some extra side to side stability for highway travel.

 

[pman7]

Re: Bunk positioning.

Thanks to all of you for the feedback. I guess I'll drop the idea of the perpendicular 2x4 to add support.

My boat's bottom isn't the typical v-bottom. At the stern it's actually more similar to an aluminum jon boat. The bow is v shaped to cut the waves but the back is pretty flat. It's not as flat as a jon boat but it's close. The back has a subdued keel ridge and then two small ridges further out about 15 to 16 inches away from center. My bunks will fit right up beside on the outside of the ridges.

I'll be adjusting everything to the lowest height possible. As it stands it looks like, at the lowest adjustments, it will still be at least an inch taller than my other trailer. But my other trailer has my boat on it and that could account for an inch of height. Both trailers have leaf springs and I would imagine a 700 to 800 pound (when fully loaded with gear) boat would drop the trailer height an inch. The new trailer is rated about 1485 lbs.

 

[JeffsAV]

Re: Bunk positioning.

I have, I think, the same boat you do. I am needing to adjust my trailer bunks as well. Your description of your trailer setup is close to what I have as well. Would you please post some pictures of your boat/trailer for reference?