New bunks, end-up or sideways?

[reelfishin]

I am setting up a trailer for one of my boats and wanted to get a few opinions on which way I should set the bunk boards. I am replacing all the brackets so I have a choice, either to set then end wise or flat.
I feel that endwise is stronger and supports the weight of the boat better, but flat they will spread the weight out a bit and support a larger area on the hull, but they will be more likely to flex and give, and not as strong overall.
Any one have any other opinions or reasons for either choice?

The trailer currently has the boards laying flat and has recessed bolt that are near imposible to keep tight. The bunks also flex a lot and don't support much weight between the uprights. I can pull the mid section of each board away from the hull enought to get my finger inbetween with the boat on the bunks.
Also, should I use 2x4 or 2x6 boards? The longest flat section on the hull is only about 8' long, so I also don't see the sense in making them any longer since they won't contact the hull up front anyhow. The current bunks are 16' long and have those roller conversion strips on them that simply do not work.

Also, am I right in that the lower keel rollers should support the main weight and the outer bunks should only level or support the boat? Thus allowing the boat to roll somewhat freely back and forth? In other words, more weight on the keel than on the bunks?

 

[tashasdaddy]

Re: New bunks, end-up or sideways?

the keel roller are to help load the boat and keep it centered. when the trailer is pulled out of the water, 90% of the weight, should be on the bunks, rocking back and forth on the keel, puts a lot of stress on very small areas. also the bunks should extend atleast 1 1/2 inches beyond the transom. we don't know the size, weight, or style of the boat, so 2x4,2x6,flat or upright, i can say at this time . i know a lot of larger boats use 4x6.

 

[jeeperman]

Re: New bunks, end-up or sideways?

No way should the weight of the boat be supported by the keel rollers.
If you only have three or four keel rollers, your putting the entire weight of the boat on about three or four spots that are about 2" sq. max.

I would be inclined to use the 2x6 laid flat. Then in between the brackets where your getting the sagging, I would bolt the longest 4x4 I could fit to the underside of the 2x6.
Since the boat only rests on 8' of the current 16' bunks, the weight of the 4x4 under the 2x6 is about a wash by eliminating the unused other 8 feet.

 

[tashasdaddy]

Re: New bunks, end-up or sideways?

let's see what size the boat is. a picture would even be better.

 

[reelfishin]

Re: New bunks, end-up or sideways?

The boat is a 19' V hull and it weighs in at about 1700 lbs on the trailer with the motorand fuel. The current trailer is a single axle that is too light and a poor fit, I am refitting a larger twin axle for it. The old trailer and the new trailer currently have those roller strips which were most likely added to replace wood bunks at some point. I don't like how close the metal rail sits to the boat when it's on these rollers so they are going away. I do have room to seat a 2x6 on each side, but it would mean that loading each time would require an exact placement with no room for error. My thinking was that if I turned the bunks upright, I could use two sets of bunks, one set mounted low, the other up near the chines. Teh bow rollers on both trailers are shot, they are loose and the centers are all worn out letting the boat to ride dangerously close the the metal frame.
The first pic below is of the old trailer and the rollers, you can see how close the rail is to the hull, the rollers are also near impossible to turn with weight on them, they shift sideways and bind against the metal rail they are mounted to. Since they do not roll freely, the boat can only be floated on and off, so there's no sense in having rollers. I have a new set of these and they are the same way, so it's just a poor design not that there's something wrong with them.
In the second pic, the last four rollers of each bunk do no contact the hull, the trailer was orginally set for a 21' boat with a shallow V. I won't need the last support or the added length, on the old boat these bunks ran nearly to the bow of the boat, that's not posible on my boat. The hull continues strait and level for about 8' then begins a sharp rise to the bow forming a V.
The easiest thing to do would be to simply carpet two 8' 2x6's and mount them right on the same brackets that are already there, adjusting them to fit the new boat. I was just thinking that it may be stronger to run two rows of vertical bunks which cradled the hull over a greater area. I like a boat/trailer combo that sort of cradles the boat on it's own without having to worry about how well centered it is. The existing bow rollers on both trailers are badly gouged and broken, it appears they've been taking a beating during loading and unloading. The bunks and keel rollers are about equally loaded.

 

[tashasdaddy]

Re: New bunks, end-up or sideways?

the trailer in the picture the rollers are mounted on a 2x4, and there is enough bracket left to raise the bunks, the spacing of the braces is good, i just go with 2x6 flat,there's plenty of support. seeing it already has 12 " keel rollers, throw a couple of 12" self centering roller on there. i have 2 on my trailer. http://www.iboats.com/Self_Centerin...d.238442--list_time.1176411364--view_id.56624

 

[Frank Acampora]

Re: New bunks, end-up or sideways?

I have a 15 fott glastron deep vee that I set up with 4 X4 bunks. I beveled the inner 2 inches to 22 degrees (The deadrise on the hull) and left the outer 2 inches flat. The inner two strakes on the hull ride on the flat portion. I did this because the strakes are usually where stringers are glassed in and are the stronger spot on the hull. With the center rollers set up to just touch the hull when loaded, the boat self centers every time. I back in until the rear roller is just even with the water and crank up the boat. It doesn't take much effort and the extra effort over float-on is worth it having a self centering boat and looking competent at the ramp.

 

[eli_lilly]

Re: New bunks, end-up or sideways?

I have 2x6 bunks laying flat right now and they have sagged way too much between the brackets. In the next couple of weeks I am replacing them with 2x4 on edge.

-E

 

[reelfishin]

Re: New bunks, end-up or sideways?

I am leaning towards switching to a either two or four 2x4's on end, I ordered the brackets and will try it, if I don't like it I can always go back. My main concern is tossing the roller bunks. They might work ok on a flat bottom boat, but are worthless on a V hull. I also considered using two 4x4's, but they tend to split with age too often.
I am having trouble finding new u bolts to match this frame, the crossmembers are 2'" x 4" channel, not the more common 1 1/2" by 4" channel. I may be able to save the old one's but would rather have all new. I may just end up drilling and bolting the new brackets on though.

Another thing I was thinking of was that if I use 2x6" boards flat, I will be adding that much more friction if I have to winch the boat forward. The 2x4's on end will glide the boat much better. Besides, if I am under the stringer, the hull won't have any flex anyhow, so having a wider board won't add any strength. The current trailer uses rollers, my concern there is how close the frame is to the hull, the would be fine, even though they won't roll under weight, if the rollers were about a half inch larger in diameter.
I have considered adding a set of bunk slides but I will only do that if I see the need down the road. They do eliminate the need for carpet and they don't hold sand like carpet does.