Replacing bunk boards on trailer

[SEA3PO]

I am working on my trailer for my tug...same size as my C-Dory and probably 1000 pounds heavier...
What are U.H.M.W. boards? Is that the plastic wood stuff? I see them advertised in the catalogs. I was just thinking of using some pressure treated pine 2X4s from the lumber yard. Is redwood strong enough?? that would resist the weather better.

I also was thinking of buying the carpet covers at Home Depot rather than West Marine.... (outragious price) is there anything special about the carpet used in marine applications vs commercial outdoor carpet?

Joel
SEA3PO

[Captains Cat]

Hi Joel, UHMW is Ultra High Molecular Weight Polyethylene, sort of like the plastic lumber, may be one and the same in some applications. I'd not hesitate to use Pressure Treated stuff though and cover it with a synthetic carpet of some sort meant for outdoor use. You could probably replace it every 2 years for the cost of the UHMW stuff. Go for it!

Charlie

[Da Nag]

RE redwood - it's not what it used to be. You're probably better off with pressure treated wood from a rot resistance standpoint.

I'd also be leary about the poly boards - structurally, they don't handle the same loads as wood.

[thataway]

Ultra High Molecular Weight boards are made of plastic products. They are resistant to some weathering, but are not as rigid as wood products, so that I don't think that they would be as good for trailer bunks. There are UHMW plastics used for "slicks" on top of the bunks--and I have that on my float on trailer. I have heard of high density polyethylene bunks for small boats on lifts--but not on trailers.
http://www.ultimatebunkboards.com/index.html I have not used these, but I think you will need more support on a trailer.

Cypess is probably the best wood for trailer bunks, if you can find it. There are several dealers who advertise it. For my lift bunks I use southern yellow pine, knot free, true dimensional, salt water pressure treated. The salt water treated boards have 10X the toxins which the regular treatment is. They cost more, but last a very long time in full time imersion.

I would consider 2 x 6", but in some applications 2x4 may be enough.

I use double thickness of the home depo carpet on the lift bunks. I use Monel staples for attatching (Monel will last much longer than the SS staples, and are availabe at many hardware stores.

I think that you should be able to find adequate material at HD--but also there are a number of other suppliers on the internet who are cheaper than West Marine--and about the same product.

Hope that helps.

[Sneaks]

Joel, AFAIC redwood, preferably heartwood, is strong enough. I've replaced bunkers and always used redwood. Also if truth be known, I've always used Home Depot type outdoor carpeting as well. The only caution I can add is to be absolutely sure to use only stainless steel staples (or Monel) and don't staple on the "boat" side.

No, I didn't always use spendy heartwood but I did use select quality clear boards.

Don

[Da Nag]

[thataway]

Agree with Da Nag, and would not use "slicks" on a C Dory per say. The area of contact on the Tom Cat is the deep v part--and it may scratch some, but with the problems launching the cat--it seems to have solved it.
The same slicks have been used by the Glacier Bays on similar trailers for a number of years--and solved the same problems that the Tom Cat has.

Mary Kay Liquid Rollers will work fine on conventional bunks if you need them.

With the slicks, you need to have an additional set of chains to be sure that the boat does not slide foreward--or backward-=not depending on just the winch post--our trailer has a large welded steal tube as a foreward stop, reaching ot both hulls, rather than the central single roller on some trailers.

[Jack in Alaska]

I put a new Road Runner trailer under my 22' C-Dorythis past summer.
The supplied bunks were 2x6 covered with black carpeting. I replaced them with rough cut spruce 4x6 with teflon strips on the top. No need for carpeting. It all works great at a low cost.
The hassle was replacing them with the boat on the trailer. Lots of jacking and bracing.

[therrick]

Joel,

I replaced the bunks on my trailer this summer. The previous ones were pressure-treated lumber, but were of a single 4x6, and they had warped and no longer supported the hull evenly. Most of the pressure-treated (p-t) lumber available at home improvement centers is of poor quality and prone to twisting and warping. What I ended up doing was to laminate three pieces of 1x6 decking together for each bunk. The varying grain structure in the three pieces will tend to add strength and counteract stresses from warping (think plywood). When picking out the decking, I looked at the end of each one. For each bunk I bought two cut from the center of the tree and one that was flat sawn toward the outside of the tree.

Grain in boards cut from the center will look a bit like this at the end:

|||(((O)))|||

The grain in flat sawn boards will look more like this at the end, but more wavy:

__________
__________
__________

I put the flat-sawn board in the center of the bunk sandwich.

The three pieces were glued together with Gorilla Glue which works well on the typically wet p-t lumber. I got the big bottle and coated both surfaces even though the instructions say you don't have to. I glued two pieces together on a fairly flat surface and before the glue set up I used 1 5/8-inch deck screws to clamp the pieces together, then added the third piece with glue and screws. Screws were placed about 16-inches apart, one line at the top, one at the bottom, staggered so they aren't directly across from one another.

I flattened the top side (decking is rounded a bit on the edges) to eliminate pockets where water and dirt may collect beneath the carpeting. If you have access to a table saw, large jointer or planer, or a power hand plane it's not hard to do.

Also, I replaced the two old bunks with four new ones. The center two are about eight inches apart, divided by the center strake, the other two are just inside the outer two strakes. I had to drill new mounting holes in the trailer frame for the two new bunks.

Good luck,

Tom

[ffheap]

Joel,

I recently had the boards replaced using green lumber 4" by 6", the 6" being the top and bottom. I had to do this because the roller at the back fell off. I covered the boards with plastic covers purchased at West Marine. The plastic covers most of the board, but you have to make sure that the V slots go from back to forward, out to in, or the boat will slide out, not in the center.

Since replacing the carpet, I can winch the boat on to the trailer alone. Not bad for an old guy. I may replace the plastic with Teflon, which should move the boat much easier.

You have to make sure you have good guides, or the boat will slide off to the side. You might make the boards a bit longer, and cut them to size at a later time.

Joel, it is easier than you think. It's the idea of the project that is overwelming.

Fred

[C-Hawk]

Joel,

I'll have to agree with the pressure treated wood (green board) over the poly. We installed some of the poly on a deck by the beach, here on campus, and it did not stand up to the u.v. of the sun. We had to replace several planks due to warping.

[Jack in Alaska]

therrick,

You made a good point in choosing your boards from the correct part of the tree. I forgot to mention that.

I chose my 4x6 rough cut boards so that the tree center is in the center of the board as you explained. I also have the 6" side up.

Jack