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Author Topic:   What material for trailer bunks?
Chuck Tribolet posted 08-24-2004 11:53 AM ET (US)   Profile for Chuck Tribolet   Send Email to Chuck Tribolet  
What would you make trailer bunks out of these days? My
Shoreland'r all-bunk trailer currently has two 10' 2x4s.
Dunno what they are made of. After six and a half years,
I'm starting to think about replacing them, but with what?

The trailer gets dunked about two days a week, twice each
day, always in salt water.

A couple of years ago, I would probably have used pressure-treated, but today's copper-based pressure-treated
stuff has some nasty galvanic action, and the last thing
a salt-water trailer needs is more corrosion.

So maybe some nice clear redwood, maybe upsized to 2x6 (I've
got room) because redwood isn't the strongest stuff?

Or just a good fir, well sealed?



andygere posted 08-24-2004 11:59 AM ET (US)     Profile for andygere  Send Email to andygere     
You are correct to stay away from pressure treated, it is typically lousy lumber. Good con heart redwood isn't a bad choice, but it tends to end split. If you can find some nice dry stuff without knots, it will work fine. It's worth paying a little extra for the kiln dried stuff. A few coats of linseed oil will help it last a little longer. Red or white cedar is also a good choice, but might be tough to find. Southern Lumber on Alma would be your best bet for that. I think some type of cypress is used by a lot of the trailer manufacturers, but it would be hard to find around here.
Joe Kriz posted 08-24-2004 12:11 PM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     

Andy has good suggestions and there has been different discussions on the best wood.

Here is what one of the largest trailer manufacturers in CA told me what they used.

Trail-Rite trailers told me they used green fir becuase it would conform (bend) to the shape of the hull bottom as the wood cured. Remember, the bottoms are not flat on our Whalers. The bottom starts out on one angle in the rear and starts getting more angled the further forward. Hence, the use of green lumber (not dried).

I have used green fir on my trailers and have never had any problems but I am not in salt water very often.

One other thing Trial-Rite started doing was only covering the top and the 2 sides of the bunks. They told me this allowed the water to drain from the wood quicker and not keeping the draining water trapped against the bottom of the wood.

2x6's would be the way to go if you have the space. 2 long ones (10') and 2 short ones (5') on the outside is what I have. Makes the boat very stable and solid on the trailer.

Tom W Clark posted 08-24-2004 12:39 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Andy and Joe have pretty much beaten me to the punch.

Do NOT use pressure treated lumber. Never mind about the nasty chemicals, P.T. lumber is typically of a very low grade. This is because P.T. lumber mostly need only lay there and not rot. Apart form decks, it is not use for much structural spanning.

Redwood or Western red Cedar are both excellent for rot resistance but they are soft. The fact of the matter is Douglas Fir is highly rot resistant itself, probably more rot resistant that any other soft wood apart from Cedar and Redwood.

Joe is right about the use of green lumber. That has been my understanding as well. Kiln dried lumber would not be preferred because KD lumber is more brittle than green or air dried lumber. (Traditional boat builders would never use KD lumber. The would always have a stash of lumber stickered and drying for future use.

In the case of your Montauk, I do not think it is really that important to go to any extraordinary lengths to get a certain type of wood. If you can get green Douglas Fir, great. If all you can easily find is KD Fir, then I bet that would work fine too. Just don't go the The Home Depot and buy that crappy Hemlock they tend to sell. Go visit a REAL lumber yard.

Phil Tyson posted 08-24-2004 06:16 PM ET (US)     Profile for Phil Tyson  Send Email to Phil Tyson     
Keep in mind that salt water helps preserve the wood. Most wooden docks/floats in New England are not PT. Those that are PT are overkill and overly expensive.

Going green helps but I don't think you need to go with expensive stuff like cedar/redwood. Fir is a good choice.

bsmotril posted 08-25-2004 10:40 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Cypress is the best all around wood to use for bunks. it is very stright grained like Fir, but holds up much better against rot. Cypress is what is used by most of the manufacturers for their trailers. BillS
andygere posted 08-25-2004 04:54 PM ET (US)     Profile for andygere  Send Email to andygere     
On the west coast, redwood is often the cheapest lumber available, and is sold just about everywhere. I suggested kiln dried because of my experience with sopping wet, overweight, knotty and split-prone construction common redwood. Con heart is a little better, but not much. The kiln dried will shrink, split and twist a whole lot less, but not might conform to the hull shape quite as well. I used kiln dried con heart on my keel roller Montauk trailer and it worked fine. Since Chuck's is a bunk style trailer, green wood might be the best call.

TWC, Southern Lumber is a real lumber yard with prices to match! They do have good grade stuff, and will do mill work while you wait for a nominal charge. I had them rip and surface the teak I made my RPS seat riser from, and ended up with zero wasted wood as a result.

RonB posted 08-25-2004 05:58 PM ET (US)     Profile for RonB  Send Email to RonB     
Not being a structural engineer or anywhere near that qualified, I'll ask the following stupid question? Can the new plastic planking sold at Lowes/Home Depot that is used for decks be suitable for trailers? You could still put carpet over it. About twice as expensive as normal grade lumber, I just don't know anything about it holding up, strcutural integrity and such.
coralgater posted 08-25-2004 09:54 PM ET (US)     Profile for coralgater  Send Email to coralgater     
Cypress is probably the best timber to use and avoid
using carpet (holds sand grain) Try the teflon strips
on bunks for quick,easy entry.
Chuck Tribolet posted 08-26-2004 12:51 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Andy, I haven't been there in a while, but a couple of blocks
south and a block east of Southern is Aura Hardwood Lumber.
Better prices, has stuff that Southern doesn't (like ApplePly
maple plywood), but doesn't cut. I got turned on to Aura
by a cabinet maker buddy.

Fortunately, I'm not in a rush. I'm going to accumulate all
the hardware (SS carriage bolts, carpet, Monel staples (and
a new staple gun to replace my 35-year-old cheapie), etc.)
then get the wood, then drop Adm. Linda and the whaler on a
nearby lake while I take the trailer home to redo the bunks.

And a fresh can of Silicone. No paraffin. ;-)


andygere posted 08-26-2004 01:26 AM ET (US)     Profile for andygere  Send Email to andygere     
Thanks for the tip on Aura lumber. I like Southern but their prices are outrageous. Let me know when you are getting close to doing the trailer work. Nancy and I will be doing a weekend cruise in the early fall, and you can borrow my slip for the weekend. In fact, it's empty right now and will be for at least another week since I have Namequoit on the trailer for the trip up to SF for Royce's fishing tournament. I also haul the boat for a while in the winter when fishing has slowed down (or been closed!) and I need to do some projects, and there are always projects.
striper swiper posted 08-26-2004 08:09 AM ET (US)     Profile for striper swiper    
Chuck,check your local boat dealer that you may be friendly local dealer gave me 2 carpeted (brand new}bunks for free,he has about a half dozen just laying around from the people who bought trailers but wanted to convert them to rollers instead.
skred posted 08-26-2004 08:25 AM ET (US)     Profile for skred  Send Email to skred     
I'm with Ron B. The synthetic lumber now being manufactured is pricey, but you only buy it once. It certainly is strong enough, impervious to salt or fresh water, and since you'd cover it with some sort of bunk carpeting, color is not an issue. I understand it's made from many kinds of recycled plastic.
Legobusier posted 08-26-2004 08:32 AM ET (US)     Profile for Legobusier  Send Email to Legobusier     
I can give a semi-educated info on this: The synthetic stuff (Trex and the like) is typically non-structural, decking and/or trim boards. Most of them have very little bearing capacity and deflect quite easily, so I don't think (for the most part) it's an adequate solution for a trailer - especially an all-bunk trailer as Chuck has.

There may be a "structual" member out there in synthetics, but it's yet to hit the main-stream if so or it is of a profile not compatible with a trialer. (Timber-Tech makes one that's a tounge-and-groove plank with a fin profile that's quite strong)

There are plenty of pvc/fiberglass/resin products that you could also consider (similar to vinyl fence posts) but why re-invent the wheel here?

Just my opinion of course.


bsmotril posted 08-26-2004 10:13 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
The Trex and similar decking would not work at all for bunks. If you look at their web sites, or lieterature, you'll see that the open span recommencadations (IE Joist spacing) are much less than that of regular wood. That is exactly what you don't want for a bunk unless it is a very short one. It deflects under load much more than wood. Bills
skred posted 08-26-2004 10:42 AM ET (US)     Profile for skred  Send Email to skred     
Well, so much for ecology....

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