Proper wood materials for marine use

[hectoretc]

Greetings all,
From my readings on this forum, it appears that Teak and Mahogany are the woods of choice for marine work, but a quick peruse of my local do it yourself stores confirms my suspicion that these woods are not normal stock in Home Depot and Lowes kinds of retail suppliers.
So first, is there a “short list” of wood products that are good, better, best to be used in marine applications, and second, is there generally a source for these kinds of materials in larger metropolitan areas (i.e. Minneapolis MN), or via internet?
I'm thinking terms of battery box, shelves in the cuddy or other interioir accouterments, cuddy hatch doors and perhaps some exterior handholds or railings.
Any and all suggestions/recommendations are welcomed… Thanks!

[kokko]

Since we live in the twin cities you can find the lumber you need at Forest Products Supply, 2650 Maplewood dr, Maplewood 651 770 2834

A year ago two of my mahogany coatings were trashed so I built three new ones.
You might also consider the plastic lumber which you can get at home depot. T here is also marine grade Plasteak available

[GreenLake]

I'd argue that there's a place for other materials for some of the non-standard additions you seem to be planning for your boat. On a DSII Some of them would look OK (if not actually better) painted than varnished wood in my view. That means, you could laminate a battery box, use any of the structural marine foam boards or, in a pinch, use epoxy-coated plywood (painted afterwards).

Any wood that you leave varnished will need fairly regular maintenance, less frequent, of course, if well protected inside a cuddy, but if you have freeze-thaw cycles where you store your boat you will get cracks.

Epoxy coating well-dried wood (all 6 sides of each piece) will cut down on swelling and shrinking with moisture and temperature, so any coating will last longer.

Having worked on a friend's plywood dinghy, I've been impressed with the simplicity, strength and durability of the epoxy coated plywood construction. Add a few strategic strips of fiberglass tape for reinforcement, and whatever you build will be plenty strong and stand up to years of abuse.

[Matt Arian]

Has anyone used staining products for their decking? For example, the infamous "Thompson's Water Seal", or any other exterior deck stain? Also, what are the common methods and products used for treating wood on boats?

For those of you wondering, yes, I am new to the hobby/sport. Looking at restoring a DS so I'm trying to get a rough estimate of what's involved.

[kokko]

practical sailor does regular reports on marine wood varnishes.

[GreenLake]

Practical Sailor is a great little publication.

The wood on a DS1 is accessible on all 6 sides of each piece (true for the floorboards as well, if you take them apart).

With that, it's feasible to epoxy-coat them before applying varnish. Once you use epoxy, you essentially seal in/seal out any moisture, so you don't ever want an open side where moisture can get in.

By eliminating moisture movement, you'll make life easier for the varnish that you still need (to protect the epoxy from UV). The lack of expansion means no more cracks and the varnish will stay in better condition.

I've done my thwarts and coamings that way (on a boat that's tarp-covered 11 months of the year - essentially only uncovered when used). Before, I would have to redo the varnish every year - it would flake off. Now I've finished two seasons of heavier than average use, and the varnish still looks pristine. (I used waterreducible Linear PU from SystemThree for the final coats).

If the epoxy were to ever get UV damaged (because of insufficient coating with varnish) I suspect the work required to restore it would not be insignificant. However, I think given the relatively small number of pieces, that's a tradeoff I'm willing to make.

On the other end are people who rather like to do constant small touchups. For those, one or the other of the oils or oil like materials, like Cetol, would probably be best. They don't fail dramatically, and you don't need a lot of prep to touch up. But you have to do it frequently.

The middle ground between these extremes is to use varnish. I've had bad experiences with using PU based varnishes directly on wood (or over a wood conditioner). They would look fine for a season. Sometimes more, sometimes less, but then flake. Getting back to bare wood was a hassle, but didn't improve longevity. Perhaps a different varnish might have had a slightly better lifetime, can't tell.

Read the review and pick your poison.

[jdoorly]

I've tried a bunch of different varnishes at different price points but it always comes down to you get what you pay for. I cannot fault Petit/Z-spar Flagship varnish plus it contains 6 times the UV inhibitors than their second level varnish Captains. But it's hard to find under it's list price of $38/qt. Everything else has some trade-off I can't live with, like my current test of water based varnish which gets cloudy when it rains and peels off in 6 months!

I've used a lot of mahogany, oak and plywood on my boat and I agree with greenlake you'll be happy with just about any wood if its encased in epoxy! Except the pine boards manufactured from pieces of smaller boards finger-scarfed and glued together: They just seem to come apart at the seems after awhile.

[talbot]

Back to the wood question, most of my wood additions are made from the red oak commonly available in the specialty woods area of Home Depot or Lowe's. It's varnished, and I have not yet had any rot, even on backing plates that are between the decks. There is some staining where water gets in around improperly sealed screws or bolts. I made sure than any such wood is replaceable (i.e., screw it in, don't glue it in).

[GreenLake]

Red Oak, if I remember this correctly, is actually not one of the really rot resistant species - in contrast to European oak which is shipbuilding material par excellence. Red Oak is not recommended for use on boats - although if you dry-sail your DS and garage it when not in the water, that will probably help preserve the wood..

So, use white Oak.

Or, just go and epoxy-seal your backing plates.

Any of the laminating epoxies will do. Laminating means it's formulated to wet out the laminate and usually with rather lower viscosity than "glue" epoxies. (I've used the ClearCoat or the Silvertip laminating epoxies from SystemThree, but you may have other suppliers that are more convenient).

A good seal requires more than one coat. Since you need to coat all sides, supporting the piece while the epoxy cures can be a bit tricky. For backing plates, I'd rest one side on a piece of wax paper (or plastic foil). That can leave small ridges or bumps, which for backing plates are of no consequence. (My coamings I rested on a sort of "nail bed" which allowed me to coat all sides at once and left 4 very small indentations on the back side.)

Unlike varnish, you need to mix up the epoxy, but then it applies easily with a cheap disposable brush. It will build much more quickly than varnish and normally levels out nicely, no matter how thick the brush marks looked during application. Epoxy will heat up during cure, so it will get thinner before gelling and finally hardening. So you need to watch out for drips and runs (don't apply too much), especially near vertical sides.

For backing plates, if possible, drill holes ahead of time, so you can coat them at the same time.

If you do have to drill later, or if you ever want to use wood screws, fill the hole with epoxy to seal it. Carefully wax your screw or bolt and insert it. Threads will form in the epoxy, but the wax will allow the screw or bolt to be removed later.

Backing plates are ideal for this kind of epoxy-sealing as they do not get UV exposure, and, if done right, you never need to worry about rot.

[talbot]

Didn't know that about red oak, but I looked it up and that's correct. As I said, I haven't had any problems yet, but if I'm still alive when it rots out, I'll replace it. Looking for white oak locally, it seems that people grow it but don't mill it here. I found it at online craft stores catering to woodworkers.

[Matt Arian]

I miss the days of local fine wood and lumber suppliers. So many memories of walking into one with my grandpa... nothing beat that smell of various fresh cut woods.

Although we are blessed here in Colorado as we do have one supplier who (as far as I can remember) can get pretty much any kind of wood, from cherry to applewoods to all sorts of mahoganies. So I would imagine they can get white oak and teak as well. It's been a looooong time since I've been in there, so I'll call them up today and see what they still supply. Their name is Alpine Lumber, for those of you who are interested.

[GreenLake]

Although, for ordinary backing plates, I wouldn't normally pick solid hardwood. My choice would be marine plywood.

[talbot]

I think it depends on the location. Maybe it's the quality of marine plywood at my local supplier, but my oak (even tho' it's red oak) has held up a lot better than the plywood I've used. However, the oak is rigid and it can split. The plywood really comes into its own on any curved survace, like under cleats on the inside of the cuddy top.

(I know this for a fact. I actually once soaked an oak panel, build a form, and wet-fit the oak to match the curvature of the roof. As I recall, it was a long winter, with lots of rain and lousy skiing. There is no end to the expensive and time-consuming tasks that bored sailors will come up with in the off-season.)

[GreenLake]

True marine plywood would use glue that can withstand all sorts of abuse. The main advantage might be the absence of a dominant direction of grain in plywood. As you point out. That eliminates the risk of splits along the same. For backing plates underneath the deck ordinary plywood without any obvious protection beyond a layer of paint has endured on my boat for decades. (Installed anytime between factory and PO, hard to tell). However. if I had to install something for the bilge I would be more selective and definitely use epoxy as well.

[hectoretc]

I know I used to know this, but seem to have forgotten. Can anyone remind me of the difference between "marine" and "non-marine" plywood?

And regarding backing plates for cleats and such is there anything at all approaching a "rule of thumb" sizing for a backing plate, i.e. X sq. inches per 100 lbs expected load or twice as big as you think it might need to be, or anything at all like that?

Lastly, from the double-tabernacle discussion, I am (at this point) thinking I need to install a partner reinforcement piece inside my cuddy roof ostensibly around the blow-hole to support my mast surgeries and the moved stress points it's inducing. I think I’d like to try to form the backing board piece to the fiberglass, or maybe it’s not necessary and/or worth the effort? In other words install as a shelf with matching hole, attached at the edges rather than using it as a “whole surface” large backing plate.
I don’t think I have ever (ever being a really long time) done the soaking wood, forming to a curved surface process and would like to try to understand it a bit more. It’s obvious to me, (which doesn’t mean it’s true) if I put a piece of wood behind a curved structure, put some bolts through, or clamps around both and tighten, the wood will begin to bend to the structure shape, and the structure will begin to bend to the wood’s original flat shape, basically arriving at some middle null point that will depend on the strength and flexibility of the two components. The idea being (I assume) that soaking the wood makes it more pliable so it gives more than the mold and If the form is strong enough, it will not give at all, so the null point will becomes the shape of the form.. Assuming all of that is close to true, I still would be concerned that the fiberglass roof of the cuddy is curved in a both planes and drilling several holes in the fiberglass to “pull” the wood up to its shape seems counter-productive.

Even if it works, at that point I have bent “wet wood” to conform to the cuddy ceiling, so then what? Actually I’ll save that question because I’m fairly confident I’ve not accounted for something in this process and the answer is going to be different than my supposition.