I had a wood boat several years ago that had been "varnished" with epoxy by a previous owner. It had done exactly as Gunni suggests, clouded, cracked and peeled from the substrate. It looked horrible. I bet it looked good when first done though. Problem is though that there was no way it would last. The finished was doomed by not having been topped off with a coat or two of UV-stable varnish and it had received exactly zero maintenance.
As a member of the ACBS I am a wood boat follower, and can tell you that many of the trailer queens you see at the old wood boat shows have a base coat of epoxy laid over a well-prepped raw wood surface. The advantage of the practice is that you get a VERY high solids build coat that is thick; it gets you a skin of material that is as thick as even 10 or more coats of varnish from a single coat and it is self-levelling. The sanding down to a mirror-flat surface can usually be done much more quickly than with the relatively slow "varnish, let dry, sand, varnish, let dry, repeat as necessary over the next 30 days" method. The epoxy trailer queens will still always have UV-inhibited varnish, often several coats, in order to give that "varnish" look that you just can't get with Cetol, or even spar urethane, which has a more "plasticky" look to it.
The other show boats done in a traditional method will often have 30 coats of varnish build up, where each successive coat is applied, then the high spots are sanded down with each successive coat slowly filling grain and other low spots. I usually did 14 to 16 coats of varnish on my boats....
I did one boat as an experiment. I used oil-based deck and porch paint in a satin finish for my topsides, and I used spar urethane for the bright work. The boat is beautiful, and to the casual observer is a stunner, but a wood boat afficionado can walk up to the brightwork and immediately tell it isn't varnish. Spar urethane is also a hell of a lot slower than even real varnish; it just doesn't dry very quickly and is always slightly soft compared to varnish, so surfaces are more easilly scuffed.
I am rambling but let me get to two key points and a debatable opinion:
1. Teak and Mahogany are naturally oily. Applying any finish to freshly sanded Teak or Mahogany is like trying to paint the surface of a pond. Your finish will not stick, but rather just lies on the surface. You need to use a good solvent, I usually recommend acetone, and scrub the surface well to remove surface oils from the wood. Get a good pile of clean white rags, soak them liberally and go at it. The rags are going to turn red as the oils are removed from the wood. Changing rags often, scrub liberally until your rags quit changing color. You will know at this point that you have removed surface oils to the depth of penetration of the acetone.
After drying out, (it doesn't take long, acetone flashes off FAST!) move QUICKLY into finish mode. I am talking minutes, not hours. You want to get a thinned-down first coat of finish down, (whatever finish) quickly, before the oils down deeper in the wood have a chance to migrate back to the surface. The thinned first coat will penetrate INTO the wood, rather than lying on the surface and will provide a mechanical grip that subsequent layers can effectively adhere to. If your finish is IN the wood rather than just ON the wood it will have way less opportunity to peel.
2. There are varnishes out there that can be applied VERY quickly. Intelux has their Jet Speed product which can be over-coated twice every day. in a climate-controlled area, (garage) you can get 10 coats on in a week. This gets you a quick high-build with multiple coats, and as a benefit, you can move into a finish schedule that only has you sanding every fourth coat, as opposed to after every coat. This is possible due to solvents migration. IF you can get a subsequent coat on top of a dry-but-still-green prior coat, the two will fuse together chemically without the need for the mechanical bond that sanding provides. This is extremely beneficial if you have done any staining work prior to finishing, as you can have a thicker coating at first sanding, helping prevent sand-through of the stain. Understand that even with Jet Speed, one needs to apply a final top coating of UV stabilized varnish. I like Interlux Schooner personally, but have also used Epiphanes with good results.
3. Lastly, (and some will debate this) there are some people who believe that the last coat you apply prior to putting a piece of brightwork into service should be left as applied and un-sanded. Their rationale is that the UV inhibitors in the material migrate to the surface of that coat and that final sanding and bufing is a no-no in that it theoretically removes the UV layer in the final coat. I have no experience with this, and Chris P. might have insight, but know I fall into the "I don't want to redo it any more than necessary" camp so for all my brightwork projects that will be exposed outdoors, I never sand a final coat.
Put it this way: If I decide I don't like how the last coat looks, it ain't the last coat...
. It looks much like the day I put it on. No peeling, no rub through, no problems mon!
