I am at the planning stage of replacing some deck hatches on a sailing boat. The framework is mitered, to prevent endgrain being open to the sea, but as these are stepped on they also need to be strong.
I see the altenatives being miters with routed slots for loose tongues, or mitered mortice and tennons. Anyone have any experience with this type of work?
Thanks.
BernardR
I'm not sure this is a valid concern, since the hatches will have to be sealed by either thick paint or thick varnish. Any unprotected wood, end grain or not, will be damaged terminally. Strength is probably a lot more important, and the traditional approach is to half-lap the corners, often with a dowel through the joint for extra strength.
Sat, Nov 27, 2004, 12:49pm (EST-1) snipped-for-privacy@cox-internet.com (Bernard=A0Randall) says: I am
I'da asked at news:rec.boats.building
JOAT Measure twice, cut once, swear repeatedly.
These are natural teak hatches, no paint or varnish, washed with sea water.
Bernard R
Okay, obviously we're not big on salt water boating here in the desert, but. . .
I was under the impression that even teak decking and hatches got finished with something like spar varnish on boats. Untrue?
(BTW: Spar varnish is loverly stuff, even if you never get within a hundred miles of salt water. I use it to protect my relief carved signs, which are usually displayed outdoors. Stands up well to desert sun and the occasional torrential downpour.)
--RC
Sleep? Isn't that a totally inadequate substitute for caffine?
I know I made a joint like this before. From above it looks like a miter joint but from below, it looks like a lap joint. If your fram is to be made 4x4 you cut all 4 pieces to 4' lengths then cut the miters only half way throught the thickness of the work. Use a chisel or router to remove the waste.
Salt water boats typically do not have any finish on the exterior teak deck areas, this particular boat is 25yrs old and though the framework is still good the teak strip veneer (simulated planking) that covers the marine ply panels is wearing through.
Most of the hatch cover frames I've seen were either dovetailed or box jointed. I'd recommend varnishing the hatch covers even if larger expanses of teak deck are left to weather.
Bernard Randall wrote:
Nope. Spar varnish is the bendy stuff (and UV proof too). As a compromise it's thus likely to be poor on finish and abrasion resistance. Dreadful stuff for use on deckhouses. Looks ugly when you put it on, then gets worse with wear.
As to whether you paint something onto your decks or deckhouse trim, then that depends on taste, money and footwear. Best stuff is battleship grey paint, nicest looking stuff is oil. Most people go somewhere in the middle.
The best joints IMHO for this sort of thing are a secret comb joint under a mitre - a modern variant of secret dovetailing. There's a square-toothed box joint cut over the inner 2/3rd of the joint and a plain mitre outboard of that to hide the end grain. Bit slow to cut because you need either a finger jig and a router, or you rout them and square the ends by hand and chisel.
In the sailing community the preference is untreated teak for all hard usage areas and lots of varnish for all brightwork. On a boat things get banged, dropped etc, a treatment that will quickly damage a paint or varnish coat, added to which bare teak is a much surer underfoot than a painted surface. I'm talking sailing boats here where you have to be on deck in all weathers as opposed to motor boats where you can stay nice and warm in an enclosed cabin.
I wrote in an earlier post in this thread that the framework face is 1 1/2" wide x 3/4" thick so to get a decent comb joint I would probably need a
3/16" x 1 1/4" router bit, which would be slow going at the best. I made some CAD drawings of the loose tongue and haunched half M&T and came to the conclusion that the M&T gave the same interlock volume as the loose tongue, but was easier to cut the mortice using a morticer than having a special set up to do the routing for the tongue method.Anyway thanks all for your input.
BernardR
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