New fore hatch

[dur]

My existing hatch needs replacing. It is a simple open box with sides about 8 cm deep. The old one is ply sides and top and has lasted well but I have in mind to use iroko, at least for the sides. The question is how should I make the joints between the sides on the four corners. A mitre joint would protect the end grain but be tricky to fasten. Dovetails would be a good test of my woodworking "skills". Does anyone know the proper way? All suggestions gratefully received (well most anyway).

 

[howardclark]

I would avoid dovetails except perhaps where there is a strong pulling force such as on a draw front.
As you say mitres would avoid end grain showing - if you are cutting by hand best to use a good mitre guide and excellent saw! My wooden hatches and hatch covers are made this way. With mitres you really need to rely on a glue to hold together so epoxy, Balcotan or Titebond III. My preferred is epoxy.
If I had to replace I think I would also consider following a more simple route using a rebate, then screw and plug;still shows some end-grain though.
I've made various things in Iroko, but the grain is awkward, it will blunt your tools and iroko dust is unhealthy; if the pennies stretch far enough teak is easier.

 

[Mirelle]

Just how proper?

1. "Proper":

Dovetails

Not really very hard to do.

2. "Lloyd's Yacht Prize":

Hidden Dovetails, so no end grain is visible.

Really quite hard to do.

NB. Use a slow hardener if gluing with epoxy.

 

[Blueboatman]

Re: Just how proper?

Half tenons quite acceptable-used a lot on eg Maurice Griffith stuff,and can be a bit 'less than perfect',they are strongest if you use slightly thicker wood,say real25mm,all epoxied together and to the top,which can either be routed in flush with the sides or plonked on top but then you have to attach some mitred half round stuff to hide the end grain.

 

[Peterduck]

Re: Just how proper?

You will [hopefully] do this just once, but you will look at it many times. If you don't give it your best effort, or even improve on your previous best, you will be haunted by the sight of those joints every time you see them. When moisture turns end-grain black, you'll kick yourself for taking a short-cut. Of course, you may be the kind of bloke who doesn't give a rat's, but I doubt it, because you've raised the question in the first place.
Peter.

 

[Blueboatman]

Re: Just how proper?

You are right of course! Do it once,do it right.
Maybe practise those hidden dovetails on something else first.
A search of secondhand yachting book suppliers will turn up useful books,one that comes to mind was Jurds Yacht Joinery.
Teak is a very nice wood to cut joints into..of course

 

[tcm]

Hidden dovetails

bit of nightmare to do these without a lot of experience and appropriate jigs. They are a dovetail with a mitre on the outside.

I would gues that they are not needed really. You could mitre the sides and fixe with glue and internal pins, and win strength in other ways as below.

Note that the flat top itself should be a mitred 4-part piece glued up in a box jig or long clamps to avoid end grain as well. The joints are important the sides less so as they can be worked/sanded down after assembly of course.

The top DOESN'T need to be 25 mm cos it will weight a ton. It could be perhaps only 15mm thick. But the clever bit woukld be to make it look at least 50mm thick if you additonaly fit and glue four mitred "thickening" pieces to the underside exterior lip of the flat top. It would then look and feel suitably chunky without actually being so. And this would give extra strength to those sides too, now fixed at top with dowel and at sides with glue and/or hidden screws.

Then of course radius the corners in plan and the whole exterior lip in profile and the hatch will have no external grain and no screws or dowels visible, seem more massively-built than it really is which is a wholly valid weight-saving trick and ensures that the hinges get ripped off a bit less frequently.

If you dowel the top, best is to use "assembly time" dowels same as the real dowel but heftily sanded down so only final assembly with unsanded dowels force the holes.

To especially gladden the heart of people like Mirelle on their tour of inspection and perhaps even win the Yacht Prize, you could perhaps "fake" hidden dovetails by making suitable near-invisible chisel marks along the inside of the mitred corners, ahem

 

[dur]

Re: Just how proper?

Thank you to all for your various thoughts. It sounds as if I should experiment first and see what I can manage. I think I will start with a decent scale drawing as tcm's note makes me realise I haven't thought enough about how the top will fit to the sides . It is a biggish hatch on a small foredeck so has to be able to take someone dancing on it.

If I have had a go at something I like to make a reasonable job if I can. Its just that everything takes me so long that the rest of the boat looks as if I don't give a rats!
Max

 

[tcm]

Hatchtop dancer

Slight change then. It will lose a lot of strength with the top being made of four parts in a diamond.

So make the top (for a big piece) from a series of tongue/grooved boards, all mitre-edged. You can still have the thickening pieces at the sides.

If this is all getting a bit hairy scarey (or at least time consuming) then a true gentleman would get it made. A bunch of true craftsmen are to be found at www.waywood.co.uk who made me one or two things that are still perfect fifteen years later.

 

[Spuddy]

Well, Mirelle's right up to a point. I find dovetails easy cos I was a chippy then a woodwork teacher. Ususal guide is about 1 for every inch. You really need someone to show once. Problem here is the endgrain; it WILL shrink and expand, go black and weaken joint over time.
I did do secret mitre dovetails once ( on a sewing box for ex memsah'b - had to do my own sewing though); the idea is OK but they are a real so and so to fit and will probably be too sloppy therefore and too weak.
I did do a new forehatch for a friends Percy Mitchell 4 tonner. Did a sort of rebated joint with a mitre on the outside - by hand; nowadays I'd look for a suitable router cutter first.
The other Maurice Griffith thing is the double walled hatch - got an inner box so any leakage gets trapped in the moat. There must be people on here who have had Practical experience. Is it worth the hassle or is a strip of neoprene round the mating surfaces just as good.
Too much information? sorry

 

[dur]

Thanks again.

I think, for me, secret dovetails are only on with a router guide - which I might be able to borrow. If not I think I will have a go at mitred rebates. There are cutters which will do a variation of this but they are expensive (£80.00 or so) and would need a decent router table which I don't have.

If it goes well I'll let you know. If not it'll be lots of poxy filler and several layers of thick paint!