How about a steel, welded, galvanised skylight ?

[PeterSibley]

I know the idea will not delight some but for an ocean going yacht (which may encounter very heavy conditions )a skylight that can be dogged down hard enough not to leak at all would be a great thing .

Now much as I love wood it does appear as though steel might be the right material for this job .It's too big a job for me to cast in bronze but in steel it's not an overwhelming job .

What does the panel think ?

[The Bigfella]

No, No, No.

[The Bigfella]

Try this one. Half inch toughened glass... don't do the ventilating bit perhaps...

http://www.woodenboat.com/forum/showthread.php?t=67118&highlight=Duffy+Dodge

[PeterSibley]

Yep ,I've looked at it in depth but don't reckon its up to blue water ...especially in depth .Lovely work though Ian :),a credit to you .

I want something that will open when necessary to provide ventilation and then dog down to be totally waterproof .

[The Bigfella]

I haven't had any leaks... but then again, it hasn't had green water over it. I reckon that, without the grille at the front, and maybe with a canvas cover.... ?

[RFNK]

Well, this member of `the panel' :rolleyes: thinks it should be strong and functional but will probably look awful! You're also likely to run into trouble with the hinges where the galvanizing will wear. There are plenty of wooden hatches with glass that are very strong and have lasted very many years. Why not just replicate one of those? You can run bronze rod or strap through or over some sections for reinforcing if necessary. Rick

[2MeterTroll]

cast it in sections that bolt around the glass. if you cast a 3mm groove into the ends that fit together you can seal them water tight with a bead of 5200, aquaseal or aquarium sealant. if you add pins in the sections it will act like a single unit when its bolted together and dogged down.

[dhic001]

Rather than steel, which will rust in time, what about using aluminium? Could be a good way of getting the strength without the negative of rust streaks. If you are worried about strength, take a look at what Dashew did with the FPB83 Wind Horse, see: http://dashewoffshore.com/glazing_decision.asp

Daniel

[PeterSibley]

An interesting link Daniel , thanks .It says there that the glass strength increases as a cube of the thickness .I had always thought it a square ?

I think I'll stay with steel over aluminium ,I can tack a steel construction together then get someone like Pipefitter to do the real welding .As to hinges Rick ,plastic sleeves solve that problem ,Ralloy or something similar .

2MT ,bronze would be great and believe me I'd MUCH prefer it but the tech challenges are beyond me ...I know just enough to know what I don't know !:D

[2MeterTroll]

Might you could find some one who would know?

I just think With all the bron... hmm why not SS and heat it till it bronzes? its a known temp and if you bake it it will go deep and stay that color for awhile. just a thought.

[PeterSibley]

I don't think my budget would run to hiring a foundry to cast such a project ,it would run thousands.As to galv steel ,I quite like it ,it's durable and easily replated .

[The Bigfella]

C'mon Peter... its a wooden boat, not a steelie.

[Ron Williamson]

I like galvanized.
Do it.
If it sucks,do it differently.
R

[peter radclyffe]

its a good idea Peter, we use steel hatches on trawlers & drive the bolts from below for when the hatch needs replacing

[PeterSibley]

Thanks Peter , encouraging !

[George Ray]

If you have access to a galvanizing facility (hot dip or spray metalizing) then I think the idea is brilliant. Steel is a joy to fabricate, .... unlike stainless that eats up your cutting tools edges unless they are the most expensive (cobalt/carbide/bimetal) and feed&speed are just so, and crack unless your design, welding technique and alloy selection are proper. Don't get me wrong, I like doing stainless fabrication, but the cost differential is significant.

[Paul Pless]

Weirdness abounds... our noted home bronze caster talking about welding up and then galvinizing a skylight.:confused:

Peter, if you trust wood for the rest of the boat, then a well engineered and well built wood skylight of appropriate size should not be a concern.

[Paul Pless]

> :D

[George Ray]

http://www.duckflatwoodenboats.com/pics/for%20sale/largepics/BrynhildSkylight.jpg
http://www.discoverycoastyachts.com/1931exmissionship/skylight.jpg
http://i128.photobucket.com/albums/p200/cruizin31/skylight.jpg
http://i128.photobucket.com/albums/p200/cruizin31/Hetdeck1.jpg
http://4.bp.blogspot.com/_-31fAcVP5sk/Sa7LbczukoI/AAAAAAAAAF0/L5FoOgfFLkY/S600/00020-deckshouse+with+spiral+staircase.jpg
http://ericsonalbergclassic.homestead.com/files/closeup_of_wood_skylight.jpg

[peter radclyffe]

yes but a wooden skylight is a lot of time, if you can galvanise corten steel it may last 50 years or more, & if you smooth paint finish it , it does not need to be unattractive

[donald branscom]

I would just get a bunch of money, and buy a Lewmar stainless ocean hatch, and bolt it in place.
If it leaks then tell Lewmar.

Steel - Cutting, welding, sanding, hinges, machining for an "o" ring, (where you gonna get that), and fitting and hot dip galvinizing. Then the glass.

Stainless steel-Cutting, welding, sanding, hinges machining for an "o" ring, (where you gonna get that), and fitting and sending for electropolishing. Then the glass.

[john92021]

Hi Peter, I happen to have a solid bronze hatch with big dogs at my cottage on Vancouver Island CA. It weighs about 100 lbs. If you are coming up this way we can make a deal, too big for my boat, thought it would make a good medicine cabinet ;)
John

[Bob Cleek]

Thanksgiving is one of those days when everybody has dead time in the morning.
Me, I burned out on the Macy's parade in about ten minutes, as soon as the first cup of coffee was done, and here I am killing time. Shows you've got a fertile mind, though, Peter!

Hey, there are as many ways to build a skylight as there are skylights. Sure, you could make one of steel. However, you'd have a much nicer skylight for a wooden boat if you built one out of wood and cast some really nice bronze fittings for it. A steel skylight on a wooden boat would look a lot like the nice wooden skylight on the fibreglass boat pictured above... out of place.

Figure the weight of the largest wave imaginable breaking on top of your skylight and then calculate the pounds of weight per square inch. I think when you do that, you'll find even the traditional wooden skylights are well within the strength parameters. If you want to weld up a bulletproof unit, that's not rocket science, either. The Navy's been doing it for years. Metal hatches and skylights are SOP. It's just a matter of taste, really. Properly built of wood, metal or even plastic, they'll all do the job.

[PeterSibley]

Thanks everyone , as I suspected it was not an entirely popular idea ! I am influenced by Don Street in this and the fact that I intend to sail the Tasman ,a notoriously rough stretch .

Street ( in "The Ocean Sailing Yacht" ) says that for a blue water yacht a traditional skylight is a "museum " piece .A bit cruel and I definitely love the appearance ..but when I think of Bob's situation of large breaking waves and roll overs, steel has my attention .Wood will probably survive but if it didn't I'm dead .

Thanks Peter Radclyffe for your encouragement .:)

[donald branscom]

A wave breaking over a boat can exert 77,000 lbs., per square inch.
A hatch should not even be on the fore deck if it is possible to avoid. and never over a bunk.

There is nothing wrong with a steel hatch.
If you want one you can buy them in the back of National Fisherman magazine.

If you make one correctly you should check the prices first because even if you are a good welder and craftsman you may need some machining too. Plating process for sure. Epoxy paint will work, or powder coating. IT really just all comes down to the cost.

To keep water out, it really needs a machined groove with rubber one piece "O" ring. No matter what it is made out of.

And good dogs to keep it in place.

[PeterSibley]

A machined groove or perhaps a groove formed of 2 sections with gasket rubber insert ? Fabrication is a lot easier and cheaper than machining .

I'm interested in the paint idea ,I had thought galvanised but the finish if pretty industrial ,paint is smoother and I could choose a pleasant colour .

[bruce w]

go for a composit job, galv steel wood face'd

[George Ray]

Just thinking .....
(1) The skylight has evolved because it does it's job well and makes life much nicer aboard.
(2) Many design decisions are heavily influenced buy events/circumstances that occur exceedingly rarely.
(3) Many times skylights are built to cover and fasten to seriously strong and well framed deck opening. Given that as true, a serious cover can be made to slip, slide, or dog in place inside or out side, instead of or along with the skylight.
(4) Where is the weakness? Will the whole skylight be swept away or the glass breached?
(5) Would a metal frame covered in wood (perhaps ply covered in veneer) achieve both goals? Industrial strength and classic aesthetic.

[PeterSibley]

go for a composit job, galv steel wood face'd

I have thought on this , a few problems with wood movement versus the steel but possible .

[2MeterTroll]

I think its a great idea. however i think galv is just gonna be heavy and require to much maint. You can use lighter gage ss and dont have to maintain it as often. no matter what you do if you take a really hard one things are going to leak. if its not a hatch it will be the deck itself. even steel boats that get hammered really hard spring leaks.

like George said we worry about things that dont happen very often.

[PeterSibley]

Some things only have to happen once .

[2MeterTroll]

Peter if its that bad the once is going to sweep your deck from stem to stern. Every vent porthole and hatch in the skin of the boat is gonna let in water. your right but i am just saying

[PeterSibley]

Peter if its that bad the once is going to sweep your deck from stem to stern. Every vent porthole and hatch in the skin of the boat is gonna let in water. your right but i am just saying

I agree entirely , it's just that a sprung or missing skylight makes a very big hole .The others , perhaps less so .

[2MeterTroll]

It is a conundrum; one that i to have, in the planning for a large boat. however i am going to put in the skylights cause the compromise is to make a dark cabin that takes power to light at a comfortable reading level.

[PeterSibley]

I definitely need a large opening skylight , both for light but more especially here for ventilation .A boat can be unliveable here without the latter .
I'll be investing in pyarmid lens for light ...BTW ,is it possible to buy just the glass lens over your way ? I can cast the housings myself .

[George Ray]

http://glassian.org/Prism/Deck/index.html

http://www.mysticseaport.org/index.cfm?fuseaction=shop.museumStore&storeNavigationID=20DFADB4-B0D0-D05E-1AF8D96DB01BC796

[py]

Use wood. But why bother asking if you already have your own answer and don't really want to hear anything else?
Phil

[PeterSibley]

Thank you George ! Just what I need .:)

[PeterSibley]

Use wood. But why bother asking if you already have your own answer and don't really want to hear anything else?
Phil

A good question .I would indeed be very pleased if someone posted information about a wooden skylight design that was completely waterproof and capable of surviving a breaking wave or rollover .

I like wood , it's strong and easy to work with but I am also aware of it's limitations ,if those limitation can be overcome with good design I'd like to know about it .

I assure you I'm not in the" I don't want to hear anything else !" camp .

[George Ray]

Another option:
Mold one using your choice of composites and finish with a bonded veneer. Epoxy, carbon, kevlar, and some foam would be so light that you could use 3/4" plexi for the lights and still be less than std skylight weight.

[willmarsh3]

Maybe what you want to do is lash a dinghy over the skylight for the passages that you expect might be rough. Or make a custom cover that is through bolted on the cabin top. Remove it at the end of the passage to reveal the beautiful wooden skylight.

[Chip-skiff]

Maybe what you want to do is lash a dinghy over the skylight for the passages that you expect might be rough. Or make a custom cover that is through bolted on the cabin top. Remove it at the end of the passage to reveal the beautiful wooden skylight.

Brilliant!

If you're in a big blow with green water breaking over the deck, you will most certainly not be down in the cabin reading a bloody book. So the need for natural light is dependent on conditions that allow you to relax somewhat.

[CapnJ2ds]

Wood is good, but let's not get obsessed here!

The basic rule #1 of wooden skylights:
"Some skylights leak all the time, and all skylights leak some of the time."

I had an awful skylight on one boat. Turned it into a Griffiths-type double coaming hatch that looked like a skylight - worked well. I think the same idea would be even better in steel.

If it's a steel hatch you want, go for it! Galvanising or powder coating will - maybe - improve looks and longevity, but so will a good paint job.

The only real drawback to a good, strong steel hatch is its liking for a diet of fingers. Gas strut?

[CapnJ2ds]

Brilliant!

If you're in a big blow with green water breaking over the deck, you will most certainly not be down in the cabin reading a bloody book. So the need for natural light is dependent on conditions that allow you to relax somewhat.

Have been a couple of times in a blow when after all was snugged down tight on deck and the boat was lying a-hull all we could do was go below, keep ourselves fed and watered as best we could, and - read books. (Takes the mind off the noise and the prospects outside!)

[PeterSibley]

Wood is good, but let's not get obsessed here!

The basic rule #1 of wooden skylights:
"Some skylights leak all the time, and all skylights leak some of the time."

I had an awful skylight on one boat. Turned it into a Griffiths-type double coaming hatch that looked like a skylight - worked well. I think the same idea would be even better in steel.

If it's a steel hatch you want, go for it! Galvanising or powder coating will - maybe - improve looks and longevity, but so will a good paint job.

The only real drawback to a good, strong steel hatch is its liking for a diet of fingers. Gas strut?

That last is a very good point !:D I've experienced quite a few wooden skylights and all so far have failed the leak test .The double coaming idea is good but makes opening a problem ....it does allow ventilation though .Thanks for the idea .:)

[Todd D]

How about epoxy/carbon fiber with a wood facing. That will be much stronger than an equivalent weight of steel, so you can make it lighter for the same strength. If you really want to make it bullet proof, sandwich in some kevlar between layers of carbon.

[jonboy]

Steel will be heavy but if of sufficient scale totally rigid. Only large section hardwood profiles give the rigidity and then you're back to the tried and tested....

In my limited experience anything not utterly rigid can be compromised .... a recent venture on a steel yacht with aluminium skylights was spoilt by the light being pulled down in haste in a heavy sea and a bight of cordage from a stowage got trapped.. the hatch didn't shut, so leaked...even though apparently well fastened.. we couldn't see anything wrong from inside and weren't going out to have a look...
Because the lightish construction allowed the hatch to be fastened, at a slight twist, and it never really sealed well again...
Sorry to bang on about rigidity but one wouldn't have been able to close the light if it was substantially made and there was something impeding the seal...so making us aware of a problem that manifested itself only when there was some serious topsides sea flying about... and coming inside in doses...
gut feeling tho' is like with like....wood hatch wood boat, steel with steel...

[PeterSibley]

That's the feeling I'm getting too .Rigidity is essential and there are only a few different ways of achieving that within weight and COST constraints ,some of the alternatives offered would be excellent but are well outside my budget . Wood and steel seem the only affordable options .

[2MeterTroll]

Well lets dissect it a bit. if you want ridged wood ply is a good bet. ply can be machined, cut or laminated to allow for glass. there is no need to do it in sections. getting the water off the window as fast as possible is a good idea. IME its not the hatch that leaks its the glass. a knife edge in a soft seal is not going to let water through unless it has paint or something else on it that wont allow the seal to conform to the edge. I think laminating the ply together with a good lip over the glass so you can put a wide seal around the glass would be a fine thing. its not going to go any where if its dogged down, you can make bars across the glass on the inside and out side so it has some protection. add a bit of vainer and varnish and you got a handsome hatch that fits all the criteria you have set out.

[PeterSibley]

Thanks 2MT , you may well be correct ! Thinking ,thinking !

[peter radclyffe]

Peter can you look at old steam tugs, some of them had portlight glasses in steel skylights over the engine room, & also i think some old trawlers,with steel coamings
you have severe seas there from what you say, i remember a story about a Hull diesel trawler 200ft having its superstructure swept clean off the boat off greenland, & being towed back to Hull by another trawler, i often think of that tale when im repairing a boat ,
i re-sealed the hatches on a jongert last year, i was amazed at the reputation these boats have, go- anywhere bollix,
the hatches have no outer flange,
so as you know, in a depression at sea the inside pressure can be greater than outside, which can blow the hatch perspex off,
the hatches are only coastal ,
for sure not enough thought is given to a boat's weak points,
& if a jongert sank like this
who would know why it sank , rant etc

[KAIROS]

Since you mentioned you were using the prisms for light, assuming then that the hatch does not need a light (window), and you want something hell-for-stout, you might look at these. Various materials and configurations. Probably less than 2000 US for what you want, but available used too (fish boats).

I spent much time and money engineering a hatch. When I was done I wasn't sure I should have tried to better what's out there. But, I'm not a caster/fabricater.

http://www.freemanmarine.com/ProductsHatches.htm

[Lew Barrett]

Why not do a hatch (or hatches) instead of skylights to meet all these various requirements? You get good venting when needed, light when needed, (you can even glaze the hatch ala Chris Craft or use one of your new found deck prisms) and.....no leaks.

It can be made of wood. You dog it down when underway and it can't go anywhere.In nice weather or when it's hot and you want light down below, open it. So much less troublesome all around. I don't miss skylights on Rita. We have a hatch forward. It never leaks, can be opened in the warm weather for full light and air, or left just ajar at anchor and dogged down lickety split in rain or when underway. You never want them open underway so no big deal.

Unless you simply must have a skylight, why not solve your problem simply?

[Chip-skiff]

Have been a couple of times in a blow when after all was snugged down tight on deck and the boat was lying a-hull all we could do was go below, keep ourselves fed and watered as best we could, and - read books. (Takes the mind off the noise and the prospects outside!)

Right. But a headlamp does fine for that, and you can buy one for $15. Waves breaking over the incredibly expensive skylight would tend to distract me from reading. And at night, you'd use a lamp regardless.

[PeterSibley]

Since you mentioned you were using the prisms for light, assuming then that the hatch does not need a light (window), and you want something hell-for-stout, you might look at these. Various materials and configurations. Probably less than 2000 US for what you want, but available used too (fish boats).

I spent much time and money engineering a hatch. When I was done I wasn't sure I should have tried to better what's out there. But, I'm not a caster/fabricater.

http://www.freemanmarine.com/ProductsHatches.htm

Thanks KAIROS ,I'm having a very good look through that site .

[donald branscom]

Check out the book called Steel Away. Great book showing many details of building and fittings for steel boats. a must have book.

[PeterSibley]

http://www.abebooks.com/servlet/BookDetailsPL?bi=1228454646&searchurl=sts%3Dt%26tn%3DSteel%2BAway%26x%3D23%26y %3D20
Thank you Donald , an addition to my bookshelf !

[PeterSibley]

From rereading the above it seems that the main features required are strength to resist seas, stiffness to allow very hard dogging ,very adequate seals to resist breakng seas .

I'm beginning to think that a combination of metal and timber will do the job .Possibly a metal and rubber seal system , couple of interlocking W sections with rubber at the apexs screwed very solidly to the wood ? If strong enough this could also allow the stiffness to allow multipoint dogging from inside .It would be good if the hinges were one with the steel construction too.

[peter radclyffe]

you can make custom seals with silicon mastic, press to a taped former, let it dry, however i dont know if its U V resistant, but it may be worth trying if you need a certain shape you cant buy, we used it for hot water cooling gaskets on pipe flanges,

[The Bigfella]

The seals on my hatch are 10mm square timber that goes into a routed out section in the butterfly wings that has Armaflex tape for it to seat into. Ain't no water getting through there.

[cookie]

The seals on my hatch are 10mm square timber that goes into a routed out section in the butterfly wings that has Armaflex tape for it to seat into. Ain't no water getting through there.

Any chance of seeing a picture?

[The Bigfella]

from the link in post 3.

http://i240.photobucket.com/albums/ff112/igatenby/iansecond/b1-1.jpg

http://i240.photobucket.com/albums/ff112/igatenby/iansecond/b15.jpg

[cookie]

Ah, cheers!

[htom]

I think that shape trumps rigid in battling the sea. My dream ships have for years had hatches in the shape of super-ellipses, providing no sharp corners for the sea to grab. A modified Griffiths design, with the drains larger on the inside than the outside, so that a striking wave's pressure would be reduced on the inside. Molded Lexan so there wasn't a flat there, either.

[peter radclyffe]

Peter if you go with wood or anyway for proportions here is a skylight for a danish 16 meter, 40 ton kotter fishing boat, which i guess you canhttp://i791.photobucket.com/albums/yy195/helpME7/img386.jpg scale down to maybe 50 mm side wall thickness

[PeterSibley]

Thanks Peter ,I'm thinking of a combination of timber and steel . Steel specifically to weld up a double interlocking W M as a seal, stiffener and base for a dogging mechanism .