Butterfly Hatch

[Tony Bilello]

I am finally going to build a butterfly hatch for my sailboat. I know how to build the hatch itself. My problem is trying to figure out how to stop the leaks from the piano hinge. I'm thinking of running an extra piece of wood under the joint where the hatch closes and make a channel to run the water out of the ends of the hatch. Does anyone know of any other way?. Butterfly hatches are known to leak at the hinge area, but they are sooooo cool looking as well as functional.

Thanks in advance

[Bob Smalser]

A hatch is basically a flat box that fits over a coaming.

The coaming is bolted thru the deck to the carlins (or hatch frame) and sealed with gaskets both at the deck joint and where the box fits atop it.

The piano hinge is outside the coaming at the deck level, and can't leak.

There are other ways to do it, but they eventually leak.

[Tony Bilello]

Thanks for the reply. I made a quickie sketch to show you what I had in mind and where the problem would be. As I'm writing this, I just thought of another method. .....Put the piano hinge outside the frame as opposed to inside. With the hinge outside, I can get a fairly tight fit and a thin piece of weather stripping could fill the crack.
What other ideas do you have in mind.
I work offshore and wont be home til Tuesday nite.
Wed or Thurs I plan on buying the teak.

Thanks in advance

[Bob Smalser]

First of all, it takes a lot of deck to stand up to cutting through it for a big hatch and supporting the loads with cripples and doubles (carlins). Especially a sailboat. Design isn't my lane....you should go to the design forums at Boat Design.net or Woodenboat.com and listen to card-carrying architects and engineers.

Second, under no circumstances draw this hatch yourself. These aren't really simple. Copy something proven if you expect a leak-free installation. Chapelle's Boatbuilding and McIntosh's How to Build a WB among others detail various hatches. These scans come from McIntosh, only because Samuel Manning's drawings are clearer.

All successful hatches, whether as shown or built into larger dorade or greenhouse structures, are variations of the coaming beneath a box I described in my first post:



The wood frame bolted to the deck is the coaming. It's cover is the box.

McIntosh draws a small, ventilated dorade skylight suitable for a 30-footer's deck, but it's bolted down. If you use Lexan instead of glass to better take abuse, you could make it into a hatch by adding a coaming and piano hinge.

[Tony Bilello]

The butterfly hatch is fitting over an area where a regular hatch came out of. I thought of the butterfly hatch instead of the run of the mill hatch like I had. I also realize that the hardware will cost as much as a new standard hatch.
As for drawing the hatch itself, it is not rocket science, just good joinery. I am an accomplished woodworker and retired engineer and have worked on many boats. I have seen many plans in many books and butterfly hatches are famous for leaking. Even the ones that are factory built on very expensive boats.
I was hoping that someone had some kind of solution that I had not heard of or read before.
I also planned on using lexan as you also recommend. Most I have seen go with a 1/4" and I am happy with that. There will be either stainless steel or bronze tubing running laterally over the glazed area to protect it when standing on it. I have an older 39' 1976 Allied Ketch. I am replacing the hatch under the mainsail.
I have no idea what you are referring to as the "coaming beneath a box." Can you send me a sketch. I am having trouble visualizing it.

Thanks again

P.S. I am offshore right now and I cant download a lot of things. If you have a sketch can you send it as part of this post? Maybe then I will bw able to get it.

[Martin King]

Here's a skylight hatch I built for my boat that's based loosely on a design
by my father. I opted for twin bronze gutter pipes and went with
stainless piano hinges and retaining frames. The glass is 1/2" beveled safety.
This basic design has been used on many custom boats. It's been installed
now for over 4 years and has yet to leak.

[Tony Bilello]

Im just bought some more teak. A few months ago, it was $16.50/Bd. Ft. The other day it was up to $26.75/Bd. Ft. I am still recovering.
I will be gone for 2 weeks and when I get back I will start my project. Is there any way that you could get me some details of the bronze gutter pipes like sketch or photos?
I assume the gutters detour the water that leaks through the piano hinge to go overboard. Is there any weather sealing involved?

[randall rosenthal]

martin.....that hatch is drop dead gorgeous. i have an old boat and have been picking away at it for 10 years...some wood work but....wow...very very impressive...................very.

[Khalid Khattak]

Wow Nice butterflie hatch

[Patrick Grady]

Depends on the boat and where it will be sailed and expected resale value. Martin King's butterfly hatch is a work of art but better suited for inland lakes and coastal waterways, not serious offshore sailing. Notice that Martin's butterfly hatch occupies fiberglass real estate just fore of the main companionway hatch which has a storm cover - storm covers exist because sliding angry water will defeat any movable/openable hatch in a miserable millisecond. Beyond gasketing issues, the relentless summer sun will work and deteriorate all finishes and joinery and will reduce all lexan and teak artworks to drips and boat-roting seepage. Visit a boatyard's old skeletons in the back lot and you will see the wood cracks leveraged by time and nature's elements. The piano hinge design is also a disaster-corrosion, sand grit sealing issues will make you hate music. I appreciate the beauty of a butterfly hatch, but if the future owner of your boat is an experienced sailor, removal of this hatch will be on the short list.

[Martin King]

Depends on the boat and where it will be sailed and expected resale value. Martin King's butterfly hatch is a work of art but better suited for inland lakes and coastal waterways, not serious offshore sailing.

My boat goes offshore and that hatch
has yet to leak. Moreover, that same design has appeared on many
custom yachts that cost millions and sail all over the world.

I appreciate the beauty of a butterfly hatch, but if the future owner of your boat is an experienced sailor, removal of this hatch will be on the short list.

Yeah right. You gonna tell the next owner of this yacht he needs to replace
his skylight with some aluminum and plastic before heading offshore?

[Kent Parker]

Beautiful workmanship Martin!

Is this a Herreshoff design ? I owned a Nereia for some 18 years, my uncle had one for 20 years. We've logged well over 20,000 offshore miles in the design with cabin top hatches that did not even approach the sturdiness of yours.

Cheers,

Kent

[Martin King]

Is this a Herreshoff design ?

Thanks Kent. No, my boat and Chanty pictured here were designed
by my dad, Bruce King, a big fan of Herreshoff.

Here's a deck shot of Hetairos. She's logged over 120,000 miles since her launching. She's
been everywhere, from Alaska to New Zealand. Plenty of wooden
deck superstructures here including a fantastic 10 sided skylight.

[Kent Parker]

Wow Martin....what a great mentor to have.

I've long admired your fathers designs and appreciate the Herreshoff influence in the shapes that have produced such beautiful shapes as Whitehawk, Whitefin and Saskianna.

What a great world you must be in.

Cheers,

KP

[randall rosenthal]

i'm with you martin...ive sailed with far far inferior hatches. is maintenance required? its a boat right?

and again as a boatsman and professional wood worker.....very very nice.