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I've been considering trying my hand at a complicated (for me) mod during the winter season and I'd like some advice from those with mould making and fiberglass skills.

I'd like to make what I'm going to call a "Pilothouse Hatch". It's a replacement for the sliding hatch on the M that goes up 18" above the deck. It will have a 45 degree forward angle, a 3rd black bandit stripe, and will have smoked lexan windows on all four sides to match the look of the boat.

The purpose is to proved standing headroom for me (I'm 6'5") and eventually to allow safe piloting of the boat from inside in inclement weather via auto helm remote. It will function exactly as the current hatch does.

My plan is to take the existing hatch off, mock up the height extension directly on top of the original hatch but slightly inset using layers of 1" styrofoam and tape. I would then Vaseline this assembly and place this "plug" upright in a cardboard box with an open top.

I would then use two-part pourable urethane foam to fill the box around the plug, all the way over it. When expanded and hardened, I would remove the plug, clean off the hatch, and re-install it onto the boat non the worse for the wear.

Now having a urethane foam mould, I would sand and finish the interior to smoothly match the contour of the original hatch. I will precut the lexan windows, and tape them onto the mould where they will go on the finished piece. Once the mould is shaped and finished, I will wax the interior of it as well as over the lexan windows with a pourable wax like paraffin, and use a heat gun to make sure it's smooth. This would complete the mould and make it ready for gel-kote.

For gel-kote I would mask off the black stripe and paint it on, then when it dries pull up the masking and finish the mould in white gel-kote.

Next would come four layers of 6oz fiberglass cloth and resin in the typical 3:1 resin to cloth by weight ratio, and left to cure.

When cured, I'd remove the new shell, cut the base edges off and smooth them, and cut out the holes for the windows. I'd remove the windows from the mould and install them. They should be an exact fit. At this point it should be complete and ready to install.

Criticism of this method would be appreciated, since it will be my first attempt at any of this.

I would recommend you not mold to the windows, the opening should be slightly oversized to allow for sealant to act as a filler for uneven expansion between fiberglass and lexan. By bonding a spacer in the mold, you would also eliminate any line from the tape.

After waxing, what kind of tape will you use that sticks to wax (for the black stripe)?

Careful the urethane foam does not collapse the plug inside the box as it expands - I used this foam to back up a interior door repair - the foam made the door swell to wider than its original width.

I would consider coating the inside of the foam mold with something that gives the foam a hard surface that can be sanded and shaped (fillets and such).

Now to qualify my suggestions, I have not done this kind of molding but I did spend alot of time examining tooling in the aircraft factory (molds for the YF-22 and the cancelled A-12). I also designed F-16 support equipment that was manufactured using molds.

Catigale here on station Cuttyhunk harbor....

Couple of raw thoughts on this

1 Calculate the total mass of your mod and double check how much weight you are putting up relatively high on the boat. Stability issues ? To mod alone won't make y our boat unsafe, but you should know exactly how much of the righting moment you have lost with the mod.

2. Could you fab the whole think out of wood first ...and check form and function?

3 I believe on the the hatch is plywood core so you can walk it...I'm 73 inches tall 225#....I walk on the hatch top and load it with another 100 pounds or so when I raise the mast....new design has to take probably two people standing on it perhaps? If you decide to core don't forget to go back to (1)...

I confess you have inspired me to think about getting another 6 inches of head room on my in the same way!!

I too have plans to fabricate fiberglass projects for the boat. At home I have some bookmarked links that I'll send you.

A couple of considerations about your proposal... will the height of your pilothouse hatch not interfere with the mast being lowered? Expanding foam may blowout the box or deform the mockup. Try your proposal on a smaller scale test piece to see how it works.

Check out Youtube videos for speaker box projects. Neat the shapes that can be created with fabric over frame.

I have made complicated one offs from foam and Fiberglass. A new helm seat as an example.
I wound recommend NOT doing the pouring foam bit. Make the mock up out of plywood and cheap body filler, stirafoam or whatever. Get it look great. Carve out the window insets with proper gappage. Set it on the boat for appearance check.
THEN cover it with a few layers of glass after everything is baby smooth and prepped with release agent. I would add a few wood supports. Then lay up the real hatch inside this. It will already be smooth.
Yes it's work. It's just like they make moulds everywhere. It's for a reason. There is no shortcut if a factory finish is what's needed. Plus you can use the mould over again OR sell it to someone else (hint) and recoup some of your expenses.
Would I do it this way? No. I am not that much of a stickler for exact factory match. I try to make it better then factory if I can in strength and function and don't care as much if it matches the factory finish. I would build it out of foam core and take the complete structure to an auto shop where they could spray the gelcoat if I wanted better then a brush on job. The foam core will be light stiff and strong. You can bend and sculpt the curves you will need to keep it from looking like a box with some windows in it.
Sounds like a great project.

Ixneigh

You might consider obtaining another cover and altering it rather than a new build. You would get the top structure and deck texture for the cost, some chopping and built up structure and you would likely see a usable result much quicker. The thing about molds is that you think you are halfway there when you have a decent shape, but it is only about 15% of the journey. There is a huge amount of effort in getting a smooth ripple free surface. The effort really pays off if you make multiples.

I am 6' 5" myself...I understand. Interested project idea!

K9Kampers wrote:Will the height of your pilothouse hatch not interfere with the mast being lowered? Expanding foam may blowout the box or deform the mockup. Try your proposal on a smaller scale test piece to see how it works.

Check out Youtube videos for speaker box projects. Neat the shapes that can be created with fabric over frame.

Thanks for the responses all--Catigale, I'd do the mass increase calculations. I'm not super worried about it but definitely good to know. Hatch on the M is solid fiberglass with no core, and I can stand on it with no worries at #250. I think I'll angle in the sides to increase the arch function and match the slope of the boat anyway, but I will run the numbers to determine how much fiberglass it's going to take to stand up to me standing on it.

I lack the skill to build anything to precise dimensions. I' planning do mock this up in CAD and have the styrofoam layers CNC cut and bonded together to make the plug.

This may well interfere with mast lowering. I've decided to mould the plug in styrofoam, and I'll lower the mast and fit the plug under it to be sure there's clearance. Could be a deal breaker. The trick with the expanding foam is to allow the part you don't care about (the box) to expand rather than the part you do (the styrofoam plug). As long as something can accomodate the expansion, it shouldn't deform the plug.

The whole point of doing a mould rather than glassing over a foam core is the gel-kote finish. If I can achieve something reasonably close to a smooth gel-kote finish just glassing over a foam plug and then spraying on gel-kote, then I'd much rather do that. I can have the foam core CNC cut to CAD precision out of marine-grade foam, which I would then glass over inside and out to get strength. I've got a bunch of hull moulding calculations to make sure the core is the exact right thickness at all points to achieve maximum shear wall strength.

I should investigate that. Much more compatible with my skill set than manual shaping.

What about a dodger, instead? Lighter, quicker and probably cheaper. Took about an hour to install the one I got from Bluewater Yachts. It makes a great pilot house to block the wind, rain and spray. Adds light and headroom, so I really can stand up at the galley. I also got the zip in cabin doors and the connector panel, so the bimini becomes a cockpit tent. It's easily detached for trailering and doesn't interfere with rigging or sailing. It also ads resale value, where a lot of DIY doesn't. But don't let me deprive you of the joy of modifications you make yourself. Especially if you get to learn new skills and use cool tools.

Bill McClure wrote:What about a dodger, instead?

A Dodger makes a whole lot of sense, which is probably why I'm not attracted to it

The real reason is that we trailer a lot, and I'd want to have something that doesn't add time to the setup or teardown of the boat.

That said, I'm a fundamentally lazy and failure-averse person, so a dodger in the hand is worth two pies the sky.

I'm going to play around with the tape measure and CAD package and try to convince myself that it's a good idea. I may forgo the complication of windows and and black stripe, and just build a 6" higher version of the stock hatch cover to accomodate my standing height inside the boat. As a first test, anyway.

That's the greatest answer I've ever heard. Do you mind if I use it sometime?

Bill McClure wrote:That's the greatest answer I've ever heard. Do you mind if I use it sometime?

Feel free! It's kept me from wasting a lot of time AND from achieving greatness. Both are acceptable outcomes.

Thanks!!!

Bill McClure wrote:What about a dodger, instead? Lighter, quicker and probably cheaper. Took about an hour to install the one I got from Bluewater Yachts. It makes a great pilot house to block the wind, rain and spray. Adds light and headroom, so I really can stand up at the galley. I also got the zip in cabin doors and the connector panel, so the bimini becomes a cockpit tent. It's easily detached for trailering and doesn't interfere with rigging or sailing. It also ads resale value, where a lot of DIY doesn't. But don't let me deprive you of the joy of modifications you make yourself. Especially if you get to learn new skills and use cool tools.

I gotta second this. We have a dodger and it gives us LOTS of headroom. If you got the extra goodies even better. Takes about 90 seconds to fold up/down. Windows allow to pop up and look out and stay dry.

Nevertheless, I would love to see this mod. It sounds very interesting.

I like the idea! Could look cool too.

A dodger (partly) solves the mast- raising interference issue as well, being a “convertible” top. The dodger also stays put, and doesn’t slide back and forth like the hatch does. Of course, you could affix your pilothouse hatch onto the hatch rails so it stays put too, and still retain the use of the factory hatch(?) A possible alternate anchor point for the mainsheets /traveler if made sturdy enough (?)

If you use the canned foam that’s specifically labeled for windows and doors, it’s a low-expansion formula over regular expanding foam. Less likely to seize up windows and doors when misused. And cardboard boxes too!

If you get a custom dodger with that nifty black strip incorporated into the design... does it become an artful dodger?

Never mind. Just introducing a little twist.