Hardtop - Materials

[sailorsocal]

Want to place a hardtop over my center-cockpit (Whitby 42) and know there are a number of possible solutions. I quickly took a couple of door skins and laminated them together to get the final dimensions I needed and painted them for an initial design prototype. It works great but time to do something more permanent. I will be placing solar panels on top and would like it to be as light and structurally sound as possible which work against each other. Thought about doing just what I did but coating with epoxy or epoxy & glass.

Also considering plastic extruded sheets, aluminum, and stainless steal. These various items could be joined together with a strip between the sheets that has sealant to minimize any leakage.

Anyway, thinking of what opinions have been used and provide the lightest and strongest top possible that is quick and cheap. hehehe, yeah right. But we all think along these lines and I hope there are those who have experience and knowledge of where I'm going with this. There are new materials that may be available which I just don't know about.

Anyway, looking for inputs and appreciate the time you all take to give it to me so to speak.

Thanks. John

[toddster8]

I'm kind of in the same design phase as you. Doorskins are light and convenient, but they are laminated, and I doubt that it's marine-grade lamination. (Wrinkly doors seem to be one of the signature design features of run-down mobile homes and fleabag apartments.) I'm thinking 1/4" marine ply as core material. I used 3/8" for my sliding hatch and sea hood and that seems strong enough to dance on, but maybe a bit heavy for a dodger.

[s/v Jedi]

I think you can use your prototype as a mold: make foam core material to fit on top of the prototype exactly, maybe use a couple little pieces of double sided tape to keep in place, then epoxy a fiberglass skin onto the foam. When cured it should hold shape, ready to turn and do the other side, the edges etc.

[JPA Cate]

How strong will you want it to be? Enough for two people to stand on it to flake the sail down on the boom? Will it have small ventilation hatches?

Once you know how strong it needs to be, see if you can find out if Jedi's suggestion would be the strongest: so far, it's the lightest method suggested. Also, might be able to use vinylester with the foam and glass. Otherwise, respirators with the epoxy.

[toddster8]

I checked with my marine plywood supplier and they do stock 3mm okume, which would basically be marine-grade door skin. But if you've already gone through that step, the idea of using it as a mold sounds good.

Darn... I probably have enough 3/8 on hand in the shop already to do the job. Why did I buy so much?

[SV Liberty]

I've thought a lot about a hardtop on my Morgan 416 OI. The thing is, I'd like to follow the contour of the existing soft bimini as absolutely closely as possible. I've seen too many hardtops that looked too squared off, not curved enough. One idea I've considered is removing my bimini mounted solar panels (one on each side of the boom) and setting them into (making them part of) the new hardtop. Efficiency may be boosted by having panels open on bottom so cooler, and lower profile. If you use foam core material the hardtop will be thick (thicker than glass covered doorskins anyway) and light. Cut openings the size of solar panels (slightly larger), glass in the foam core edges of the openings, then seal the panels into the hardtop.

I'll be interested to follow your project. Whitbys are nice cruising boats.

Dave
SV Liberty

[Matt Johnson]

If you need to stand on it, use a foam core. If not, Azek pvc sheeting is light, paintable and you can epoxy/tape the seam if you'd like.

Matt

[motion30]

Home Depot and Lowe's both sell thin fiberglass sheets designed to be used in commercial kitchens and bathrooms one side is textured and one side is smooth they are very thin perhaps two layers would be necessary. Something to look at

[UNCIVILIZED]

Here's another thread with a bunch of ideas & resources that relate to this Best Hardtop Bimini Ideas - Page 2 - Cruisers & Sailing Forums

[SV Bacchus]

Originally Posted by s/v Jedi

I think you can use your prototype as a mold: make foam core material to fit on top of the prototype exactly, maybe use a couple little pieces of double sided tape to keep in place, then epoxy a fiberglass skin onto the foam. When cured it should hold shape, ready to turn and do the other side, the edges etc.

This could be a great idea, I think it would give strength while staying light. This probably goes without saying but think the whole process through, start to finish. By that I mean embed conduit for wire runs, if needed. Think about mounting, where will the upright bolt? Inside that point cut out the foam and set in something solid to bolt to, i.e. a square of plywood.

A lot of planning now will save much work later and you will end up with a professional looking job.

Matt of MJ Sailing on YouTube built his own. Lots of thought went into it and when done he found out he needed to lower it for boom clearance. Even the best thought out plans have kinks! However, that episode is good to watch as he did a great job. Actually it may be spread out over several episodes as it was a lengthy, time consuming process. Funny he called it a dodger???

https://www.youtube.com/watch?v=sAuYuq1oZIQ

Good Luck with it!

[SV Bacchus]

Originally Posted by SV Liberty

One idea I've considered is removing my bimini mounted solar panels (one on each side of the boom) and setting them into (making them part of) the new hardtop.

I'm always wanting to do stuff like this because it is neat, looks great and well, I just like it. But, I always wonder when the panels go to crap will I be able to fit new panels into those spaces? With your luck, maybe. With my luck, never happen!

[toddster8]

BTW: The Dashew's "Encyclopedia of Cruising" contains some handy guidelines for deriving the size and proportions of dodgers. Handy for those, like me, who have just been looking at other boats and scratching our heads.
I've recently seen a few larger boats with opening hatches (or zips) in the tops, so that the helmsman can poke his head up above. (e.g. s/v Delos' new dodger) Seems like an interesting idea for a smaller boat like mine, that necessarily will have a low overhead. Maybe too small for such features, though. On the other hand, with the boom swinging across, that little window might turn into a horizontal guillotine...

[Cotemar]

Azek sheets 4x8 feet x 1/2 thick at $110 each.

Very easy to work with using wood working tools.

No finish work or painting is required as the sheets are white throughout.

Warranty is for 25 years.

Sheets come in different thickness and 4x8 or 4x11 foot sheets.

www.azek.com/azek-sheet
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[Azul]

Originally Posted by JPA Cate

How strong will you want it to be? Enough for two people to stand on it to flake the sail down on the boom? Will it have small ventilation hatches?

Once you know how strong it needs to be, see if you can find out if Jedi's suggestion would be the strongest: so far, it's the lightest method suggested. Also, might be able to use vinylester with the foam and glass. Otherwise, respirators with the epoxy.

If you are going to use foam as a core it will be necessary to use epoxy resin as vinylester and polyester resin will dissolve the foam. I thought this might be a surfboard shaper's urban legend but a test proved it to be true. It is easy to shape EPS foam with a sander, or you can use 1/4 inch plywood which bends easily. Even covered with finishing cloth and resin I wouldn't plan on being able to stand on it. Without practice making molds or shaping EPS foam, the easiest plan is to use plywood and cover it with fiberglass finishing cloth with resin, the same way a stitch-and-glue dinghy is constructed.

Try to match the lines and crown of your coach roof to make it look aesthetically pleasing. It is impossible to "bend" EPS foam (the type used for surfboards etc) and tape it to another surface, it must be shaped and then covered. Numerous DIY videos are available on the subject of shaping and covering foam with fiberglass.

[UNCIVILIZED]

Originally Posted by Azul

If you are going to use foam as a core it will be necessary to use epoxy resin as vinylester and polyester resin will dissolve the foam. I thought this might be a surfboard shaper's urban legend but a test proved it to be true:

The above's incorrect, in that if you use any of the foams commonly used in boatbuilding, they're entirely compatible with a variety of resins. It's the household type building/insulation foams which have problems with the styrene in non-epoxy resins.