Hard Top DIY Bimini & Dodger Materials?

[PuttingDoctor]

I had a hardtop / Bimini system built years back for my Irwin 38’. I got the last WaveStopper made before the inventor passed away. He used molded polystyrene for the tops and regular canvas type tubing for support. The result was very attractive. Once installed my canvas man added his touch. The corners of the Bimini Isenglass were very solid an not removable though the center panel was.

[bcboomer]

We're going with the fibreglass hard dodger top with Sunbrella/O'Sea removable panels. The top was made by a pro with Nida-Core. Reasonably light. As mvweebles suggested we're using track on the top with a double welt so we can zip in any combination of window and screen we want.
The end result will be about the same as having a new fabric dodger made and I haven't seen any locally made dodgers that fit properly. Every one has ripples in the plastic and most have wrinkles in the fabric.

[zstine]

Since this is non-structural, you really don't need fancy, expensive marine grade foam which is typically PVC, PET or Polyurethane. The pink extruded polystyrene insulation foam you get at HomeDepot would be fine. BUT you have to use Epoxy not Polyester resin! Another cheap option is 1/4" or 5mm Luan plywood. With Ply you can use Polyester resin, though I prefer Epoxy. One layer of 1708 on each side should be fine... or any number of glass fabrics adding up to about 20oz per side. Nida core is probably the cheapest marine grade core material, but being a honeycomb, it is a bit of a PITA to work with since edges have to be filled special and it is not perfectly flat.. H80 divinycell is a common marine grade core material, but it is expensive to ship and not generally available locally if you are not in a ship building area.


Any of the above core material should bend to the contour of the top of your bimini without scoring. If you want to curve the edges down ~90 deg like the fabric typically is, then you would need to score that area. No "mold" needed, just bend the core material over the frame using straps and clamps and lay up some glass to hold it's shape. Once cured you can remove straps/clamps and finish laying up the glass layers.

[Opie91]

Decided to do exactly what you are thinking about. Just a heads up it is a lot of work. Build a stainless frame for it since I want to mount two 345 watt solar panels above the Bimini. The frame took about 60 hours to build and the top has taken about 40 hours so far.

The top is about 66" long and 88" wide and is build out of 13mm Carbon-Core(similar to Nida Core) with 1708 and 1808 biaxial on the top and 1708 on the bottom. The edges have a 1.5" strip of Carbon Core bonded to them to stiffen up the whole thing. It was pretty strong before the lip but it also helps hide the stainless frame top bar.

So far have used a little under 6 gallons of polyester resin, 1 gallon of bonding compound. Expect to use about a gallon of fairing compound and a gallon or so of gelcoat. It is supper strong and weighs about 40ish pounds.

Used about 105 feet of stainless for the frame. That includes the solar mount that will be on top as well.

[c.K.]

Originally Posted by Tspringer

Hello!

The Bimini top and dodger top section for our 2005 Beneteau 473 are worn out. Threadbare... sun shows through... goners and need replacement!

So I plan to build "hard" fiberglass replacements.

The concept here is to have the new hard Bimini and dodger top to be custom built to fit the same space and location as the sunbrella pieces that they will replace. The new hard Bimini top and dodger top will mount to the same typical alloy tube frames.

The new pieces must be strong but very lightweight. There will be no need to walk on the new pieces and only lightweight semi-rigid solar panels will be mounted on top. Both the new Bimini and dodger top will utilize new sunbrella and isinglass enclosure panels that I will also build.

So the key factors for the new hard pieces are lightweight - strong - easy to work with.

My thoughts are to use a flexible foam core to mount to the frames and then reinforce with fiberglass. What core material this will be is one of my primary questions.

What are the best core material options? Where can these options be sourced?

What options are there for pre-finished sheets that can be bonded to the core to simplify construction?

I have a good bit of fiberglass and construction experience but an not up to date with all the best current options. The end product will be solid, white in color with a nice surround and it will be as simple as I can make it.

Thanks!


Terry

hey Terry
I built a dodger using the modified ss frame as a base
2 layers of door skin glued to gather glassed over
Curved door skin is super strong cut our windows and used the cut outs to have poly carbon windows baked To shape ( not very expensive) also reinforced back end of the new doger with six layers of the same door skin glued to gather ( staples) took the rough arch out shaped it glassed over and mounted a curved traveller on top Very tough to bend
needless to say had to design 2 hard points to attach to cabin
still need to finish the project but it is super strong looks good as well

[coopec43]

Originally Posted by Tspringer

Hello!

The Bimini top and dodger top section for our 2005 Beneteau 473 are worn out. Threadbare... sun shows through... goners and need replacement!

So I plan to build "hard" fiberglass replacements.

The concept here is to have the new hard Bimini and dodger top to be custom built to fit the same space and location as the sunbrella pieces that they will replace. The new hard Bimini top and dodger top will mount to the same typical alloy tube frames.

The new pieces must be strong but very lightweight. There will be no need to walk on the new pieces and only lightweight semi-rigid solar panels will be mounted on top. Both the new Bimini and dodger top will utilize new sunbrella and isinglass enclosure panels that I will also build.

So the key factors for the new hard pieces are lightweight - strong - easy to work with.

My thoughts are to use a flexible foam core to mount to the frames and then reinforce with fiberglass. What core material this will be is one of my primary questions.

What are the best core material options? Where can these options be sourced?

What options are there for pre-finished sheets that can be bonded to the core to simplify construction?

I have a good bit of fiberglass and construction experience but an not up to date with all the best current options. The end product will be solid, white in color with a nice surround and it will be as simple as I can make it.

Thanks!


Terry

Maybe this link would help?

I've only ever used Airex (for the hull) and Divinycell for the deck. I am happy with both but I'm certain I'd never use Balsa.

I don't know whether the problem has been rectified over the years but Airex used to weaken when it was exposed to direct sunlight e.g. in a deck of a boat

https://fiberglasssupply.com/core-materials/

[David Mathis]

Have you considered using your existing threadbare top as a form to support fiberglass cloth then coating it with resin? You will have numerous drips so if you do this while it's on the boat, be sure to cover everything under the top. For more strength, apply a second coat of the fiberglass cloth and more resin. For the final coat, mix in whatever tint color you prefer. The original threadbare cloth will become a permanent part of the finished product so consider applying a final tinted coat on the underside. It won't support much weight but, for the application you describe, it should suffice.

[sailingharry]

As I read this thread, I have to I have to wonder why it needs to be strong? If you are doing a direct replacement of a Sunbrella bimini, does it need to be any stronger than the Sunbrella fabric? Could it simply be two or three layers of fiberglass laid into a mold, it would still be flexible but once attached to the framing should be stiffer than the fabric was.

[rslifkin]

Originally Posted by sailingharry

As I read this thread, I have to I have to wonder why it needs to be strong? If you are doing a direct replacement of a Sunbrella bimini, does it need to be any stronger than the Sunbrella fabric? Could it simply be two or three layers of fiberglass laid into a mold, it would still be flexible but once attached to the framing should be stiffer than the fabric was.

Strength requirement will depend on how much wind you want it to withstand, if you want to mount anything to it, etc. And there's likely a minimum to avoid it flexing to the point where things begin to crack.

[CarinaPDX]

You might usefully spend some time perusing this thread: https://www.cruisersforum.com/forums...ps-175159.html . It is quite a large collection of ideas.

Greg

[capn_billl]

I made a hard top for a previous boat out of 1/4" poly plastic. Available in several basic colors including tan, and easily formed with a heat gun.

Cable clamps with bolted through holes finished the job, and a square of Flextape to seal the holes.

I used it for a decade, and the new owner jumped in joy inspecting it.

Still looked beautiful, and watertight with zero maintenance, strong enough to survive several tropical storms that hit the Texas coast.

I used the existing Bimini supports with a few added reinforcements.

It was strong enough I could carefully lay on it, although it wasn't really designed for that.

[Joli]

We built a hard top, dodger and bimini before going cruising three years ago. It's carbon and balsa. It has soft sides that roll up. It's held on deck with 8 bolts and can be removed by removing those 8 bolts. Hard tops are great!

[AJA]

What page? Is there a link?

[AJA]

Originally Posted by Scubaseas

Thanks for sharing this. Hard top Bimini is on my to do list also. Greatly appreciate the info you have here.

What page? Is there a link?

[AJA]

Originally Posted by PuttingDoctor

I had a hardtop / Bimini system built years back for my Irwin 38’. I got the last WaveStopper made before the inventor passed away. He used molded polystyrene for the tops and regular canvas type tubing for support. The result was very attractive. Once installed my canvas man added his touch. The corners of the Bimini Isenglass were very solid an not removable though the center panel was.

Could you post a pick? I’m planning on making a hardtop for my Irwin CCKetch. 37’