Hard Bimini Top Build

[Typhoon]

Plywood was dried for a month in an oven . Moisture meter showed no moisture at all . Surface was ground open with 40 grit . Wood was saturated before laminating. This is a Bimini top , not a transom , so I didn't stress to much about using polyester . It will outlast any canvas top .

The key now is to make sure it is well sealed up from water intrusion . I'm sure this top will outlast me.

Regards John

[Squanderbucks]

Just wondering why you choose plywood instead of structural foam board? Booth work of course but FRP covered over wood has a habit of swelling if any moisture gets in through a penetration from mounting screws, etc. - leads to cracks along the edge seams. weight up top can be a difference as well.

I've worked with both over the years and had a couple of projects need cosmetic fixing or replacement when the wood swelled. Thinking of a bow pulpit that was glass over wood that held the windlass. Finially removed and replaced it with one where I made a mold and made the whole thing out of 3/8" FRP with no wooden inner form.

[Fore and Aft]

I made almost the same Bimini and on the edge I used pvc pipe covered with glass and rebated two skin fittings into the forward end so I could collect rain water. I used the pvc pipe just because I like the sexiness of a big round edge.
Cheers

[Typhoon]

Originally Posted by Squanderbucks

Just wondering why you choose plywood instead of structural foam board? Booth work of course but FRP covered over wood has a habit of swelling if any moisture gets in through a penetration from mounting screws, etc. - leads to cracks along the edge seams. weight up top can be a difference as well.

I've worked with both over the years and had a couple of projects need cosmetic fixing or replacement when the wood swelled. Thinking of a bow pulpit that was glass over wood that held the windlass. Finially removed and replaced it with one where I made a mold and made the whole thing out of 3/8" FRP with no wooden inner form.

I was going to use a foam core , but then I would have had to put plywood on all the compression points . I am going to use vary large stainless plates under the top to give it even more strength , by the time I did that on this small top I am almost 50% plywood so it made construction easer to just do the whole thing in ply wood.

Regards John.

[Typhoon]

Originally Posted by Fore and Aft

I made almost the same Bimini and on the edge I used pvc pipe covered with glass and rebated two skin fittings into the forward end so I could collect rain water. I used the pvc pipe just because I like the sexiness of a big round edge.
Cheers

I understand , I like the sexiness of the varnished teak edge .

Regards John.

[daletournier]

Hi John, Bristol 45.5 were mainly center cockpits but were also produced with a aft cockpit? which one do you have?

Interested to see how it turns out. I would like eventually to build a hard bimini, I just don't see many done well from a asehtic perspective.

Did you consider anodized aluminium instead of ss , if so why did you chose stainless? I'm thinking aluminium, I currently have an Atlantic arch which is Aluminum, strong and light.

[Typhoon]

We have a Center cockpit Bristol 45.5 . The present dodger/Bimini makes the boat look like a bus so I wanted a very thin profile Bimini . I picked stainless poles for there bling appeal . I like shiny things . I will be replacing the current dodger as well as soon as I get the Bimini up . I like a canvas dodger but the new one will be much lower so I can see over it when I am standing behind the wheel . The hard Bimini will overlap the dodger and I will have attachment there to close the entire cockpit with removable clear panels creating a full enclosure for the cold days . Which we have plenty of up here.

Weight was never a concern . The boat weighs 18 ton so an extra 135 lbs is like a flea on a camels behind .

Regards John

[gulfstar37]

Keep the pictures coming. Can't wait to see the beautiful finished project.

[Typhoon]

Just finished fairing and priming the top . I think I will put the teak edge surround on before I paint it .

Regards John

[jimbunyard]

Originally Posted by Cadence

John, it looks good but polyester resin on plywood. I hope you saturated the ply with acetone thinned resin prior to glassing it or used rough sandpaper to give it some tooth.. A little West System or System Three for a small job would have been worth it.
I guess it is after the fact advice, best of luck.

6 gal poly 175.00

6 gal West 660.00
6 gal Mas 607.00
6 gal Sys3 525.00
6 gal R/R 367.00 (Resin Research)

To beat a dead horse a little more, polyester is perfectly acceptable in this application. Edges have to be sealed and fastener holes have to be cored, but when using plywood for a core material this must be done for epoxy as well...

Certainly looks good so far.

[Cadence]

Originally Posted by jimbunyard

6 gal poly 175.00

6 gal West 660.00
6 gal Mas 607.00
6 gal Sys3 525.00
6 gal R/R 367.00 (Resin Research)

To beat a dead horse a little more, polyester is perfectly acceptable in this application. Edges have to be sealed and fastener holes have to be cored, but when using plywood for a core material this must be done for epoxy as well...

Certainly looks good so far.

I believe the epoxy would be worth the money in the long run. Poly tends to delaminate on plywood. JMHO

[Terra Nova]

If absolute lowest cost were always the determining factor, decision making would be a no-brainer. It is for some.

[jimbunyard]

Originally Posted by Cadence

I believe the epoxy would be worth the money in the long run. Poly tends to delaminate on plywood. JMHO

In my experience, poly/wood delamination is almost always caused by water intrusion, and this is true for epoxy/wood as well, though the greater bond strength of the epoxy helps in this regard.

In John's description of his process, it seems he's covered the bases, the only caveat I see is using wood with zero moisture content; given the slight permeability of poly resin, a very good, impermeable, two part epoxy primer and some kind of two part finish (acrylic?) seems necessary to avoid possible eventual delamination caused by the expansion of the wood as it reaches a more natural 10-15% moisture content, and the contraction of the poly resin as it looses volatiles, a situation that may or may not be encountered with epoxy. Had epoxy been used, a less expensive finish coat and primer could be applied so who knows where the actual final cost would have wound up...

In either case, the life span is likely decades, given its' intended use, so it's kinda a moot point with (for me) merely academic interest.

Originally Posted by Terra Nova

If absolute lowest cost were always the determining factor, decision making would be a no-brainer. It is for some.

'Lowest cost' is not determined by a single factor. If one product provides the same service as another product that costs three times as much, then to buy the more expensive product is foolish. (even if one has money to throw away)

For those that don't have money to throw away, the default position is to use the product that provides the overall best value; i.e. lowest cost.

Sometimes that means paying more up front, for a variety of reasons.

Sometimes that means knowing when to use the the less expensive product, because, for example, it has properties not needed in a specific application.

A logical case might be made for the use of a thrice-expensive product based purely on an unknown life expectancy, or any combination of that and of perceived shortcomings, or ignorance of the real properties of a correctly used product.

Obviously, experience is important in making these decisions, and since 'experience' is somewhat subjective...

[Typhoon]

Next step . Getting the teak trim ready for the outside edge of the top . This will also serve as a hand hold .

Regards John

[Typhoon]

This takes awhile . Epoxy one side on move to the next . But it looks great . And will have a continuous hand hold down the side deck to the aft deck .

Regards John