We cruise on our Gulfstar Auxillary 41 centre cockpit. Our bimini is now
old and will need replacing this season. I have been thinking of replacing
with a hard bimini that will last longer than a sunbrella one, allow the
mounting of solar panels, water collection & other cockpit ammenities.

I am considering building one myself. Some folks at the boat-yard suggested
building one out of some kind of foam, that can be cut & fit & when the
desired shape is reached, painted with resin to harden and so on.

Anyone built a hard bimini? Advise? Used this foam stuff?
Advise?...what's the stuff called & where can it be aquired? Advise on
bimini for a cruising boat?

Thanks all!

Glenn.
s/v Seawing

On Sep 26, 8:21 pm, "Glenn \(s/v Seawing\)"
wrote:
We cruise on our Gulfstar Auxillary 41 centre cockpit. Our bimini is now
old and will need replacing this season. I have been thinking of replacing
with a hard bimini that will last longer than a sunbrella one, allow the
mounting of solar panels, water collection & other cockpit ammenities.

I am considering building one myself. Some folks at the boat-yard suggested
building one out of some kind of foam, that can be cut & fit & when the
desired shape is reached, painted with resin to harden and so on.

Anyone built a hard bimini? Advise? Used this foam stuff?
Advise?...what's the stuff called & where can it be aquired? Advise on
bimini for a cruising boat?

Thanks all!

Glenn.
s/v Seawing

Use marine ply and cover with cloth..You can use just about anything
as a core I guess including foam, bimini's leak..wear out...and all
around are a pain in the ass.

I buildt a hard top after 2 bimini's.... best thing I ever did for the
boat.

http://sports.webshots.com/photo/272...63212926LiUcvQ

I guess with the proper foam and resin you could build lighter and
stronger.

Joe

In article .com,
Joe wrote:

On Sep 26, 8:21 pm, "Glenn \(s/v Seawing\)"
wrote:
We cruise on our Gulfstar Auxillary 41 centre cockpit. Our bimini is now
old and will need replacing this season. I have been thinking of replacing
with a hard bimini that will last longer than a sunbrella one, allow the
mounting of solar panels, water collection & other cockpit ammenities.

I am considering building one myself. Some folks at the boat-yard suggested
building one out of some kind of foam, that can be cut & fit & when the
desired shape is reached, painted with resin to harden and so on.

Anyone built a hard bimini? Advise? Used this foam stuff?
Advise?...what's the stuff called & where can it be aquired? Advise on
bimini for a cruising boat?

Thanks all!

Glenn.
s/v Seawing

Use marine ply and cover with cloth..You can use just about anything
as a core I guess including foam, bimini's leak..wear out...and all
around are a pain in the ass.

I buildt a hard top after 2 bimini's.... best thing I ever did for the
boat.

http://sports.webshots.com/photo/272...63212926LiUcvQ

I guess with the proper foam and resin you could build lighter and
stronger.

Joe

I keep thinking that an old van roof might do as either a template, or,
with a bit of ingenuity, the real thing! When was the last time you saw
a van with a rusty roof?

:-)

--
Molesworth

On Sep 27, 7:16 pm, Molesworth wrote:
In article .com,





Joe wrote:
On Sep 26, 8:21 pm, "Glenn \(s/v Seawing\)"
wrote:
We cruise on our Gulfstar Auxillary 41 centre cockpit. Our bimini is now
old and will need replacing this season. I have been thinking of replacing
with a hard bimini that will last longer than a sunbrella one, allow the
mounting of solar panels, water collection & other cockpit ammenities.

I am considering building one myself. Some folks at the boat-yard suggested
building one out of some kind of foam, that can be cut & fit & when the
desired shape is reached, painted with resin to harden and so on.

Anyone built a hard bimini? Advise? Used this foam stuff?
Advise?...what's the stuff called & where can it be aquired? Advise on
bimini for a cruising boat?

Thanks all!

Glenn.
s/v Seawing

Use marine ply and cover with cloth..You can use just about anything
as a core I guess including foam, bimini's leak..wear out...and all
around are a pain in the ass.

I buildt a hard top after 2 bimini's.... best thing I ever did for the
boat.

http://sports.webshots.com/photo/272...63212926LiUcvQ

I guess with the proper foam and resin you could build lighter and
stronger.

Joe

I keep thinking that an old van roof might do as either a template, or,
with a bit of ingenuity, the real thing! When was the last time you saw
a van with a rusty roof?

:-)

--
Molesworth- Hide quoted text -

- Show quoted text -

I was thinking on the line of an Airsteam camper chopped..or carbon
fiber if I re-do mine.

Joe

Subject

Building a male mold for a bimini is very straight forward.

A basic 4x8 sheet of 3ply, 1/2" plywood is about 42 lbs.

Divinycell foam is about 6 lbs/ft3.

Trying to fabricate a bimini using plywood will end up being a top
heavy slug and totally change the sailing characterstics.

You simply don't want to go there.

Lew

Good advise Lew, thanks. Have you worked with this foam before? Trying to
figure out how it is to work with and the general methodology of working
with it (& maybe some of the pitfalls).

Glenn.

"Lew Hodgett" wrote in message
...
Subject

Building a male mold for a bimini is very straight forward.

A basic 4x8 sheet of 3ply, 1/2" plywood is about 42 lbs.

Divinycell foam is about 6 lbs/ft3.

Trying to fabricate a bimini using plywood will end up being a top
heavy slug and totally change the sailing characterstics.

You simply don't want to go there.

Lew

"Glenn (s/v Seawing)" wrote in
message news:UW_Ki.8439$x%6.7141@pd7urf2no...
Good advise Lew, thanks. Have you worked with this foam before?

Built a 55 ft Bruce Roberts double head sail ketch using 1" Airex foam
for the hull and 3/4" Divinycell for the deck.

It is a very mature construction technique.

Lew

Glenn (s/v Seawing) wrote:

Good advise Lew, thanks. Have you worked with this foam before? Trying to
figure out how it is to work with and the general methodology of working
with it (& maybe some of the pitfalls).

Glenn.


I have.
It's a bit more challenging than plywood for one off coring.
But it would be the way I'd go if I were going to do this.
It's a weight issue.

For all the ins and outs may I refer you to the amateur built aircraft
industry - composite moldless construction as developed by Burt Rutan.

There is quite a bit of prior work to study there - and besides, you are
not worried about the wings folding so it's nowhere near as critical.


I recently made a pair of bunk shelves for my boat.
It's a Catalina Capri 18 - pretty small inside - although is seems big
enough outside.

The shelves are urethane foam cored with woven fabric skins. And West
resin - since that was what I had handy.

I used 5 ounce BID (BI Directional) glass (cuz that's what I had handy)
with 4 or 5 layers to get a good solid surface. Besides, the cores were
only about 3/16" thick, hence the heavy skins.

Wish I had taken pictures as I went along - but as usual I was too busy
wetting and squeeging.

They came out ok though. Haven't managed to paint them yet because I
took them out to the boat for installation fit - and they have been
there ever since...


For what you want to do I think I'd recommend something between 1/2 and
1 inch thick foam for the cores. I'd also make a plywood form to set
the desired curvature - and probably vacuum bag the skins.

Figure the bottom side could have lighter skins because (usually) nobody
will be walking on the bottom surface.

Look at what they call "units" in boat building rather than using woven
glass for something like this. (Cloth would be way expensive compared
to the boat unit approach). Units (as I understand it) are two (or
more?) layers of dissimilar materials - chopped strand matt and woven
roving or woven matt and woven cloth fabric.

I'd really like to buy Roger Long a cold beer and get all this straight
from the sea horse's mouth. All my experience is aircraft work - which
is quite a bit lighter stuff.


You may not absolutely need the vacuum bagging on a panel this size, but
if you've done it before you would know why you'd want to go to the
trouble and expense. (Better bonding to the core material - and a lot
easier surface finishing)

But it could be done as a straight forward hand lay up quite
successfully.

For a first time project this is really a bit big.

Building an airplane, one usually starts with a rudder and fin.
Small pieces to learn the techniques.

Then advance to the bigger and more critical structures.

I'd kind of like to do a project like you are discussing as the next
step before laying up an entire hull and deck.
'Specially if someone else is footing the bill


For what its worth, Glenn.


Richard Lamb



A few Marine Links:

http://boatdesign.net/articles/boatbuilding.shtml
http://boatdesign.net/articles/foam-core/index.htm
http://www.marinecomposites.com/ = excellent info!
http://microship.com/resources/micro-trimaran.html


Aircraft links:

http://www.maddyhome.com/canardpages/main (everybody)
http://www.maddyhome.com/canardpages...Dembs/Ch14.htm
http://www.ez.org/resource.htm

Now, you see that? Ingenuity...it's one of the things I love about cruising
sailors! :-). Van with a rusty roof...make me laugh...might just make a
great template or mould too.

Glenn.

"Molesworth" wrote in message
...
In article .com,
Joe wrote:

On Sep 26, 8:21 pm, "Glenn \(s/v Seawing\)"
wrote:
We cruise on our Gulfstar Auxillary 41 centre cockpit. Our bimini is
now
old and will need replacing this season. I have been thinking of
replacing
with a hard bimini that will last longer than a sunbrella one, allow
the
mounting of solar panels, water collection & other cockpit ammenities.

I am considering building one myself. Some folks at the boat-yard
suggested
building one out of some kind of foam, that can be cut & fit & when the
desired shape is reached, painted with resin to harden and so on.

Anyone built a hard bimini? Advise? Used this foam stuff?
Advise?...what's the stuff called & where can it be aquired? Advise on
bimini for a cruising boat?

Thanks all!

Glenn.
s/v Seawing

Use marine ply and cover with cloth..You can use just about anything
as a core I guess including foam, bimini's leak..wear out...and all
around are a pain in the ass.

I buildt a hard top after 2 bimini's.... best thing I ever did for the
boat.

http://sports.webshots.com/photo/272...63212926LiUcvQ

I guess with the proper foam and resin you could build lighter and
stronger.

Joe

I keep thinking that an old van roof might do as either a template, or,
with a bit of ingenuity, the real thing! When was the last time you saw
a van with a rusty roof?

:-)

--
Molesworth

That's a great looking bimini Joe. You didn't happen to keep a photo-record
of the construction did you? Any advise on construction?

Glenn.

"Joe" wrote in message
oups.com...
On Sep 26, 8:21 pm, "Glenn \(s/v Seawing\)"
wrote:
We cruise on our Gulfstar Auxillary 41 centre cockpit. Our bimini is now
old and will need replacing this season. I have been thinking of
replacing
with a hard bimini that will last longer than a sunbrella one, allow the
mounting of solar panels, water collection & other cockpit ammenities.

I am considering building one myself. Some folks at the boat-yard
suggested
building one out of some kind of foam, that can be cut & fit & when the
desired shape is reached, painted with resin to harden and so on.

Anyone built a hard bimini? Advise? Used this foam stuff?
Advise?...what's the stuff called & where can it be aquired? Advise on
bimini for a cruising boat?

Thanks all!

Glenn.
s/v Seawing

Use marine ply and cover with cloth..You can use just about anything
as a core I guess including foam, bimini's leak..wear out...and all
around are a pain in the ass.

I buildt a hard top after 2 bimini's.... best thing I ever did for the
boat.

http://sports.webshots.com/photo/272...63212926LiUcvQ

I guess with the proper foam and resin you could build lighter and
stronger.

Joe