TWL: Flybridge hardtop
This winter I want to make a F/B hardtop for my 1972 48ft Hatteras. the
hardtop is to be about 9.5ft square. I want to be sure to have a slightly
curved top for looks and to quickly shed water.
Any suggestions ,experience, in fabrication? Or source of used hardtops?
Absent any other ideas, I would bend laminated ribs in a jig and glue them
to the curve I choose, then fasten them to 3/8" plywood every two feet to
force the plywood into a curve. Then I'd fiberglass both sides and paint with
a two part linear polyurethane. (The aft end will be bolted to an existing
aluminum radar arch and I'll used forward corner braces at right angles made
from SS handrail hardare.)
(My gosh that sounds like a lengthy process!! What isn't on a boat??)
Rob Brueckner
Rob Brueckner wrote
This winter I want to make a F/B hardtop for my 1972 48ft Hatteras. the
hardtop is to be about 9.5ft square.
Absent any other ideas, I would bend laminated ribs in a jig and glue them
to the curve I choose, then fasten them to 3/8" plywood every two feet to
force the plywood into a curve. Then I'd fiberglass both sides and paint
with a two part linear polyurethane.
REPLY
I used to work at a marina that built hard tops in that fashion.
Boy were they heavy. Adding that much weight high up will affect adversely your vessel's stability.
Have you looked into the light weight foam core and kleg cell construction techniques used by the big boat builders.
Another alternative is to cut the ribs from 1/2 sheet stock and create an egg crate type structure then skin it over. This covering can be a very thin door skin type
layer or fibreglass sheeting about 1/8" thick
This is how Rayburn Yachts create lage surface area hard tops.
Their deck beams are fabricated from 1/2 sheet stock with a 1 1/2 " wide cap glued to each edge of the web.
House construction uses the same technique and calls these beams "glue-lams" or some such word. The effect is like a fabricated roof truss.
Very strong, yet lightweight compared to conventional construction.
cheers
Arild
In keeping with Alex's suggestion, one product you should look into is
Nida-Core. The company's web site is http://www.nida-core.com/
I used their extruded honey-comb sheets when reworking Sanderling's top
deck a couple of years ago, using it for the deck core instead of marine
ply. Light weight, strong, easy to work, etc.
At 11:36 AM 10/18/2002, Arild Jensen wrote:
Rob Brueckner wrote
This winter I want to make a F/B hardtop for my 1972 48ft Hatteras. the
hardtop is to be about 9.5ft square.
REPLY
I used to work at a marina that built hard tops in that fashion.
Boy were they heavy. Adding that much weight high up will affect
adversely your vessel's stability.
Have you looked into the light weight foam core and kleg cell
construction techniques used by the big boat builders.
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Bob McLeran Email: mailto:rmcleran@ix.netcom.com
M/V Sanderling Until Oct 28, 2002, at Washburn's Boat Yard, Solomons, for
Hampton 35 Trawler annual maintenance, then heading for Florida Nov 2.
Rob Brueckner wrote
This winter I want to make a F/B hardtop for my 1972 48ft Hatteras. the
hardtop is to be about 9.5ft square.
Absent any other ideas, I would bend laminated ribs in a jig and glue them
to the curve I choose, then fasten them to 3/8" plywood every two feet to
force the plywood into a curve. Then I'd fiberglass both sides and paint
with a two part linear polyurethane.
Snip
Reply
I agree with Arild the plywood/fiberglass construction is far too much
weight up that high.
You may want to consider tubing. Skooch has a pipewelders aluminium tubing
half tower. Its covered with fabric laced to the side tubes. Its relatively
light and works great. It has been on the boat for over 10 years in the
tropics and still looks great. I suspect I will need to replace the fabric
in a few years, but that should be fairly simple.
Drawbacks are it would require professionals to install ie . . cost. It
came with the boat, but I would guess you would be north of $20,000 to get
the piplewelders folks to do it.
You can see how it looks at www.trawler.org. I haven't worked on the web
site for a while, but Skooch's original photos are there.
Skooch Hatteras LRC 42
Worton Creek, MD
David Stahl
Beacon Technologies Inc.
Serving The Delaware Valley
Business and Residential Internet Services
Dear Rob,
I have built two pilothouse hardtops, both about 10x14'. Both
were enclosed pilothouses with aluminum framed windows. The
first used klegecell foam core (2" thick) with glass on both
sides. The layup consisted of one layer of 18 oz biax w mat over
the entire top, with two layers over the center 5' (top &
bottom).
The second hardtop used a plastic honeycomb called Nidacore, 1.5"
thick with a similar layup. The Nidacore is cheaper and
stronger, but you have some additional finish work to do on the
edges. I used nidacore with two layers of biax w mat on each
side for the 4 corner uprights, about 2' long and 3' high. The
windshields give some lateral stability to the top; you'll have
to have some diagonal bracing to achieve enough stability with
only SST tubing for your supports.
Be sure to incorporate some pvc conduits inside the hardtop cores
and note carefully where they are. You will inevitably decide
somewhere down the road to add lights, speakers, electronics, or
something else requiring wiring. Just as a crude check on how
extensive a project this is, I charged $18k for the second
pilothouse, including the $4k cost of the manufactured opening
windows. The first pilothouse is on my own boat, Winnie the
Pooh, a 46' troller yacht.
Mark Richter, homeport Stuart, FL
presently in Madisonville, LA
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Arild wrote
I used to work at a marina that built hard tops in that fashion.
Boy were they heavy. Adding that much weight high up will affect
adversely your vessel's stability. Have you looked into the light weight
foam core and kleg cell construction techniques used by the big boat
builders.
Comment:
After making the original post I had occasion to stop by the yard where a new 85 footer is just now being laid up.
Construction is a a mix of various types of coring material.
High density foam is used in places where a lot of sculpting or form fairing is required.
Nidacore and Klegcell is used for flat rigid bulkheads that impart maximum strength to a panel.
Inside the main deck, the relatively thin flat layers are reinforced with a box channel construction and the rounded corners are formed by using foam strips which
are cut and sanded to shape.
While I was there the crew was preparing to lift the engines into place but they had to lift the deck molding out of the way.
The 20 foot by 15 foot panel weighed in at a few hundred pounds.
That compared very favourably with the 1200 + pounds that a 10 X 12 hard top built in the conventional way using plywood and 2X3 wooden beams all covered
with fibreglas.
Critical stress points have aluminum plates imbedded inside the structure to spread the load and accept threaded fasteners.
Regards
Arild