bertram 25 bulkheads coosa / pvc board

[spencer]

I am in the process of repowering my 25 bertram, the foward bulkheads, where the lower helm is supported on the starboard side and the port side which has the vberth door attached to
The previous owner replaced with the bulkheads with starboard, which failed to support the vertical weight of the helm, and was warping.

Would coosa alone be okay for this application, 3/4 inch with no glass or does it need to be skinned with glass.

Also there is a interior pannel made of starboard with is not structural but forms a closet area, and recomendations for a
light weight board to use that could be painted?

It appearts that the original bulkheads were thru bolted to the deck floor and also the cap and tabbed in to the hull side
will this suffice or should it be epoxied the the cap and floor?

[Joseph Fikentscher]

Make sure to post some pictures as I want to replace my bulkheads also. I think I would probably use Coosa and coat it with glass then tab it in as the old one was.

[Bob H.]

Spencer, I used 3/4 coosa with a layer of 1708 on each side. That should give the bulkhead plenty of strength. Capt. Pats building tips shows how it's done. No hard angles to hull sides. Plain coosa won't cut it. More pics will help us point you in the right direction. BH

[CamB25]

If it were me, I would not use coosa due to the labor required to glass and fair prior to painting (and it's overkill for strength). I would make a sandwich of 2 pieces of smooth FRP wall panel epoxied to a 5lb divinycell core. The smooth FRP will be ready for primer and paint with a simple sanding. I would bond the lower portion of the panel to the deck and bolt/screw the cap/helm station. Easy-peasy.

These liners were made in a similar manner - FRP surface, 3 lb divinycell, 12oz biax on the back. Once they are fit, I'll sand the FRP and paint. The bow seating is 3/4 coosa, glass, fairing compound, etc...lots of work. The inside surfaces of the storage areas are lined with the FRP over the rough glass - done.




Here's link to the FRP mfg. I have to order the smooth FRP from the building supply store. They tend to stock the pebbled finish version
http://www.cranecomposites.com/industri ... uentia.php

You can buy the divinycell from a number of sources. I get mine from Fiberglast:
http://www.fibreglast.com/product/vinyl ... nsity/Foam

Cam

[spencer]

Thanks guys
I have a panel of 3/4 inch preskinned
Panel think nida core was consenting this, already finished
Need to cut the shape only drawback would be compression when thru bolting
And holding screws

[CaptPatrick]

Spencer,

See: Sleeving Through Bolt Mounts and other hardware mounting in composite materials.

[John Swick]

Spencer,
The original bulkhead on my B25 sport convertible was 1/2" ply w/formica on both sides.
Because it's a relatively minor structural point I used 1/2 " ply coated with West System epoxy on both sides and a finish coat of high gloss white.
That was ~10yrs ago and still looks great, was dirt simple and quick to do.
I'll try and put up some pic's.
Don't over engineer it....save your energy (and money) for other projects.
Good Luck.

[captbone]

1/2 or 3/4 AB plywood with 1708 and epoxy will last a lifetime. The enemy of good is better. Realistically those bulkheads made out of ply and wrapped in epoxy will last a lifetime considering that the 1/2 & Formica lasted 40 years.

The 10 lb weight savings and increased cost with little benefits makes me vote for plywood wrapped.

Just my 2 cents.

[spencer]

When u guys reinstalled your new bulkheads did you thru bolt them or epoxy them in place or both
Looks like mine had a lot of flexing due to the poor choice of material

[CaptPatrick]

Bolting is pretty much the only solution for HDPE, (Starboard)... But other materials would be better done with epoxy and tabbing. Be sure that any bulkhead that runs up to the hull is tabbed both sides and has a 1/4" of space between the bulkhead edge and the hull. Without that space, you'll have a hard spot that will ghost through, crack your paint, and can eventually even cause the hull to crack and fail...

[John Swick]

As per the original construction, mine are thru bolted on top (to the deck cap), and lagged into a molded in notch of the cockpit floor liner.

[spencer]

Thanks guys
Will start to post some pics of progress