On Aug 23, 3:07 pm, "Lew Hodgett" wrote:
OK.

You build the hard bimini on the ground, then put it in place with a
crane since it will be about 12 ft x 12 ft, maybe more, and weigh
250-300 lbs.

It will be totally self supporting requiring only some 2" pipe posts
in the corner to support it.

It will be totally clear underneath, part of the beauty of foam core
construction.

You will probably have to raise the boom about 12" and recut the main,
especially when you include the solar panels.

Get a copy of Fred Bingham's book, Practical Yacht Joinery. It has a
lot of info that will be useful for this project.

You will need a roll of 17OZ double bias glass (Knytex DB170),
probably about 6 sheets of 3/4" Divinycell, a 500 lb drum (55 gal) of
laminating epoxy and a couple of 5 gal pails of hardener.

You will also need a couple of 30 lb bags of Dic-A-Perl, HP500, to
make fairing putty.

As far as the front "windows" are concerned, have to think about that
a while.

This is a simple, straight forward process, but a hell of a lot of
hard work

Are you sure you want to open up this can of worms?

Lew

If you want to scare me off, tell me about the itch of fiberglass, I
dread it..

I think I'll adjust the dodger downward rather then adjust the boom
upward. It's a tall dodger now, so there is room for adjustment.

I was imagining that it would be built in place, is that a bad idea?
My boom and six dock apes should hold 350 pounds, but will use a crane
if we have to.

I'm surprised at the amount of epoxy needed. Thanks for the warning.

-Koos.

If you want to scare me off, tell me about the itch of fiberglass, I
dread it..

I understand.

I think I'll adjust the dodger downward rather then adjust the boom
upward. It's a tall dodger now, so there is room for adjustment.

It's your call, but you need at about 6'-8" standing room as a basic
design goal. Might trim an inch or even two, but that is cutting it
close.

I was imagining that it would be built in place, is that a bad idea?

YES, bad idea.

Trying to work while up in the air as oppossed to standing on the
ground.

Sanding dust and excess resin dripping on the boat raather than on the
ground.

Want me to go on?

My boom and six dock apes should hold 350 pounds, but will use a
crane
if we have to.

In this application, the boom just gets in the way.

A crane doesn't get an itch.

A crane doesn't loose it's grip.

A crane doesn't get distracted by a pretty girl.

Want me to go on?

I'm surprised at the amount of epoxy needed. Thanks for the warning.

Do the calculation yourself.

Use 17 OZ/sq yard per layer of glass.

Lets say 3 layers of glass per skin or 6 layers for both skins or 102
OZ/sq yard of bimini.

102/9 = 11.33 OZ/sq ft or 102/9/16 = 0.708 or 0.71 lbs/sq ft.

Assume the epoxy weight = glass weight + 20% for drips, waste, etc
120%*0.71=0.85lbs/sq ft of bimini

If you add a 4th layer of glass, add 34%.

If you have 150 sq ft of bimini, you could get by with 150 lbs of
epoxy which would be about 4, 5 gal pails.

By the time you buy 4 pails, you are probably 75%-80% of a drum price.

That's why I suggested a drum, you can always find some good use for a
half a drum of resinG.

Lew

Thanks for the details Lew.
I ordered that book you mentioned (already have his "simplified"
book).
-Koos.

wrote

Thanks for the details Lew.
I ordered that book you mentioned (already have his "simplified"
book).

Take a look at how cambers are laid out, that will be your starting
place.

Lew

I must be missing something here. A dodger is just a roof. Why all the
epoxy and glass? I wouldn't use any glass and just use wood and epoxy
for sealing. You should be able to build it in place and wood is alot
easier to work with than glass. Either paint it or leave it natural.

Bob

On Aug 23, 11:03 am, wrote:
Thanks to everyone for the replies to my prior questions about epoxy
and fiberglass (discounting the use of polyester). You help and
experience is appreciated.

I'm planning to build a dodger for my sailboat, still researching and
discovering..

After photographing hundreds of hard dodgers, and studying them
carefully, I know that hard angular corners will not look good on my
boat. I need to round the edges/corners to match the rest of the boat.

What techniques should I research for changing the hard corners where
two ply surfaces connect? How do I shape those round edges smoothly to
have a professional looking curve?

Plywood seems to be a good core for the large surfaces. I may use two
or three 1/4 ply layers glued with epoxy. 1/4 inch ply will allow some
curve to the sides and top, and having multiple layers will provide
strength. This is a 50 foot boat, so 1/2 to 3/4 inch thickness would
not look too flimsy, and the boat can accommodate the weight.

My question at this time is how do you make a smooth tidy round corner
where the sides and top meet, and where the sides and the front of the
dodger meet. It seems that connecting the ply large surfaces together
would add structural strength, but that would cause a hard angular
appearance.

Thanks for your input, (and please forgive my lack of experience).

-Koos.

wrote:

I must be missing something here. A dodger is just a roof. Why all
the
epoxy and glass? I wouldn't use any glass and just use wood and
epoxy
for sealing. You should be able to build it in place and wood is
alot
easier to work with than glass. Either paint it or leave it natural.

This is going to be a large, say 12x12 rigid dinghy that will support
a solar panel farm.

Wood is heavy, wood will rot, and wood is weak when compared to a foam
core complete with knitted glass and epoxy skins.

The above structure would add a lot of weight high above the water
line if made of wood.

Just for reference, a 4x8x1/2 sheet of plywood weighs about 42#, while
a 4x8x3/4 sheet of Divinycell weighs about 16#-17#.

Lew

On Mon, 27 Aug 2007 20:21:58 -0700, "Lew Hodgett"
wrote stuff
and I replied:

This is going to be a large, say 12x12 rigid dinghy that will support
a solar panel farm.

Wood is heavy, wood will rot, and wood is weak when compared to a foam
core complete with knitted glass and epoxy skins.

Canoes and Kayakers will disagree. I had this discussion with one of
the SNGlue/Strip kayakers, and they were very strong about wood vs
foam....either snglue or strip.

However, I have to admit that if the result is stiffness, noit inpact
strength, then fioam wins at a given weight.



The above structure would add a lot of weight high above the water
line if made of wood.

But not if made of wood (strip or sng ply) with the same skins or less
(agaon local impact strength)

Just for reference, a 4x8x1/2 sheet of plywood weighs about 42#, while
a 4x8x3/4 sheet of Divinycell weighs about 16#-17#.

For this purpose you need quite thin ply...1/4 or 3/8, and then less
glass or WHY because it's better for puncture.

Moot point. Just presenting the other POV. In my time I have tried
both, and find it hard to really fight one way or the other.


Lew


Human bevaviour: Bestiality with a brain

Lew Hodgett wrote:

wrote:


I must be missing something here. A dodger is just a roof. Why all

the

epoxy and glass? I wouldn't use any glass and just use wood and

epoxy

for sealing. You should be able to build it in place and wood is

alot

easier to work with than glass. Either paint it or leave it natural.


This is going to be a large, say 12x12 rigid dinghy that will support
a solar panel farm.

Wood is heavy, wood will rot, and wood is weak when compared to a foam
core complete with knitted glass and epoxy skins.

The above structure would add a lot of weight high above the water
line if made of wood.

Just for reference, a 4x8x1/2 sheet of plywood weighs about 42#, while
a 4x8x3/4 sheet of Divinycell weighs about 16#-17#.

Lew


That's for the foam panels only.

Add the glass and epoxy and it will be nearer 43 pounds

"cavelamb himself" wrote:

That's for the foam panels only.

Add the glass and epoxy and it will be nearer 43 pounds

The total weight is a function of the number of layers of glass in the
skins, so the total weight probably exceeds 43#, but did you bother to
calculate the stiffness of the foam/glass sandwich which is what truly
drives the design?

Lew

coming back to this subject....

Hard Dodger story at SailNet
http://www.sailnet.com/forums/showthread.php?t=37194