Forming rounded corners with Fiberglass and ply.
 

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.

Forming rounded corners with Fiberglass and ply.
 

Use a quarter round trim strip to form the corner, where you have a
radius on the outside, and a square corner inside, which you can trim
or fillet. For other than 90 degree corners, trim the strip on a
table saw. Use thin plywood and build up the edges to meet the trim
strip depth and accept screws holding it together.

Arrange to remove the plywood mold plug from the inside by covering
the outside with waxed paper. After you have built up sufficient
thickness of glass, drill out the screw heads and remove the screws to
remove the mold panels. Fill the screw holes.

I considered just glassing over the old canvas, for that slouch hatted
look.

Terry K

Forming rounded corners with Fiberglass and ply.
 

wrote:

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.

You are going to end up making a male mold and then doing a classic
"one off" construction.

I definitely would NOT use plywood as a core material, but rather use
1/2" Divinycell foam.

Best guess is probably about $3/sq ft for full 4x8 sheets.

Probably get the job done with 2 sheets so estimate maybe $200 for
foam.

Foam can be cut into strips to go around corners, I've done it several
times.

You do realize that this will be at least a 2 year project and cost at
least $1K before you are done.

Lew

Forming rounded corners with Fiberglass and ply.
 

On Aug 23, 11:05 am, Terry K wrote:
Use a quarter round trim strip to form the corner, where you have a
radius on the outside, and a square corner inside, which you can trim
or fillet. For other than 90 degree corners, trim the strip on a
table saw. Use thin plywood and build up the edges to meet the trim
strip depth and accept screws holding it together.

Arrange to remove the plywood mold plug from the inside by covering
the outside with waxed paper. After you have built up sufficient
thickness of glass, drill out the screw heads and remove the screws to
remove the mold panels. Fill the screw holes.

I considered just glassing over the old canvas, for that slouch hatted
look.

Terry K

Thanks Terry, that is very helpful.

I think you are suggesting that I make rounded corners from molds, to
be added to the structure afterwards. So I would make the structure
using wood in the corners to provide strength, and then add the
rounded corners and finish them. that is my interpretation..

I might be able to use the existing cabin-house as a male mold to get
the same curve? Using wax paper and protecting the area with plastic,
I could perhaps use fiberglass and epoxy to form the corners for
adding to the dodger later. Let me know if you think this is a crazy/
unworkable idea.

Thanks for the ideas.

-Koos.

Forming rounded corners with Fiberglass and ply.
 

On Aug 23, 12:12 pm, "Lew Hodgett" wrote:
You are going to end up making a male mold and then doing a classic
"one off" construction.

I definitely would NOT use plywood as a core material, but rather use
1/2" Divinycell foam.

Best guess is probably about $3/sq ft for full 4x8 sheets.

Probably get the job done with 2 sheets so estimate maybe $200 for
foam.

Foam can be cut into strips to go around corners, I've done it several
times.

You do realize that this will be at least a 2 year project and cost at
least $1K before you are done.

Lew

Thanks Lew,

Thanks for the foam suggestion. Why not ply? Because it rots? Because
it's heavy? Other reasons?

I should explain that the sunbrella dodger/bimini/surround I have now
is ugly, too vertical and also it has aged. It would cost $2,000 to
$5,000 to fix it or to replace it (change the shape).

I'd like to make a full hard dodger and combined hard bimini to cover
the entire cockpit. Then add sunbrella sides and soft windows aft of
the dodger. I'd like to be able to open the center window of the
dodger, for ventilation. I may have a window in the ceiling (bimini)
to see the sails, but probably not. I will probably have brackets for
mounting solar panels, and may include a conduit for power cables.

To have a shipyard build this would be very expensive (double the
above numbers), and I'm not confident that I would like the result. So
I expect my project to be expensive, when it's all done.

I plan to make some form of disposable mock-up, to determine the
details. It should be the right height, it should allow visibility, it
should be aesthetically acceptable, it should allow crew to work the
lines and winches etc. Until I'm happy with this aspect, I won't begin
construction.

Yes it will take a long time, especially considering my other
projects.. I was hoping to get it done within a year though (probably
not)..

Thanks for your advice.

-Koos.

Forming rounded corners with Fiberglass and ply.
 

wrote:

Thanks for the foam suggestion. Why not ply? Because it rots?
Because
it's heavy? Other reasons?

Before I get into the details, one question.

Is this by chance a center cockpit boat?

Lew

Forming rounded corners with Fiberglass and ply.
 

On Aug 23, 1:15 pm, "Lew Hodgett" wrote:

Before I get into the details, one question.

Is this by chance a center cockpit boat?

Lew

Yes it is. A Gulfstar 50 center cockpit Ketch. They usually have an
ugly phone-booth style dodger and surround/windows. Something like
this one;
http://tinyurl.com/34bc4k

May I add a question? With the foam, should I plan to build a wood
frame to provide the structural strength? So the foam is attached to
the frame, rather than just fiberglassing the foam pieces to each
other?

Also, your website, any updates? I'm interested in your project. Your
help is appreciated - thanks!

-Koos.

Forming rounded corners with Fiberglass and ply.
 

wrote:

Yes it is. A Gulfstar 50 center cockpit Ketch. They usually have an
ugly phone-booth style dodger and surround/windows. Something like
this one;
http://tinyurl.com/34bc4k

AH HA, new game plan.

Look at the "roof" of the bimini/dodger of that G/S50..

Think, "How would I make that out of cored fiberglass and use roll up
side and front curtains?".

You simplify comstruction as well as end up with a place to "plant
your solar garden."

It is/was my game plan.

If that interests you, get back to me.

BTW, don't think of it as a telephone booth, think of it as a covered
patio.G


http://LewsSailBoat.googlepages.com/home


Lew

Forming rounded corners with Fiberglass and ply.
 

On Aug 23, 2:09 pm, "Lew Hodgett" wrote:

AH HA, new game plan.
Look at the "roof" of the bimini/dodger of that G/S50..
Think, "How would I make that out of cored fiberglass and use roll up
side and front curtains?".
You simplify comstruction as well as end up with a place to "plant
your solar garden."
It is/was my game plan.
If that interests you, get back to me.
BTW, don't think of it as a telephone booth, think of it as a covered
patio.G
http://LewsSailBoat.googlepages.com/home
Lew

Lew,

A patio is right. It was made for sitting in, not sailing in.

Forward visibility is compromised (smudgy, warped) especially in our
fog and rain. Hard windows would be better. Crew have to fight it to
use the winches (can't even make make a half, never mind a full turn).
It leaks and drips in too many places, even into the companionway. The
boom scrapes and chafes on the stainless tubing, tearing the
sunbrella. It's very ugly, does not fit the lines of the boat, see
here http://tinyurl.com/36ofeo

I have to totally redesign it, or use the boat as a dockside patio, or
sell the boat..

So I want what you say, but with a hard dodger up front, and redesign
the patio cover to make it functional and visually acceptable.

I've been googling the foam, thanks for the lead on that.

I've seen your advert before, in the live-aboard list I think. I'm
sorry to hear you are selling, but I'm sure you have thought about it
and are making a difficult but good decision.

Best wishes,
-Koos.

Forming rounded corners with Fiberglass and ply.
 

wrote
A patio is right. It was made for sitting in, not sailing in.

I have to totally redesign it, or use the boat as a dockside patio,
or
sell the boat..

So I want what you say, but with a hard dodger up front, and
redesign
the patio cover to make it functional and visually acceptable.

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

Forming rounded corners with Fiberglass and ply.
 

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.

Forming rounded corners with Fiberglass and ply.
 

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

Forming rounded corners with Fiberglass and ply.
 

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

Forming rounded corners with Fiberglass and ply.
 

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

Forming rounded corners with Fiberglass and ply.
 

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.

Forming rounded corners with Fiberglass and ply.
 

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

Forming rounded corners with Fiberglass and ply.
 

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

Forming rounded corners with Fiberglass and ply.
 

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 :)

Forming rounded corners with Fiberglass and ply.
 

"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

Forming rounded corners with Fiberglass and ply.
 

coming back to this subject....

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