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Old 20-10-2020, 07:58   #1
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The GIANT Performance Catamaran Build/Refit Thread

The time has arrived.

Time to get this catamaran finished.

Iím going to share the process with everyone in a huge thread.

There will be many questions, a lot of blood, sweat and tears. And thousands of hours of work involved.

I ask that posters please to be nice. Please donít trash talk my boat or me personally. Iíd like to share the experience with everyone, but if it goes all negative and stressful I wonít have the energy to post.

I welcome all opinions and encourage them. However, a decision will be made and run with once all the opinions are in. Please accept that your input may not necessarily be followed.

Note: The boat has a design philosophy.

1) Lightest weight possible construction
2) No seacocks, no zincs.
3) As much as possible off the shelf, easily replaced and inexpensive (less marine stuff). Marine where necessary however, like fuel lines and such.
4) Epoxy can be lethal to me. Wet epoxy, sanding dust, basically anything. PLEASE DO NOT SUGGEST EPOXY. However, the boat is made of epoxy and corecell, vacuum infused.


With that out of the way, letís have some fun with this!

Iíll start with my first problem. Damn windows!!!
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Old 20-10-2020, 08:28   #2
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Windows

I have enormous Lexan bridgedeck windows on this boat.

Most are 4’ x 4’ sections.

There are no frames, per se. There are open holes the window rest upon.

This DOES NOT WORK due to the 1/2” of daily thermal expansion and contraction with these Lexan windows

The windows are also severely wrecked now from Florida mold. Yes, apparently it can eat polycarbonate too. Left gouges where it was growing

I need a new window plan. BUT... I cannot be cutting into the epoxy or using epoxy to do this.

My thought is to get flat glass sheets to replace the Lexan and put a U channel on the bottom and top of the glass, using Dow 795 to seal between the window panels where they join each other. The upper U channel will direct the water from the roof onto the window. The lower U channel will hold the lower part of the window in place. All else will be Dow 795 or similar that works with glass.

I just don’t know the best way to secure the aluminum U channel to the deckhouse. Adhesives would be best. Maybe epoxy just this once and have my girlfriend do it?

That’s my initial plan.

Thoughts? Better ideas?

This is my 5th try at these damn things. I’m at my wits end.


Note: all my pics may be rotated forever on this thread. The forum incorrectly ignores EXIF information and doesn’t rotate the pics. Hopefully, they’ll upgrade it sometime.
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Old 20-10-2020, 10:52   #3
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Re: The GIANT Performance Catamaran Build/Refit Thread

Thinking of getting 1/4” tempered safety glass in clear and putting a 3m tint film on it to keep it together if it shatters.

Certainly weighs more than polycarbonate unfortunately, but at least it’ll be nice to look through and won’t be subject to ridiculous thermal expansion, making it leak.
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Old 20-10-2020, 12:46   #4
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Re: The GIANT Performance Catamaran Build/Refit Thread

I'd talk to the Seawind guys and try to find out what thickness of tempered glass they use in their similarly dimensioned windows.

Our new boat will have smaller spans and 8mm is the recommendation if going glass.

Matt
Quote:
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Thinking of getting 1/4Ē tempered safety glass in clear and putting a 3m tint film on it to keep it together if it shatters.

Certainly weighs more than polycarbonate unfortunately, but at least itíll be nice to look through and wonít be subject to ridiculous thermal expansion, making it leak.
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Old 20-10-2020, 13:04   #5
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Re: The GIANT Performance Catamaran Build/Refit Thread

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Originally Posted by funjohnson View Post
I'd talk to the Seawind guys and try to find out what thickness of tempered glass they use in their similarly dimensioned windows.

Our new boat will have smaller spans and 8mm is the recommendation if going glass.

Matt
I was thinking of going up one size to 3/8 or about 10mm, so good point. The large span probably needs more glass.
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Old 20-10-2020, 13:10   #6
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Re: The GIANT Performance Catamaran Build/Refit Thread

My boat has similar windows.

The old bedding for the polycarbonate windows was cracked.

I replaced with black 3M 5200, 3/4 inch around the window.

No issues since.

The expansion of polycarbonate isn't that different from fiberglass.

You can screw the U channels to the base, and seal with 3M.

Also use H channels between sections. (also seal).
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Old 20-10-2020, 13:12   #7
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Re: The GIANT Performance Catamaran Build/Refit Thread

Quote:
Originally Posted by Chotu View Post
Thinking of getting 1/4Ē tempered safety glass in clear and putting a 3m tint film on it to keep it together if it shatters.

Certainly weighs more than polycarbonate unfortunately, but at least itíll be nice to look through and wonít be subject to ridiculous thermal expansion, making it leak.


Our boat has 4mm tempered glass that has a mirrored coating. Probably a smaller window than yours. Ours also has some bend, so the thinner glass bends easier. Iíd go with with a coating, as the filmís generally donít last that long. I know our windows have been hit by snatchblocks many times with no damage.
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Old 20-10-2020, 13:28   #8
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Re: The GIANT Performance Catamaran Build/Refit Thread

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Originally Posted by capn_billl View Post
My boat has similar windows.

The old bedding for the polycarbonate windows was cracked.

I replaced with black 3M 5200, 3/4 inch around the window.

No issues since.

The expansion of polycarbonate isn't that different from fiberglass.

You can screw the U channels to the base, and seal with 3M.

Also use H channels between sections. (also seal).
These windows are moving 1/4 inch each, each day.. Thatís a half an inch movement between two of them.

The fiberglass doesnít change size at all.

Are you sure about this?
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Old 20-10-2020, 14:21   #9
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Re: The GIANT Performance Catamaran Build/Refit Thread

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Originally Posted by Training Wheels View Post
Our boat has 4mm tempered glass that has a mirrored coating. Probably a smaller window than yours. Ours also has some bend, so the thinner glass bends easier. Iíd go with with a coating, as the filmís generally donít last that long. I know our windows have been hit by snatchblocks many times with no damage.
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Interesting. I was going to use the genuine 3M film as a dual purpose solution both for tinting and in case it broke.

A smashed window still stuck to the film should stay pretty well intact and keep the water out like safety glass.

Itís a tough call on the thickness because I want to also keep things light.

Plans call for polycarbonate or acrylic. But Iím tired of the problems with them.
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Old 20-10-2020, 14:55   #10
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Re: The GIANT Performance Catamaran Build/Refit Thread

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Originally Posted by capn_billl View Post
My boat has similar windows.

The old bedding for the polycarbonate windows was cracked.

I replaced with black 3M 5200, 3/4 inch around the window.

No issues since.

The expansion of polycarbonate isn't that different from fiberglass.

You can screw the U channels to the base, and seal with 3M.

Also use H channels between sections. (also seal).
The channels all sound like a good idea. H channel as well. Thanks for that.
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Old 20-10-2020, 15:51   #11
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Re: The GIANT Performance Catamaran Build/Refit Thread

The larger the window the greater the thermal expansion. If the windows are bonded in, the thickness of the adhesive bonding the window must be proportioned to the thermal expansion. Which means that larger windows need a thicker layer of adhesive between them and the structure they bond to.

One option would be to add structure in your current openings to, for example, turn a 4' X 4' into 4 each 2' X 2' windows. This would lessen the required bond line.

MatWeb is an excellent source for material properties. There are a large number of versions of polycarbonate and acrylic listed.

An average number for coefficient of thermal expansion for polycarb is around 39uin/in/degree F. Using a temperature range of 60 degrees F, which is pretty large, a 48" window will see movement of .112". The 1/2" figure you have is not real, it would require a temp range of 268 degrees.

An adequately thick layer of a silicone adhesive designed for this purpose should be OK. You will want to use an adhesive specifically made for this purpose. At a guess the adhesive should be at least 1/4" thick. There are manuals available on the web.
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Old 20-10-2020, 16:08   #12
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Re: The GIANT Performance Catamaran Build/Refit Thread

Thinking out loud about the thermal expansion:

-1/2" seems crazy on 4 feet...dumb question, but is this for real? I had a plexi canopy on an aircraft that was a little more than 4' long where the plexiglass was glassed in all around the periphery, and a lot of small planes have similar canopies...see #2

-Let's say you install the plastic windows when all is cold. IF the perimeter of the window is fixed (VHB tape or goop), what fraction of an inch of expansion occurs as a slight ballooning out of the window vs what fraction is trying to translate past the fixed edge of the window? On small planes at least any expansion has to balloon out/suck in (including high speed and aerobatic planes subjected to impressive dynamic and torsional stresses) where thermal expansion doesn't seem to be an issue for some reason...though again in these installations the periphery of the ~window is secured without benefit of flexible tape/goop (though ~soft Sika is sometimes used, as much for vibration attenuation than perhaps thermal expansion).

And FWIW, a fiberglass plane with a 28' wingspan doesn't grow/contract 3.5" depending on ambient temperature.
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Old 20-10-2020, 16:23   #13
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Re: The GIANT Performance Catamaran Build/Refit Thread

I had used an online calculator with a 60 degree temperature differential (not too high since the material gets very VERY hot during the day). That was for an 8ft piece.

I cut the 4x8 pieces into 4x4 to reduce some of that. The calculator I used still said it was 1/4”.

But that’s only one of the problems. The other problem is how mold can destroy the Lexan. It ate pits right into it. Also, it’s all cloudy and foggy after 5 years.

So, I’m all done with that material. These were always “temporary windows”, so maybe it’s just time to upgrade to the real ones.

I’m drawn to the weight advantage of Lexan but it’s just not a long lasting material.

Thinking of the monohull I sold this summer: it had 35 year old acrylic and 35 year old glass. The acrylic was not something you could even look through. The glass was as good as the day she was built.

I may go light on the glass but also have a storm board or two handy in case of disaster.

However, using the 3m ballistic film, that could be enough with 1/4” tempered glass given this is how it works. This video is 1/4” tempered glass like I think I’ll use for weight purposes.

In the event seas are smashing it, the stuff is literally bomb proof, bullet proof and behaves like this.

Seems like a good balance between weight, visibility and strength under distress

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Old 20-10-2020, 16:48   #14
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Re: The GIANT Performance Catamaran Build/Refit Thread

Hey Chotu! Woo-hooo!

My only comment at this point is remember to retain the "lightweight" aspect in the back of your mind as you select your window material(s)...

LittleWing77

P.S. The windows in Training Wheels' picture (Post #7) look pretty cool, eh?

Also - take a moment and pause. A couple of years ago you were almost ready to pack it in...and here you are!
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Old 20-10-2020, 17:34   #15
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Re: The GIANT Performance Catamaran Build/Refit Thread

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Hey Chotu! Woo-hooo!

My only comment at this point is remember to retain the "lightweight" aspect in the back of your mind as you select your window material(s)...

LittleWing77

P.S. The windows in Training Wheels' picture (Post #7) look pretty cool, eh?

Also - take a moment and pause. A couple of years ago you were almost ready to pack it in...and here you are!
Ugh. Youíre right!!!

418lbs (190kg) for 1/4Ē tempered glass

184lbs (83kg) for 1/4Ē Lexan.

If Iím going to fight Lexan again, I really need to ask a lot of questions about mounting it and sealing it.
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