GT23

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drbobopp@gmail.com
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Re: GT23

Post by drbobopp@gmail.com »

Ok, I'll take that advice. Sounds easy! ... well, sounds doable.

What about the "two-layers" of cloth recommendation? Do y'all think that is wise?

And must the second layer be laid down while the first layer is still curing? This would obviate the need to sand the whole bottom between layers, obviously, but would seem an undertaking....

Thanks everybody!

bob

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Re: GT23

Post by fallguy1000 »

How often do you intend to beach?

Pictures, please, so we can see if you are ready.

Two layers is harder to do wet on wet on hulls because you need access. The way it is done it to run a strip of glass down the middle and then an overlap of 2" of the keel and then an overlap of 2" on the keel on pieces 2 and 3, but without seeing the hull and understanding dimensions, I can't give you better advice.
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Re: GT23

Post by Dougster »

Lithium-ion battteries? They are usually smaller.

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Re: GT23

Post by BB Sig »

drbobopp@gmail.com wrote: Thu Jun 15, 2023 9:16 am Ok, I'll take that advice. Sounds easy! ... well, sounds doable.

What about the "two-layers" of cloth recommendation? Do y'all think that is wise?

And must the second layer be laid down while the first layer is still curing? This would obviate the need to sand the whole bottom between layers, obviously, but would seem an undertaking....

Thanks everybody!

bob
In my discussions with Jacques about this boat, he recommended that for over 90 hp (if I remember right), dual layers on the inside and outside before installing the framing. I believe he wanted the stringers installed, but that may have been because mine were already installed, and it would have been a mess to redo that.

I'm not on here much. Feel free to contact me in a PM, and I'll give you my phone number to discuss things. That goes for anyone building a GT-23.... I still want the bulk of the discussion here to capture it, but sometimes it flows easier the old-fashioned way of talking.

Barry

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Re: GT23

Post by drbobopp@gmail.com »

Sorry took a bit to get back to y'all..

To respond:
We will beach from time to time.... We are in the Florida Panhandle/South Alabama area.... rivers and bays and the ICW. All sand. And shallow. Eagles, manatees, dolphins. The GT-23 will replace our pontoon boat as our "touring" boat. We have had a ball on the ICW in summer, going from marina to marina, using hotels. But you haven't experienced electrical storms until you've experienced Florida lightning. It is terrifying on the open pontoon boat, and no real cabin from the rain either. And in the summer, thunderstorms are daily affairs. So we are building the GT-23, with its cabin. ..........So yes, in our Gulf Coast travels we will beach occasionally to explore.... Six times a year, say.

I have my wife working on pictures... Thanks to whoever posted the 'how to' sequence.

Thanks to everyone. As always, I learn stuff here. I did not know there was a "green period" with the epoxy, but it makes sense... Even in Alabama, the stuff is still a little tacky the next morning. So it can be second-layered without sanding! Who knew? ..... Opens all sorts of doors.

I'll have more questions. I'm a little ways from glue. Getting bottom and side panels situated or stitching right now.

I'll send pics. (well, my wife will)..Thanks again, y'all

bob

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Re: GT23

Post by TomW1 »

bob the GT23 sounds like the perfect boat for your needs. Just take your time and you will be fine. Two layers of glass on the bottom will work fine and as long as you do it within 12-16 hours of each other a chemical cure will be obtained and no sanding is needed. One thing you might want to consider is coating the bottom with graphite powder to epoxy at a ratio of 25 to 75% ratio to prevent scratches when beaching the hull. You will need 3 to 4 coats. Please feel free to ask all the questions you want, members have built multiple boats and have been on the forum for many years. My specialty is helping the builder determine what the top speed of his boat will be and what prop he needs to acquire that based on the weight of the boat as built.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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Re: GT23

Post by drbobopp@gmail.com »

Thanks Tom and others...Very helpful information. I will likely follow all of these recommendations, including the graphite epoxy recommendation.

I used truck bed liner paint on the Phillip Bolger Oldshoe sailboat that I built last year. I will use the graphite on the GT-23, but does anyone have any observations to make about the use of Truck bed paint on boat bottoms?

Sorry that I've not gotten any pics up. No promises, but I'll try.

My question today:
How to best orient the two bottom fiberglass cloth layers?

I have her all stitched together, and the chines and other seams 'spot-welded' with epoxy, and now the stitches are all out. (BTW, I have used zip ties and electric fence wire for the stitches--just because that's what I had laying around--but now that I've used copper, I'll never go back) ...

I am ready to glass her bottom. I am aiming for a good planing hull, as we have lots of slick water here in the rivers and the Intracoastal Waterway and protected shallow bays of NW Florida/Alabama/Mississippi. I will be asking for motor advice later, but for now plan to use a 110-150 HP OB. Thus I will be following the plans and installing two layers of fiberglass cloth on her bottom (and another on the inside).

So here is my question: Should these two layers be BOTH installed longitudinally, or would it not be stronger to install the layers perpendicular to one another? Plans show a longitudinal orientation, with three strips of 50inch cloth running stem to stern. A second layer is recommended for horsepower above 90, and this is planned. But we are not instructed as to whether the second layer ought run fore-to-aft like the first layer, or across-ships? Does this question make sense?

Thanks, y'all,,....bob

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Re: GT23

Post by BarraMan »

"So here is my question: Should these two layers be BOTH installed longitudinally, or would it not be stronger to install the layers perpendicular to one another? Plans show a longitudinal orientation, with three strips of 50inch cloth running stem to stern. A second layer is recommended for horsepower above 90, and this is planned. But we are not instructed as to whether the second layer ought run fore-to-aft like the first layer, or across-ships? Does this question make sense? "
I assume that the plans call for 'biax" or "double bias" cloth (same thing!) so the glass fibres will at 45 degrees to the long axis of the cloth. So - two layers, longitudunal and overlapped at any joins by 6" (150mm).

In my opinion, its difficult to do 2 x layers on a BIG boat within the 12-16 hr window that Tom quotes above, given the size of the job (How do I know? :D ) Just give it a light sand with 120 grit paper between layers and it will be fine!

Image

I'm in two minds about graphite/epoxy! :doh: I put 3x coats on the bottom of my boat but don't think it gave much rub resistance. What it does it lets you see where the rubs are!

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Re: GT23

Post by fallguy1000 »

120 grit is a bit light, Lee.

Best epoxy bonding is better around 40 grit which also knocks down the stitches which are not really structural...
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Re: GT23

Post by fallguy1000 »

Perpendicular? No. That would make the tows all same direction.

Varying the tows offers the most strength as long as the tows are longest away from neutral axis. This explanation does not need to be defined here as the tows are equal in biax.

But, what you can do is turn the glass 30 or 45 degrees. However, this can be a big negative in a planing hull. Why? Well, you can end up making ridges (with required overlaps) in the hull bottom and induce drag.

The best strategy for the bottom is to keep overlaps in longitudinal direction and with waterflow. Otherwise, you'd need to perfectly fill and fair tbe bottom.

A bigger thing to watch for in a planing hull is to avoid hook on the bottom.

The glass strength business is basically only going to offer you about a 5% increase in hull strength; if that.
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