GT27 Build (Wes K)

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fallguy1000
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Re: GT27 Build (Wes K)

Post by fallguy1000 » Wed May 15, 2019 8:59 am

Correct.

If the boat is in reverse trim; you would have really messed up the cabin. A channel is a trip hazard. If you wanted a real outdoor shower; then you could just run a drain tube to the pump basin from the shower drain as well. But I don't think you have enough space for that.

Just run the bilge pump off the bottom and drain out from that same basin.

In my state we have a plug law. For your plug; you might want a screw type instead of lever to make sure it doesn't come out in a week stay on the water.

Lots of people just put a pan of water out for dirty feet. A dishwashing tub works well, but a washdown hose is nice for most any purpose. When you build it; build a washdown hose you can use to clean up other stuff like fish slime, etc.


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Re: GT27 Build (Wes K)

Post by jacquesmm » Wed May 15, 2019 10:29 am

How about a plain drain through the transom? Simple, safe and you can plug it.
On anchor, empty, the boat will trim down by the stern which is normal.
The boat is designed to be light. If you plan to load her with a lot of gear and comforts, you could raise the cockpit floor and maybe give some slope towards the stern. I would leave it as designed. As you say, she is not an offshore boat.
I don't like the reverse slope at all.
You can have a bilge pump but drain from the stern side.

For the shower, the sole of the shower will be below the DWL. That means a small sump with a pump. That's how it is done in large boats. Some drain in the bilges. It's OK if you are careful not let the water sit there for too long.

The bracket looks fine as you drew it.
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Re: GT27 Build (Wes K)

Post by fallguy1000 » Wed May 15, 2019 1:52 pm

jacquesmm wrote:
Wed May 15, 2019 10:29 am
How about a plain drain through the transom? Simple, safe and you can plug it.
On anchor, empty, the boat will trim down by the stern which is normal.
The boat is designed to be light. If you plan to load her with a lot of gear and comforts, you could raise the cockpit floor and maybe give some slope towards the stern. I would leave it as designed. As you say, she is not an offshore boat.
I don't like the reverse slope at all.
You can have a bilge pump but drain from the stern side.

For the shower, the sole of the shower will be below the DWL. That means a small sump with a pump. That's how it is done in large boats. Some drain in the bilges. It's OK if you are careful not let the water sit there for too long.

The bracket looks fine as you drew it.
No reverse slope Jacques. That was all in the preamble.

Everything is at the stern in the discussion.
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Re: GT27 Build (Wes K)

Post by Chuck H » Wed May 15, 2019 8:48 pm

I don't know what Fallguy has against self bailing cockpits but I can't think of one reason not to build the sole above the waterline (doesn't have to be 4-5 inches more than the designer specifies) and have large pluggable drains. They cost nearly nothing and when plugged don't affect normal operation at all. When needed they can save lives and keep your boat from sinking or your expensive outboard from being swamped.

Absolutely the best value in boating safety.

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Re: GT27 Build (Wes K)

Post by fallguy1000 » Wed May 15, 2019 11:55 pm

Chuck H wrote:
Wed May 15, 2019 8:48 pm
I don't know what Fallguy has against self bailing cockpits but I can't think of one reason not to build the sole above the waterline (doesn't have to be 4-5 inches more than the designer specifies) and have large pluggable drains. They cost nearly nothing and when plugged don't affect normal operation at all. When needed they can save lives and keep your boat from sinking or your expensive outboard from being swamped.

Absolutely the best value in boating safety.

Chuck
I just haven't seen scuppers in many houseboat styled vessels. My boat has no need for them is all.

For this boat, he could scupper as long as the scupper is above a fully loaded cockpit full of people ppi. Waterlines tend to move.

But if you have to raise the sole up that much; it seems a waste of height to me. And scuppers are also better where they cannot sink the boat. Not sure if he can get that positive buoyancy or that high is all. Flapper blah blah..

Having been on a boat where water is entering from a failed clamp, I would want the helm nearer to the scuppered area to make sure you aren't taking in and I believe the helm is in the cabin.

My position here is nuanced. Could work, not my favorite idea.
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Re: GT27 Build (Wes K)

Post by OrangeQuest » Thu May 16, 2019 8:09 am

Could always have a rinse off platform that has scuppers to drain back over board and use a wash down hose. The deck could be close to the ladder so you have to walk over the wash down deck to get to the main part of the boat. Then a bilge to inspect condition of hull while on the water. (bilge starts filling up with water then you know the hull is leaking or there is uncontrolled water getting in the boat) A small 500 gph pump with a float switch that kicks in when water in the bilge starts coming up and then a whole lot bigger bilge pump, manual switched, for when there is a lot of water coming on board that should not be there. Screw type garboard plug for when trailered and exposed to the rain. The garboard plug could be attached to the keys to the boat so when you go to use the boat and grab the keys you have a reminded that the plug needs to be put in.

If you are going to be using sea water for washdown then the pick up has to be below the water line and are also areas where a busted hose or fitting could let water in uncontrolled. With or without scuppers then you will still have to deal with those things with mechanical methods.
"that it isn't just an ordinary sort of boat. Sometimes it's a Boat, and sometimes it's more of an Accident. It all depends." "Depends on what?" "On whether I'm on the top of it or underneath it.

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Re: GT27 Build (Wes K)

Post by wkisting » Thu May 16, 2019 9:10 am

Thanks for the input all. I'm leaning toward simple-is-best: a garboard drain plug set at the lowest point of the transom, with a little well there large enough for a bilge pump. Sole left at the height spec'd by the designer. Water draining aft into the well, where it will either go out the drain (if open) or out the bilge pump (if at sea).

For the washdown system, I'm thinking about no thru-hull, but instead a hose that can be stowed in a compartment, but taken out and run over the side to the water when using the washdown sprayer to rinse off. I've seen other boats rigged that way, but don't quite know how well that works with the pump, as that is a lot of lift to bring the water up over the side of the boat. It would have to have enough pressure to lift the water, pull it through a 5 micron filter (just to remove scum, not to make it drinking safe), and still have adequate pressure to trigger the on demand heater. That might be a tall order, but I don't really know since I've never tried building such a system. Another possibility is to draw water thru the hull from a seacock, of course. If I do that, I would use my usual practice of building a small compartment around the seacock (typically inside a seat) that reaches well above the waterline so that if the seacock leaks/fails it doesn't admit water to the rest of the boat to risk sinking her, but keeps it contained.
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Re: GT27 Build (Wes K)

Post by BB Sig » Thu May 16, 2019 3:15 pm

What's the stringer height at the stern in a GT27? The GT23 is ~9" and supposed to float in 6" of water. The study plans for the GT27 say float in 8" of water. If the stringers are ~10.5" or higher, I don't think you have much to worry about with self draining. :)

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Re: GT27 Build (Wes K)

Post by jacquesmm » Thu May 16, 2019 4:09 pm

Correct, the stringers tops are above the designed water line. the cockpit is self draining unless the boat is exceedingly heavy but even in that case, this is not an ocean going boat and the scuppers if any, can be plugged.
The top of the sole is at 10" above the fairbody (bottom, no skeg).
The DWL is at 8" above.
Here are the figures for 8 and 10" draft.
Sorry for the presentation, I did it all manually 20 years ago, no sophisticated app like ORCA that I use now but the figures area accurate.
All in inches decimal. Origin is lost somewhere in CAD space, the model moved = disregard the centroids locations.

-------------------Hydrostatics at 8:
Volume Displacement = 139403
Center of Buoyancy = -151.467, -122.903, 4.51116
Wetted Surface Area = 24917.8
Waterline Length = 262.529
Maximum Waterline Beam = 94.934
Water Plane Area = 22032.7
Center of Floatation = -135.686, -122.903,8

= 80.7 cu.ft = 5,163 lbs

-------------------Hydrostatics at 10:
Volume Displacement = 184759
Center of Buoyancy = -146.838, -122.903, 5.6154
Wetted Surface Area = 27161.7
Waterline Length = 275.173
Maximum Waterline Beam = 95.466
Water Plane Area = 23293.1
Center of Floatation = -129.751, -122.903,10

= 107 cu.ft = 6850 lbs

PPI = 845 lbs.
----------------------------------------

I would be surprised if anybody would build and load that boat to get to 6,850 lbs but keep in mind that this is calculated at level trim. An heavy engine will trim the hull down by the stern but with the volume of your bracket, you should be fine.

One more thing: this is technical and we are in the non technical part of the forum. I don't mind but replies will be slower because I do not visit this area every day. If one day you want a fast reply, post in the other part of the forum.
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fallguy1000
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Re: GT27 Build (Wes K)

Post by fallguy1000 » Thu May 16, 2019 4:40 pm

At those types of numbers, a scupper is a great idea if you opt to go that way. I just hate to see some of the amateur builds end up with water backing in on loading.
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