Function of design

[Salmoneyes]

I've seen "squat boards" used as the name for boards added at the stern of Chesapeake Bay work boats to prevent the boats from "squatting". Typically the boards were used when more powerful engines were install in hull designs originally intended for sail or low power engines. I've never seen a notched transom as illustrated in the first post called "squat boards".

My searching came up with that as well. In fact a very informative (for me) article about transom design exists and although it is a bit of a read, I did learn a lot. Unfortunately it only provided a paragraph to the design I am asking about and it more or less says what philSweet said in the begining.

https://www.glen-l.com/phpBB2/viewtopic.php?t=27907

 

[Salmoneyes]

I extended the sides of the aft boxes down about 1/2 inch below the box bottoms to form little skegs. In a following sea, I lower the motor so it doesn't surf up behind me. .

You seem to have some personal experience with this transom design.. Please feel free to share some photos, and or the specifications plus your full opinion...

 

[SamSam]

I've always thought of squat boards as being extensions of the hull bottom, usually added as a remedy, which were just permanent, un-adjustable trim tabs.

A lot of times those hull extensions, as in the op, are used as bait wells. Sometimes they won't have pumps, but will have holes in the sides and back for water exchange. They still work as anti- squat, trim tab devises while running, but holes have to be drilled high enough or provisions have to be made to scoop water into them while running so they don't drain out.

I even took mine to Belize, where it went bow down in Gails Point faster than you can blink when a 14 year old kid jumped up to the bow while under way with 2 grown adults.. It was scary fast how quick she went under

A friend had one of those "Gheenoe" boats with apparently too big a motor. He was out duck hunting and put it in reverse and the boat just drilled itself under water. He was surprised how fast it all happened too. Took him and his buddy 6 hours to slog out of the marshes.

 

[Salmoneyes]

I've always thought of squat boards as being extensions of the hull bottom, usually added as a remedy, which were just permanent, un-adjustable trim tabs.

A lot of times those hull extensions, as in the op, are used as bait wells. Sometimes they won't have pumps, but will have holes in the sides and back for water exchange. They still work as anti- squat, trim tab devises while running, but holes have to be drilled high enough or provisions have to be made to scoop water into them while running so they don't drain out.



A friend had one of those "Gheenoe" boats with apparently too big a motor. He was out duck hunting and put it in reverse and the boat just drilled itself under water. He was surprised how fast it all happened too. Took him and his buddy 6 hours to slog out of the marshes.

Interesting idea to use for bait, but clearly it provides "space" that can bill utilized...
After reading that transom design tutorial, I feel I understand how the genesis of adding "something" to the transom, allows for more modifications, more additions, until you eventually get back to where you started only it is now a longer boat....

I am very interested in the claim that it improves its ability to be towed. This is a benefit I can utilize.

I also like the idea of moving that weight forward, in relation to the hulls LWL. Im sure there are negatives to that, but for my use, it would benefit. Hopefully someone will chime in and provide me more understanding, so I can properly weigh those benefits...

 

[philSweet]

Mine is a little cat dink. I built and launched it in a three day weekend. Picked up the material Saturday morning and was in the water Monday night.

Some photo's here, but not showing what you want. Will try to find some better ones.
TEOTWAWKI Boat https://www.boatdesign.net/threads/teotwawki-boat.42752/page-2#post-548067

And a decade or so later -
Laminating Polystyrene to Ply https://www.boatdesign.net/threads/laminating-polystyrene-to-ply.55053/#post-765747

 

[Salmoneyes]

Mine is a little cat dink. I built and launched it in a three day weekend. Picked up the material Saturday morning and was in the water Monday night.

Some photo's here, but not showing what you want. Will try to find some better ones.
TEOTWAWKI Boat https://www.boatdesign.net/threads/teotwawki-boat.42752/page-2#post-548067

And a decade or so later -
Laminating Polystyrene to Ply https://www.boatdesign.net/threads/laminating-polystyrene-to-ply.55053/#post-765747

I like it.. I have looked very serious at that design. ( I have a Livingston) and there is a lot about those that works for my project. I sent for study plans on this

Boat Designs and Kits | Spirited News https://spiriteddesigns.com.au/news/ripple_tender?category=1

 

[jorgepease]

Besides all mentioned, very many skinny water flats boats have sponsons. Among other things they serve as a step for waders returning from fishing, keep the stern from digging in when popping out of a hole, slower planing speeds, help contain the raised water level along with a pocket tunnel. You have to make sure to rake them or they can keep the bow down and don't let them be too long or it will mess with your steering. I think the use is limited on the boat you show.

 

[Salmoneyes]

Besides all mentioned, very many skinny water flats boats have sponsons. Among other things they serve as a step for waders returning from fishing, keep the stern from digging in when popping out of a hole, slower planing speeds, help contain the raised water level along with a pocket tunnel. You have to make sure to rake them or they can keep the bow down and don't let them be too long or it will mess with your steering. I think the use is limited on the boat you show.

Finally,, a name to go with it... Sponsons... I looked it up... Thank You

"help contain the raised water level along with a pocket tunnel"
Need an a bit of explanation on this

"keep the stern from digging in when popping out of a hole,"
This is a good thing for my project

"slower planing speeds"
To be clear,,, are you saying
the boat goes slower once planed (not a deal breaker for me)
or
the boat planes at a slower speed (this is a big benefit to me)

"You have to make sure to rake them or they can keep the bow down"
I will assume this is like a trim tab effect, if the "sponson" has a downward angle in relation to the hull, it would push the bow down.
This is interesting, but In my case, I am considering trim tabs since this boat will be what Im calling a "truck", as opposed to a "taxi" unless that angle can be determined to work best in light or heavy mode.

"too long or it will mess with your steering".
This would not be desired, so figuring out that relationship will need to be addressed.

These are all great points, and I appreciate this response. Anytime I can solve a problem I don't know exists yet, I am that much farther ahead...

 

[jorgepease]

The boat planes at a slower speed (this is a big benefit to me) - yes, the boat can stay up on plane at slower speeds, this is what I mean. If your boat is intended to plane then rake the sponsons up the same °angle you want the bow to come up but I wouldn't angle them down. I have seen transoms inset 24 inches + with no problems, more if also using a jack plate. If the boat is to have a tunnel then the shortest jack plate works best.

When used to increase the ability to run shallow, a small tunnel the last 4-5 feet of the boat lifts water which shoots up into the area between the sponsons. On my old boat, for example, using a heavy cupped prop, I have run in as little as 2" of water. The prop is raised above bottom of boat between sponsons. It doesn't sound like that is what you are going for.

 

[Salmoneyes]

The boat planes at a slower speed (this is a big benefit to me) - yes, the boat can stay up on plane at slower speeds, this is what I mean. If your boat is intended to plane then rake the sponsons up the same °angle you want the bow to come up but I wouldn't angle them down. I have seen transoms inset 24 inches + with no problems, more if also using a jack plate. If the boat is to have a tunnel then the shortest jack plate works best.

When used to increase the ability to run shallow, a small tunnel the last 4-5 feet of the boat lifts water which shoots up into the area between the sponsons. On my old boat, for example, using a heavy cupped prop, I have run in as little as 2" of water. The prop is raised above bottom of boat between sponsons. It doesn't sound like that is what you are going for.

Thank you for the clarification...

Running shallow would be a benefit, not necessarily a requirement...

I spent time in Belize where we ran up these little creeks to get fresh water. Hadn't thought about that but it is a plus to be able to do that, which hauling weight is the main criteria...

 

[jorgepease]

if hauling weight, running skinny are important, then go with a flat hull.

The one I built, shown, was amazingly stable because it had an almost 8' beam, low to the water so easy to load stuff, and super shallow running. The more weight you put on it the better it runs lol.

I have crossed a hard rock bottom with 9 people aboard and barely any water (less than 3 inches) at slow speed because the water pressurizes, flattening and lifting the boat up. It's really cool feeling, you go slow so as not to starve the tunnel of water which is good anyway because it's dangerous.

The big flat bottom with a tunnel is a lot of drag so if you want a fast boat it's not for you. The most important part is to get a good cupped prop from one of a few people that really know how to do it and they are all in Texas LOL Baumann Marine are the guys that did mine.

 

[Salmoneyes]

if hauling weight, running skinny are important, then go with a flat hull.

The one I built, shown, was amazingly stable because it had an almost 8' beam, low to the water so easy to load stuff, and super shallow running. The more weight you put on it the better it runs lol.

I have crossed a hard rock bottom with 9 people aboard and barely any water (less than 3 inches) at slow speed because the water pressurizes, flattening and lifting the boat up. It's really cool feeling, you go slow so as not to starve the tunnel of water which is good anyway because it's dangerous.

The big flat bottom with a tunnel is a lot of drag so if you want a fast boat it's not for you. The most important part is to get a good cupped prop from one of a few people that really know how to do it and they are all in Texas LOL Baumann Marine are the guys that did mine.

I really like this. I would love to be able to strap that to the deck of our motorsailer and have all that usable deck space on the tender. Plus mine hangs over the stern a bit so actually gives me more deck length. I’d love some info on her numbers.

 

[Squidly-Diddly]

I have been working on a custom dinghy build, and have some help from a professional architect but do not want to be annoying with too many questions, so I am interested in spreading that load a little..

I came across this little Garvey Boat design that has an interesting stern concept. I am just curious what others think of the advantage or disadvantage of moving the transom forward like this.View attachment 143875

that looks comfy and ergo-metric especially for sitting on and as others have said will help float the heavy motor, and no doubt make the whole boat feel more stable.....but....

consider these brackets that do the opposite. Main advantage seems to be letting the hull and prop do their very diff tasks better by a bit of separation.The Benefits of a Bracket on Your Outboard-Powered Boat https://www.powerandmotoryacht.com/maintenance/the-benefits-of-a-bracket-on-your-boat

But I guess the extensions (I'm thinking they are extensions, not "moving transom forward") will be above water when planing so it would be just normal transom.

Maybe make hybrid float/water ballast extensions that partly fill with water ballast at rest then eject it when hull tips to start planing, similar to RIB rescue boats.