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Discussion Starter #1 (Edited)
I’ve been designing my own
5m aluminium skiff to run 40hp. I’m looking for opinions from anyone with building skiff knowledge. This model Is 3D printed and painted 1/20 scale. I need the bow sitting a little higher in the water. If I change the sides from 25 degrees to 15 degrees it will help me increase the surface area on the bottom or am I better to reduce the deadrise at the front 1/3 section of the bottom? I’m trying to achieve 200mm draft. Current estimates calculations about 350mm. Boat weight about 250kg and 100kg motor. Rear deadrise 4 degree changing to 8 towards the bow.? Thanks in advance
upload_2018-12-12_0-59-56.jpeg

upload_2018-12-12_1-5-4.jpeg
 

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Lowcountry Degen
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Could it be some infill settings, or support structure causing the bow to be heavy? What software are you using to slice/process the print? If it is the design itself and not the print causing it to sit uneven, then I would either have the chines taper towards the stern or carry the 4 degree deadrise further forward. Looks good though!
 

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Brandon, FL
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Why so heavy of aluminum?

If you are going to be hitting ground then by all means use the 5. But for the sides and deck you certainly could go less and shave a bunch of weight.

Also, what is the hump all about? To me it looks like a sailboat style hull and those perform miserably when converted to power boat.

The two ways to lessen draft is 1) lighten the load and 2) increase size of wetted surface.
 

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Discussion Starter #9
Why so heavy of aluminum?

If you are going to be hitting ground then by all means use the 5. But for the sides and deck you certainly could go less and shave a bunch of weight.

Also, what is the hump all about? To me it looks like a sailboat style hull and those perform miserably when converted to power boat.

The two ways to lessen draft is 1) lighten the load and 2) increase size of wetted surface.
4mm plate makes it much easier to weld and to manufacture without it bowing and causing problems. I haven’t figured the out the bump yet, as it may be during 3D printing. I need to check the model. Increase the welled area is the advice I’m looking for. Thanks again
 

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Brandon, FL
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If you use stiffeners you will be able to reduce thickness even below 4. Then adding the cap will also increase stiffness.

Most aluminum boats here are made from .08 or 2 mm.

If you span big areas you will need thick aluminum. If you use stiffeners you can use lighter.

Look at some pictures and you will see the use of stiffeners.

This gauge is also used in airboats where they take a beating from driving on land.

If I were building I would use 12 ga for bottom and 14 for sides and cap. This would be less than half the weight you originally designed.

On another note, wouldn't the 5 be hard as hell to bend?
 

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I Love microskiff.com!
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If you use stiffeners you will be able to reduce thickness even below 4. Then adding the cap will also increase stiffness.

Most aluminum boats here are made from .08 or 2 mm.

If you span big areas you will need thick aluminum. If you use stiffeners you can use lighter.

Look at some pictures and you will see the use of stiffeners.

This gauge is also used in airboats where they take a beating from driving on land.

If I were building I would use 12 ga for bottom and 14 for sides and cap. This would be less than half the weight you originally designed.

On another note, wouldn't the 5 be hard as hell to bend?
Didn't think he ever spec'd 5 mm, thought he was saying 5 meters long?
 

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I am, without a doubt, a total idiot when it comes to boat design and fabrication, so please take all of this with a grain of salt, and make sure to use Bob Ross for the voice in your head that reads it. Here goes....
Most aluminum boats may be .080, but they aren't welded. To effectively weld .080, it takes a whole lot of coin in a MIG setup, or ya have to bust out the TIG. If you TIG a boat made of .080, the end product will make the rack of 2x4's at Lowes look straight and true. The thinner you go with aluminum, the harder it is to weld, and the more bracing you're gonna need. Why take weight out, just to put it back in and make life harder? Thinnest airboat bottom I'd consider running dry with is 3/16"....1/4" would be better, and don't forget that the polymer takes the beating, not the aluminum.
SeaArk does build a bunch of boats out of .125"....same as 1/8"....not the same as .125 gauge. Not being a unit of thickness Nazi, but I know how convoluted things can get in an international debate such as this. (My business revolves around thickness of steel, and is spread across 3 continents. It gets hard to follow!)
.125", in my dumb ass opinion, is the thinnest practical aluminum to use for a plate boat. I've built a few pond hoppers out of .090", but they ain't very tough. FWIW, I have plans to build a new skiff over the next year or so, and the bottom is already in the shop and cut....out of 1/4". I'm goin on an oyster smashing mission!
Now that I've thrown gas on the fire, when does this build commence?
 

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Brandon, FL
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There was an custom aluminum build on here not too long ago...anyone remember it and find a link he could use as a reference?
 

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Discussion Starter #16
I am, without a doubt, a total idiot when it comes to boat design and fabrication, so please take all of this with a grain of salt, and make sure to use Bob Ross for the voice in your head that reads it. Here goes....
Most aluminum boats may be .080, but they aren't welded. To effectively weld .080, it takes a whole lot of coin in a MIG setup, or ya have to bust out the TIG. If you TIG a boat made of .080, the end product will make the rack of 2x4's at Lowes look straight and true. The thinner you go with aluminum, the harder it is to weld, and the more bracing you're gonna need. Why take weight out, just to put it back in and make life harder? Thinnest airboat bottom I'd consider running dry with is 3/16"....1/4" would be better, and don't forget that the polymer takes the beating, not the aluminum.
SeaArk does build a bunch of boats out of .125"....same as 1/8"....not the same as .125 gauge. Not being a unit of thickness Nazi, but I know how convoluted things can get in an international debate such as this. (My business revolves around thickness of steel, and is spread across 3 continents. It gets hard to follow!)
.125", in my dumb ass opinion, is the thinnest practical aluminum to use for a plate boat. I've built a few pond hoppers out of .090", but they ain't very tough. FWIW, I have plans to build a new skiff over the next year or so, and the bottom is already in the shop and cut....out of 1/4". I'm goin on an oyster smashing mission!
Now that I've thrown gas on the fire, when does this build commence?
Hopefully February I’ll start and my builder recommended 4mm plate to make it easier to weld and solid. My goal was about 250kg and 200mm draft excluding the big fellas on it, fishing gear and motor.
 

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I am, without a doubt, a total idiot when it comes to boat design and fabrication, so please take all of this with a grain of salt, and make sure to use Bob Ross for the voice in your head that reads it. Here goes....
Most aluminum boats may be .080, but they aren't welded. To effectively weld .080, it takes a whole lot of coin in a MIG setup, or ya have to bust out the TIG. If you TIG a boat made of .080, the end product will make the rack of 2x4's at Lowes look straight and true. The thinner you go with aluminum, the harder it is to weld, and the more bracing you're gonna need. Why take weight out, just to put it back in and make life harder? Thinnest airboat bottom I'd consider running dry with is 3/16"....1/4" would be better, and don't forget that the polymer takes the beating, not the aluminum.
SeaArk does build a bunch of boats out of .125"....same as 1/8"....not the same as .125 gauge. Not being a unit of thickness Nazi, but I know how convoluted things can get in an international debate such as this. (My business revolves around thickness of steel, and is spread across 3 continents. It gets hard to follow!)
.125", in my dumb ass opinion, is the thinnest practical aluminum to use for a plate boat. I've built a few pond hoppers out of .090", but they ain't very tough. FWIW, I have plans to build a new skiff over the next year or so, and the bottom is already in the shop and cut....out of 1/4". I'm goin on an oyster smashing mission!
Now that I've thrown gas on the fire, when does this build commence?
.125 guage was copied off there website fyi
http://seaarkboats.com/boat_models/view/94
 
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