Input needed please

G'day all,
As you know I'm rebuilding/recreating my timber boat. Now the current concern I have is the boats sides. I have built them straight up. Not flared out. She looks a little odd atm so I'm not sure if its an optical illusion that will go when she's got the ply sheets on or wether I should look at changing it now before it gets too late. I liked the straight sides on my Bayliner 3055 but not sure about it on this. Will it act differently in the water because if this?

Also the beam of the boat is 3100mm at the centre and 2000mm at the transom. I've kept the 3100mm at the centre but have widened the transom to be 3100mm as well. My reasoning is that I wanted it to be wider to be more symmetrical and to have more room at the back. In doing this do you think this have any affect on the way she handles and her stability.

In relation to the front ribs, should I make the bottom rib shorter to allow more angle on the side rib or do you think this'll be fine?

Before I started to build her the keel looked quite large but now it looks rather small. Should this be made higher or wont that really matter.

Ok well that's the issues I have at the moment Any and all relevant input would be highly appreciated.

Thanks ;-)

Regards Matt

iPad Forum Runner

Above the water sections should have very little to do with how the boat handles.

Widening the stern will only have an effect if you plan on higher speeds and will create just a tad more (probably not noticeable) drag...it again is negligible at very slow speeds and only stats to ramp up past 10 knots or so.

Slab sides are easy to build but often not as easy to look at......that's why most designs have a little something to them. Sometimes it's for deflecting water (flare) and sometimes the shape will add strength.

Shortening the bottom rib will reduce displacement so I think the better option would be to increase beam (unless a little deeper doesn't bother the design).

Hendo78 said:

...that's the issues I have at the moment Any and all relevant input would be highly appreciated.

Thanks ;-)

Regards Matt

iPad Forum Runner

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Matt: You should be able to get some good input at the WoodenBoat
Forum.

The WoodenBoat Forum

Larry M said:

Matt: You should be able to get some good input at the WoodenBoat
Forum.

The WoodenBoat Forum

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Yeah posted there but can't post pics due to some quota or something so kinda useless

iPad Forum Runner

The Eagle sides are straight up and down until the hull rolls under about a foot under below the water line but the bow and stern have a flare/salt up to the gunnel so the water is pushed/splashed to the sides. A straight up and down bow causes a wetter ride, than the bow with a flare/slant is a much drier ride.

Widening the stern will make the boat harder to steer control in falling seas. The Eagle stern above the water line is the full beam but the stern is round and at the water line is starts to roll under so following seas go around and under the stern. Most commercial trawler full beam stern but have a modify fan tail. So the stern can be the full beam but start slanting rolling at the deck level. Also the boat can still have a swim deck.

I would not make the boats bottom more flat than what it is. If anything make it narrower so there is more of an angle and the boat sits lower in the water for stability. The Eagle is 58 ft but only 14 in the beam, many long range boats have a small beam to length ratio.

Phil Fill said:

The Eagle sides are straight up and down until the hull rolls under about a foot under below the water line but the bow and stern have a flare/salt up to the gunnel so the water is pushed/splashed to the sides. A straight up and down bow causes a wetter ride, than the bow with a flare/slant is a much drier ride.

Widening the stern will make the boat harder to steer control in falling seas. The Eagle stern above the water line is the full beam but the stern is round and at the water line is starts to roll under so following seas go around and under the stern. Most commercial trawler full beam stern but have a modify fan tail. So the stern can be the full beam but start slanting rolling at the deck level. Also the boat can still have a swim deck.

I would not make the boats bottom more flat than what it is. If anything make it narrower so there is more of an angle and the boat sits lower in the water for stability. The Eagle is 58 ft but only 14 in the beam, many long range boats have a small beam to length ratio.

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Hi phill. Thanks heaps for your input. Do you have any pics of "The Eagle" and her hull I can see so I can marry up your descriptions? Thanks again for you input mate!
Regards
Matt

iPad Forum Runner

It will be Monday as this weeks its Thanks Giving holiday.

Hendo, I`ve joked about Aussies having a pet kangaroo, wallaby,dingo,wombat, echidna,platypus etc, and you have one sharing the dog bowl! Now they will think we all have one. Maybe we do....

BruceK said:

Hendo, I`ve joked about Aussies having a pet kangaroo, wallaby,dingo,wombat, echidna,platypus etc, and you have one sharing the dog bowl! Now they will think we all have one. Maybe we do....

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Hahahahahahahaha

iPad Forum Runner

Phil Fill said:

It will be Monday as this weeks its Thanks Giving holiday.

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As promised.

This is the best picture. You can see the Eagle sides are straight up and down and start to roll below the water line. The stern is round which makes getting away the dock easier and the waves pass around and under. The bow does have a fail to it so the waves are pushed/splashed to the side, which makes a drier ride. The keel and Bilge are filled with concrete we do not get pushed around very much.

Hopes this helps

Can I say that designing a boat that's under construction, from pictures posted on a web forum, is not really going to produce anything useful. A boat, any boat, is not a collection of parts, it is (or the good ones are) a integrated system. The hull shape is related to the engine, gearbox, propellor, length, beam, depth, displacement, accommodation, range, speed, fuel capacity, and on and on.......

If you don't want your money and labour to be a complete waste, some forward planning might be in order.

At this point all I know is the beam is 3100mm (at rail or chine?).......What's the final length, speed, power, etc?

Are you building to a full set of plans or are you just sort of eyeballing the thing? The cross section you show in your first post does not resemble what you are actually building in the photos.

I don't think the boat will look less slab-sided or straight up and down when you install the plywood sides, I suspect it will look even more so. Like a giant packing crate.

How important are aesthetics to you in terms of this particular boat?

Do you have a drawing, picture, or plans you can post of what you want the boat to look like when you're done?

there's a lot of hand built, eyeballed, third world boats that do just fine....

Safe boats are built after buoyancy and stability equations have been solved that were based on the design of the boat. One should understand buoyant force, be able to analyze the case of bodies floating on a fluid, be able to use the principle of static equilibrium to solve for forces involved in buoyancy, define the conditions that must be met for a body to be stable when floating in a fluid, and understand metacenter and be able to compute it's location relative to the center of gravity, plus know where the KG is and what the moment of inertia will do at varying degrees of roll and pitch. One should also understand displacement. I realize that many trials and errors from 'eyeballed' projects made boating possible today, but with the availability of software today, why not just draw what you want on the computer and let it tell you if it will work. Autodesk sells AutoCad, and there are others out there that are fantastic tools. Some programs can even pinpoint places where you will need to hand fair the skin. I do not think that drafting the boat on a program takes away from the joy and satisfaction of building it yourself, I think it's prudent.

Anthonyd said:

Safe boats are built after buoyancy and stability equations have been solved that were based on the design of the boat. One should understand buoyant force, be able to analyze the case of bodies floating on a fluid, be able to use the principle of static equilibrium to solve for forces involved in buoyancy, define the conditions that must be met for a body to be stable when floating in a fluid, and understand metacenter and be able to compute it's location relative to the center of gravity, plus know where the KG is and what the moment of inertia will do at varying degrees of roll and pitch. One should also understand displacement. I realize that many trials and errors from 'eyeballed' projects made boating possible today, but with the availability of software today, why not just draw what you want on the computer and let it tell you if it will work. Autodesk sells AutoCad, and there are others out there that are fantastic tools. Some programs can even pinpoint places where you will need to hand fair the skin. I do not think that drafting the boat on a program takes away from the joy and satisfaction of building it yourself, I think it's prudent.

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Sure if that's what you want and care...

An over sized plywood shoebox with an outboard can do the great loop..and with reasonable care be just as safe as what many of us drive.

psneeld said:

there's a lot of hand built, eyeballed, third world boats that do just fine....

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ps....

Yes, and folks drown in them every day as well. But traditional, indigenous designs are always evolutions (usually tiny evolutions) of boats that have been built for generations. And do not underestimate their creators, they are very experienced people doing something they and their fathers have been doing a long time.

Hendo has owned a previous boat, but there's no indication he's built one in the past.

As to the great loop? It appears Hendo is some distance from that (though I can't tell for sure). It looks like he might be in Austrailia (?). Lots of open water around Australia......Southern Ocean, Indian Ocean, Tasman Sea, Coral Sea, and the Timor Sea.......None of those are really suitable for plywood shoeboxs......

Tad Roberts said:

ps....

Yes, and folks drown in them every day as well. But traditional, indigenous designs are always evolutions (usually tiny evolutions) of boats that have been built for generations. And do not underestimate their creators, they are very experienced people doing something they and their fathers have been doing a long time.

Hendo has owned a previous boat, but there's no indication he's built one in the past.

As to the great loop? It appears Hendo is some distance from that (though I can't tell for sure). It looks like he might be in Austrailia (?). Lots of open water around Australia......Southern Ocean, Indian Ocean, Tasman Sea, Coral Sea, and the Timor Sea.......None of those are really suitable for plywood shoeboxs......

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as well as those designed by high priced NAs....

Jesus. I'll keep my questions to myself next time ya pack of savages lol

Thanks to the guys that helped with pics and suggestions tho.

Hendo78 said:

Jesus. I'll keep my questions to myself next time ya pack of savages lol .

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Set the `roo on them.
I`ve heard of `roos attacking dogs after luring them into dams. Fortunately your guys seem good mates.

BruceK said:

Set the `roo on them.
I`ve heard of `roos attacking dogs after luring them into dams. Fortunately your guys seem good mates.

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Hahahaha yeah typical keyboard worriers. It's normally the case that these guys are the ones to scared to actually get off their arse and do this kind of work but put down anyone that tries. Water off a ducks back for me mate! If all else fails ill send in the Roo. He's a big boy now. This photo was taken ages ago. The roo stands eye level with me now!

there's a lot of hand built, eyeballed, third world boats that do just fine....

The successful are usually built by "traditional" boat builders.

There may not be a set of plans on paper, or a CAD CAM 3D ,

But when building the same basic boat for a few generations , Eyeball, from a builder that spent 30 years learning isn't bad.