# how long should my keel be

Discussion in 'Boat Design' started by matheo, May 4, 2021.

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1. Joined: May 2021
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### matheoJunior Member

yes you are writing about the power and I'm just going to tell you that the sketch I drew here is prety wrong I am gonna redraw it today

2. Joined: May 2021
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### matheoJunior Member

thank you for the heads up I shall rethink my drawing cause this one is highly wrong

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### bajansailorMarine Surveyor

Before you start sketching again Matheo, can you compile a list of what you want this boat to be able to do for you?
For example, how many people it has to carry, what speed it has to be capable of, is it for flat calm water only, or will it have to cope with slightly rougher water as well, what will you use it for (fishing, sightseeing, having a beer on......?) - the more constraints that you can establish before hand, the easier it becomes to design the boat.

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### matheoJunior Member

It will mostly be used for cruising and a bit of fishing and the max people I'll let on is 4 or 5; the water is relatively calm with medium wave at worst. Oh and I'm thinking of making the hull more of a deep v than what I sketched.

About the speed, I have seen old ships and how they do an interior engine with a rudder to turn but I'm wondering is there any other way to do it like a exterior engine that can be lifted out and into the water, and if there is, does the back of the boat have to be flat for it?

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### bajansailorMarine Surveyor

Yes, this is called an 'outboard engine'.
It clamps on (or is bolted on to) the transom.
An outboard engine would be the most logical choice for a 6 metre long motor boat.
The transom should be raked aft by about 12 degrees - ie it should not be vertical.

It sounds to me that a standard Australian aluminium 'tinny' motor boat around 6 metres long would suit your requirements?

6. Joined: May 2021
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### matheoJunior Member

Well yes but I want to make it myself out of wood and also you said the transom should be around 12 degrees but can the botom were it meets with the keel be curved slightly. I don't want a harsh angle on there and right now. I'm tryng to get better at drawing and woodworking so I'm making it small but later when I'm confident enough I will make it a 12m long boat. I'm new to thi.

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### bajansailorMarine Surveyor

Most motor boats around 6 m. long, in timber and fibreglass, have a 12 degree rake on their transoms if they have an outboard motor.
I am not too sure what you mean by having the bottom curved slightly where it meets the keel. You could round off the timber in way of the joint so that it is not a sharp angle, re getting paint to stick to it.

Have you seen any existing boats that you like, which have provided a basis or inspiration for your design?

8. Joined: May 2021
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### matheoJunior Member

So I have redrawn the plans
imgur.com https://imgur.com/D3h1dei
The edge to the poop deck and to the front will be smoothed out
This should be more accurate and by the way i am still deciding if i want to fibreglass the boat or keep it as a wooden boat since I'm trying to go for an old ship from the early years, now I haven't taken anything from other ships but the closest to my design I know of is the Spanish galleon

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### bajansailorMarine Surveyor

What are you going to do with a 6 metre long 'replica' of a Spanish galleon?

Here is Matheo's updated sketch - is that a chine that you have drawn in the body plan?
If so, then you have not shown the hull sections above the chine.
It appears to be almost double ended - there might not be much room on the transom for an outboard motor. And the top of it would have to be within that aft castle. And depending on the actual shape of the hull sections aft, there might be quite a lot of hull in front of the outboard engine propeller, reducing it's effectiveness.

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### matheoJunior Member

First of all there is no chine; second I drew the transom at a 12 deg angle and the boat will sink 1m into the water an I believe that should be enough

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### bajansailorMarine Surveyor

Matheo, I admire (and am worried by) your confidence in this design - for instance you mention "the boat will sink 1m into the water an I believe that should be enough".

How do you know that this will happen?
You have not finalised a body plan, you have not calculated a volume of displacement, and you have not done an initial weight estimate for all the materials that will go into building this boat.

Does anybody else on here have any thoughts re Matheo's design please?
As I think that I am on a totally different wavelength to his way of thinking.

12. Joined: May 2021
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### matheoJunior Member

If the weight of the boat alone is not enough, go up and look at the top photo you will see that the ship cabin is 190cm leaving 10cm for a ballast just in case and that ballast can be filled with other concrete or preferably a corrosion resistant metal.
And honestly speaking by estimation it should work but I'll need to have a second opinion from an expert oh btw I'm reworking the design cause this one is a bit wrong

Last edited: May 9, 2021
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### Mr EfficiencySenior Member

Matheo, bajansailor is the very model of a polite and helpful correspondent, but I can envisage even his patience being tested by this project, which appears to be headed for disappointment. If it is headed anywhere. If you are so enamoured of the Spanish galleon, be faithful to the design and replicate it scaled down, which would at least have novelty value, otherwise think of a boat that is more practical. At present you will end up with something that lacks either attribute, the novelty value or the practicality. And worse still, be as ugly as sin !

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14. Joined: May 2021
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### matheoJunior Member

My good sir bajasailor is a great person an I am not denying that and as I have stated before I have only taken a slight bit of inspiration from the spanish galleon and as I have said earlier I am redrawing my scetch and giving it a v hull with chine , sorry if I seem disrespectful but truly I am taking into consideration every single bit of information

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### clmangesSenior Member

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