Need Boart design advice / new user

[cekuhnen]

Hi

I am curious about different hull configurations.
I am going to work on a project for a paddle
man powered boat for a lake like environment
and would like to know more about hull designs
in terms of stability and maximum usage of
administered man power through the bike like
propulsion system.

I tried to google hull design aspects but found
no usable information similar to a basic introduction
into boat design.

Could anybody give me some advice for where to
look?

Thank

Claas

[alan white]

Lots to learn. The typical paddle boat seen on most ponds around here is very inefficient, meaning slow.
A faster boat would be longer and either have a pair of slender and long (at least 14 ft) hulls, with the driver in between, or a single narrow hull up to 20 ft long.
There are books that explain the whys and wherefores of hull designs, what shapes do what, and some basic formulas.
The Nature of Boats by Dave Gerr is good. Another hint is to read what kayakers have to say about hulls. They discuss some fine points about hull shape such as the prismatic coefficient, speed potential of a given length, and why a shorter hull can win a race even though a longer hull is potentially faster.

Alan

[cekuhnen]

I agree that this is a rather aggressive undertaking.

However all we would like to design are boats for
a lake scenario.

The propulsion system is based on what you use with
a bicycle for one or two humans to power man.

Additional functions could be space for relaxing / swimming dock
and others.

I am not even sure of the hull shape will have such a significant impact
on the speed because it is man powered anyway.

I am just curious if you could give me a direction. It seems that there
is hardly any thing on the internet for it.

Claas

[alan white]

"I am not even sure of the hull shape will have such a significant impact
on the speed because it is man powered anyway."

The opposite is true. The hull shape is much more important when it is man-powered.


You are already on the best forum for designing an efficient hull--- and building it too. Be patient and ask specific questions.
Regarding using the hull for other purposes like lounging, you'd better decide ahead of time whether you want a boat or a dock. A boat that's stable enough to swim and lounge on will move like a pig in the water, nevermind go in or out of the water without a winch.

Alan

[cekuhnen]

Hi

than you for the tip. The problem I have is that I do not posses the
knowledge you have. You said that the hull is important when being
man-powered - like a paddle boat.

Those are possible application for our project:
- movable swim/tanning platform
- fishing boat
- fitness alternative
- lifesaving vessel
- children’s play vehicle
- and others

My question is simply how has the hull to be for example:
stability - lets say it is a boat which has more a function of a play area for kids, or tanning

stability - for lets say it is actually more for rescue purpose

stability - lets say when the boat is also easy accessible for diving meaning leaving and entering the boat without shaking it seriously

speed - lets say the boat could also be equipped with a kite and making use of wind power in addition

Does this help?

[dragonjbynight]

My suggestion, for what it is worth, is to slim down your list of uses, as each one has different aspects that would require different things. The main theme of your boat seems to be a platform type, as a paddle boat. As was suggested earlier, they are very slow and if you have spent time in them, take a lot of energy to get them anywhere, specially in rough water. A small trade of for stability, instead of speed. For a platform though, it would work for diving, swimming and so on, but unless your using it as a lifeguard platform, would not be the best boat for lifesaving, as speed becomes a factor.

[cekuhnen]

Where ever motor driven boats are present of course
paddle boats would not make much sense for life saving.

However in this case they are more thought as a platform.
Probably much better for the lifeguard than risking the own
life as well.

But yes this is a problematic application - probably not even a good one.


Maybe my question is too much common sense you for guys - I am
totally new to boating. However what affects stability and speed.
A wide boat seems to be stable for - how far does this influence speed?
Read the more you have wet surface the more resistance - the slower it is.

However I have no practical experience to back this up.

To make the boat easy to maneuver and also as fast as possible with
the given propulsion system how has the hull to be? Flat - deep - short - narrow ... ?

I hope you see here that I have barely any starting point.

[tinhorn]

It's been too long since we had a pedal-power thread!

There are some cool links on these pages:
http://www.recumbents.com/WISIL/hpb/boat.htm
http://www.humanpoweredboats.com/index.htm

I'm approaching the process from the opposite direction - I've already purchased a couple hulls and tooling for one of them. My challenge will be maximizing the efficiency of the existing design. This forum is a great place to learn.

As Alan and Dragon have suggested, you may discover that you need a few different designs to meet all your needs. A one-man fitness boat may also make a decent kid's boat, but probably not a good fishing boat or swim/tan platform. Is yours a commercial enterprise, or are you building in the garage with hopes to market it when the design is worked out and proven? If this is a low-budget project, what would be the primary use of your first design?

[cekuhnen]

This is actually a student project.

So this is not for a company.

We also will only have 6 weeks - it is a summer school project.

Different target needs will be evaluated - however when it comes
to the actual boat hull design things might get more complicated
because marine design is not a big part of our school.

Based on the target needs than the appropriate hull configuration
and added functionality should be explored.

The boat design should meet requirements for 2 axis rotational molding
process thus we will only do model mock-ups out of foam and cad models.

[alan white]

The nearest I can come to an answer to what hull type you might want would be a 12 ft punt with a 3 1/2 ft beam and a flat bottom. Slow to propel, but probably much faster than a standard paddle boat.
If speed is desired at the cost of some stability, then a sit-down-in canoe 16 ft x 3 ft, with a slightly rounded bottom. Such boats already exist, of course, that also use pedal power.

Alan