First boat design

Hi everyone,

I have no experience in boat design yet and was wondering if some of the more experienced opinions would be able to advise me. I started building the plug a fortnight ago, the frame is made of maritime pine and the skin is made of MDF. I am now filling with plaster. The humidity is very high at the moment in France and the drying times are very long. I question everything in my spare time and I have come to doubt the initial shape of my boat. I'm ready to start again, but this time I want to be sure of the shape.

The basic idea is to get a 26' lenght boat, very wide out of the water early with the smallest possible engine, which explains the low V of the boat. There is still a bit of it in the bow to break the waves (the bay is not entirely protected from the waves). But I'm afraid my form is not good.

In fact I think the bow of the front of the boat starts too far forward. I have no idea of the final weight or centre of gravity of the boat, I just have a shape on Rhinoceros for now. Also I did'nt draw the lifting strakes but I planed to create 2 each side of the boat.

Some pictures are attached to this message, it would be so helpfull if some of you could tell me what they think about this draw. I can also send the Rhino field if required.
(The transom angle is actually 15° unlike the Rhino images)

Thank you very much in advance,

Paul Henry.

 

Welcome to the Forum Paul.

You are certainly jumping in at the deep end now!

This is something that you should have established (even a rough estimate initially) before you even started to build the plug.
Are you planning on using this plug as a male mould to then build a foam sandwich fibreglass hull?
Are you planning on installing an inboard shaft drive engine, or maybe an inboard engine with an outdrive leg, or maybe an outboard engine (or a pair of engines)?

Re how you are ready to start again, bear in mind that if you buy a set of plans from a reputable designer, the cost will probably be 1% (or less) of the cost of actually building the boat.
Have a look online, do some googling, have a look especially at
Duckworks Boat Builders Supply https://duckworks.com/
They have lots of interesting designs available - see if you can find anything that comes close to what you have in mind.

Re how your design is 26' (I presume it is not 26 inches long re 26"), then the 26' motor boat in the link below might come close to what you are looking for?
Berry Point 26 https://duckworks.com/berry-point-26/

 

Thank you very much for your reply!
Actually I was planning to create a polyester mould from this plug, then create my boat (and others if functional) from the mould.
The idea is to install an outboard motor, I guess a 250 hp would do the trick, but there would be the possibility to install a pair if needed.
I agree that it would be easier to buy an existing design, but I find it much more fun to create my own. I'll do it if I do not succes..

 

Sorry, I didn't see the last part, I meant 26', not 26". The aim is still to get a shape that takes off and can reach 40mph

 

Paul, there are reasons why a course in boat design might typically take 3 years to complete - and even then, it takes experience to design a successful boat, especially one that can do 40 mph safely.

It is perhaps fortunate that you came on here at this stage, before progressing any further.
By building first a plug, and then a mould, and then your first boat, you are building 3 boats (and paying for the materials for these three boats, and counting up the hours of labour you put in to building them) - all with no guarantee that the boat will work well.

Please take heed of TANSL's advice, and start again.
Or simply buy a set of plans for a boat that you like, and then you are free to tweak it so that you can say it is more or less your design - but tweaking it might not necessarily 'improve' it.

You will not know if it is a success or not until you build it, and subject it to a sea trial - and by then you might have spent 50,000 euros (or even much more) on your project, and many hundreds of hours of labour.
Is it worth taking this risk?

 

Thank you for your answer TANSL,
I'm not sure if I expressed what I was really looking for when I posted. I'm not looking for someone to provide me with a design that matches what I'm looking for, but rather to find out if the bow advancement at the front of the boat is consistent, or if I need to start over by redesigning my hull.

 

It is true that spending a few hundred hours of work and tens of thousands of euros for a failure is not the goal. That's why I'm taking advantage of the stand-by time imposed by my drying time to question my hull design. I'm not against turning to a real designer and paying him to tell me what he thinks before abandoning my existing plug. But any case I am not looking for perfection for my first model, so I am ready to modify the mould if some details are not optimal. I have no specific request in terms of speed or motorization. I just want the general shape of the hull to be right, I'll work out the rest. Also, I'm not asking for 100% certification that the hull is viable, I just want to make sure there are no major defects (including the bow advancement), I'm also wondering if the chine shape (flat to the famous bow) is correct.

 

You don't have to hire a na to be able to apply logic to a design.
I am very sorry that my post has bothered you. I delete it immediately and please forget what was said on it.

 

Planing hulls at that size are simple animals, and outboard powering can make up for a lot of non optimal design, so it will probably be ok, but what a lot of work you have set yourself up for to build a boat that, as far as I can see is doing nothing particularly new or different.

If you are looking to sell them commercially at any point, a 26 foot boat, to be a commercial success is 95% styling, marketing, looks, price, equipment, interior/ deck packaging and about 5% hull design. Although an atrocious hull design can of course ruin the whole thing, and it's not expensive to get it looked over by someone qualified.

I can't stress how important it is if there is any commercial thought around this for the future to look at what boats in the 26 foot size range are selling. The forefoot silhouette in particular is critical at the moment, and let's just say that the Miami Vice look went out for powercraft long, long ago!

 

Can you post a copy of the body plan showing the sections forward of amidships please?
And if possible, a plan view showing the waterlines?

You need to establish your Statement of Requirements (SOR), as mentioned in TANSL's now deleted reply, before any designer can tell you what they think about the details that you posted in your first post above.

But the shape of the hull will be very dependent on the desired speed, and the typical sea conditions (flat calm, or rough, or typically somewhere in between?) will be a contributing factor as well.
Not to mention the weight - has your program calculated the displacement at the waterline shown? And have you done a rough weight estimate of the boat to see if she might float at this waterline?

But you have not shown anything re the chine (in plan view) or the hull section shapes forward of amidships, so nobody can offer comment as to if the chine shape is 'correct' or not.
However in your Side View, the shape of the chine does not look right to me, re the tight curve upwards as it goes forward - but it needs the hull sections to be shown here as well.

 

There is absolutely no problem for me, on the contrary, thank you for your constructive answers!

 

Thank you Jakeeeef,
It's very true that there is nothing new or particular with this boat, I just thought that the shape was nice and I think the 90's style is comming back in France.
Also, the 26' market is not the better but it's the maximum size authorized in a new big harbor neer my area, so I thought it was a good idea. Also, with a 26 feet boat, there is the possibility to rent it to almost any kind of people, which I wouldnt like to do with a bigger boat...
There is a lot of competition from the big American, European and even French brands, but there are very few local manufacturers in my catchment area, and one former (now defunct) manufacturer used to make a big splash with this kind of forefoot silhouette. His boats still sell a lot but are only available in 20' and 36' (very flat). I thought that a middle ground would sell ?

 

I didn't do any calculation for the moment, I'm going to fix it this weekend by sampling if that's the right method?
Yes my doubbt comes from this curve.
I'm sending a picture of the sections from 0 to 360 cm with a 40 cm space, is that what you want ?
Again thank you very much for your advises.