CNC Plans not Included

Boats are a slow sale no matter who built or designed them.

I am going to be building to CE specs so can't do this without a designer, don't know how well-known he will be, hope it can be Grainger but for sure will be somebody excited and into the project.

The main reason for drawing this is to familiarize myself with and start creating a build plan. But I am also learning the software which is going to be a great help because everything is going to be CNC and I am talking about stuff the designer probably won't provide.

The other reason is, as much as I like the look and practicality of the Grainger cats, there layout is not very nice. Single planes, as few steps as possible, single height ceilings and on and on...

End of March my house goes up for sale!

 

Just read an interesting article on displacement being more important than DLR ... so if it has a waterline of say 5' but then just below the surface, it tapers to a smaller radius (underwater soft chine) something like the image below, do you see anything wrong with this? Then we could keep straighter lines in the hull.

 

Hull flare

Why does the hull flare below the waterline? That makes no sense to me ?

 

It's wettednsurface for no benefit ?

 

It's actually a pucker, nobody wants chines above the surface but if we have a gradual rounded hull at a 5' waterline that boat is not going to float deep enough. I should have drawn it as a straight line to the small rounded keel. Actually it's over exaggerated, the keel would be larger, less V but I just want to know if this strategy is ok so I can continue drawing the rest of boat lol

Should look more like this ... Do you see any problem with this

 

Jorge,
The answer is here just above... You have the most ideal hull designed with no chines or fluff to the displacement required, just smooth convex surfaces then to the inboard side apply a champher panel or double champher to fit your bed accomadation. The champfer will smooth the transition of connective bulkheads across the wing and viola in one paragraph yo have the smooth racy outside with the business on the inside. If you are creating tooling for the hull/s this gives you maximum versatility in future modifications to adjust & cut/shut the moldings for variant purposes/models for power or motor sail, extra displacement can be added with a center wedge if required.
I would steer away from reverse bows, essentially to me they are a styling fad unless at the bleeding edge of speed & cut down on useful deck area. A straighter or straight sheer will also aid versatility. Transoms can be varied to alter styling from one model to another if the length is in the tooling. Just adding as your early discussion referred to tooling and multiple builds to offset costs- very hard to design to please each owner but a degree of customisation might assist, various graphic devises can be added to topsides also.
Jeff.

 

Huh? How can an article say displacement is more important than DLR- DLR is a ratio of displacement to length- you can't separate one from the other!!!

Your drawing above shows a higher wetted area for a given displacement- it's not ideal and still more difficult to build... have a look at the sig45 again Jorge, they have provided ample room in a 45ft hull when you have 60ft to play with... smooth clean lines , simple to build...

 

Ok I am going to leave it to a designer then, I am just going to design a fantasy boat so I can learn this software.

Groper this is the paper, I might have understood wrong - http://eprints.soton.ac.uk/46442/1/071.pdf

 

The paper says exactly what I've been harping on about... 7.2.and 7.3 on page 15.

Displacement to length ratio is dominant factor.
B/T RATIO only has small effect.

What you need to extrapolate from this is also what it means for beam / length ratio. - if the b/t (beam to drapht) ratio is made smaller, then accordingly the beam to length ratio must be larger image order to achieve the same displacement for eqivalent DLR comparisons. Ie the hull can't be deeper and wider on the same LWL and be the same displacement, it would have to displace more...

All this means is is doesn't really matter all that much if you hull dimensions change a little with respect to waterline beam- with reasonable limits of course. Provided you keep weight modest for its length to maintain favourable DLR it's always going to perform well...

As to its weight- for a given length hull, one with a large cross sectional area, ie volume inside, will be heavier than one with a more modest crossectional area of course. Do an exercise and see how the weight changes by choosing a panel weight per area and multiplying out the cross-sectional area on the bulkheads and the hull shell for 1 foot of hull lemgth. You should notice a pretty significant change in weight with relatively small changes in hull diameter...

 

Can you please link the article? It does not seem to make sense to me. If you make the displacement lower and the length stays the same the displacement to length ratio just got better. Edit, I saw it was linked. That's the one which proves DLR is king. Its an old favorite on the forum and I linked it quite often in this forum. It also shows one hull which had less resistance as the beam to length ratio got fatter. This goes to show how little things like that matter when it compares to DLR.

I have noticed Grainger prefers a certain hull cross section shape. He seems to not use the common semi circle. He likes to use a more triangulated semicircle as drawn above. I wonder if that promotes the a narrower waterline on the "high" hull under sailing loads. This shape was easy to spot in a yard with plenty of Graingers. The hull shapes were distinct and had this in common.

 

I'm the type of guy that has to hold it, smell it, kick it etc... Sorry for my ignorance on that article.

I know this is an impractical shape but I am going to draw it anyway because it gives me both side access to a queen size aft bed and 5 feet of floor space between full size cabinets. The horizontal oval shape also means wind sheer is about 4' from surface water and I don't totally blow my ratios ... so as impractical as it is, I am intrigued

Here are some pics as I learn more on Rhino. Going to have to get a license because can't save any of my work but for now I am just practicing.

 

I like it. Its your best yet IMO. Your underwater hull shape is a little like what I was trying to explain I have seen on Graingers. I could not find any pics on the net to explain it. I guess as your boat heels the low hull will get a wider BT, but as the paper linked shows this is of little importance compared to DLR. It gives a massive amount of space inside and looks fairly aerodynamic.

 

I am completely blown away by how much interior room this approach gives

 

This looks just like a Shuttleworth. Perhaps you could contact him for the design?

He already has a design like this in 50ft. He could probably tweak it a bit for little cost to stretch it out to 60ft for ya

I think your mad tho 50ft is enough for me... the cost of rigging a 60ft version would cost more than my house...

 

Yeah, a lot like the Dogstar except he accentuates the curves more and chops up that deck space. I think I can cop a part of his strategy and make it look more modern, the Bimini and sunset seats will help.

50 ft is def too small for me, I think you are mad lol!! I spent 4 years in the merchant marines on thousand foot long boats and after a while those got too small )) The way I look at it, I need almost the same rigging because I want it set up for shorthanded sailing.

Mario has been looking for spots to build. He says there are a lot of them but best bet might be some seaside agricultural land which we could get a variance on. His family has crane trucks and forklifts, he has connections to get us electric and water, all we need are the hangars if we go that route. I think a boat club could actually work in Croatia. We want to build a charter fleet of small power cats as well too, everything has to be to CE specs though.

Im getting excited man!! Want this phase of my life to end and start the new!!!!!!