MacGregorSailors.com

How are you planning on creating this hull? Molding it?

Standard fiberglass or carbon composites?

I wonder if you could tank test this with a 3D printer creating a test hull.

The hydrofoils are horizontal, which is perpendicular to the daggarboards. This allows the vertical forces to be applied to each side.

I have not thought about getting it 3D printed, but it sounds like a great idea! I have recently been informed from another member that a person can get a year long permit to trailer a 10' wide boat. So i think i will modify it for 10' instead of its current 8' beam.

The structure was to be built from 1/4" wood core with the outside fiberglassed. then when the shape is held in place, i would remove the bulkheads and fiberglass the inside. It was my intention to make it all one single piece, not bolted together sections. Who knows, i may not even find time to build this in the end. It is what i want to do though!

This will explain the bow just a little bit

http://www.aeroyacht.com/catamaran-lear ... cing-bows/

The description on the wave piercing bows has two items to highlight -
Applicable to larger boats (35 foot and up)
Seems applicable to displacement hulls. Counterintuitive it one want the speed advantage of a planning hull. If you were to bury this type of bow while under plane, it could be a very interesting ride.

Chopper, I have a 3D printer and would be happy to print it for you. More importantly, I have some custom software I developed that can make solid whatever triangle soup it is your CAD package exports. Send me an STL export and I'll get it setup for you.

Couple of questions/concerns I have:

1) Why not a wider flatter stern for better stability on a plane without foiling? Planing hulls need form stability to keep them from entering oscillating rolls that can build up. It's why classic sailing hulls make terrible speedboats, and the cleverest thing Roger MacGregor came up with: front half sailboat, and sails bow down, rear half power boat, and powers bow up. This allows the X and M to benefit from a hull transition for free. Also it'll create much more cockpit room and space for all those motors and the other rudder you'll need. Look at the Volvo open boats, you'll see the hull design I'm talking about.

2) the tumblehome bow will dig in at speed if it hits a wave and put the boat stern over bow. You can't use them on a high speed design, they're for displacement hulls only. Also they impart an opposing force to an inward roll when turning which contributes to turn instability. I'm uncertain why they're making a comeback, as naval architects abandoned their use 100 years ago with plenty of data on their riding characteristics. That said, I do like the plumb bow on our new boat: very dry, rides through waves well, and meets docks with plenty of surface area . Plumb bows are the way to go.

Beautiful CAD work.

mastreb wrote: the tumblehome bow will dig in at speed if it hits a wave and put the boat stern over bow. You can't use them on a high speed design, they're for displacement hulls only. Also they impart an opposing force to an inward roll when turning which contributes to turn instability.

The boats from the last America's cup look like they had this type of bow. Those large catamarans pitch-poled quite a few times. Spectacular to watch. I was glad I wasn't on them.

Instability planeing- When the dagger boards are lifted, the hydrofoils still act as trim tabs that are flat. I do want to give it a 10' beam now that I know it can be trailered at that width.

As for the bow- Normally, we look to the racing community to see the direction of performance and efficiencies. Each pontoon on a catamaran has no height to their sides. If you want to get height on it, they would need to be really long so the ration would match a height to length. Monohull seems to get a lot more height out of the boat relative to the length and thus, a smaller boat would benefit. With the advent of a wider hull, the bow will grow far more boyant, far sooner because of the width, especially if I want to include a planeing hull to the equation. The trick I think, is to get the water a quick path off of the top of the deck. I could raise the top deck's center to help, but I don't see a need for it yet.

So the hydrofoils add many benefits to the boat by allowing a sailboat hull with the ability to be stabile on a plane. The monohulls use of the piercing bow decreases its probability of pitch-poling relative to a catamaran.

I will send the solidworks data to anyone who wants it.

How will trim tabs in the center of the hull work? I thought these were generally located close to the stern.
I also recommend using caution on applying catamaran principles to a monohull. The two types are not interchangeable - what works on one is generally not applicable to the other.
Also consider the current design: 28 feet long, a very narrow stern suitable for a displacement sailboat - not a powerboat, a narrow bow that has little ability to withstand pitch poling, and a wide midships. This is really looking like a displacement hull, not anything suitable for a planning hull.
Recommend considering that a boat such as this is a fine balance in compromise - an attempt to optimize an area has numerous side effects - many often at odds with what was intended.
Have you ever designed or built a boat before? Recommend you check out Dudley Dix Design http://dixdesign.com/designs.htm to see what has been demonstrated to really work. He has a 28 footer about the same dimensions you are presenting.

Correct, trim tabs are put on the back of boats that plane since they usually don't build planeing boats with holes through the middle. Luckily, we have slots that are designed into the boats!

I am sure people asked steve jobs or Bill Gates about their credentials about computers. they should have been tar'ed and feathered if they didnt, before they did. Maybe even the wright brothers if they have ever designed and built a plane before they built it. There are a number of parasites that feed off of the innovators in society, yet never contribute to the innovation. I do not need to have ever put out a fire in order to justify my use of an extinguisher. I do appreciate your concerns of the design, and would gladly listen to any input. But if you wish to input, I humbly ask that you also contribute maybe 1% into finding ideas that will work and not just why it cannot. The wright brothers didn't make flight by listening to only nay-sayers.

By the way, I just bought the book you just suggested. That was helpful info

Easy big fella
This is a forum, we discuss. Sometimes it may be even be helpful.
As far as judging my input, I actually design and make things - including building a few boats and a whole bunch of additions to the current boat. Oh, and all that aircraft stuff too. So if I comment on appropriateness or safety, it is because I am interested/concerned. Personally, if an idea I put forth is truly nuts, best someone tells me before I spend a bunch of money and get someone injured - and this forum has plenty of helpful people to "educate" me.
I am very interested in seeing examples of your work - we even live fairly close. I plan on getting the boat wet in the next month after I modify my forestay.

I have only built one boat, and it wasn't a sailboat. I look forward to all info, but please accept an intellectual exercise on how can it work. I do also want why it cannot, but not that as a sole function of input. This is more for education and challenge, but also for pure fun. I identify that this is a Macgregor site, and this incorporates Macgregor ideas.

I do hope to see you this summer. We have at least three other Macgregors on post at Fort Belvoir, so we all need to meet.

It's extremely important to listen to thoughtful dissenting opinion, evaluate its merits, and then forge ahead anyway.

Most radical inventions (as opposed to improvements) come from people outside the professional field whose mindset hasn't already been fixed by orthodoxy. But 99% of those attempts fail, sometimes spectacularly.

We remember the names of those who succeed, however, so I say venture forth, and if you fail, fail safely and spectacularly. The worse case with this hull is that it won't plane and won't foil, and you'll left with one hull of a displacement sailboat (after you pour some lead in the bilge to correct whatever instability problems you find after building it).

Also, do you know how you intend to build this?

I'm developing a hull building method (no particular boat in mind) based on the 3D printing of small connecting joints to panels of marine foam core. The idea is that with just two inexpensive tools, an FDM plastic extrusion 3D printer, and a 2D CNC hot-wire cutter, you can assemble any hull form like a 3D puzzle and then glass over both sides of it. So there's no mould necessary, no tooling necessary, and--most importantly--no skill necessary.

What I'm working on is software to reduce any hull form to triangles (easy), optimize coplanar triangles into larger polygons (easy), create the list of foam panels from surfaces and 3D connectors from edges, and then software to create the geometry of each individual panel and connector. The connectors are created specifically for every joint, so they have exactly the right angles necessary to join the panels correctly and can join interior geometry such as bulkheads, liners, and even cabinets. The triangles and foam core will even be cut with indicators showing exactly how to connect them and to which panel, so it's literally "assemble by numbers" and the parts will be ordered to come off the 3D printer and the 2D cutter in the order of assembly, so you can run the printing and cutting while you're assembling in your garage. Each connector will take something like 2 hours to print, so if you've got a "high rez" hull with lots of small triangles, you could be a many hundreds of hours in print time alone.

Happy to work with anyone who wants to try it out once its ready to test.

Ah, the naval version of IKEA furniture. Will the assembly directions be written in broken English to make more realistic?

Ten foot beam on a 28 foot boat seems excessive.
That bow seems like it will scoop up spray and throw it on the passengers while under sail.
The foil system seems prone to damage from groundings. And expensive to fix or replace.
There does not seem to be enough rocker in the bottom to be able to go about reliably.

It's important for a family sailboat to be comfortable. Dry , easy to handle and forgiving of error.
Making a boat this size from scratch will cost double what a tricked out Mac will cost. You'll want to at the very least tank test this, and maybe even get a marine architects input else you may wind up with an expensive yard ornament.
And even if it tank tests well, it still won't mean it will be a fun and forgiving sailboat.
How will it sail with only half the boards down? Or none at all? Will it be well balanced and a pleasure to steer? Or something that goes off course if you take your eye off it for a second ? Will it go about well? Or stop and hang in irons?
Will it sail well at slow speeds? Yes actually sailors want that. And the current Mac is slightly lacking.
How about balance with reduced sail? Don't forget all the other junk like having enough room for anchors on the bow, dedicated space for a fire extinguisher...Tslking to you Roger and enough outside storage for gas and other stuff.

Ix

Chopper Pilot wrote:I have recently been informed from another member that a person can get a year long permit to trailer a 10' wide boat. So i think i will modify it for 10' instead of its current 8' beam.

8-1/2 ft wide is legal on all interstates except for some specific restrictions (mostly in the north-east; look for the circle with the slash "no 102" signs), and for some access distance away, with no permits. Over that, and it's a state-by-state thing for permits. If moving around within a single state, it's no problem, but if towing from here to Florida (for instance), it's a lot of permits, and possibly an "Oversized Load" or "Wide Load" sign.

Just something to think about.