When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Trim Tabs on a well designed hull allow the hull to run at its optimum running attitude over a broader range of speed, sea conditions and weight distribution. For example if the boat can plane at lower speed and still keep its bow down cutting an oncoming chop it is essentially running on its lines and the good characteristics of its hull design are working. Calling Trim tabs a crutch for bad design (if it is a good design to begin with) is like faulting an aircraft designer for including flaps for low airspeed performance. I think what we have here is an engineer who is accustomed to having an extra 25% runout of any adjustment beyond what should be needed. I'm not sure what 'philSweet' is getting at but I would state its obvious that you need no more trim than that required at WOT.
Location: united states A boat that requires drives to be fully tucked in at WOT and interceptors down at WOT is unusual. Can you describe in more detail what happens if the drives are not fully tucked in and if the interceptors are not mostly down approaching WOT? Location: Australia Worth trying bigger, wider tabs as an experiment, doesn't necessarily create more drag either. Originally Posted by Mr Efficiency Worth trying bigger, wider tabs as an experiment, doesn't necessarily create more drag either. Originally Posted by tunnels How can more surface area in the water not create more drag ? Originally Posted by tunnels What is the better trim tab and wide one across the boat ??
I've uploaded several pics of a very successful one of the French Navy, a bit too big, but a good example of the results obtained when a boat is designed for efficiency and not fashion. The boat is very heavily built (Lloyds A100) as shows its displacement of 41 metric tons full loaded.
I have built about 11 or 12 skin-on-frame kayaks, and a number of small sailboats using the construction method. The project is a concept project for a 12m powerboat providing an advantageous hull design for different functions.
The vessel would have a top speed of around 50kn and cruising around 30kn, at both these speeds it must provide a secure interior environment and excellent handeling.
While the GINA uses neoprene it endures relatively little force from wind while driving, the force produced on a planing boat are considerably greater hence the need for a stronger material.
Location: Port Orchard, Washington, USA As petros points out, almost any medium strength flexable material (such as walrus skin or intestine) can be used (even in high speed boats) like in kayaks, umiaks and other skin-on-frame construction.
A vessel is nothing but a bunch of opinions and compromises held together by the faith of the builders and engineers that they did it correctly.
Location: Great Lakes I have a V hulled inflatable catamaran that provides a nice soft ride.
So you would have to have a mechanical arrangement where when the keel went down to increase the V, the chines would go back up the amount to keep the fabric tension the same. It is also possible to use inflatable chambers to tension the skin, but to prevent flutter it would have to be fairly high pressures. You might also consider just having hinged hard panels on the underside of the hull to changes its effective shape. Location: Warsaw Suitability of modern cruiser racers to extended blue water cruising? I have been looking into buying a 43-50ft yacht for extended blue water cruising with family crew. All these boats are good blue ocean going boats, but not necessarily easy boats with a reduced crew (you don’t say about the crew). About the keel (bulbed fin) I would look for one attached to the boat through a metal structure.
For me the ideal boat would be either a fast twin keeller (there is none on the market for the size you want) or a fast boat with a lifting keel. The other is the Lansart 47, an aluminium boat (based on the Open 60 racers) that will probably make an ocean passage faster than any other boats that I have mentioned.

Which brings me to your question: we will probably be sailing with my wife + some friends most of the time. I don?t know if you have seen the 46RS (it is not on that thread cause it is out of my budget). I believe that it was what happened with the Lansart 46 (they advertised a very good price), with the Irisoft 44 and also with the Alliage Azzuro 42 (picture).
About the Allures 44, I have seen the boat at the Paris boat show and the interior, if a little bit rustic, seemed of good quality and very adapted to living aboard. The main (big) deception was the complete lack of visibility forward (from the interior of the boat). That means that the boat has a good downwind performance and an average upwind performance, but one that is a lot better than the OVNIS and the like. Of course, the performances can not compare with any of the boats we were discussing previously.
Location: gREAT lAKES Stability I'm pretty sure offshore seaworthiness is not limited to stability. It only takes one bad experience and your significant other will change your boat dreams forever. You can come from Newport to Hamburg in reasonable time (see HSH race earlier this year), but then, if you start Friday evening, what will you do on Sunday?
Location: Wisconsin Sams original question is certainly very relevant for many of us who intend to live for an extended time on a yacht that will also see extensive blue water cruising. It would be nice if we could come up with the top 100 (or whatever number) ?must haves? for a blue water cruiser. I would like the opinion of a broad sector of the boating community who has spent some time crossing oceans, concerning this matter, especially as it relates to design characteristics. Good thing if you're designing a packaging machine, but hydro doesn't really degrade over time the way machines do (I haven't seen gravity break yet). But do you run your boat at maximum negative sterndrive and tab trim to optimise WOT and still not achieve a good pitch angle for maximum speed?
Your comment about critising aircraft design is wrong as that's exactly what flaps are for, to improve low speed performance(like a boat) and your comment overlooks the fact that planes don't usually use flaps to correct wing profile at WOT maximum speed for a light load.
My comment are about a boat designed very recently by a well known designer with an International boat builder.
The question would be 1)has it got enough at WOT and 2) Is it achieved with a satisfactory balance of organic inbuilt hull trim as opposed to external devices. As you can see, there is nothing fancy but just optimization born from years of experience at sea.
I also have an idea for a pocket cruiser with a small cabin that uses skin-on-frame construction just like a traditional kayak (but larger and with a heavier frame). Similar to the GINA I want to be able to modify the exterior hull with a series of actuators creating a deeper V for high speed planing and be able to reduce the V for a slower cruising speed, perhaps with the capability of altering the hull into a tunnel hull form in rough conditions.
We are planning to start in the Med and then potentially continue to the Indian Ocean and SE Asia. I have been to Hanseboot once and it was by far the best place I have seen to get an overview of the market. Of course you can adapt them for that use, but as fast cruiser racers, their standard rig is one adapted to crew racing (X-yacts and Arcona). For the intended use you want to make of the boat, I would be ( and I am in my case) more concerned with the way the keel is attached to the hull and with draft.
It is the case with the Grand Soleil and with the X-Yachts and also with Luffe 43 and I believe that will be also in the new Luffe 45.
It is a very good cruiser, fast for a cruiser, but not on the same league as the other boats we were talking about (even if I positively hate those fake aluminium applications, on the boat?s interior).
I think that?s why boats like the Lansart 46 or Irisoft 44 (picture) don?t stand a chance in what regards a possibility of a significant boat production. About this one I am sure that it was what happened because I have personally talked with them (as you know they have turned to bigger sailboats and discontinued the 42). I like to travel, but because I sail solo or with inexperienced ?passengers? I have all my navigation stuff (electronic) on the cockpit.

I have read several boat tests and heard personal comments and the idea I have retained is that it is a very good boat with very good performances (for a centerboarder with a non profiled and non ballasted keel). Those with experience certainly have some strong opinions as to preeminent design characteristics, gear, and amenities that they would not want to do without if making extended open water voyages in their own vessel. If you look at the modern inboard tunnel jets ( Phantom sport jon, Seaark predator, Harbercraft extreme shallow ) you will notice some major differences. There's no reason to provide more trim capability than that required at WOT with full tanks. If so there's really no value in these trim devices, because if they don't achieve a relatively flat pitch at WOT with maximum negative trims then they'll be very little use to adjust for sea conditions.
Lots of places out of reach and most important, a reduced capacity for taking shelter close to the shore.
I checked the 44 in January, finish what not so convincing, recently I saw a later hull, looks better now. Quote from their brochure "The keel of the Dehler 44 is not simply flanged onto the ship's bottom, but is recessed by up to 300mm into the hull's interior. They have been built in such small numbers (sometimes only one or two boats) that their price goes over the expected (and advertised) production price. Of course, on the Southerly that?s different because you have a good all around view from the interior and therefore you can navigate the boat from there. If those boats were cars, the Allures would be a fast All-ground machine, the Etap a fast Sedan and the others, sports cars. You may want to have a look at the Glen-l builders forum as there is an archived discussion regarding pwc powered boats. If a good planing trim is achieved at cruising speed, typically trim is too low at top speed. I became interested in the BMW GINA car concept using fabric as a skin for the car and was wondering if there are any such flexible materials that could be used for boat hulls? It is important to remember that the small waves in a sheltered place are connected with the distance you are from the shore. The high forces to which it is exposed are thus discharged into the yacht's sturdy bottom structure". But the Southerly is a semi-custom boat and I believe that if I had the budget for that boat, I would have no problem in ordering the interior alterations to fit it to my needs.
Have sailed already about 1500 sm in different conditions in the Med and she's performing surprisenly well. If the specification is interceptor, then surely one that occupies a greater wide of the hull could be the ticket.
A flexible material would allow the hull to subtly change shape to suit it's desired function and allow it to alter it's wetted area.
I am from Finland and have spent most of my summers in our very rocky archipelago since I was 15 - quite different sailing from what we have now in mind. While this is marketing speak and the design remains to be proven, it is nice to see that some manufacturers are innovating to improve safety matters.
Mostly trim tabs and low stern drive trim are needed while getting to plane or at (low) cruising speed.
The skin from the GINA is not strong enough to withstand the slamming forces produced by high speeds on a boat. Maybe you will find something which suits your needs, or at least it will help to specify them. Keels (and rudders - several Swan 45 rudders fell of from the early samples) still seem to be a vulnerable point.

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