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post #4338 of Old 05-13-2013 Thread Starter
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Hulls and sailboats: J 105/A 35

Originally Posted by MrPelicano View Post
And while I'm in posting-frenzy mode, let me take a minute to express my sincere thanks and appreciation to Paulo and the other posters in this, my favorite SailNet forum. Believe it or not, after finding this forum, I started on page 1 and read through all 400+ pages, over several days, until I got caught up. Can't begin to say how much I learned, along the way, and how many images and videos of beautiful boats, in exotic locations, engaged in terrific sailing I enjoyed.

Of course, the process of choosing a performance cruiser has now become even more difficult than before, since my attention was drawn to the Dehler 38, the Elan 400, the JKM designs, and others. Don't know how I'm going to settle this problem, but am certainly finding the process delightful.

So, thanks again and keep feeding us a steady diet of amazing boats.

Thanks for your words.

Getting back to that race (San Francisco to Hawaii) if you wanted to do it again solo or duo in a boat slightly faster than the J105 and more easier to sail (even more faster on account of that), in a boat with a far better cruising interior, the recommendation would be obvious: The A 35.

Other boats would be equally suitable but with a poorer cruising interior: A31, JPK 10.10, Sunfast 36. All would also obtain good results in crewed racing (with a different rigging).

If you only wanted to do the race for the fun of it without concerns with the rating or handicap classification (and the same with crewed racing) you could go fast and have fun with a Opium 39, a JPK 38 or a Pogo 10.50. They all offer a more spacious cruising interior and in some cases a really a very good one.

If you wanted to do that in a boat with a great cruising interior (but also on a more difficult one to solo sail and overall probably slower), that could also obtain great results in crewed racing, you could do it on any Salona, with any Elan or Dehler, with the First 35, with the J122, an Arcona, Grand Soleil and many other boats. of course you can do that too with the First 40 but that one has a very poor anchor locker and that is a no no for cruising, at least for me.

Not all of them are as well suited for solo sailing and I am not talking about rigging. I am talking about hulls and boat that have less or more stability at small angles of heel. That has to do with beam, with transom design and beam brought aft. Of course, that is globally prejudicial for upwind sailing so the boat, unless is not to be used in a regatta field (like the Pogo), has to be carefully balanced in what regards upwind and downwind sailing, solo and crewed sailing.

One of the best in what regards that is the A35. The boat is not only a chronic winner of the Transquadra in solo or duo as it is a IRC champion with many major races on his belly.

Let's have a look at the hull of a J 105 and the one of a A35:

We can see that on the lateral view there is not a big difference. The A 35 is a more modern boat and has a tudder with less wet surface a bigger waterline but the keels are not that different (the A35 can have also a bulbed keel, it depends on the handicap system the boat is racing).

But regarding the superior view things are much different. Not only the A35 has more 20 cm of beam as it have it pulled aft.

The weight is favorable to the J105 (3515kg against 4450 kg), the B/D is very high and similar to both boats (44%). The A 35 has more 20cm of draft but the J105 has a small bulb so things should not be much difference, except that those extra 20cm of beam on the A 35 will make the GZ bigger and will provide more stability that is used for carrying more sail area: 67.5m2 against 53.60. But the bigger difference is on the sail area each boat is able to carry downwind: where the A35 can carry a spy with 95m2 while the J 105 was one with only 77m2.

What makes that possible it is not only the difference in RM provided for more beam and more weight but also the difference in the transom and the aft part of the hull that makes the boat easier to sail and manage:

The easiness to sail fast downwind is one of the things that makes the A35 a great short crew racing boat. Going very fast downwind, while on the j 105 the roll movement of the boat, induced by waves or the lateral component of the mainsail has to be carefully counteracted by the weight of the crew and an experienced helmsman on the A35, at small angles of hell that fat ass starts to produce RM that rapidly grows with a small increase of heel. That produces a dampening effect that diminishes greatly roll and makes the boat easier to sail.

On the J105, with less beam and with a skinny ass the boat needs to heel to provide any significant RM to counteract any unbalance and then the force provided will only be stopped with heel on the other side and a roll movement is created that an autopilot can have trouble stopping.

On the A35 the hull shape will stop that movement without intervention. That's why you can sail fat ass solo boats fast downwind on autopilot while that can be tricky on narrow boats with a narrow transom.

In what regards absolute performance a narrow boat with a big and very experienced crew compensating all unbalances and keep the boat straight downwind in an equilibrium act will have less drag and the boat will be fast but that can be so difficult that designers have bean learning that even there some compromise is the best option at least for Ocean racing. For solo sailed boats that compromise is just a bigger one.

Upwind if the boat is well designed the extra drag is almost (or all ) compensated by the extra RM and the possibility to carry more sail. Again all is a question of compromise.

Boats with the transom brought back sail with an asymmetrical wet surface and that explains why twin rudders make sense even in not very beamy boats but with the transom brought back. The rudders are that way at the middle of each asymmetrical sail surface. Being asymmetrical and oblique will also increase slightly the LWL and increase hull speed.

You should be happy in having such a big choice. The real question is what you are going to do with the boat and what compromisse are you willing to take in what regards upwind and downwind sailing, solo or crew racing and cruising, not mention price. There are boats for all the tastes



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Last edited by PCP; 05-13-2013 at 12:11 PM.
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