29' sailing boat design

I was make a 10m class boat design a few days ago. But now, I think that it is too big to make a single(or two person) long voyage.

For some law and business rule, a small boat is suitable which LOA short than 30'. And min. draft of less than 4 feet (3 feet be better ) , 10 feet breadth.

A bigger and comfortable boat may be need L40', D4', B12'(had better not more than 3.5m, because the size be suited to land transportation).

 

29'
displacement: 5000KG/11000LBS

39'
displacement: 13000KG/26000LBS

 

29'
only 2 seats for outdoor, make the biggest space inside for a long voyage.

 

Your English is infinitely better than my Chinese. But, sorry to say, your English is not very precise. So, those of us who use English certainly get the main idea, but are a little unsure of what to say that might help.
But I will give it a try.
Certainly a 29 foot sailboat is large enough for one or two people for a long voyage.
Your main goal should be to have EVERYTHING as simple as possible; try to avoid anything that is tricky, complicated, high tech or troublesome to fix.
You also want a boat that does not need constant attention to stay on course.
You seem to want rather shallow draft. Your drawing suggests you are considering a bulb keel that will raise and lower. The trouble I see with this type of keel is that they are normally used on hulls with low initial stability and so with the keel raised they are very tender. If you are considering doing any sailing in areas requiring shallow draft, I feel you will be happier with a hull with a hull form with more initial stability and a fixed ballast keel.
It is not comfortable to make a long voyage sailing at a large angle of heel.

 

I have trouble in the keel. You can see a bulb keel in my drawing. but that is a sketch plan only, because I hadn' t made up my mind yet.
A buld keel is very good for speed racing. but for the lack of relief and assistance to long-distance navigation was not appropriate. Such as fishing nets floating in the water can easily make you into a desperate situation.
As you said, after raising the ballast instability. But this problem is not large, because the boat are usually in shallow water at this time activities, and do not use the sail, relying on power (as in the harbor). In use sails, when ballast is put down for them only.

For the complexity of the ocean environment, intuition told me I should use a traditional FULL KEEL. But it cost so high, it would be more deep-draft, and the resistance of big slow boat speed. In addition, my ship is steel, and to do that kind of structure is relatively more complicated (in the steel boat is very easy to do BULB KEEL).

FULL KEEL There are many advantages for voyage. For example there are no moving parts, so there is no fault. Can easily cross the water barriers, such as fishing nets and even ice. and it is safe when grounding occurred(BULB KEEL It's almost irretrievably broken) .

But I hope the boat can also be in shallow water activities. So retractable structure is almost inevitable...Maybe a "L" bulb keel.

My poor English is so disordered, I hope you can understand... ^_^

 

Hello again,
In post #5 your English is quite good, I must say, so you don't have to apologize. Maybe you were in a hurry on your earlier posts.
Are you choosing steel because you have metal working skills? And are you planning to build your boat yourself?
A full keel can be simply made in steel by making what looks about like a long sloping trough that tapers at bow and stern. So it would not have to be complicated to build. Of course it would need transverse framing.