vendredi 25 décembre 2009

Keel lifting

There is one big issue on this boat, that is how to lift the keel. The original design calls for the use of the main sail halyard and the boom. Obviously, when you do this, one can no longer sail... It is an issue for me, because most of the time, where I sail, you need a shallow draft to launch or come back to shore. I do not need to be able to really sail, but I need to be able to lift the keel enough, so that I can jump in the matter and be able to pull the boat aground or to the slip way and trailer.
So, I put some thought in it and drafted several designs. I could instal a lifting tool on the deck, but it requires some installation and I won't be really able to sail with it in place, because it interfers with the boom. Another design is the one bellow.
In the lower position:

The lifting system is made of 2 sheaves attached to the re-inforced roof. 2 lines are attached to the keel, just above the hull. One winch will pull everything up or let it go down.

mardi 1 décembre 2009

Another day, another dollar...!

After building my first and second dinghies, I have a better idea about this kind of construction cost. And it costs, a lot. I receive often questions about how much it costed me to build Kerness. And honestly, I have not done any accurate calculation, but this was not cheap. One would think that building your own boat is cheap, but when looking at good quality plywood, epoxy, sails, trailer and all the jewerly, it adds up quickly.
So for this SB18, here is my budget:
Marine plywood okoume: $2,000 - 43% of the hull cost.
Other material (lead, fir...): $1,000 - 21% of the hull cost.
Fiber glass: $ 800 - 17% of the hull cost.
Epoxy and filer: $ 900 - 19% of the hull cost.
Total for the hull: $4,700 - 44% of the project cost.
Rig (aluminum spars): $3,500 - 33% of the project cost.
Sails (dacron): $1,500 - 14% of the project cost.
Trailer: $1,000 - 9% of the project cost.
Total project cost: $10,700

It better be fast...!

This week, I have had some rough quotes from various suppliers for about everything. I am still looking for a good way to cast the keel bulb. I am not keen to handle 360 lbs of melted lead...! So I am looking for a local foundery who would help me out. My next step is to buy the douglas fir required for the keel and then shape the bulb keel and get all this on track...

dimanche 22 novembre 2009

Sport Boat 18

So, now I have the drawings of the Sport Boat 18. A few data:
Length: 5.5 m
Wength at Water Line: 5.2 m
Draft (centerboard): 0.18 / 1.4 m
Draft (lifting keel): 0.46 / 1.57 m
Displacement: 663 kg
Ballast (centerboard / keel): 182 / 166 kg
Sail area: 22.4 m2
I really like the design of this litle boat. It looks very nice and must be very fast.
I went through several blogs of boat buiders and I have two fundamental questions that which I have difficulties to decide:
1- Lifting keel or Centerboard
2- Mast step on keel or mast step on deck
I would like to be able to take the boat in shallow water. Though it is not an absolute madatory thing, sailing in protected waters in the Houston area or at our place in Britany requires some ability to sail in shallow waters. The lifting keel system on this sport boat requires the main sail hallyard and the boom. So impossible to lift the kill at sea... It is a disadvantage in my eyes. However, this is a sport boat, if I start to question the fundamentals of a boat that is supposed to go fast, I should rather built a less extrem design, with a centerboard... I have looked a lot at the drawings, and I think I may be able to have some system install to lift the keel "partially" to meet my criteria. This may be adapted at a later stage. The other issue is trailer and launching from the trailer. Here again, I will need to look at how this can be done easily.
The other question regards the mast and it mainly concern the ability to rig up or rig down. I was more in favor of keeping the original design, but rigging up a mast 9 m long will be a difficult operation. I am looking at a carbon fiber mast to see if I can have it lighter than the alluminum mast. I have seen some of the SB18 under construction for a roof stepped mast. I do not really see how the mast can be rigged up with a hinge system on top of the roof. There are at least one interference with the cuddy top and one with the keel in its upper position.

After putting a lot of thoughts in all this, I am glad I come back to the original design of the boat and wont have to denature it.