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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > Question about sail area
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Topic Review (Newest First)
10-31-2013 06:34 PM
Chikokishi
Re: Question about sail area

Zedboy,

The biggest reason why my boat is like this is because i want to have the appearance of a large cutter rig boat. I am going to be using small pulleys and everything to give sort of a scale effect. Of course i know that a small dingy with like 60ft2 would be practical for small lake use and the such. Over my past few years i have built plenty of plywood and stitch boats. starting with a Harley 8, then i build a pair of boats for my gf and I, then i built 2 PD racers (My avatar is the latest one) All of them were quick built, covered with cheap house paint and enjoyed for a summer before being recycled.

This boat is actually a senior design project for my college... as such it has to be "professional" and i have to make all sorts of calculations and reports and prove that i am not copying other ideas and all this jazz. That is why my goal has been to make a boat that is short enough to evade needing tagged and such (12' is the length at which boats need to be registered here) which is the reason for the 11.75~' length. The reason for the full keel and the push to make a very sturdy design even in such a small boat is that i mean to take it to a lake around here that is... just terribly shaped. It is a very long lake and it sits in a low valley. The wind that blows along it goes from tip to tip and the waves are known to be in the realm of 8' ad i know of a few stories of even large power boats being swamped by rogue waves. Of course these were caused by a sudden upcoming of a storm.

That being said, i am trying to design a small boat for my girlfriend and i, that from a distance looks like a beautiful, large, classic cutter. Along with that i wish for a very sturdy sailing boat (as much as i can gather with this length) and being able to turn around and such are of no importance to me as this boat will only be used for fun days out on the water. Speed is not important to me either, although i only expect a speed of like 4-5 knots tops out of it anyway. the reason for strip plank and opposed to plywood is Girlfriend is tired of flat boats... she wants a beautiful curve. We are fibreglassing the boat because we are tired of them deteriorating over time... we used house paint of the first boat to save money, and we varnished the one in my avatar quite a few times... but the varnish just didnt like being outside in the winter here so it is toast. Lastly, the reason of this boats design is that we do not wish to build another one for a while and i want to be sure that we love everything about this one. and a open hull dinghy looking thing is not something i am interested in ad i am unable to build a 40' cutter. So a 11.75' cutter it is to the best of my ability.

The front and back of the boat will both be solid air boxes, and the seats will also be sealed so that in the event of capsize the ship will stay on the water... this is one of my major methods of combating the potentially dangerous lake.

Anyway, this is a huge post.

Cheers!
Chiko
10-31-2013 06:33 PM
paulk
Re: Question about sail area

The drawings look lovely, and the sailplan appears to be well-proportioned. I would question the need and desirablility of a cutter rig in a boat this small, however. If you're likely to be sailing on smaller lakes, you're also likely to have shifty winds and have to tack frequently. Having to tack two jibs can become old quite quickly - right about the time you have to tack again before you have the second jib fully trimmed.
10-31-2013 06:05 PM
zedboy
Re: Question about sail area

You're building a 12' boat. Why not build a 12' boat that performs much better all around and give it a flatter dinghy-type bottom and a fin keel? It's not like you're heading around Cape Horn. Design a good grid to spead the load and it will be plenty sturdy.

(I spent a lot of time and love on a full-keeled boat)

(If I was building a 12' boat I would stitch-and-glue plywood and get out sailing but maybe you're really into woodworking or want the experience)
10-31-2013 05:51 PM
Chikokishi
Re: Question about sail area

Strip planking covered in fibreglass following instructions in "Building Strip-planked boats" by Nick Schade
10-31-2013 04:14 PM
zedboy
Re: Question about sail area

How are you planning to build?
10-31-2013 04:08 PM
Chikokishi
Re: Question about sail area

Wow, that picture came in much bigger than expected. If you right click and click "view image" itll make it fit your screen better. Also, if you notice i followed some earlier advice and got the transom out of the water. And i smoothed the nose up a lot.

Chiko
10-31-2013 04:06 PM
Chikokishi
Re: Question about sail area

Been doing lots of looking around and thinking about what i want the boat to be like. Ive decided to go with a much more classic looking hull shape and dropped the fin notion completely. After about 8 hours of work i ended up with this:


I am debating on whether or not i want to flair the waterline out wider or not.

But that aside i am now reworking where i should have my sails.. and how much i want. I am basing a lot of knowledge on existing boats which is leading me to many hours of looking at pictures.

Anyway, this is just my current progress. Ill chime in when ive made it further.

Chiko
10-30-2013 01:29 AM
Chikokishi
Re: Question about sail area

Hey everyone, sorry for the late reply. I never got a notification of replies! Ive been doing some refining on the boat, and we want to build the keel as more of a full keel than a fin. So i will be extending that keel to the full back of the boat and making it a bit deeper. I know that fins thin and deep are much better for maneuverability and such, but i want a nice sturdy boat. The LOA is 11.5 due to laws in my area (we are striving to miss the criteria to register boats) also the boat is this small because i drive a 4cyl toyota truck. Much bigger and i doubt i can get over the mountain passes here!

The position of the keel in the above design is based on my understanding of the need to centre the keel on the centre of sail effort. This was a large push for my original post involving sail area. However, now that i am considering running the keel full back my large question now is... What is the difference between a keel that runs fully from front to back, and a keel that starts at about 1/3 back and continues all the way back? If i understand right, if all your sail area is forward of your keel resistance your boat will tend to steer downwind - not good in an overboard situation!
If you are doing a full keel does centre of keel really matter?

I cant submit images or links anymore, unsure why.

Again, sorry for late reply!

Chiko
10-25-2013 08:42 AM
bobperry
Re: Question about sail area

Chiko:
Your rig looks OK to mme.

But I think your keel is too far forward and may result in too much weather helm. I would move the keel as far aft as possible.

Why do you have so much hollow in the bow? On a small boat like this I would give it a lot more deck beam forward. With that rig and keel the boat will not be close winded so why have such a fine entry? I'd push more volume into the bow.
10-25-2013 03:37 AM
zedboy
Re: Question about sail area

Chiko you are on the right track :-) I don't know if you realize how lucky you are to have gotten Bob interested, but I think he will have some very constructive suggestions.

I'll just give you my opinion on what you specifically mentioned: the boat in my avatar is my old boat, SA/D around 12-13, long shallow full keel. She was fun, and tracked great, but slow and hard to maneuver especially astern. I sold her and got a much more modern centerboarder with a planing hull and SA/D in the low 20s (depending on crew) - going fast is a blast. In a second I would tell you make the main/fore area as big as possible (and plan for reef points in the main), and go with as high-aspect-ratio and deep a keel (and rudder) as you possibly can.

Other notes: first, get your transom above the waterline a bit. You want a clean exit; what you have now will create a lot of drag. Second, it looks like your LOA is 12 feet, but you're adding a sprit. I don't know about your budget or planned construction methods, but if you can skip the sprit and bring the LOA up, there is no substitute for waterline.
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