10 ft "cabin" cruiser

It seems that the more panels I put on....the smaller the boat seem to get
Only 4 ft wide bottom but surely looks inviting for pounding.....
Have no idea why I've put that redicilous little skegg there....

 

the skeg will help her track

 

I guess I can use all the help I can get to keep such a little vessel on track.
The more "she" takes shape the more I wonder how on earth such a thing can sail.That it looks more or less like a boat might not be enough to make it act like one LOL !!

 

smaller boats than yours, not only sail but race. El Toro dinghy 7'11" loa is one.
http://sailboatdata.com/viewrecord.asp?CLASS_ID=3822

 

Westel; fear not, your boat is going to sail. Up until now you have done a creditable job with the build. Several of us have taken an interest in what you are doing and we hope for the best.

We have picked on your design but not on your building skill and resolve. Aside from building drastically heavy, you do not have nearly enough aft rocker in the bottom. Look at the El Toro profile in Yobarnacles link. That little boat is designed to displace about 125 kg including the rig and skipper. See how much rocker the Toro has? Never mind, your boat will sail in spite of that.....just not very well. It will be advisable for you to give the little hooker all the advantage that you can from this point on.

Advantage item #1: Give her something that will help her "hang on". Hang on means to not sail sideways. The chine runners are the least efficient of the several methods. If I guessed at the relative efficiency score of chine runners, lee board, centerboard, dagger board, the runners would get a score of one while the lee boards might get three and the dagger board five.

A dagger board need not be on the center line. You could move the case toward the side so as to interfere less than if in the center. Not the most ideal situation but a viable option. Lee boards are better than nothing but they are less efficient because they run in the boats wake and they also ventilate which diminishes efficiency.

If you are determined to avoid a centerboard, lee boards, or dagger, then consider putting some runners on the bottom that are parallel to the center line of the boat. Runners would consist of planks on edge such that they have a depth of 10 ....12 cm or so. Do not run them all the way forward so that they intersect the chine. Not too far aft either. The boat is already going to be difficult to tack because the bow will be so deeply immersed. Bottom runners also protect the bottom if you beach the boat. They will work better than the chine runners.

You are going to need a big rudder. The rudder itself will help with reducing leeway. It needs to be big for more than one reason. The other is that it might help get the boat to the next tack. The boat would normally pivot from a point somewhere near the centerboard if you had one. The process of pivoting causes the bow to swing more or less sideways as the boat goes around. The aft section also slides sideways when you turn, so take the skeg off. You have a lot of immersion at the bow so it will need some force to push it around. The rudder only works when the boat is moving so getting stuck in irons is not good. When you go to tack you can sometimes help the boat by moving yourself (your weight) far aft so as to raise the bow as much as is practical.

Sorry about all that unsolicited verbiage. I'm on your side here so I want the boat to please you when it is done.

 

Hello messabout,

I don't have the impression that people here are "picking", they give their opinion in a most sincere and polite way, as you did, which is highly appreciated.
Perhaps I want "too much" for "too little" boat,I mean, with only 10 ft to spare there isn't much room to keep it looking like a traditional sailboat, have a bunk, sitting headroom,cokpit,cabin,cook a hot meal,easy enough to trailer here, easy and cheap to build etc...etc....
Inspired by Matt Layden's Paradox I opted for a flat bottom with chine runners.
The free mind of a novice (like me) sees no problems in combining (stealing) idea's to reach the desired visual compromise without too much thinking of the technical aspects.
The skeg is a good example.I just wanted a skeg but have no clue if this is workable with chine runners, never asked myself the question why Paradox didn't have one.....
It will keep here on track before the wind but can imagine,after your explanation, that the skeg might interfere with tacking, I don't know.
Keep it or removing it, I don't know.

I can imagine that more bend in the bottom would be benefitial but how to combine that with a flat inside floor of at least 1.80 m and the pointy sailboat bow I wanted......without "distorting" the shape I had in mind, I have no clue.
Less rocker seemed the solution to me but probably at cost of performance.... the difference between a dreamer like me and the experience of the practicalist I guess...

Getting her on and of the trailer will be 99% of the time a one man job so the flat bottom will be easier....I guess.

I don't mind too much about performance but as one poster here said, she needs to be able to keep you out of dangerous situations.
Getting away from the shore for example can be helpfull to keep the boat,and yourself, in one piece.

I agree that she needs a a big rudder anyhow.

Thanks for your (appreciated) opinion.

 

A quick glance at the history of sail will convince you that most small to medium sailing vessels had alternate means of propulsion. For centuries, it was oars. The Cost Guard requires aboard, a paddle or oar or some propulsion in addition to sails.

Considering your excellent wood working skills, this is within your capabilities.
https://www.youtube.com/watch?v=dtv-5t8F29U

This would keep you off a lee shore or get you back home when becalmed.
Replaces your rudder, temporarily. Or maybe design it as an accessory attachment to your rudder, or...many possibilities.

 

Thanks yobarnacle for the link, I didn't know about it.
Looks an interesting alternative for oars....hmmmm....must get that grey jelly in my skull into thinking mode !!
First thought would be to try to find ways to use that power fin to double as a self steering vane....somehow. Never need the two at the same time I guess.

 

I also am impressed with the obvious speed achieved for the boat shown in youtube.

The wigglewaggle of the boats heading seems to me an energy waste and an annoyance.
I have been thinking about possible benefits of TWO of these FIN drives with the tillers connected by a flexible yet sem-rigid tube, fiberglass probably better than pvc.
Pushing and pulling fore and aft on the center of the tube would cause it to bend in an arc, thereby shortening the chord length between the tiller ends. This would cause the FINs to move outboard away from each other. Their side forces would be opposed, reducing or eliminating the yawing. Releasing pressure on the tube so it sprang straight or pulling it to center, straightens it, eliminating the arc and spreading the tillers and thus allowing the FINs to approach each other and the centerline of the boat, again counteracting each others side force. No or little wiggling of heading.
Maybe the FINs start off with a bit of toe in, so they flutter an equal amount either side of straight ahead. An eccentric cam, motor driven, could also operate the deflection into an arc and then straightening of the connecting tube. A simple roller in center of tube would be a low friction follower. Might require so little watts as to make solar cell power (as well as hand power) viable.

Pushing on the connection tube to bend it in an arc, might be more easily done with legs.

 

Indeed the boats seem to zig-zag a lot with this system but they move at amazing speed.
Perhaps that a noisy,stinking outboard is the simplest solution

Is there any "rule of thumb" to calculate the rudder area for a sailboat ? I know I need a "big" rudder but how big is big ?

 

Recommend check out some similar sized or slightly larger boat designs and copy rudder.

 

Spend a few bucks and get the book, AYRS #79,Rudder Design For Sailing Craft and you can't go wrong.
I did for my Buccaneer 24. I chose a transom mounted skeg rudder and it worked fine. See:- http://smalltrimarans.com/blog/?p=11744

 

Made a quick sketch of how my rudder might look. It's based on.....how I think it just looks right .... might be a technical disaster though.

 

That's a mighty nice looking trimaran Patrick !!!!
Remember as a young guy reading J.Wharram's book about his first Tongaroa.Tried to get more info about it but in the dark ages before the internet this wasn't as simple as I thought. Magazines where the only source of info and foreign magazines about sailing those odd looking sailboats simply weren't available overhere.
Managed to get a copy of that book many years later though.

I understand your approach oldsailor of buying books to get familiar with aspects of sailboat design but I'm not that kind of person. Knowing myself it would only lead to more doubt about what to use/do.
I enjoy "fiddling" around in my little chaos called my workshop without too much structure in the whole process.
Books and studying never was my kind of thing, watching someone doing something with his hands or solving a problem intrigued me since childhood.
Thanks for the link.

 

Epoxied the hull sides and the bottom in place.Coated the bottom with epoxy and added the chine runners.Flipped the boat over and start rough cutting the aft deck.
Will give the whole interior a coat of epoxy.
Looking at the pictures,the chine runners seem rather small although I kept about the same dimension as on Paradox,hmmmm.....