My own design

Hi everybody:

I just decided to post a design I drew up on my computer. I drew it up over a five year period as I tried to master a computer drafting program. It took me this long because 1.) I would get frustrated then quit and 2.) I wanted to make as complete construction drawings as I could. I ended up with 18 sheets of them. The sheets, however, are small. Only 8.5 by 11in. The reason for this is to make them easy to copy, easy to mail, and easy to handle in a small shop.

The boat in question is a 3 by 12ft, deep rockered scow, that is meant to sail in small lakes and bays and to act as a low intensity trainer to introduce new, non super jock types to sailing. I wanted it to be safe enough to send a seven year old out in on a warm day when the water was warm as well.

When knocked down, it is supposed to fill up with water but not flip over. Ballast and floatation are arranged so when the gust is over or the sheets released, the boat will level itself so the sailor can bail it out and get back under way without outside help. It is meant for someone who has only seen pictures of a sailboat to be able master without coaching

It is also designed to be worked off a sandy beach with no dock, pier,or warf in sight. And it was designed to be buildable by someone from the ten thumbs school of boat building such as myself

I am now going to try to attatch the presentation drawing. (drum roll)

Bob

 

My own design 2

O.K. I'm going to try to post it as a jpeg now. (drum roll)

 

First and only question Sharpii2 - does it fulfill your expectations. If so - congratulations. It fills a long felt niche - an as-safe-as-dammit sailing craft for the young and inexperienced.
Great stuff.

 

Simple, functional, fits your needs, perfect!

 

Good stuff! I've been struggling with Auto Cad for a few years off and on, congratulations!

When do we get to see a photo of one in the water?

 

Totally irrelevant - but another similar quote (by an anonymous bureacrat) is: "Well it works in practise... But will it work in theory..."

 

I honestly don't know. I am rerally wanting to build a prototype to make sure it works in practice. I have little doubt about the hull shape or the sails.

Its the steering system, the unigue (at least for me) 'short sweep' auxilliary system, and the placement of the side mounted dagger board that has me worried.

The boat was really designed for my own use. I'm really in to hassle free sailing and I designed the rig to be most useful when the wind is blowing good. A boat this small would be a real hassle to reef while under way. The sail will most likely have one reef point, though, so I can go out on really windy days. The hull is meant to be driven hard. And it will have some heavy framing to prove it. I once had a Super Snark out on a 30kt day. It made a rooster tail!

For its type, it will be a heavy boat. It will weigh in at about 165lbs with just the hull and rig. And its ballast box will hold up to 75lbs in sand bags. The ballast box will usually be empty. Its main purpose is for when the boat is used by small women and children.

I hope to have the boat built by the time of my godson's 7th birthday. If I have it built by then, my only fear is that then I'll have build another one.

Bob

 

You might try building a model first.

I assume you intend for the boat to sailed flat (no heel), the offset dagger board should not be a problem. Leeboards have worked for years.

 

Sharpii - try a simple roller reef. For a craft that size hunt around a junk shop or recycling area for an old roller blind of the appropriate size. Scrap the material - keep the roller 'boom'. Reefing will then be a matter of a 'cord' tug away....

 

Thanks for the advice RH.

I Plan on building a 2ft model that will displace around two pounds.

As for the offset dagger board, I have calculated that with the windward chine just touching the surface, there will still be enough area to do the job. At that point, the WL which is 8 to 9ft will increase to 10 to 11ft, depending on load carried.

When I did the stability calcs for this, I was surprised at how far the windward chine would come out of the water before the transom immersed. Both the rudder blade and the dagger board had to be lengthened substantially.

As for leeboards. Been there, done that. In order to work properly they need to be weighted. If the boat were 4 by 16ft, I may have considered them. As it is, with my 200lb butt on board, It is kind of like King Kong on a small tug boat. Everything will work best if I just sit still.

As for roller reefing, done that too. Slab reefing the sail on shore seems to be the most practical (cheap) solution. I'm also trying to keep cost and complexity down.

Thanks again, everybody, for your comments.

Bob

 

Sharpii2;
I've been fooling with scows and sharpie type skiffs for a long time. Your little scow is about as simple as it can be made. Boats with shapes like that sail best and fastest when heeled. You can probably improve the design some by pinching the bow and transom in toward the center line. Not for esthetics but for the benefit of the underwater part when heeled.

Pay some attention to the section centroids. Boats like this usually align the centroid centers at about 15 degrees of heel. If they are not aligned you will have either weather or lee helm. Lee helm at low angles and weather helm at angles above the optimum.

Keep the boat light and use less sail area. Then reefing will be less problematic. My own opinion is that the use of ballast on a boat as small as this is a felony. I think it'll work better if you give it a bit more midship beam and leave the ballast ashore.

Best of luck. The little boat is cute, simple, and it will be great fun when sorted out.

 

your design

Looks like fun to me! If you could make the model 4' or a little bigger it might be more help and the radio stuff wouldn't be as high a proportion of weight- assuming you make it rc .
Good luck and good sailing!

 

Good looking boat Bob!

Yoav

 

Thanks for your measured critisism.

Just about every point you mentioned, I have thought about.

With fore and aft curve in the sides, the boat would definitely sail better. But that would come at the cost of increasing the beam to make up for not only lost displacement in the ends but lost righting moment there too. The biggest loss, though, would be loss of construction simplicity. There is no way that I can concieve that the boat could be built with curved sides without having to first set up some kind of strong back structure to keep everything in aligment.
I would also have to have either an internal daggerboard slot or a much more complicated leeboard arangement.

I do expect to have some lee helm due to how the water will go around the heeled boat. You are absolutely right about that. I am expecting to have some negative lead to make up for it. If there is any lee helm, I expect it to be modest.

I disagree with you about the ballast. First off, the ballast will be used only with underweight skippers. It will come in the form of sand bags which have relatively low specific gravity and are very easy to put in place and remove.
I find them necessary to keep the boat's minimum displacement around 300lbs. If the boat sails too high in the water, it will become a large rocking horse with sails. The wind will blow it around and the rudder will often come out of the water. Making the sides curved and reducing the rocker drasticly would have dealt with that problem nicely. The boat then would be light for its beam and would stop short at just about every ripple it hit. It would need a bigger rig to compensate and would then be yet another clone of the ubiquious light sailing dinghy.

My goals were different than that. I wanted a boat that was both simple and sure footed. One that would not turtle if capsized. And one that would have no trouble comming about. One that was relaxing rather than exciting to sail.
I would also like to be able to put two of them on a snow mobile trailer, so when I took a friend sailing that friend would have a boat of thier own to skipper.

I have, howeveer decide to change the leeboard arangement. Instead of having one board going through a rack, I have decided to go with two pivoting leeboards. This could cut the sailing draft considerably and make the boat able to hit underwater obsrtructions without fear of dammage. The leeboards will be held down with bungee cords.

Thanks again for your comments.

Bob

 

Sharpiie2
Your reply to my post respectfully acknowledged. Please know that I had no intention of criticizing your project. The only intent was constructive.

If you build the boat from plywood. there will be no problem to pinch the ends a bit. The project can be done stitch and glue fashion quickly. Bringing the ends in to about 60% of the max beam will not affect righting moment enough to say grace over. Some of the Gurus say that two thirds of the righting moment is created by the middle third of the boat.

If you leave the sides plumb and parallel, as drawn, you won't even need stitching. This is about the easiest build I can think of. Your design has merit, as is, that I am coming to terms with. As a matter of fact, I'd like to exchange notes with you about dimension etc. Maybe I'll build one too. I have to draw the line before we get to the lug rig however. I once got bashed by a lug yard when the halyard let go.

Are you familiar with Mike O'briens "six Hour canoe" ? He has whomped up the most simple canoe like boat that can be imagined. It can probably be built in six hours but that does not count finish work. Your scow trumps his canoe for easy build.

On the subject of lee boards, I can recommend Phil Bolgers method. The board is attached only by a short length of rope. It pivots perfectly and will wing out when on the weather side. That means that you can simply ignore the one not in use. That satisfies the "relaxing rather than exciting" part. In addition the board can be brought aboard by simply flipping it up over the gunnel. Simplicity is beautiful.

Bolger has been way into this simple is beautiful concept for ages. He has several little designs that are somewhat similar to yours. Among them are Brick, Micro, and Old Shoe. I once sailed an Old Shoe on a breezy day. It was way faster than imagined and gave the Laser guys some trouble. The Lasers were over powered but the God awful ugly Old Shoe was not. Alas the Old Shoe had 200 pounds of ballast and would literally fly to windward. On that day ballast was NOT a felony.


Regards
Gene