Desperate to sail 2015

Forgive me if I appeared dismissive of what you suggested. I greatly admire your ideas. It's just that I hope to accomplish many requirements with this boat: unstayed mast to allow for dipping lug, leeboards that don't require raising and lowering when tacking, yet easy to raise in seconds when approaching shallow waters, and the whole construction which could be rigged and removed from boat in 10-15 minutes (because I'll have to do this every day). That's why I'm still searching...

I updated the box design, most noticeably - increased distance between the bolts to decrease leverage ratio.

http://static.dyp.im/m8YL9Znhqp/9e45a52d7ea2a60435bbeb36b9765c63.JPG

But probably this won't change a lot, so I have an idea which I took from your design. What if I make leeboards boxes just like the ones in the screenshot, but take a rope and loop it around the boat, just in the height of the bottom leeboard box part? I could add some screws or something there so that the rope doesn't slide down. If tied tight enough (I have an 8mm low-stretch climbers rope of sufficient length), it would press the lower part of the box so tightly against the hull, so that even on the windward side the box could not be bent away by the leeboard forces.

Of course, the more obvious way would be tying these two boxes together UNDER the boat, instead of around (like sharpii2 suggested), but since I have no strap, the rope of such diameter would add too much water resistance.

What do you think of this idea? Is it still not strong enough?

 

The rope may or may not add a lot of resistance (drag). It is worth a try.

There are aircraft that have a deliberate ridge or hump on the wing so as to generate some turbulence at that particular point. The disturbed surface flow tends to re-attach itself to the wing, aft of the hump and that helps the overall lift for the wing. Those gadgets are often called "turbulators". It is highly unlikely that your rope will act in the same way as a turbulator. I just throw this in to suggest that sometimes what seems a disadvantage is not quite so bad after all.

 

Why couldn't you take two boards and put them across the gunnels, one on top and one underneath, drill a few holes through both of them, insert some bolts and tighten them up so they clamp unto the gunnels. Then you make a hole for the mast. Like this but using two boards and straight bolts.

Or make something like the picture. Then you just have to figure out a bottom step.

Do the same sort of contraption for some lee boards.


That way you can easily move them around to get them in the right position.

How much time do you have to do all this?

 

Sam,
this looks like what he drew from the start but with some nice iron angles. Consensus was that lateral forces would have too much leverage for the pivot. That old design would be enough for a canoe sail of 20 to 30 sf. I think he has more canvas in mind. How much? good question.

Laukejas,
I think a strap around the leeboards at least 8 inches down from the top mount would keep it from levering outward. It would be nice if the bottom of the leeboards braced against the hull.

OK here is the culmination of all the best advice in one; you are planning to do the unstayed mast support, and you could make the leeboards on pivots like you originally planned, but angle them inward so they brace against the hull and have a rope around the hull to keep them from deflecting away from the hull or fore-aft like on my concept. The last point is that the rope holding the boards in and upright does not have to be fixed, it can run through the bow eye then up over the bow into the cockpit where it is cleated. When you want the boards up, just uncleat the front and pull the aft rope. This would save you from having to build those leeboard boxes.

 

Hi Laukejas.

A few brief comments before I go.

1.) I don't think a dipping lug rig will work well for this boat, or on a lake with winds that vary in direction. The dipping lug rig is best for narrow boats which are heavy for their Beam, but not necessarily heavy for their length. Such boats have a lot of momentum and keep moving well, while the lug is dipped. The boat you have, with its utter lack of aft rocker and immersed transom, is likely to lose momentum quickly. Add to that winds that vary in direction and you may be bobbing around, struggling to change tacks, and being blown further and further down wind.

A standing lug will probably work best for you, as it is a good short tacking rig. In case you don't know, a standing lug has a yard that crosses the mast, just like its dipping lug cousin. The difference is that the lower forward corner of the sail attaches to the mast, not the bow of the boat.

2.) I have an idea for a Lee Board arrangement that might work for you and meets all your requirements, which are, IIRC:

a.) they have to be able to be retracted quickly, and
b.) they both have to be down at the same time.

This idea is a derivative of a system I used to turn a four man inflatable raft into a sailboat.

I don't have time to sketch it now, but I will tomorrow. It will be quite reliable and very easy to make. It will also work well with your mast step system.

 

Thank you all for so much information since my last post. There is definitely a lot to consider!

SamSam, the design you posted is beautiful and highly customizable (could be used by boats with various beam). However, I'm afraid that Skyak is right: for boat such as mine, and sail area of 60 square feet it might be not strong enough.

You asked how much time do I have. I will stay by this lake until 25th of this month. So, the sooner I finish the work, the sooner I can start actual sailing. If the rig proves it's worth, I could sail again next year (hopefully no one will steal this boat!)

Skyak, I really like your idea. It makes a lot of sense. Actually, I went ahead and made one of the leeboards. It took me something like 6 hours, but it is very smooth and strong. Reason why I did this now is because I want to varnish them with 3 layers, and time between new layer should be no less than 24 hours. So it will take me at least 3 days until they are usable - I could use that time making mast support or leeboard boxes.
I forgot to take a picture, I will post it in about 14 hours. But it looks like this:



I decided to go with design which could be compatible with leeboard box, or at least to allow for more options, as well as providing more area. With 28.5x100cm it has around .16m^2 (1.72ft^2) submerged area. Considering 5.5m^2 sail, this is 2.86% ratio, a bit below 3-3.5% (what is usually recommended).
Now call me lazy or tired, but I shudder from the thought of making another leeboard. I'm starting to think that maybe I should get along with one right now, and when I get on water, and see that if that is not enough, make another.
Also I calculated that I do not have enough materials to make two leeboard boxes.

Is my fear, that this leeboard alone might be too small to handle drift for that sail area, valid?

With this kind of design, maybe I do not need any screws at all. I could use the "handles" I made on the top of the leeboard by passing a line around them, and lashing it to the hull. The second support point would be as you suggested, Skyak - another line running lower. I'm a bit afraid to make that line go through bow eye - it might break it... And I'm not sure it won't jam. Some testing is in order. But anyways, it can be done.

Sharpii2, your point about dipping lug makes a lot of sense. You see, I wanted dipping lug at the first place because in my original design, mast was in the middle of the boat. I was afraid that the mast will divide sail in two on the bad tack, and the drag will be so bad that I won't make any windward distance on that tack. That's why I wanted to dip the sail. But with current design mast is much more forward, so maybe most of the sail will be aft of it, making bad tack not so bad.
You're suggesting standing lug - did you also had a boom in mind? I really like booms. Much more control over the sail shape. A bit of a headache, but still

I'd really like to see your idea, if you have time. Also, do you have photos of the raft? What you're saying is unheard of to me. I have paddled these rafts many times, and I can't imagine how in this world that could be possible, considering their unstable shape.



Tomorrow I'll continue working on the mast support and the mast itself. So I still have some time before I decided how to fix the leeboard.
There will be one another day for making the sail.

 

Don't forget flotation, it looks like it will sink if it turns over.

 

One more thing. While googling, I came upon this:

http://freepages.genealogy.rootsweb.ancestry.com/~fassitt/canoe_mirror/manning/manning_leeboard_2.gif

Also looks like a very interesting design. Such a leeboard should work on both tacks also, correct?

Sharpii2, I forgot to ask - what about balanced lug instead of standing? I heard it has advantage of being self-vanging, while standing one handles gust better, and has more windward potential. Is that true?

 

Sorry, I didn't catch you, what exactly will sink?

 

hey Laukejas,

I caught your thread late as I have been traveling. That last image of a lashed lee board is an excellent means to adapt to your project. do not worry too much about the lee board size, rule for small boats is about 5 percent of sail area, but it could be both larger or samller and still work fine. I also suggest you consider a cord going under the hull between the lee boards if you can not make them strudy enough by just attaching them at the top, at the speeds you will be going the extra drag will not be signinficant anyway (it is not like that hull design will be very fast under sail anyway). Strength of the lee board installation is more important than a low drag design. you can reduce the drag some by rounding the leading edges of the lee boards and the rudder.

Although the lug rig is simple, I have found that they are not very controllable. I do not care for them, particularly if they are hastily made. I suggest you consider the lateen rig or a simple modified junk rig. both of these will give good performance without needing to be optimized for camber/shape, and they are easy to single hand and control. They also resist flogging and can be dropped quickly. The forces on them are relatively low so you can get by with a shorter cantilevered mast.

On your mast question, if it will be unstayed the max stress occurs at the base, and you can taper it uniformly down to about half the dia at the top.

I look forward to following this years project.

 

It does indeed look designed to be used as a single lee board to handle both tacks. Adding upward projection and the prop pole going to the other side is what makes it capable of handling forces either way.

 

Petros! I have been waiting for you So glad you could join in.

You see, the last image... This is a very good design, yes, but I have already made my leeboards, and they lack the upper "handle" like in that image. I could glue and screw on another plank, but the leeboard is already done and varnished, so I don't want to mess it up...

Here is my leeboard:

http://www.boatdesign.net/forums/attachment.php?attachmentid=93308&stc=1&d=1406977379

I really don't see how can I adjust it for this system... It's a pity I didn't find this one earlier. I would have left myself at least one 150cm board, then it would be possible. But all I have are 100cm, just like the ones my leeboard is made out of.

Do you see how can I adjust my leeboard to make system like in that drawing? I want as much of the leeboard in the water as possible...

 

One more quick question: I started working on the mast today, thinning it with hand plane (I'm not in hurry to shorten the mast, since I can do this anytime), and noticed that it is not very straight - it leans to one side a bit, but worse, there are sections that are bent out quite a bit. If I were to straighten it with hand plane, diameter would be dangerously small in some places.
How can I straighten out these sections without thinning? I know there is a method with boiled water, but the mast is really big, and I certainly don't have this option. Would placing it on the ground and applying weights on these curved sections for some time work?

 

The boat. Without flotation, fiberglass sinks.

 

There ain't anything I can do about it, Sam. I think this boat has some buoyancy tanks, but not much. I can't add anything, I simply don't have the materials. I guess I'll just have to be careful.

P.S. Even one more question about the mast. I'm thinking of varnishing it when it's done. Is that a good idea?