Desperate to sail 2015

The mast step of a stayed mast has forces that are primarily downward. A board with high friction rubber under it will not move. Similarly a clamp with rubber under it to protect finish will not slip. Or more specificly you should be able to get friction force of 60 to 70% of the clamping force.

Another trick in a pinch is to use hot glue -or any glue that can be removed easily -it can add lots of shear strength.

 

It depends on the wood. White oak would be fine. At any rate it will most likely bend severely before it breaks so if it bends an ugly amount you should ease up on the sheet. It will give plenty of warning before breaking.

 

It's actually a simple pine in my case. Okay, if you say it's enough, I'll go with narrowing the mast.

Have to go sleep now. I will reach the boat tomorrow, take pictures and get back here again.

Thanks for support!

 

You said you were desperate to sail. My claim would be that if we only had a week I could make this one and start sailing miles, and you would be hard pressed to make a better sail boat that would pass my mileage in the week.

This is the rig you build for your dingy when your yacht sinks in the middle of the ocean.

 

Skyaks suggestion about using a back stay is the most simple of solutions. Let us hope that the boat has some handles or some feature that would allow tying off a simple back stay.

I'd also use a fore stay so that the back stay will always remain sufficiently tight to counter the mast forces. In a perfect world you would use wire stays, but if using rope, then you may have to adjust it from time to time because the rope will stretch when stressed.

 

Hi Laukejas.

Looked at your original drawings.

The Lee Board structure looks way too weak.

The board to windward is going to want to pivot outward. It will have at least ½ meter to 2 cm of leverage. That is a 25:1 mechanical advantage.

Also, the bracing you show to support an un-stayed mast assumes a certain depth of hull. If the hull is actually deeper, no problem. If it is shallower, a lot of cutting and cursing is in store.

Below, I have a sketch that I’m pretty sure would work (see attachment).

The mast sits on a fore and aft piece, which in turn sits on two cross pieces. These cross pieces are intentionally drawn wider than the boat. Stays, which hold up the mast, are attached to their ends.

The cross pieces are held on to the boat by bridle lines which pass beneath the hull and are cinched up tight with a lanyard on one end. This is about the strongest way to attach it to the hull, without clear attachment points on the hull, as it puts the hull along this line under compression, which is the force it is designed to take. This bridle could be a line, but it is best as a strap of some sort, such as seat belt webbing.

The structure must be placed on the boat so the forward cross beam is forward of the boats Max Beam and the aft beam is aft it. This way the shape of the boat itself will keep the structure from sliding forward or aft.

The Lee Boards sit on fore and aft pieces that are near the ends of cross pieces. Each Lee Board has a 4 x4 cm flange that is slightly longer than the board itself. These flanges sit on top of the fore and aft pieces just mentioned. They are held in place with a line on one end and an elastic cord (see dotted line) on the other. They are free to pivot outward and the elastic cord insures against the Lee Boards hitting underwater obstacles.

The Lee Boards are drawn with a 1:12 aft rake. This is in anticipation of the boat having a sheer line that is higher in the bow than the stern, which will cause the structure to sit on the boat, tilted aft.

The Lee Boards should a piece mounted to them which will but up against the hull. This piece is not shown as it should probably be designed on site. This piece will help hold the Lee Board more or less vertical and parallel to the boat’s center line.

 

All right, I arrived at the place. Took a look at the boat. As expected, it is completely different from what I expected. At 3.1m LOA (and waterline of around 3m) this fiberglass fishing boat appears to have been designed with engine in mind (flat bottom and 90 degree stern plate, looks like planning arrangement). There are, however, reinforced holes for oars. Boat doesn't look new, but not worn as well. It has some strange deck lines whose purpose remains a mystery to me.

Please, take a look at these photos. And don't mind the oar. Boat's owner said he will bring new ones tomorrow.

http://www.boatdesign.net/forums/attachment.php?attachmentid=93204&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93205&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93206&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93207&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93208&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93209&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93210&stc=1&d=1406668276
http://www.boatdesign.net/forums/attachment.php?attachmentid=93212&stc=1&d=1406668276


Obviously none of my previous designs will work. I brought a chair, and sat at the boat for an hour or two. Finally, it appeared to me that the best arrangement here would be unstayed mast with following arrangement:

1. Cut a plank that fits horizontally onto the floor just in front of the seat, lying parallel from it (and perpendicular to the keel). It would naturally have no tendency to move sideways or backwards (because of boat sides and the seat). In the center of it, make a hole or some sort of plug for the mast to fit in.
2. Place two parallel 40x40mm beams on top of the rails, connected with short cross-beams to connect them. There would also be two short cross-beams in the center between those two beams, making a rectangular hole for the mast.
3. These two beams would have a sideways lying U-shape with a clamp on each end, so that the whole structure could be "slided" from the bow on these extended surfaces on the sides of the boat. When in place, they would be clamped tight with those clamps. This way, it would have no way to move in any direction, except slide more aft or back to bow if clamp friction force would be overcome by mast forces.
4. Additionally, there would be a beam on each side, lying on these extended rail surfaces from the oar mounting point (screwed into the hole), and connecting to aforementioned parallel beams which hold the mast. This way, it would finally prevent them from sliding back and forth.
5. Leeboards could then be added at any place along those beams.
6. If needed, stays could be added at any place here, however I hope I can do without them.

I know this is very difficult to imagine, so I'm making a quick sketch with CAD to show it.


sharpii2, thank you for such extended description with an actual sketch. It's unfortunate that you did it right before I'm posting images of the boat. What you suggested would definitely work, but it looks very complicated, it would take a lot of space onboard, and I'm afraid it might be not possible to row if wind were to calm.
However, your leeboards make much more sense than mine. I didn't understand your explanation about mounting them, but it seems that your leeboards wouldn't be retractable. I need them retractable AND working on both tacks. Is that possible with single attachment point?

 

Okay, I've done rough model with CAD. Here is the screenshot:

http://static.dyp.im/kYeDD1PoAz/cf7888ba59b1557822ec45593c37a1c0.JPG

Some details aren't done, but this is the basic thing. Does it look strong enough? These are clamps on each side of double cross-beam, and the other beams which lie on rails are to prevent slipping forwards or backwards.

I have doubts about mast step - maybe I could extend a beam towards the bow - it would be a very strong support. I could also join the double cross-beam to it, if needed. Will try to model tomorrow.

But with current arrangement, how does it look? Is the principal idea worth a dime?

P.S. The leeboards here could be attached to that beam which lies on the rail at any point. I only wish to make it retractable/turnable for shallow waters, and strong enough to work on both tacks. Any ideas on that?

 

If I were in your position I would use rope as stays from the bow eye and the two oarlocks. With the mast step right in front of the seat it will be secure for a small sloop rig. For leeboards I would put short ones strapped tight against the hull attached to a board under the rail. The hull already has a sharp chine and lets be honest, this is not going to be high performance. Poor leeboards might be worse than none at all. Sharpii's point is valid.

The boat is a POS that was painted just before you arrived. See if there is any matching paint left (looks like they ran out) or if you can get some to match. If you can get it and some auto body filler you can do anything, fix and paint before you leave.

 

I agree, this won't be high performance. I don't need much speed, I just need decent upwind performance - I hate spending 3 hours getting to upwind destination and going back in 10 minutes.

Good eyes, Skyak! Indeed, this boat was painted a week before I arrived. I forgot to mention it.

Today I started with the easiest part (to try out what works and what not) - rudder (oar) attachment point. Here is the result:

http://static.dyp.im/DfarCA5665/6d232146259fd8476dcf25c894dd1b4b.jpg

This clamp holds so tightly that I can almost lift the boat by it. I know it has only one axis, but with boards so thick and the screws so large, it works. I also drilled a hole for oar - tried it and it fits perfectly.

Learned many things in the process - like if I rev up the drill too much, and the wood starts to smoke, it will become so hard that nothing is going to drill through it anymore... Or that the jigsaw cannot cut at an angle (or maybe I don't know how?)

I talked with boat's owner, and he allowed me to drill one or two holes on the deck, as long as they are above waterline.
So I drilled four. On the rails, just in front of the center seat. Two cross beams will be screwed to these holes, and the mast will fit in between these beams.
For additional support, I'll make some more beams to prevent mast from falling forwards.

Here is the foto earlier today where I placed all the timber in the arrangement to show my idea (they aren't cut to length yet):

http://static.dyp.im/HWo9J4FYHA/cb59dee7ae525898c0daf78d34fb939a.jpg

The mast step board will be shorted, and will feature a U shaped mast fitting point, as well as door hinges for diagonal and longitudinal beams.

These two beams which lie on the rails are meant for leeboards.

How does this look to you?



Skyak, what did you mean by " For leeboards I would put short ones strapped tight against the hull attached to a board under the rail."? I can't visualize it.

P.S. You suggested stays several times. I want to try out dipping lug - I even have an idea of a dipping lug with boom, which I need to check out. Is it possible to combine stays with such rig?

 

I don't have much time but attached is a sketch of how three boards strapped under the rail could give you all the mounts you need for a stayed rig including leeboards.

Most jigsaws have a foot that is held by a screw in a round fitting. Loosen the screw and the foot tilts to any angle.

A lug sail can work on a stayed mast but it's rotation will be limited by the stays. This is not a problem if the upper yard is well below the point (at the top) that the stays attach to. If the upper stay swings 45 deg to each side that should be plenty.

About your unstayed mast support; If the boards are bolted to each rail and the forward deck it works. Could you save a lot of boards by just screwing the mast step to the seat pedestal and have no boards needed to hold it?

 

Thank you, Skyak. I really appreciate the effort and time you give to help me out. The sketch is clear. It is really interesting approach, very astute and simple. Only I don't see what would hold the boards if the windward leeboard would try to pivot out... The transom mounted board is pretty far away - I guess the board would twist... Or maybe I misunderstood something.

About the lug - yes, but I said dipping lug. The yard needs to swing all around the mast - I can't see that happening with stays...

I will check out the jigsaw tomorrow morning, but as much as I saw, the blade can be only tilted along the cut axis, not perpendicular to it...

A quick sketch of what I mean "cutting at an angle".



This is front view. Blue is the jigsaw, black is the plank, red is the saw itself. The saw is moving "away", not left or right.

 

About my sketch -if the windward leeboard pulls away from the hull I would attach the rope or strap around the hull lower or add a strap lower. In practice the short upwind leeboard will tend to be out of the water when there is any wind force. Another thought is that the leeboards might best be very low aspect, say 6 inches below the bottom and two feet long.

About the jigsaw; look at the bottom of the foot. Is there one screw head holding the foot? Loosen that screw and the foot will rotate to cut at an angle. This is how all the jigsaws I have owned work. The blade movement relative to the motor and handle is always the same. Only the foot moves.

Of course you are right that the lug can not rotate around a stayed mast.

 

I see... Well, but your design relies heavily on stays. I have nothing against them, but I would really want to make without them this time. If it doesn't work, I'll add them. Anyways, your design makes sense. I think I can take some ideas from it.

The friend I mentioned earlier advised me to make boxes for leeboards as well. I'm starting to thing that maybe this is for the best... Very complex thing to do, but at least I'll have no doubts if I hit the storm.

I modeled it with CAD again. I calculated it, and I think I still have enough materials to actually make this. Maybe there is a better, simpler design, I don't know. If you have suggestions, my ears are all open

http://static.dyp.im/cL23jYB9dV/06557e26c9cded124fe8340265eb7e13.JPG
http://static.dyp.im/FfCl2uwrSB/550e8ea19195ef89636bca834aa941c5.JPG

 

I understand and accept this is your design -I would have it no other way. But when such a question is asked I consider it a challenge. Asked and answered.

About your lee board holder; the leverage of the forces on the leeboard outward (leeboard on windward side) is too great. Similar to the problem you just pointed out on my last sketch. And I am sure your answer is that the board will never be on the upwind side. If not the leverage (>10:1) will pull the bolts through the wood.

My best suggestions are still the boards strapped under the rim and no board at all, just the chine.

Paradox is an example of a flat bottom boat with no boards and a lug rig.

https://www.youtube.com/watch?v=R7dziswouKA