Kotik, Kotik, Kotik!

[IanMilne]

Re: Kotik, Kotik, Kotik!

Thanks for those thoughts, guys.
I have decided to glue a piece of oak along the bottom of the block, with a s/bronze 100 x 6mm bolt (long thread) screwed up on each side of the pivot bolt. I have just ordered the bolts.
I have weighed the whole centreboard this morning. In its present state it is 45kg. The pivot bolt is 20mm (3/4") stainless steel 316. The top end of the board will remain square and be a fairly close fit in the case. Should be good.
Cheers all,
Ian

[Daniel Noyes]

Re: Kotik, Kotik, Kotik!

I think the 1/2" pin cantilevered off the main ballast should be more than adequate to hold up that 23kg board.

I think you are right, all the strength of the board as far as lateral pressure should be held by the box, not the bolt... especially if the bolt hole through the board is a tad oversize, then the bolt is just there to capture one end of the board and keep it from falling out of the box all together...


I just was thinking it is an odd way to hang a centerboard... was this done to simplify the casting of the ballast keel by eliminating the need for a slot in it? and why not have the centerboard pivot up inside the hull, even if it is an off center board... ?

guess it's a little late to be asking this now... gorgeous job on the build, looking forward to seeing the interior come together.

[skaraborgcraft]

Re: Kotik, Kotik, Kotik!

I just was thinking it is an odd way to hang a centerboard... was this done to simplify the casting of the ballast keel by eliminating the need for a slot in it? and why not have the centerboard pivot up inside the hull, even if it is an off center board... ?

It keeps the simplicity of fabricating a ballast casting, but more importantlt, in my mind at least, it allows all the backbone of the boat to stay solid, and also raises the slot from the very bottom of the keel, so is more unlikely to jam the slot with mud and stones.

[Daniel Noyes]

Re: Kotik, Kotik, Kotik!

It keeps the simplicity of fabricating a ballast casting, but more importantlt, in my mind at least, it allows all the backbone of the boat to stay solid, and also raises the slot from the very bottom of the keel, so is more unlikely to jam the slot with mud and stones.

sure, all legitimate reasons for an off center board... my questions were about the reasoning for placing the pivot point of the board on the exterior of the hull... I have seen several centerboards that drop past a keel rather than through it, but have never seen one of those boards pivoted on a pin and appendage exterior to the hull.

[IanMilne]

Re: Kotik, Kotik, Kotik!

Thanks, Daniel. Glad you like the build so far. Ian (skara) gives three of the reasons why I like this centreboard arrangement. Another one is that it allows for a wide bench/quarter-berth/whatever on the same side as the case and a decent walkway down the middle of the boat to the forward cabin which I plan to have, forward of station 4, as shown in the plan above which Dirc has provided. I also like the idea of having the pivot bolt below the hull. (It will have a nylock nut on it.) I will take your advice and make the pivot hole in the board a slack fit on the bolt.

Here is what I have done today:
Stripped some paint,


shaped a piece of oak,


and dry-fitted it, with temporary screws. I expect the bolts tomorrow.


I will be happy with this arrangement.

And while we're here, here is a better photo of the patterns for my rudder fittings and chain plates. The foundryman will make pins out of bronze rod and cast them into the pintles. I will drill the gudgeon holes in the castings. (Yes, I will clamp them down firmly.) I will take the patterns to the foundry this week.


That's all. Thanks for the discussion.

Ian

[IanMilne]

Re: Kotik, Kotik, Kotik!

Daniel, I see your point about having the pivot inside the hull rather than below it. Then you wouldn't need the block on the outside, which would be good too. I can only say that this is the way Iain has designed it.
Ian

[peb]

In addition to W the reasons Ian has pointed out, having the pin external to the boat keeps the centerboard case lower inside and also removes any potential leaks with the pin. . Of course it adds drag, but overall I like the arrangement.


Sent from my F3113 using Tapatalk

[stromborg]

Re: Kotik, Kotik, Kotik!

I went back to page 5 because I could not remember how the CB nubbin was installed





I still think it whole arrangement is probably just fine but I also know that you will always be thinking about it if something isn't done. Here is an idea:

Do you have enough bolt length to put a strip of silicon bronze 1/4" x 1" x NL (nubbin length) under the bolt heads to act as a big rectangular washer/reinforcement plate?

[IanMilne]

Re: Kotik, Kotik, Kotik!

Thanks, peb, and Steve. You're right about it lowering the case, too. The leading edge of the board will still be 3 or 4" below the garboard when it is retracted. I don't mind that. There will a bit of drag from that and the block (nubbin?) but the motor will be on the same side so it won't be pushing me round in circles! The idea of a plate between the heads of those big bolts is what Ian (skaraborgcraft) was meaning in post #219. You can see that there is plenty of length on the bolts. I thought of that too, but I can't locate any suitably small piece of bronze plate and I don't know how I would get those bolts out to do it. Maybe by heating them with a gas bottle flame thrower, preferably without setting the boat on fire....
Anyway, I think we can leave this subject now. Thanks for all your ideas. My new bolts have arrived, so I will get off my computer and go and do some work!
Ian

[IanMilne]

Re: Kotik, Kotik, Kotik!

Well, here is that "nubbin" thing you were all waiting to see, two bolts used as drifts, some fairing, a coat of epoxy and five coats of paint later.


While the coats of paint were drying, I carried on with the off-centreboard. After I had glued the main body together and planed the faces of it flat, we tried it in the case. OK so far.


Here it is showing the copper rods to go in as drifts. It has three rods with washers and nuts through the width of it.


Gluing the top end on. The pivot hole is filled with high-density filler.


I shaped the sides as much as I can before I put the lead and the bottom end on. I made a boo-boo. The larger of the two holes is the correct one. The other one will get filled. This is for the lanyard which will come over the sheave set in the top of the case and aft to a trailer-winch of some sort. The plans give no details. See, I do make shavings now and then.

This plane was the most useful tool for the job. It is an old Stanley Record, No. 04 1/2. It is quite wide and has a good heft to it.


I will drill the lead and complete the assembly tomorrow.

Cheers, Ian

[IanMilne]

Re: Kotik, Kotik, Kotik!

And here is the current state of my workshop. We have brought Sooty Tern Trondra in temporarily. The Kotik trailer will get some modifications in due course. I intend to paint the Kotik's sheerstrake with the same green paint as on the Sooty Tern.


Ian

[Thad]

Re: Kotik, Kotik, Kotik!

A fine pair there, Ian!

[IanMilne]

Re: Kotik, Kotik, Kotik!

Thanks, Thad.

[skaraborgcraft]

Re: Kotik, Kotik, Kotik!

Thats a nice shade of green too. The family resemblance is clear to see.

[IanMilne]

Re: Kotik, Kotik, Kotik!

Thanks, Ian. Yes, I like the family resemblance too. Here's another pair, with no family resemblance at all.

This was my 17ft Swampscott dory Clarsach, that I had from 1993 to about five years ago. Those were my "sail and oar" camping days, with a bit of overlap with my kayaking (sigh). She was the Dion dory out of The Dory Book, with seam-batten construction. I didn't build her, but did her up in 1999. She was a great boat (still is, I hope).
The red one, as you probably realise, was my Eun na Mara canoe-yawl, Islesburgh.

I glued up the rest of the Kotik centreboard today, with the big block of lead, copper rods and all. I have to admit I'm glad that's done now. I can finish shaping it up tomorrow. I'm slowing down a bit now. Winter has arrived.

Cheers,
Ian