Bobstay location?

[chainyank]

Hello, as I get ready for the spring the time has come to mount the clip for the bobstay, for the bowsprit, on the stem of my kosterboat. What is the standard rule? Waterline, middle of waterline, under, over, etc? I have done the seach, even did a google pictures run. There seems to be no ryhme or reason. Any ideas?

[Bob Cleek]

Just above the waterline. If you have to work on it, there's no point in having to do so underwater! While it will get wet under way, obviously, it doesn't hurt to have it out of the water when the boat is berthed, either. You avoid corrosion to some extent (particularly with stainless) when it's dry and it's one less protrubance for critters like barnacles to grow on.

[chainyank]

sounds reasonable. it seems to always hover around the waterline.

the hardware for the bobstay that came with the boat was stainless, so one more reason to listen to what you are saying Bob.

I am painting the waterline now (bootstrip), it is about 8 cm wide, so I could have it in the white or just above. You are suggesting to have it just above the "white", or should it be painted in, or because it is stainless, it should be above, and unpainted? Sorry to be so specific, but is good to have it clear for me, and for everyone searching for "Bobstay hardware" or "bobstay location" in the search! But again it sounds like you have a very good point.

Does anyone else have something to add or is it decided?

[Bob Cleek]

By "waterline," I meant the line where the water ends and the sky begins when the boat is in the water. Where you paint the bootstripe isn't going to have much effect on that! LOL

Actually, if you have a choice, I'd say mount the terminal point just above your bootstripe for asthetic reasons. I'd think it would be less noticeable than if it were in the middle of the contrasting bootstripe color. That said, out of the water when the boat is floating in still water is the place you want it. More than one bobstay, bowsprit, headstay, and mast, have gone overboard when a stainless bobstay shackle beneath the waterline failed due to anaerobic crevice corrosion.

[Wooden Boat Fittings]

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A bit above the waterline is certainly right. I'd put it at the top of the bootstripe. (You are putting some sheer into that by the way aren't you, not having it parallel to the waterline?)

Mike
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[seo]

/Users/SEO/Pictures/iPhoto Library/Modified/2007/Sep 18, 2007/DSC04249.JPG

[Cullen T.M. McGough]

I'd take a good hard look at how the pieces of the stem are assembled, and put the through-bolt in the most advantageous position to take strain, waterline be damned.

Let's not forget the point of the bobstay is to steady the top of the mast. All other things being equal, go lower. (Wider angle, better leverage)

http://www.camphawthorne.org/finn/IMGP0296.jpg

[Vinny&Shawn]

Most bobstay hardware attach's at the LWL,this is in the vicinity of the stem and forefoot scarf, sometimes there is a stem knee at this point. Depending on the cast of the fitting,it would be bolted through the scarf and helps in holding it together.(this is also a point of strength). Other hardware are strapped from both sides of the stem and screwed or bolted athwart-ship. This is a wooden boat?
Cullen McGough,is right look at what lies behind the stem, depending on how the boat was built,put your hardware in a place where it will do the most good.

[chainyank]

I didn't realize all the minutia in this issue, good to get it out into the open.

Yes Bob, the waterline, is dependent on, er water, but the boat is out of the water now, so I though of planning ahead. With the bootstrip being over the "actual line of water" I figure it would be somewhere in it, or above.

Cullen, the boat is a Kosterboat, and the bowsprit is set to the side of the stem, and the forestay is set into the stem, and supports the mast 100% of the time, and the bowsprit adds support when in place, but of course you are right about thinking of the structure of the stem in thinking of the location of the bobstay.

Here is a good shot of the bow:
http://farm4.static.flickr.com/3539/3288313965_6b5f3ecd66.jpg?v=0

The beam leaning into the seam hits about where the old mount sat, but there was damage an a new piece was scarfed in by the previous owner, and a new location may need to be found. There is no knee in this area of the stem, and the main scraf is a good foot away. The hardware is just a piece of stainless bent into a V and is bolted with two through bolts through the stem. It ain't pretty but its what came with the boat...

The bootstrip extends down from the top of the "dark area, below the clear finished area, about 10 cm along the stem, so that is why I thought of maybe moving the new location out of the repair scarf, and into the whites of the bootstrip. ONE MORE note, is that the entire stem got an additional 3/4inch oak lam, and a stainless strap over its entire length, so that scarf is tucked in pretty good.... well have a look at the pic, if you go to flickr you can even get a bigger version if you so choose. Sorry I go so wordy, but...

[Wooden Boat Fittings]

Let's not forget the point of the bobstay is to steady the top of the mast. All other things being equal, go lower. (Wider angle, better leverage)

This is quite right. From a strictly engineering point of view the "best" place is where the bobstay is tangent to the stem, so the longer the bowsprit the lower should be the bobstay fitting.

Also strictly speaking (and all other things still being equal,) the fitting itself should be fastened to the stem as near as possible in line with the bobstay.

Neither of these criteria is necessarily easily achievable though, and all other things aren't necessarily equal either. While the fitting obviously can't be below the tangent point, it can be somewhat above it without much detriment, and unless your stem has been shonkily built any part of it in the vicinity of the tangent point should be quite strong enough to take the load likely to be imposed on it. (If you're in any doubt, you can strengthen the stem with more internal wood and/or bolt sideways through it as you would fit a rudder pintle, rather than fastening fore-and-aft as with an ordinary bobstay plate or an eye-bolt. )

Moreover, imagine the extreme of a plumb stem with a square forefoot. If you adhered to the criteria the bobstay fitting would be well below the waterline. While an occasional dunking is one thing, I wouldn't want the lower end of my bobstay to be submerged all the time (especially if it were stainless.)

For myself I'd go with what looks right, which to me is just above the waterline. So if the dark area in your photo is where the bootstripe will go, I'd be fastening the bobstay just about where the top of that prop is.
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[chainyank]

After doing some more research, I think the hardware that came with the boat may have caused that problem in the stem. I found a place that sells a chunky eye-bolt type bobstay which handles a load up to 4000 kg (thats 4 metric tons right? Sorry I am from Maine). Now I am not sure about much on this boat but the whole boat rings in at 3 metric tons (thats err, 3000 kg, right? Again with the finger counter from Maine), so I think that this eye-bolt could handle the load from just the bowsprit, or am I way off base here?

...No worries, I would never be tempted to lift her by the bobstay!