mid-boom block car / track

[kinnebrooksailer]

We recently acquired a DS1 (2833) and launched it, with a lot of reference to this forum, for a few test sails. It appears to be almost complete, and as far as I can tell, fairly original. It was fun to sail and I look forward to having an out haul and some kind of down haul!

My question is about the block that should be mounted mid boom. The block is missing, the only evidence of it is the short piece of track riveted to the boom. I found a photo in GreenLake's gallery that shows the boom, the short piece of track, and the "car" that mounts to the track providing a place to shackle the block.



D & R Marine told me the cars are no longer available and my only option is to attach a small bail to the boom. I would rather not drill holes in the boom, if I don't have to, so I am asking you folks if you have any better ideas.

Thank you!

ps - is anyone else having trouble seeing images from the gallery? I am logged in, but it tells me I am not authorized to see the images. I can browse the gallery just fine, but when they are included in a post (even my post), I cannot see them.

[GreenLake]

Images: we think that this may be a browser cache issue. Try clearing that. I also always select the "Log me in each visit" check box when logging in, which helps against being logged out if and when the forum software "thinks" that I'm done with my current "visit".

[GreenLake]

Block: if you don't mind me asking, how were you able to test sail without it?

Options:

1. try to find a used one
2. make your own
3. have a fabricator/machine shop make one
4. add a bail

(a) there are places, such as the WTB section on this forum, where you might advertise a search for a used one.

(b) you would need to modify the design a bit to make it easier to reproduce. One suggestion would be to use two L pieces held together by a square piece. You can either get a suitable L profile and cut it to size, or put a 90 bend into a suitable piece of sheet metal (and then cut to size). You then need a spacer the width of the track. You can use screws or bolts to attach the two L's so they grip the track. Use stainless for the L's and something easier to work with but corrosion resistant for the spacer. Because you can match the full length of the track, the piece should be strong enough. In the middle of the spacer you drill two holes to attach an eye. Ideally, you find one that's a simple U with both ends tapped. You'd overdrill the upper side to create space for nuts. Or you could use a regular eye strap with bolts. Again, with room on the upper side for the bolts, and the bolts cut of flush.

(c) farm that out to a machine shop. They have more tools and can probably realize a design a bit closer to the original. For example, the cars on my jib track are made from a solid block of ~1/2" aluminum with the profile of the track ground out; easy enough to do, if you have the proper tools. But then you need to anodize the piece and coat it for weather protection. You don't need to recreate the stop, btw, there's no need to have that piece removable under way. You can just tap for a bolt that protrudes and locks it in the track.

(d) just bite the bullet and add a bail. If you don't have a slot for a vang, you may probably end up adding a bail for that. I did, and see no ill effects. I riveted mine, which was a flat strip of metal, but depending on the bail you can get, a single bolt through the middle of the boom may work as well.

[GreenLake]

Two more options:

1. Find a compatible slider
2. Mount a new track with matching slider

(A) The track that's on my DS1 boom is 22mm wide. I could find two 22mm track systems online, one from Harken and one from Allen (in the UK). The Harken cars have captive ball bearings and it looks like the profile is more wedge shaped at the ends of the T bar. So cars for that track system might not fit a track with rounded ends. The Allen track seems to have the right dimensions, but it has a square drop in the middle of the T. Either the cars just bridge that gap, or their profile dips into it. If not, it might be worth a try to look for a car for that Allen track. It might be a fit.

(B) Finally you could drill out the rivets and mount a different piece of track for which matching cars/sliders are available. But you are unlikely to find one that matches the hole spacing, so you may have to drill one or two new holes anyway. Getting a single piece of track and a single slider/car may also be challenging, as they tend to be sold in pairs, and you would have to cut down the track. However, you might find something used. In that case, anything from 19 (3/4") to 25mm (1") may work.

[AlanH]

If your mainsail is loose-footed, you can wrap some 1" webbing around the boom and hang a D-shaped shackle from it. Then shackle the mainsheet block to that shackle and you're set.

My other boat actually just has a straight aluminum tube for a boom. I've taken some spectra line and wrapped it a mess of times around the aluminum, mid boom. There's a loop in the spectra, I shackle the block to that. The multiple loops have enough friction to keep the whole thing from sliding around.

[GreenLake]

Even if it is not loose footed that is a technique you could use. But like the version for the loose footed main it works best if the pull is straight down. In other words, you need center boom sheeting. In end boom sheeting part of the mainsheet runs along the boom and this has the potential of causing any strap to shift aft over time. For a lose footed main you can try to make the strap more secure by using the multiple wraps that @AlanH has mentioned. But for the trick to combine a strap with a main that uses a boltrope a single wrap works best, I would imagine.

Assuming center boom sheeting, the way you make it work if your main has a boltrope for the boom is to reinforce a small rectangle at the very bottom of the sail and the cut a slit in it for the strap. This works because for that type of main there's a bit of extra fabric seen into the sail so the very bottom part near the boom is practically slack. The slit needs to be just long enough to allow the small amount of horizontal movement as you tighten the outhaul.

BTW, this is not something from my fertile imagination, but something I did encounter while reading idly in some sailing forum. Whether here or somewhere else I couldn't tell.

I wonder whether we've now exhausted all the possibilities?

[kinnebrooksailer]

Thank you so much for all the ideas!

First, to test the boat I just ran the main sheet from the block on the end of the boom to the block on the centerboard. It interfered with the tiller, but not enough to be an issue for the sailing we were doing.

My sail runs in a track in the boom, so simply lashing a block to the boom is not so simple. The sails appear to be brand new, I am reluctant to cut them.

I like the idea of fabricating something. I have tools and some experience. I am curious on your thoughts on the attached design, which is my interpretation of Green Lake's description.

Drawing for a mid-boom car to support a shackle block

Mid-boom car.jpg (53.18 KiB) Viewed 1732 times

I am envisioning the hardware (bolts and clevis) being stainless, and perhaps the angle. But the "spacer" blocks I would rather make from aluminum just because I don't like tapping stainless. But I am curious about the comments on anodizing the aluminum. I don't have experience fabricating parts for boats or marine environments but I have also never had serious issues with oxidation/corrosion on bare aluminum. Is bare aluminum an issue?

Thank you again.

ps - Thank you also for your guidance on the images. I have found ways to make it work, but it does not seem to like multiple tabs as much as I do.

[RaleighRancher]

What about just attaching a boom bail? For example, https://drmarine.com/product/boom-bail-small/
I have a DS2 and this is how my mainsheet block is attached to the boom. Mine is riveted on but screws could be used too.

[GreenLake]

What about just attaching a boom bail? For example, https://drmarine.com/product/boom-bail-small/
I have a DS2 and this is how my mainsheet block is attached to the boom. Mine is riveted on but screws could be used too.

Yes, that's the obvious answer and the proverbial 99% of people would likely go that route. And most likely the solution I would have chosen.

But, if you want to be different and have fun building things...well, the DS is a fun platform for that.

[GreenLake]

I like the idea of fabricating something. I have tools and some experience. I am curious on your thoughts on the attached design ...

I'm going to engage you here on the design, based on now much fun it is to see whether you can pull it off, not based on the sound principle of minimal effort.

First, unlike you, I'm not set up to do nice drawings like that, but thanks for giving us a base for discussion. I'll use words to describe how I would alter the design.

1. For the spacer you can use a piece of any suitable hard plastic. That avoids issues with corrosion.
2. I had envisioned the sides to be rectangular, if viewed side on, and therefore a single piece of spacer.
3. I had envisioned some kind of "eye" to attach the block, an eye strap bolted to the spacer.
4. Now, seeing your drawing, I'm thinking shackle with the pin horizontal through the middle of the whole assembly would make more sense.
5. Everything else is as I imagined.

(B) your design with the curved sides and a pin does look like it could work. But let's consider some alternatives. You don't need very much clearance for attaching a block, so there would be no need to split the spacer in two. It's easier if this is a single piece. (A) Hard plastic should be enough, the threads don't need to do more than preventing the locking bolt from falling out. And, your design, unlike (C) does transmit the sheet load to the sides. However, as you need a pin anyway, simply get a shackle: so as in (D) do away with the curved side, make the pin of the shackle go through the spacer and use the U part to give you clearance to attach the block. It's both easier to make (straight lines) and stronger.

If you are set up for this work and find it fun, there's nothing wrong with an approach like this and you get the satisfaction of having something unique yet functional on your boat.