Adding Mast Base Blocks

[duck21]

Hello,

My current mast-base turning block configuration has blocks for the main and jib halyards as well as the reefing lines. I'd like to run the topping lift and spinnaker halyard back to the cockpit. I have the cleats, but need to add turning blocks.

According to Hunter's drawing the additional blocks can be added, but I'll need offsets so that the new blocks don't run into the existing blocks. I've circled their image in the attached picture.

My question: what are the offsets called? I've tried googling "mast base block offset" or "extension" or other things but so far haven't had any luck.

FWIW the mast is a Z-Spar, the blocks use 10mm bolts. This is on a Hunter 376. I've found blocks that (I believe) will work--but haven't found the offsets.

Thanks!

 

[JRacer]

Check with US Spars www.usspars.com They are the Z-Spar supplier.

 

[duck21]

Excellent. I've written them. Thank you!

 

[sail sfbay]

JRacer........made a good recommendation!! A photo of what you have would help.

The Hunter 46 halyards and control lines are routed from the mast through blocks attached to the mast base plate then to turning blocks as shown below then through in the cockpit. The topping lift is cleated off at the mast as shown below since it is not a control line on my sailboat.

 

[jssailem]

What is showing in the Hunter diagram appears to be the use of a Schaefer Marine backing plate to extend the connection beyond the edge of the mast plate.

 

[duck21]

Ours is currently a similar set up to yours--mast-based blocks to turning blocks (although on the 376 the turning blocks are under a cover).

I don't have a rigid vang, so the topping lift is active.

While it could usually be set and forgotten, the boat came with a Dutchman flaking system and with a bimini. I'm finding that with the topping lift tight enough to lift the boom above the bimini for storage it's a little too high for good sail shape, especially when reefed.

I've also broken the Dutchman filaments a couple of times which, according to their documentation, is because there is too much tension on those lines when the sail is under power. Their recommendation is to loosen the topping lift when under sail allowing the filaments to hang loose and the sail to hold up the boom.

Attached are pics of the current configuration.

 

[duck21]

Ooo, backing plate--I didn' try that as a search term. I'll give those a look too. Thank you!

What is showing in the Hunter diagram appears to be the use of a Schaefer Marine backing plate to extend the connection beyond the edge of the mast plate.
View attachment 195721

 

[jssailem]

I am guessing here, but a friend with a machineshop could make a plate to extend off your mast base out of polished stainless. Even put an edge on to keep is extended at the proper angle as needed.

 

[Joe]

Have you considered replacing the single(s) with double(s) blocks? Also, minimizing the turns is important to reduce friction.... in one of the pictures above there are 2 90deg turns through plastic or resin deck mounted fairleads. I would suggest installing one roller bearing organizer mounted on a small riser set at 45 deg between mast blocks and run to cockpit. It may be factory set up... but heck... it just makes sense to change it. (unless there's a mitigating circumstance, of course)

 

[duck21]

Vertically stacked or horizontal? I didn't see many options for horizontal (side by side) blocks that would attach to the mast base collar. I looked at the vertical (stacked) blocks but wasn't sure if there would be any issue with the angle as the line turns down and runs under the deck. If others have had a good experience there I would definitely consider the vertical option.

Have you considered replacing the single(s) with double(s) blocks?

 

[Scott T-Bird]

While it could usually be set and forgotten, the boat came with a Dutchman flaking system and with a bimini. I'm finding that with the topping lift tight enough to lift the boom above the bimini for storage it's a little too high for good sail shape, especially when reefed.

I've also broken the Dutchman filaments a couple of times which, according to their documentation, is because there is too much tension on those lines when the sail is under power. Their recommendation is to loosen the topping lift when under sail allowing the filaments to hang loose and the sail to hold up the boom.

Wow, you've already broken filaments twice? Last year was my first with the Dutchman system and I never sailed with tension on the topping lift/filaments. Are you saying that you have to tension the topping lift while sailing so that the boom clears the bimini? The previous owner of my boat had the main sail re-cut to clear the bimini. Apparently, he installed a bimini with a little additional height, and his conventionally-built main sail didn't clear the bimini, so he had his new main sail re-cut so the boom clears the bimini with the topping lift slack. I learned this information because I asked about the photos which clearly showed the upward slant of the boom to clear the bimini. It looked un-natural to me and the information wasn't volunteered by the broker until I asked about it specifically and got the story from the owner directly. It was a compromise that I may correct someday in the future, but it sets off a chain-reaction of adjustments to the enclosure, so I leave it alone for now.

The position of the filaments is adjustable, right? You might be able to adjust the position of the filaments so that they are a little more slack when you have the topping lift set at the sailing position (if that is what you have to do to clear the bimini). But they may be a bit too slack for dropping the main efficiently. P.O. had them adjusted so that they were just right on my boat ... I haven't played with the positioning since it works.

 

[Scott T-Bird]

A little bit sorry for the thread drift ... it seems to make it a bit more difficult with the lines being led straight aft. I'm sure that leading the lines back at a bit more typical angle would cause a major re-fit of the deck topography, so that is probably a no-go. A double block would be a nice solution, but there may be a clearance problem with the mast ... double blocks obviously take up more space on that single anchor next to the mast. You could use a double block, but it probably would still need that offset plate to get the blocks away from the mast. That backing plate looks like the right idea, but I would be concerned that it doesn't have enough thickness to resist bending. But a topping lift shouldn't be carrying very much load after all.

 

[duck21]

Unfortunately, yes--two out of my three filaments have broken while under sail. Now--I didn't replace the filaments when we got the boat, so I can't attest to the age of the line--they may have been close to end of life anyway.

With the sail up the boom WILL clear the Bimini--but with the sail down the topping lift needs to be tightened to hold the boom above the Bimini. There is probably a sweet spot between topping-lift tension/sail down vs. sail up, but I haven't found it (at the expense of the filaments). The challenge, of course, is that finding that sweet spot has required someone being forward to adjust the lift with the sail hoisted and under some sort of power. It feels like these adjustments would be easier with the lift accessible in the cockpit.

The main on my boat was new two years ago, it's barely broken in. I don't think the PO sailed very much (at least not in the past few years) so I don't know that most of this was ever really dialed in and, of course, I'm just learning the boat. There's a lot of factors at play here.

Wow, you've already broken filaments twice? Last year was my first with the Dutchman system and I never sailed with tension on the topping lift/filaments. Are you saying that you have to tension the topping lift while sailing so that the boom clears the bimini? The previous owner of my boat had the main sail re-cut to clear the bimini. Apparently, he installed a bimini with a little additional height, and his conventionally-built main sail didn't clear the bimini, so he had his new main sail re-cut so the boom clears the bimini with the topping lift slack. I learned this information because I asked about the photos which clearly showed the upward slant of the boom to clear the bimini. It looked un-natural to me and the information wasn't volunteered by the broker until I asked about it specifically and got the story from the owner directly. It was a compromise that I may correct someday in the future, but it sets off a chain-reaction of adjustments to the enclosure, so I leave it alone for now.

The position of the filaments is adjustable, right? You might be able to adjust the position of the filaments so that they are a little more slack when you have the topping lift set at the sailing position (if that is what you have to do to clear the bimini). But they may be a bit too slack for dropping the main efficiently. P.O. had them adjusted so that they were just right on my boat ... I haven't played with the positioning since it works.

 

[duck21]

If US Spars doesn't come through I was thinking of trying the backing plate but cutting it so that I'm not using the full 3 inches--that may reduce some of the lever action. I agree on the load concern. I find Hunter design interesting. I suppose I could look at some of the "Spring" blocks as well, although I don't know if they would really flex enough to allow for clearance.

A little bit sorry for the thread drift ... it seems to make it a bit more difficult with the lines being led straight aft. I'm sure that leading the lines back at a bit more typical angle would cause a major re-fit of the deck topography, so that is probably a no-go. A double block would be a nice solution, but there may be a clearance problem with the mast ... double blocks obviously take up more space on that single anchor next to the mast. You could use a double block, but it probably would still need that offset plate to get the blocks away from the mast. That backing plate looks like the right idea, but I would be concerned that it doesn't have enough thickness to resist bending. But a topping lift shouldn't be carrying very much load after all.

 

[Scott T-Bird]

With the sail up the boom WILL clear the Bimini--but with the sail down the topping lift needs to be tightened to hold the boom above the Bimini. There is probably a sweet spot between topping-lift tension/sail down vs. sail up, but I haven't found it (at the expense of the filaments). The challenge, of course, is that finding that sweet spot has required someone being forward to adjust the lift with the sail hoisted and under some sort of power. It feels like these adjustments would be easier with the lift accessible in the cockpit.

Oh ... I was certainly misunderstanding. I was under the impression that you needed to keep the topping lift tensioned while sailing. What I don't understand is why you don't just completely loosen the TL when sailing? Isn't it normal to release the TL when sailing and tension it just before dropping the sail? It's completely slack when I'm sailing, just as the documentation says. For sure, it is much better to bring the control line back to the cockpit.

 

[Ward H]

The parts you circled in the diagram clearly calls them L brackets and gives the part #.
Try calling @Dave Groshong here at the SBO store. They are Hunter parts specialist. Maybe they can help.

 

[Scott T-Bird]

The parts you circled in the diagram clearly calls them L brackets and gives the part #.
Try calling @Dave Groshong here at the SBO store. They are Hunter parts specialist. Maybe they can help.

You got that right! Great eye!

 

[duck21]

A couple of updates:

Apparently the "L" brackets are no longer available. I'm going with @jssailem 's suggestion of the backing plates to offset the new blocks. I ordered two, I'll cut them in half, drill new holes, and probably double them to add a little more strength (assuming that the threads on the blocks are deep enough to fit through the double layer. I got the blocks yesterday, the backing plates are supposed to arrive today, I'll be able to test that out soon).

This past weekend I strung new filament on my Dutchman system. I confirmed everything was properly tensioned. We sailed, (0-6kt breeze, broad reach). I went forward and loosened the topping lift while sailing, I tightened it just before we dropped the sail--no broken filaments, the sail flaked onto the boom better than it ever has before. I definitely think I will benefit from the topping lift coming back to the cockpit, but at least the system proofed out for me.

Once the turning blocks are in I'll snap some pics. In the mean time, thanks to everyone for the advice!

 

[jssailem]

Good Luck. Interested in the results.

 

[duck21]

Hi all,

I finally got the chance to construct/install the mast turning blocks (we had some unexpected things come up and didn't make it up to the boat much at all in August or September, so I just got around to this).

I used 4 inch backing plates as was suggested by @jssailem . I cut them in half, then added a second hole for a 10mm bolt. On the mast side I used a normal nut (a locking nut wouldn't fit into the slot) and bolt, I used both halves of the backing plate (for extra rigidity), and a lock washer.

On the block side I used a nylock nut and blocks that I ordered from US Spars. I used a couple of extra washers between the bottom of the block and the backing plates just to keep it from dropping down in the hole (the block is NOT threaded all the way up so there was so gap space).

I haven't had a chance to pull the top deck panel through the deck blocks yet, but I did use this to turn the spinnaker halyard which I ran back to the winch via the jib sheet blocks. It lifted our 75lb dinghy with no issue (and no bending of the backing plates). I need to buy a longer line for my topping lift this winter then will run both under the deck for better control from the cockpit.

I don't know that I would fully trust this system to ride a line up the mast, but I think it'll work great for the spinnaker halyard (which I mostly use to lift the dinghy on/off deck for storage) and the topping lift.

Pics are attached. Thanks for the tips and suggestions, everyone!