How do you replace turning blocks at the mast base

[smokey73]

I need to replace at least one (and probably more) of the turning blocks at the mast base on my Hunter 40.5. It appears that these are somehow screwed into the base itself. How do your remove these? I tried to unscrew one but it didn't want to turn and I didn't want to twist it off. Is there something I'm missing? Is the stud tack welded into the base or staked so it won't turn. Just don't want to do irreversible damage.

Attached is a picture of the turning blocks.

 

[JRacer]

Is that a Z-Spars mast? Looks a lot like my mast step on the Beneteau. If so, mine has a slot in the bottom of the step that a nut slips into and is captured. So to remove the stud just requires turning it from the top. If they are stuck, some lubricant or nut buster may be required. If it's a Z-Spar, replacement blocks can be had from US Spars in your neck of the woods, I think. www.usspars.com

Looks like this is the replacement. http://www.usspars.com/product/?part-id=288

Here is the parts explosion of the mast: http://www.usspars.com/boat-information/?vendor=Hunter&model=Hunter+40.5-Taper#section-display

 

[DougM]

I wondered where those blocks came from....
List price looks a bit hefty for a block that is essentially a POS in my opinion.
I had been looking for a block like that with a threaded stud, and couldn't find a source.
I used a spare Harken block that I had lying around and attached it to the base plate with a D shackle. It works, but doesn't look all that great. It isn't carrying a very heavy load anyway.

 

[jviss]

My mast step (C36) has a newer collar, with holes for studs to attach the turning blocks. The studs were installed with the mast collar, from below. But, you'd have to take the block off them to get them out. Mine were pinned with clevis pins.

 

[Ron20324]

I wondered where those blocks came from.......

Doug, I got my blocks from the B parts site a few years ago. Don't they list them now?

 

[Jackdaw]

List price looks a bit hefty for a block that is essentially a POS in my opinion.

Besides the price, what don't you like about it?

That design; a single pin axle on a solid wheel, is by far the strongest design for its size and a perfect application for highly loaded mast base (halyard) applications. While the 36.7 came with Lewmar parts, they were of the same basic design.

 

[jviss]

Besides the price, what don't you like about it?

That design; a single pin axle on a solid wheel, is by far the strongest design for its size and a perfect application for highly loaded mast base (halyard) applications. While the 36.7 came with Lewmar parts, they were of the same basic design.

I confess that while I'm an engineer, and have some mechanical design experience, I'm not an expert on blocks. That said, I find it counter-intuitive that an axle in a solid wheel would be "by far the strongest design for its size and a perfect application for highly loaded mast base (halyard) applications." I imagine that unless the wheel and axle were perfectly mated you would have a point, or "line" contact from wheel to axle, and very high friction as a result; and not a very good wear characteristic, either. Why wouldn't a similarly-sized, large arbor, ball bearing block be better, as for example, the Garhauer stainless or unibody blocks? And by the way, Garhauer are very economical.

 

[NYSail]

Garhauer are great products, great support. I will be replacing mine with them

 

[Jackdaw]

I confess that while I'm an engineer, and have some mechanical design experience, I'm not an expert on blocks. That said, I find it counter-intuitive that an axle in a solid wheel would be "by far the strongest design for its size and a perfect application for highly loaded mast base (halyard) applications." I imagine that unless the wheel and axle were perfectly mated you would have a point, or "line" contact from wheel to axle, and very high friction as a result; and not a very good wear characteristic, either. Why wouldn't a similarly-sized, large arbor, ball bearing block be better, as for example, the Garhauer stainless or unibody blocks? And by the way, Garhauer are very economical.

A asked a friend about this who is an engineer for Harken. She confirmed that solid axle blocks are by far stronger and more reliable (less likely to 'blow up') under load in mast-base applications. The friction is slightly higher, but just for a foot or so in any meaningful loading. Most of Harken mast-base blocks (up to 102mm) are solid wheel solid axle.

 

[jssailem]

Smokey
Examining the image, it appears the blocks are attached to the plate from underneath. The base has a hole the diameter of the stud. The stud has a cap welded/stamped to the end which captures the stud stopping it from pulling out but allowing the stud to turn. The blocks look to be designed to be captured by a pin through the stud with a circ-clip. The block (at the bottom of the three) yoke appears in the image to have a fine wire moused around the pin. Working to stop the pin from sliding out. The two outside blocks appear to be the same. The middle block has a pin that appears to be captured by a cotter pin.
I would remove the blocks and replace if that is you goal, lubricate the studs sticking up from the base.
Alternately, it appears you will need to remove the mast to get at the mast base. Remove the mast base to get at the 3 studs which I guess will slide out when you lift the mast base.
I would ditch the mouse wires and use pins with positive closure. I like the cotter pin design.

 

[jviss]

Thanks! My new boat is all Harken hardware, and I want to source a few blocks of the same vintage, 1996 or so. I'm missing a double for turning the reefing lines through 180º. Plus, the mainsheet tackle is a bit odd, with one "wrong" block included, a fiddle block, with the small sheave ignored. In addition, there's an unoccupied eye on the bottom of the boom. I suspect the tackle is wrong in multiple dimensions.

Any thoughts on size of a double for the reefing lines, say, 8mm line, 38 foot boat?

 

[jviss]

it appears you will need to remove the mast to get at the mast base

Once could probably slide the mast collar up, with the mast in place, once the fasteners are removed. On my C36 this is possible, but requires removal of the boom vang bracket.

 

[jssailem]

I use 8mm 5/16 for reefing lines on my boat. Not much to hold but I am rarely handling them where I need to hand pull them. They are a little less weight. Should do fine.

The problem with your running rigging is often an issue on a previously owned boat. Was on my boat, and was on the replacement main sheet blocks I bought to replace the light gear used by my former owner. Might be why the boat owner did not sail much.
I have used the Harken website to help communicate the various rigging designs possible with a main sheet. They have some great images that can help you to properly run the sheet through the two 3 sheave blocks that makes up a 6-1 Reeved Right Angle system.

 

[JRacer]

Here is a pictures of my Z-Spars Mast Base. Some of the blocks had been replaced at that date, the rest since. Note in the photo from the aft end the slot under the plate. That's where the nut slips in and is captured so when you thread the stud in, it can tighten properly. There is one of those slots in line with each stud hole.

 

[jviss]

Great pic and explanation! That's a convenient system.

 

[jviss]

I use 8mm 5/16 for reefing lines on my boat. Not much to hold but I am rarely handling them where I need to hand pull them. They are a little less weight. Should do fine.

The problem with your running rigging is often an issue on a previously owned boat. Was on my boat, and was on the replacement main sheet blocks I bought to replace the light gear used by my former owner. Might be why the boat owner did not sail much.
I have used the Harken website to help communicate the various rigging designs possible with a main sheet. They have some great images that can help you to properly run the sheet through the two 3 sheave blocks that makes up a 6-1 Reeved Right Angle system.

Holy Cow, John, that's it!

I apologize for hijacking the thread, I'll start a new one.

 

[smokey73]

Here is a pictures of my Z-Spars Mast Base. Some of the blocks had been replaced at that date, the rest since. Note in the photo from the aft end the slot under the plate. That's where the nut slips in and is captured so when you thread the stud in, it can tighten properly. There is one of those slots in line with each stud hole.[/QUOTE]

Back on topic. I need to remove at least one of the mast base turning blocks. If the nuts are "captured" in those slots, will they "move" when I unscrew the stud? Will I be able to re-thread the new stud? If the nut moves can I re-position it with a rod or wire so it will line up with the stud? I don't want to remove a stud and then not be able to get the new stud/block to thread back into the nut. I broke one of the blocks. As a temporary fix, I ground off the pin in the stud and attached a replacement block with a shackle and pin (that is the one with the cotter pin in it). Has anyone actually replaced one of these in place without pulling the mast and mast base? I'm not interested in discussing the pros and cons of various block, but want to know how to replace the block without getting myself in a position where I can't get the stud back in or end up twisting off the stud.

 

[Benny17441]

These blocks are somewhat overbuilt for the tasks at hand. Their strength imparts longevity even if their design does not. Simplicity adds to that strength with less parts to fail. The results are a true and tested fixture that we can rely on.

 

[JRacer]

In my case, I just unscrewed the stud by twisting the block and was able to get the old nut out of the slot. Replacement IIRC came with a new nut( or I ordered new nuts to go with the replacement, can't recall). Slid the new nut into the slot and positioned it under the hole and screwed in the new block. If yours are corroded, you may need to use some lubricant of the nut buster variety and allow that to loosen the stud/nut to allow the old one to unscrew without twisting off the stud. The slot is sized such that the flats on the nut match so with the nut in the slot, they should not turn freely. I replaced mine without removing the mast plate. I did some of them, the new ones you see in my pics, while the stick was down but have replaced the remaining ones with the stick up. Unless you have corrosion issues/or crap plugging up the slot, once the stud is unscrewed, the nut should come out of the slot without a lot of persuasion.

 

[smokey73]

In my case, I just unscrewed the stud by twisting the block and was able to get the old nut out of the slot. Replacement IIRC came with a new nut( or I ordered new nuts to go with the replacement, can't recall). Slid the new nut into the slot and positioned it under the hole and screwed in the new block. If yours are corroded, you may need to use some lubricant of the nut buster variety and allow that to loosen the stud/nut to allow the old one to unscrew without twisting off the stud. The slot is sized such that the flats on the nut match so with the nut in the slot, they should not turn freely. I replaced mine without removing the mast plate. I did some of them, the new ones you see in my pics, while the stick was down but have replaced the remaining ones with the stick up. Unless you have corrosion issues/or crap plugging up the slot, once the stud is unscrewed, the nut should come out of the slot without a lot of persuasion.

Thanks Racer. That's the info I needed! Thanks to all the others who commented too. This site is always my "go to" place for advice and info. Sorry if I was a little "short" on my earlier response but its still good to get opinions on what might be upgrades that I can consider when I'm doing work. I think I'll stick with the original block style if I can find them. I've got a temporary fix in place and will order the new blocks.