So I need to replace the mainsheet block attached to my boom (no tracker - 1975 bristol caravel 22 - single block with beckett) its the real life picture. So I happen to have a new fiddle block and wondering what the advantages/disadvantages are if I got with the fiddle block rig like the one shown (drawing photo attached). Thank you everyone!
main sheet blocks
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Since you already have the fiddle block, it will definitely be a slight improvement. It looks like you have a block at the port quarter and a block with a cam cleat at the stbd quarter? Can't really tell. Are you mounting a new location for the block and cam cleat?
Fiddle blocks are nice for some situations where you want the blocks to be streamlined. I think one disadvantage of a fiddle block is the smaller sheave diameter of the lower block. That block at the boom really wants to be a double block, not a fiddle block. The fiddle block hangs lower and you will scrape your head more often.
If I was starting from scratch in this situation and trying to match what you are doing, I would start with a block with cam cleat and becket at the port quarter, a double block at the boom and the single block at the stbd quarter. I wouldn't mount a separate padeye at the port quarter (maybe I have port and stbd mixed up - it depends on your view - I'm looking at it from the same vantage as the picture)
Do you already have the block and cam cleat on a pad mount? You may not need a pad mount if you already have the pad eye ... just attach a block and cam cleat with a shackle. There are a multitude of block selections for all kinds of set-ups.
Fiddle blocks are nice for some situations where you want the blocks to be streamlined. I think one disadvantage of a fiddle block is the smaller sheave diameter of the lower block. That block at the boom really wants to be a double block, not a fiddle block. The fiddle block hangs lower and you will scrape your head more often.
If I was starting from scratch in this situation and trying to match what you are doing, I would start with a block with cam cleat and becket at the port quarter, a double block at the boom and the single block at the stbd quarter. I wouldn't mount a separate padeye at the port quarter (maybe I have port and stbd mixed up - it depends on your view - I'm looking at it from the same vantage as the picture)
Do you already have the block and cam cleat on a pad mount? You may not need a pad mount if you already have the pad eye ... just attach a block and cam cleat with a shackle. There are a multitude of block selections for all kinds of set-ups.
I don't have end boom sheeting on my boat -- mid boom instead. But I did something similar. Modified my 4:1 purchase to a 7:1 purchase by changing out a double block for a triple and also adding another block on the boom.
At first blush, I can't see any structural downside to the modification you are contemplating.
If you haven't already included in the plan:
- You are converting from a 3:1 to a 4:1 purchase. So currently (ignoring any friction of the blocks and line) say 33.333 lbs of pull on the sheet will translate to 100 lbs constricting force on the boom. After the mod, the same 100 force on the boom will take only 25 lbs of pull.
- Unless your current main sheet is significantly longer than you need, going to a 4:1 purchase may leave you short of line. For instance if you currently need 45' of line to allow the boom its full swing out when going down wind, you will need 60' with the 4:1 purchase.
- Think it all through carefully before the effort. Doesn't look like it from your drawing, but be sure that the mod doesn't cause restrictions to the helmsman's movements, that sheet control is still conveniently oriented, and that the rerouting will get in the way of anything.
Here's a link to harken's main sheet diagram page. Might assist with ideas.
http://www.harken.com/rigtips/mainsheet.php
At first blush, I can't see any structural downside to the modification you are contemplating.
If you haven't already included in the plan:
- You are converting from a 3:1 to a 4:1 purchase. So currently (ignoring any friction of the blocks and line) say 33.333 lbs of pull on the sheet will translate to 100 lbs constricting force on the boom. After the mod, the same 100 force on the boom will take only 25 lbs of pull.
- Unless your current main sheet is significantly longer than you need, going to a 4:1 purchase may leave you short of line. For instance if you currently need 45' of line to allow the boom its full swing out when going down wind, you will need 60' with the 4:1 purchase.
- Think it all through carefully before the effort. Doesn't look like it from your drawing, but be sure that the mod doesn't cause restrictions to the helmsman's movements, that sheet control is still conveniently oriented, and that the rerouting will get in the way of anything.
Here's a link to harken's main sheet diagram page. Might assist with ideas.
http://www.harken.com/rigtips/mainsheet.php
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Whatever you do..... widen the base of your mainsheet triangle by moving the padeyes as far outboard as possible. In the current scheme you have practically no lateral control of the boom.
I'd leave the swivel block and cleat where it is.....
If you have to buy a longer mainsheet to accommodate the additional purchase... consider going down one size.... 5/16 from 3/8 for instance... it'll run through the blocks more smoothly.
Like Scott, I don't really care for fiddle blocks on the mainsheet.... but...hey.. run what you brung...
I'd leave the swivel block and cleat where it is.....
If you have to buy a longer mainsheet to accommodate the additional purchase... consider going down one size.... 5/16 from 3/8 for instance... it'll run through the blocks more smoothly.
Like Scott, I don't really care for fiddle blocks on the mainsheet.... but...hey.. run what you brung...
Scott, you are correct. I have a block on port and block with cam cleat on starboard. I didn't think of the headroom issue with the fiddle block, so I may go with the double block on the mast end instead. Also I plan on mounting to the beckett on the block with the clam cleat.
Rardi, thank you for the heads up on the sheet length and I should have enough to get away with it as is.
Joe, that's a good idea. Unfortunately, there is really no room to expand it.
Rardi, thank you for the heads up on the sheet length and I should have enough to get away with it as is.
Joe, that's a good idea. Unfortunately, there is really no room to expand it.
Pros and Cons. Your present setup has a 3:1 purchase whereas your proposed modification will be a 4:! purchase. It's going to be easier to trim the main in heavy winds. It's also going to be more difficult to ease the main in light air with the additional friction. You have to decide what makes life easier.
Looking at your picture, there appears to be plenty of room to relocate the bases.... raise the padeye levels with a wood block to clear the sideboards, like your winches do. Or bolt a couple of tangs to the gunwhales and shackle or wire the blocks there.. Besides increasing the effectiveness of your mainsheet, you will clear out more room to operate the outboard tiller.
It appears that you don't have a vang either. If that is true, then you will have no twist control once you ease the sheet. If you don't relocate the sheet legs, at least consider installing a vang to give you more mainsail control.
Ted's comment is good about increased friction.... if you increase the purchase you can go down a line size.... allowing a smoother run through the blocks. I increased the purchase to 5:1 on my Catalina 27, went down to 5/16 line.... way better.
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