Working load on end-boom H37C.

[Ed Schenck]

Thinking of upgrading to triple blocks for the mainsheet. Series 30 blocks are rated at 2000# and 40s at 2800. The sheave sizes are the same. Should I spend the additional $40. to go to the series 40? Total would be about $260. plus shipping.

 

[rhythmsurfer]

Could you consult with Harken or local rigger. I wonder how much pressure it would put on the sail?
Tony

 

[rardiH36]

Thinking of upgrading to triple blocks for the mainsheet. The series 30 blocks are rated at 2000# and 40s at 2800#. The sheave sizes are the same. Should I spend the additional $40. to go to the series 40? Total would be about $260. plus shipping.

Hi Ed:

Ever our quest for "making better"!

During my relatively brief duration in the sailboat owner thing, one thing I have noticed is our tendency with block selection is to really over-buy in respect of breaking strength.

Harken's website has a good calculator. Takes into account vector angles. That might help. Also, take a look at the catalog or web page for the blocks you are considering. Does it appear that the same block is also in a single variety? If so what is the swl for that? This will give you an idea of the strength of the sheave portion in isolation. Most likely the single x 3 will be a lot more than the triple's rating. Therefore the difference is in the housing and the shackle design.

Also consider that with our masthead configurations, the mainsail is relatively smaller that the same size fractional boat. So less sail area and windage stress.

Are you thinking about a triple on the traveler or hanging from the boom? (Sorry I don't recall details of any pics you may have posted through the years.) In either case, I would venture that the weak link in the chain (i.e. the likely lowest breaking load) would be the traveler car itself or at the actual connection points at the boom rather than a new block at either 2000lbs or 2800lbs.

I've attached a pic of my set-up. The traveler triple is a concoction of a flea market double mated to a flea market single. It's held up four years now in the winds of SF Bay's "slot". At the boom, I've added extra bails to distribute the load over a larger area. FYI, the improvement on hand-pulling the sheet with my larger ball bearing blocks (as in the pic) as compared to the standard fiddle and center pin blocks that were on the boat when I bought it ... very really noticeable. I virtually never use the winch for sheeting. See also the second pic for the cockpit control. The green mainsheet leads back to the helm. (This pic was taken soon after my modification. The faired old holes are painted over now.)

rardi

 

[Ed Schenck]

You make a good point about the "weakest link" Rardi. I'm trying to match Blaise' arrangement as seen in the two photos. Except that my cam cleat will be part of the bottom triple block. But my traveler and car on the bridgedeck are probably rated at less than 2000# working load. So why not the series 30?

 

[Jim Legere]

For me, I like big, thick sheets that are comfortable on the hands (i.e. 1/2" or, better yet, 9/16"). So the issue becomes sheave size for the rope and breaking strength is a moot point. And I agree that the traveller or something else is likely the weak link.

On the mid sheeted boom of the later H37Cs, we have 6:1 and you definitely need the cabin top winch in any kind of wind. With that nice Harken mainsheet system that Blaise has, along with the bridge deck traveller and end sheeting, I would guess a main sheet winch doesn't see much use...

 

[Steve Dion]

Ed:

I assume that you are looking at Garhauer blocks?

If you give them a call and ask for Mark, you may want to see if he will sell them at the boat show price. You are not going to save a fortune, but it leaves enough for a couple of bottles of nice wine.

 

[Ed Schenck]

Thanks for the tip Steve. I will do that. And opt for the 40s if they agree.

 

[Blaise]

Just for the record, Midnight Sun does not have a mainsheet winch. The mainsheet is 9/16" and is easy on the hands.