Arwen's meanderings

Hi everyone and welcome to my new blog. My name is Steve and i am the lucky owner of a John Welsford designed 'navigator' named Arwen. I built her over three years with the help of my father, father-in-law and two children. She was launched in August 2007 at Queen Anne's battery marina in the barbican area of Plymouth. This blog is a record of our voyages together around SW England.
Arwen has a YouTube channel of her own. Search "plymouthwelshboy".

Monday, 12 September 2016

Snotters and sprit booms

More up to date blogs about sailing and trimming a standing lug sail with sprit boom can be found in the March 2018 folder on the right hand side of this post. 

Sprit booms have been exercising my mind recently, well using one effectively. On Arwen, the snotter is a double block affair in which the tail end of the halyard runs back along the boom to cleat on top. If you want to adjust the boom, you need to go forward leaving the helm for a minute or so. I wonder if it would be better to alter the arrangement so that the tail end of the rope tackle goes down vertically along the side of the mast, through the deck, under a block attracted to the top of the front thwart and back along the centreboard side casing to the aft cockpit, from where I can better control it. I rarely ever adjust the snotter/boom when sailing, a very lazy and frankly poor seamanship state of affairs. Consequently, I really don't fully understand what the snotter and sprit boom really do.

So where am I on understanding?

The snotter tensions the sprit boom moving it forward or backward relative to the mast position depending on whether I am hauling or slacking off the snotter tackle........I think!

The sprit boom acts as vang and boom in one and requires no outhaul on the sail. The bit of sail below the boom stops the sail from hiking upwards when you ease the main sheet. And this all prevents the sail from twisting.......I think.

Bringing sprit boom aft flattens the sail and tensions leech and foot. This means that the main sheet now only ease out or hauls in the mainsail and doesn't have to tension the leech as well.........I think!

I can move the snotter position up or down the mast short distances which I think alters the angle of the sprit boom, where it positions itself in the aft cockpit (and how much I have to duck down for it to clear my head!)...........I think.......!

That's an awful lot of unpurposeful and vague thinking isn't it!

I have often wondered what would happen if I removed the sprit boom. Would it just become like a drascombe with a loose footed sail? Does it work like that or does it depend on the sail shape, cut and design?

On windy days when there are gusts and lulls, would Arwen sail better without it; would lack of sprit boom allow more upper sail twist so that in gusts wind would be spilled from the top of the sail thus reducing the need to reef so early. Using the boom, in gusty conditions with lulls, you can end up reefing and unreefing frequently which can be frustrating.

 (As an aside, on such days, my first course of action for reefing is to furl the jib and lose sail area that way. The second reefing is then to lower the mainsail slightly, move the down haul tackle up to the the higher reefing point on the luff and then raise the mainsail again slightly, applying downhaul tension. I then move aft and pull on one of the jiffy reefing lines to take in the sail at the aft end. This done, I then brail up the flapping sail. I wonder if perhaps simplifying it further might work by getting rid of the jiffy slab reefing system thingy and just take the clew off the boom and then reattach the aft boom higher up on the reefing clew).

I find going downwind that Arwen is reasonably easy to control, the sail is out fully, the shroud acts as a preventer of it going forward of the mast. The boom keeps the sail a nice shape but she does seem slow and the jib is of course blanketed completely. I guess I could use a whisker pole on the jib but I have no idea how that works in practice or whether it would make any difference anyway.

I also think that the foot of my sail was cut with a slight curve to it by the sail maker. Not knowing anything about sail design, I never noticed at the time. However, I wonder whether or not the sail should have been cut with a straight foot. It always seems to me that Arwen's sail always seems slightly billowed at the foot. The gap between boom and sail can almost be two foot......which could be due to incorrect tensioning of the sprit boom I guess............but that sail foot always seems slightly baggy irrespective of what position boom and snotter are tensioned to. In fact I would also muse on whether or not that slight looseness in the sail foot is responsible for the tension crease I have permanently in the sail from tack to clew. It never disappears, irrespective of how I adjust halyard position on top yard or tension on downhaul and snotter. It is a permanent fixture on Arwen's sail.

I do wish someone who really understood see things could come out with me and refine the system to make it so much more simpler than it feels. I feel I have over complicated things through a lack of real understanding. Don't get me wrong, Arwen sails reasonably well except in light winds, but simplicity is the key and over complicating things is daft!

No comments: