View Full Version : Lashing Blocks to Boom

04-23-2016, 07:14 PM
First post ... excuse any errors in protocol please.

Built a hollow boom from Sitka Spruce for a small sailboat and used dyneema soft shackles and bails. But using lashings would simplify construction and I believe add to spar longevity. Are there any sources on how best to lash rings to booms on small boats? Thank you!

Links to images

Shows the block attached with a dyneema bail

Shows closeup of yoke and leather

Drawing conceptualing the build

Hollow sections milled (custom shaper knife) before glueup

Ian McColgin
04-23-2016, 07:31 PM
I'm quite fond of lashing or something such. There are many ways depending on the application. One approach is a strop with each end backspliced onto the block or to a ring.

04-23-2016, 11:21 PM
Welcome to the forum :) While I'm one of its least experienced and knowledgeable members, I'd add a couple of considerations: first, make sure any lashing is wide enough to distribute pressure and mitigate point loading, especially in an area with no core. Second - and your mileage may vary - but on my very smooth carbon boom I had no success getting blocks to stay in place with lashings and ended up having to create something like 'thumb cleats' to prevent slipping.

George Ray
04-24-2016, 02:39 AM
+1 ,
I'm quite fond of lashing or something such.
I use a lot of tarred nylon net twine which lasts an amazingly long time in the direct sun but even using other less UV durable lines, to be made permanent one need only paint them to eliminate UV degradation. The paint both protects and glues the lashing in place but it can still be removed with a small amount of effort with little or no harm to the underlying surface.

wizbang 13
04-24-2016, 06:49 AM
Lashings are quiet,cheap,reliable and safe.
A"soft "eye of dyneema though,may crush or snap spruce.
Nylon is a friendlier choice.

04-24-2016, 09:25 AM
In ABOK there is a kind of multi-pass cow hitch used for hoisting a spar, #1763 & #1764. He doesn't name it, but it looks like the Prusik knot (http://www.animatedknots.com/prusik/index.php). Adjustable if you loosen it enough, like a Magnus hitch, but should stay put when taken up.


PS -- This thread (http://briontoss.com/spartalk/showthread.php?p=6635) may help.

PPS -- Here's how to post photos:
Thorne's new-and-improved how-to-post-photos™ (http://forum.woodenboat.com/showthread.php?121390-Thorne-s-new-and-improved-quot-how-to-post-photos-quot-instructions)

04-24-2016, 10:02 AM
Familiar with the Prusik ... that solution could work. Splice a loop, afix the block and wrap into a Prusik around the boom. Still thinking there must be some way that ends up cleaner.

Brightwater's suggestion made me think of that exact solution. Never would have thought of that as an analogue unless he had mentioned it. I have a buddy that makes carbon poles (for the Thistle) so I'll ask him how he terminates the lashing. Thanks!

The original boom I made had solid sections (shown in the photo in original post) that allowed drilling through the spar. But those solid sections were difficult to make since there were quite a few attachment points (vang, 2 mainsheet, outhaul) and dangerous doing it on the shaper as well. Plus I just wasn't happy aesthetically with the line passing through the boom. We'll see how these lashings work.

04-24-2016, 10:52 AM
I was looking for something with multiple turns to distribute load. You could try an anchor bend

or topsail halyard hitch.

To stop it from sliding, you might serve the mounting area with tarred marline/seine twine. A turk's head knot to either side would decorative slide insurance.

John Meachen
04-24-2016, 03:59 PM
You could secure the rope by locating a lacing eye or small bullseye fairlead,since the rope itself will handle the load and it just needs a little help to remain in place.An alternative would be to sew some webbing to a pair of D-rings.

04-24-2016, 05:11 PM
Welcome to the forum! I grew up (well - got older for a while anyway) on Ridgefield Road.

A strap can work well. I use a piece of dacron sailcloth for a preventer. It's looped over the mast & has D rings at each end. Unless under tension it will slide though.

For a small boom like this, I'd think the topsail halyard hitch pictured above would work well. Maybe sew the end so it won't pull out/through?

To show pics here - do not upload them. Go to you link, rith click, choose Copy, come back here, go to a blank space in a post, right click & choose paste:


04-24-2016, 08:13 PM
I favor multiple turns of seine twine, too. It spreads the load very well and can eliminate the need for a heavier line altogether. The details depend entirely on the nature of the hardware being attached -- does it need to flex or swivel to some extent? How much surface area or how big an opening is available? There isn't a single best way. It's true, however, that you'll sometimes need something fixed to the yard to prevent the lashing from sliding.

By the way, that's some slick work you're doing with the details. Care to share more on this "small sailboat?" I'm guessing it's small but fast, maybe a Paper Jet or some such?

04-24-2016, 08:54 PM
Another way to get lashing to stick in one place is to ... wait for it ... stick them in place. I like PL Premium but it is tan colored, so epoxy might work better. If the spar is varnished, then varnish over the lashing after gluing it in place. As above I like the tarred nylon seine twine for this sorta thing.

04-25-2016, 09:28 AM
Why a hollow boom? Is it finished? Why not a solid boom as the weight helps down at boom height to make the sail shape. With a solid boom there's less of a problem with attaching things. Consider that some boom had running battens to lash the sail's foot, others had reef combs--these are add-ons to the boom and could spread any point load for some distance. These are good for hanging things. For the hollow boom, I'd wonder a bit about a stress point on the thin walls and possible a fracture. Putting internal bracing, once the boom is together won't work out, although some external ribs might.

04-25-2016, 12:05 PM
Nothing fancy or fast ... just looking for efficient rigging. It is a winter frostbite boat, Dyer 9. We sail all winter on Sundays ... about 150 races a season. I was building an extra boat for a daughter to practice race this summer (see photo below). We have a very competitive racing fleet here in Norwalk.
Here is a link to some racing action (I was RC so I took the photos). https://goo.gl/photos/mcZxCSrMFAtPq7oL9


Ted Hoppe
04-25-2016, 03:54 PM
Nylon strapping has expectional properties. I use it on my 13' carbon fiber boom. impregnated with rubberized goop prevents it frome slippage. A elegant stitch pattern with a nicely folded tuck on the wrapped pole and connecting blocks make this solution stronger than stainless shackles and mechanical fittings with required holes, takes a few minutes to do and costs less than a three dollars. Moreover - easy to inspect and replace as needed. The large Volvo transocean racers use this solution.

04-25-2016, 04:03 PM
I'm rather jealous of that nice shop you've got!

Is the frostbiting @ the Norwalk Yacht Club?

04-25-2016, 04:48 PM
Why not a solid boom as the weight helps down at boom height to make the sail shape.

With respect, in just about every class I've ever sailed people want the lightest boom possible, to allow the boom to lift in light winds. If the boom is heavy, the weight means that the upper leach is too tight and you cannot induce enough twist in light winds, especially when there is a lot of wind shear about. When we want to keep the boom down we use the vang or mainsheet, which (unlike boom weight) can be adjusted to suit the required trim moment by moment.

04-27-2016, 08:06 AM
Chris, I'm a non-racer in a boat (Bolger's Chebacco) built for pleasure, so not acquainted with finer aspects of racing nor for that matter with a vang and the finer points of the leach that either I or the Chebacco (or both) don't have the sense to know about. I used to (on an Windmill) loosen the foot in light winds, but that was high tech for me...this many years ago. But a fellow Chebacco builder had his hollow mast crack and sever at the partners due to no internal plug at that location. And old gaffers, as mentioned, tend to have add-ons that affix to the boom so that just about anything can get on to the boom wherever it's wanted. So I added up and got the wrong boom for your racer. I'd give a bit of thought to the hollow boom and stress points however, but that's my "belt and suspenders" approach.

Good luck, and do try to get that workshop a bit messy!