Boom Vang

[GordMay]

What JeffH said.

Spring Loaded Mechanical Boom Vang (“Yacht Rod”)
According to Forespar, the minimum angle from the boom should not be less than 30 degrees and nor more than 45 degrees. Lesser or greater angles increase the compressive load beyond what a spring-loaded vang can handle. Hydraulics is the only answer beyond these angles. The “stroke’ is the total maximum compressed travel of the spring/piston. Once the spring bottoms out, the unit will fail if further compressive force is applied.

Note minimum (30) and maximum (45) angle between the boom and Forespar “Yacht Rod”.

[SkiprJohn]

Aloha Trim,
Wow, look at all that teak!! Beautiful vessel. Congratulations!
JohnL

[James S]

I'm also interested in building one if someone has some tips....I prefer to build it with the line on the inside.
I think mine would be about 2m long

[Alan Wheeler]

Well I used two lengths of SST tube. I machined up a teflon sleeve for the larger tube so the smaller could snugly and smoothly slide inside. At the other end of the smaller tube, I machined another teflon sleeve to act as a spacer so as the tubes slid in/out smoothly without binding. The ends I machined from Aluminium and anodised them myself. However a good etch prime and paint would do fine. In side the two tubes is a large Galv spring. That was the hard part to find. I wanted to find a SST spring, but couldn't find one the size I wanted. So Galv it was. It is not 3yrs or more and I just had an issue the other day with the vang binding. Turns out the inner tube I used was not SST. It was piece of tube from a chines something and was only plated. So I have the unit off the boat and am going to replace the inner tube with SST. The end fittings had sheeves in them for the line to run around.
I have it out in my shed. I will take a photo of it and post it. But I can't do it right now cause my camera card has packed a sad and won't work. I have to go buy another memory card.
As for l;oads on the Gooseneck etc, that is not actually a problem. Firstly the vang line takes the boom loading. The rigid Vang is there for no other purpose than to support the boom when the sail is down. There is no compression load seen on the goosneck other than the weight of the boom itself when the sail is down, which results in a pull not a compress. My boom is 8M in length. I have the Vang fitted at 30dg. The 30dg was to get the support down the boom more. The main issue is the boom bouncing. The further down the boom, the more support and less bounce.

[James S]

Boom bouncing...I didn't think of that...
I'm looking forward to the pictures.
I wanted to have all the lines inside but with a reasonable size shieve and 3 side by side the pipe dia gets pretty big.

[Steve Pope]

Alan I have just had some SS springs made in Auckland for my boom vang, I used the original "rusty" one as a sample and had 3 made, each one 25 mm longer than the first one, so if I need more compression I can shift the pin and install a longer one. The firm is CMI Springs 09 5794089. They do have a minimum charge of around $80.00 and I was led to believe that the 3 they made would come within that but the final bill was $170.00. That may have come about because they first made them of of spring steel and not stainless so I May (?) have paid for the error, anyway I am happy with them and the $170 .00 wasn't so far over the top given what hourly rates are these days.