Honolulu Boom / Vang

Got my AMYA mag today and I see my boom/vang is in it again. I am trying to get a follow up as I have since revised it as per tech comm. and Linville to make it legal. I was told that it ( vang ) would be fine if it was only attached to the boom in one spot and to the mast in one spot (12/30/03 ). The front screw and short pieces it screwed into have been removed. They didn’t do anything anyway. It is now a legal vang.

I don’t get the mag, but am always very interested in what I guess is a novel vang. Could you post a picture here of it? Thanks!

What issue is it? And what page? I currently have issue 142.

Issue #124 pg.25 originally. Issue#144 pg.12 recent

With acknowledgement to Rich Matt, esteemed photo editor for Model Yachting magazine, here is a scan of the published image from the most recent MY issue. This is a reprint of the first published image (MY Issue #124). We have no copies of the modified version.

Thanks to Rich Matt for pulling this from his archives.

Dick Lemke
Technical Editor
Model Yachting Magazine


The T-top boom is not new though. See America’s Cup challengers and Defenders c. 1935 (the Park Avenue boom) alhough the aim there was to control the camber of the foot of the main, not act as an end plate (which is what I assume you are getting at here).

Just a question. Shouldn’t the endplate be on the bottom of the vang?


The vang may be legal in the new configuration (with one screw removed), but at a regatta I would still protest the boom (and sails) if is still in the original configuration presented in the MY issue #124. Some areas of the boom (by the cunningham and outhaul attachment and the “T” section) are definitely outside the 3/4" diameter allowed. I would have some issues with the sails too, as Jim said in his original comments published in the magazine.

Anyway, you should definitely post a new picture of the boom.



I have never seen the way you define the “diameter” for the boom. I have always assumed that it pertained to tubular booms, and I have seen some rectangular ones on US1Ms that are at the limit or bigger.

Can you explain where that way of defining the diameter came about?

The diam. of the boom came from the tech. comm. of the time. One of the comm. thought it should be a 3/4" sguare hole. The boom top in the front is now straight and the whole thing passes through a 3/4" washer. The end plate is not used. The front screw was removed. My main issue with the committee was to get a ruling on a legal vang. I could not find any rules on it.

Hoj, I remember the article written by Jim Liville, the CS at the time, with his, and the tech committee, comments. And while I’m not a member of the tech committee, I was commenting on the old figure provided by DickL, and the issues/problems I had, and why I would protest it in a race. If you say that the new booms design passes through a ¾ washer I have no problem, but please post pictures of the new boom.


From the USOM class rules:
4.0 BOOM:
4.1 Boom and club diameters ¾" maximum.
The way I interpret this rule (and again I’m not on the tech comm.) is that the main and jib boon have to pass trough a ¾” diameter, aka a round hole or a washer but not a square, the keyword been “diameter”, and this is how I would argue my protest. In the figure provided by DickL some parts of hoj boom are larger than ¾”.


I recall the spec on booms for the ODOM, which is 3/8 inch diameter, but it also specifies a circular cross-section, so that’s pretty specific. I assumed the 1m rule implied circular also, but apparently not. I don’t have a copy of the 1m rules.

The USOM rule on booms gives only th max diameter 3/4", he shape if up to the skipper. I guess that’s the difference between a one design and a development class.

the 3/4" rule must be something from before CF tubes were invented, and you made your rig on a table saw.

What’s wrong about having rounded corners on the sails? Squared corners obviously gives more sail area, and better stress-relief, but…

The usom class uses the Head, tack, clew triangle to calculate sail area, thus the corners of the triangle must be clearly defined.

You don’t need suared corners to define a triangle. You can just approximate it using two traightedges. If you’re getting that fussy about the corners then the roach should be included in the sail area too, since it does add a sinificant amount of area to the sail(s.) We figured out how much of a difference it was, once.

Yep you can, and come up with an infinite number of different trinagles that all have different areas; so what one is the right one, the one with the most area, or the least?

I belive you’re missing the point. The triangle rule allows for quick and dirty sail area calculation. If your going to count everything, you get into the 3R/10R class method of measuring sail area, whis allows for a greater diversity of sail shapes, but takes a lot more time to calculate.

Are the sail measurement rules online?


may be look for them Tomo?
posting without knowledge of what you are actually talking about is becoming a little tiring,you have been around this forum long enough to lose the newbie tag.
Asking a question is fine…but then arguing about the answers you get when you havn’t even bothered to find out about it yourself is just lame.

I have looked, Brett. The AMYA Handbook ( which is outdated, IMO, has some information on sail measurement. It mentions that the head is the upper edge of the sail, 3/4 inch maximum, and is perpendicular to the luff. For a rounded clew, the measurement is from the aft edge of the head (or headboard, if you actually have one) to the lower edge of the main. The main on my ODOM, which was made by an approved sailmaker, has a rounded head, so I would just measure to a point tangent to the clew (or tack) attachment point (like a hole or grommet) and continuing to the edge of the material for the other sides.

So, as you can see, it does not give a requirement for pointed, or squared corners, but does give a method to involve rounded ones. I agree with Dan, that the pointed corners are easiest to use.

If there is an updated handbook, I haven’t gotten one, and I haven’t had a need to get one, until now. Mine is dated 1992. I don’t see any reason for most of the basic information to be amended. Usually the online copy has he most current information, which you know.

Maybe you think of discussions are arguing, but I don’t see it that way. If everybody has the same viewpoint about everything, then there’s nothing to discuss. You need contrasting points of view in any discussion. An open forum like this one is here to get the viewpoints of people with varying knowledge & experience to give input, contrast, some compromise (probably) and in the end, an accepted conclusion.