Righting moment

[Watershed]

I've gotten a request from Croatia for Righting Moment values. My old computer hard drive failed and is not recoverable. Does anyone have a copy of righting moment graphs from Chris Beckwith's original calculations?
Tim
Watershed
i550watershed@yahoo.com

[Tim Ford]

I will check. Have you asked on Facebook? I would suspect Andrew does.

[Chad]

i550vpp.pdf

(471.59 KiB) Downloaded 367 times

Page 2 of this report that Chris had done has some righting moment info.

[Warren Nethercote]

Presumably Lb.Ft for righting moment.

I also wonder a bit about the polars. Unless I misinterpret them, they suggest running square for best VMG downwind across a range of wind strengths, and lower boat speeds than I have experienced. I wonder which code was used - if it used the old Standfast tank data then it might be the issue.

[Big_Dog]

From what I remember from talking to Chris, this data was computer generated. The software available 10-20 years ago, were better for 4KSB design analysis, than predicting light planning hull performance. Better proprietary software was developed in house by large boat companies for their use. There have been many advancements in software since this document was done, so i'd use it as a starting point.

[admin]

Good stuff, thanks for posting that PDF Chad! I had misplaced that on some machine or another and have not seen it for quite awhile.
Jon, I agree...some of those numbers seem just plain wrong.

I would pony up for an ORR-Ez cert and see what Jim Teeters can spit out, but I'm pinching pennies these days...at least through the holidays and tax season.

[Chad]

I vaguely remember this being an ORR based analysis that US Sailing offered for almost free. The i550 is clearly not an ORR boat, and I think this kind of report didn't include any actual hull lines analysis- it's just based on the reported numbers shown.

I did some back of an envelope righting moment numbers to see if I could come close to the ones shown based on the inputs provided (150# @ 4.6'; 1300# 'sailing weight' less 800# boat weight = 500# crew ballast @ 1/2 Bmax of 8' + 1/2 Waterline width of 4.6') and got nowhere close.

Maybe the 1300# weight is just assumed to be centralized, which makes no sense in a boat that depends on crew ballast. But that doesn't come close either, unless you think the moment arm available at 1 degree is about 1/16" of an inch vs. about 4' in reality.

But the document does look official and all, so if that's what ya need to get a rating somewhere...

[Tim Ford]

A couple maybe three years ago, I was doing some work with ORA on their ORR-Ez product release. I was up in Newport and Jim and the CEO were talking about rating a Viper 640. I said, "are we in the business of rating sport boats?" And the bottom line was the bottom line.

Now ORA offers a 1-D cert (ORR-Ez) for Vipers, Melges of varying lengths, J70s and even a one-off cert for an Elliott 6.5 S.

They've been bugging me to apply for an EZ cert but it's just a waste of funds for my boat. It can be done though! Probably not the best timing...ORA is in a dynamic situation internally and with some big races on the slate, including N2B, and it's a bad time to ask.

PHRF of the Peake did not need an RM number for my rating cert.

[Watershed]

Tim I appreciate the input. I am also engaged with the French ORC trying to get them to even consider rating an i550. the builder has been ignored and given the impression that do not appreciate nor will they (provisionally) rate a home built boat. He may be in the position of having to ask "hat in hand" to even be allowed to race at each individual club.

[Tim Ford]

Tim, I saw a mention of this boat in SEAHORSE. Homebuilt plywood boats! I think I'll add 12 inches to PLANE RIDE and sign-up for the Transat!

Granted, it's one-design so no ratings, but boy does this class look familiar! Cheggitout:

https://globe580transat.com/

the video is interesting!