opinions please!

Hello fellow boat doodlers. I need some input on my dreadnought 48. Any rule of thumb on a reasonable deck height obove the LWL
I tend to set mine a little low to keep the A/B ratio down. I think the scuppers are 14-18" above the WL. I don't see much problem if you are making headway in little rollers but I think a following sea could keep the aft deck awash with no problem. With the proper math I could figure stability with say 6" of water on the deck and see what happens. What about one way scuppers? myth or a functional option? I guess what i'm asking is... Do you real designers think to yourself "On a bluewater boat I would never go less than (?)"...Any input would be greatly appreciated!
8Knots

 

Well Paul - I'm certainly no 'real designer' - but won't let that stop me from putting my 2 bobs worth in

1. Pretty much forget the A/B ratio - from all that I've read, it's inaccurate at best and misleading more often than not- an attempt to categorise craft when you don't have much in the way of hydrostatic details available. Better to go by "real" coefficients that are easy enough to calculate if you have the info to hand.

2. Rule of thumb for scuppers - you can't have too many and they can't be too big! (So long as they are smaller than your kids of course! ) I've seen quite a few variations on the one-way scupper - but rarely on an commercial fishing boats. That would be enough for me to be wary about using them.

3. Decks will only be awash if waves crash over your bulwarks or if (limited amounts) water enters via open scuppers. But they will become 'submerged at lower angles of heel - so ultimate stability is effected

 

Don't sell yourself short Will, I have every confidence you will be a great designer! Amen on the A/B ratio... I gathered that from Skene's book. To me it just seems like common sence to keep those weights down. I dislike those hulls that look like a 4 plex on a jon-boat. The math involved in hull design remindes me of all those speeches my dad gave me on "paying attention in math class" Never would have guessed that I would need to know the value of "X" Ahhhhh the lessons of life!
An off topic question for you Will.... Will you have to be "licenced" in Oz when you open your design firm? or can you just start doodling.
Thanks for the input! 8

 

Not to put too fine a point on it Paul, but ...well.... buggered if I know!!
My enrollment in Westlawn was done out of a passion for all things that float, rather than any real intention of entering the professional design arena. The market for designers in Tasmania is a small one to say the least (the only practising na that I know of recently moved to Sydney....). Like you, 1st ticket is to completely design (then hopefully build) a boat for myself. After that, who knows - it'd certainly be nice if a could pick up a couple of jobs here and there.....
btw - thanks for the vote of confidence in my future at the moment, I'm so muddled with various CAD programs that I'm not so sure that I share it

 

hmmm - didn't actually get 'round to answering your question...
I believe that (like most other places) I can call myself a designer, but not a naval architect. Though I haven't checked to find out...

 

After you question regarding Westlawn / NA qualifications, I contacted 'my local RINA bloke'. He in turn asked the CEO of RINA. His response shed some light on the topic....sort of!

So, from that I guess you can call yourself a Naval Architect almost without any formal qualifications, but RINA will not necessarily recognise you as such...
Hope that helps Paul....

 

P.E. Registration / NA title

Although precedent and common law in the US probably makes most practice of yacht design per se "drafting services" and hence practice not requiring a license, use of certain titles (and certain descriptions of services) in certain states (and Canadian provinces) can be construed as an offer to practice engineering, and hence a nominal violation of the law.

It is likely that a court would find that performing calculations and analyses not required by law and not described as "engineering", "analysis", "naval architetctural calculations", etc. in the statutes requiring them is also not practice of engineering. For example, very sophisticated analyses of sailing yacht performance would be OK, because the law doesn't require them. Likewise, checking compliance to the US boating safety act rules is "practical test and inspection", and not engineering. However, for example, 46 CFR 28.500 et seq. requires certain stability calculations of fishing vessels over 79 feet, and describes the individual performing them as having qualification in naval architectural calculations. This might be held as practice of engineering in some jurisdictions, depending on the specific wording of the controlling statutes.

This is all based on the common law, but also involves local statutes, so you should probably check carefully with your local authorities.

 

On the initial question I think 46 CFR, the USCG regulations on such things, is suggestive of an answer in the neighborhood of 1/8 the beam.

 

Thanks Steve! Thats the rule I was looking for. For the other posts above on titles I want to thank you for posting and digging in to it! I too study for my own boat someday. Unfortunatly I know just enough to keep me from buying a production boat. It's a man/pride thing too I guess
Thanks to all
8Knots