Light vs Heavy boats

[Tom967]

Originally Posted by Catamount

Tom, this is not always true. For many boats, particularly lighter boats, sailing heeled well over is not fast -- sailing flat is faster. Too much weather helm is slow -- re-balancing the sail plan to reduce weather helm is faster. In other words, often when you reef you speed yourself up!

True, for many lighter boats (mine has D/L around 200) with relatively high SA/D ratios (mine has an SA/D around 20), we might reef in conditions where heavier boats (say D/L over 300) with lower SA/D ratios (say 16) are just getting going under full sail --- BUT all our reefing has done is bring our SA/D down to be in line with that of the heavier boat under its full sail.

Regards,

Tim

That Above Quote used by Catamount..a few replies above this one..."Reefing slows you down" was twisted, taken out of context....before sentince completed... The reference was germaine to the vessel (mine-heavy) that had no need to be reefed since it was efficiently sailing full and by...Reefing in this case would have diminished my speed.."Before you comment... please read to comprehend.."

[Inthewind]

When it goes bad out there and I have been there, I feel more secure in a heavily built boat. Not saying that a lighter boat couldn't handle it, but you can feel the diifference in a light verses a heavily built boat. In my opinion, I like rugged heavily built boats. Lighter boats in light winds are faster, but I am usually in no hurry. You might get to a destination a little faster than me but you will see me there, unlike 99.999% of society.

[Celestialsailor]

If your cruising, a light boat fully loaded (and usually over-loaded) will squat and lumber and most likely loose any advantage to a heavy displacement vessel. My ingrid can take on 2000 lbs and only loose a 1/2" of waterline and the sailing characteristics do not change. She will still sail on her own without a hand on the tiller if I have done a good job balancing the sails. However...when I come into my slip, it is more like a controlled crash rather than a docking!!!

[Tom967]

Celestial...I love your quote..I was wondering where Anna Nicole fit into that equation...

Exactly right..It's called in yachts..Pounds Per Inch Immersion...in ships it was referenced as Tons Per Inch Immersion...The formulas proportional to displacement..The more weight added to a heavier boat...the less she would immerse than an equal weight to a lighter boat..

In addition moments to trim one inch a moment (weight X distance) is directly related to displacement...in short greater flexibility to loading..

The advantage of course in light displacement is generally superior performance in most conditions.... but, since all design in scantling and rigging considerations are based upon displacement data..the construction is more robust and heavier rigging mandated by the data..

Olin Stevens The dean of modern boat design summed it up best..When asked what constitutes a good ocean boat..His reply .."A strong Boat"

Since 90% of the sailing public...putz around the buoys..The interest is in performance...suggesting lighter scantlings..The successful builders..mass producing these things...a la victory ship style..

In short..If your plans do not permit long term cruising...I would opt for performance...in the lighter displacement area

Distance cruising....opt for heavier displacement... "stronger boat"

[GordMay]

PPI: The weight required to sink the yacht one inch. It is calculated by multiplying the LWL area (or WPA, waterplane area) by 5.333 for sea water or 5.2 for fresh. The PPI usually increases as the hull sinks into the water as the LWL area is also increasing due to the shape of the hull above water.
LBS/IN (saltwater) = WPA x (64 / 12)

See also - “Sailboat Design Ratios”: http://www.cruisersforum.com/forums/...tios-1197.html

[Paul L]

So the amount a boat will sink when weight is added to it has nothing to do with what it weighed before the weight was added. Overloading a boat, light medium or heavy, will have a deterimental affect on its sailing ability. An overloaded lighter boat will still typically out perform in light conditions an overloaded heavier boat. In rough conditons, the overloaded boats may both be unsafe.

Paul L

[Tom967]

Gord May:

What you have just said confuses the issue ..What you have said just confuses 99..44/100 of the people..

and that's not what this is about.. it's to educate..and that means nothing.. People don't understand waterplane areas.. Nor do they have the data available less they might have a custom built yacht..That's why I kept it simple.. "just enough to make the point" LOL

Paul you are getting confused I can see that.

If you really want to "get confused."..Go to my website on Stability and Trim...My lectures are used at the US. Naval Academy and the respective Merchant Marine Academy's..on the subject...."But don't come back to me with questions....I don't have the time nor patience to instruct...or even argue..with people who are not interested in learning..having little experience with this stuff and think they know it all...."Stability And Trim...While your at it learn Celestial..and something about upwind sailing..from a pro LOL"

I got to get back to my engine with the new fuel lines..."That I'm not a pro at..LOL

Suffice it to say I have gotten appreciative E-mails from some young budding Admirals and Ship Captains.

www.afewgoodboat.com

[jim lee]

Originally Posted by Tom967

Gord May:

What you have just said confuses the issue ..What you have said just confuses 99..44/100 of the people..

ROFL!! Well that makes me less than 1:100. What Gord wrote made perfect sense to me.

I still think the issue is people lumping light built for economic reasons vs light built for performance reasons.

-jim lee

[GordMay]

The load-carrying ability (PPI) is related to the volume of the hull, not the weight.
Hence; a very large, but egg-shell light hull, would carry a heavier load (cruising stores) than a smaller lead-heavy hull.

Tom967 has an excellent website at: A Few Good Boats .Com
(correct your link, Tom - add the 's' to boats)

Which includes a number of scholarly tutorials, including:
Stability and Trim ~ by Thomas J. Colligan (our Tom967): Seaman/Naval Architect/Yacht Surveyor
Irreverent Navigator: Seaman, Yacht Designer, Marine Surveyor

[Weyalan]

I sometimes think that people can get too focused on the trees to see the wood. At the end of the day, it doesn't, to my mind, matter whether your boat is light, heavy or medium, as long as you understand your boat's strengths and weaknesses, and adjust accordingly. There is no inherently ideal crusing boat. As a general rule, the ideal boat is the one that you've got.

[Pblais]

There is no inherently ideal crusing boat.

They can't sail themselves at any rate. Probably a good thing too. Mine would be off without me if it could.

Boats and people have limitations and Cruising is more about having fun that being any places special. You can either handle the limitations or you are not headed for the fun destination no matter what boat or crew you have aboard. As with most things there is always the bigger picture.

[Tom967]

Originally Posted by GordMay

The load-carrying ability (PPI) is related to the volume of the hull, not the weight.
Hence; a very large, but egg-shell light hull, would carry a heavier load (cruising stores) than a smaller lead-heavy hull.

Tom967 has an excellent website at: A Few Good Boats .Com
(correct your link, Tom - add the 's' to boasts)

Which includes a number of scholarly tutorials, including:
Stability and Trim ~ by Thomas J. Colligan (our Tom967): Seaman/Naval Architect/Yacht Surveyor
Irreverent Navigator: Seaman, Yacht Designer, Marine Surveyor

Volume is length X width x depth...(At the waterline. and below).That's your displacement.."That's the start of your lines plan

If a vessel is to sail on its designed waterline...That's what the vessel "Has to weigh.

Let me give you an example ...I designed back in 1988 a 40 ft vessel with a 34 ft waterline...my displacement calculations were 17,436 lbs..... on the board...Light ship was 7421...internal ballast 5150...keel bolted fin..4500 Totalled 17,071..at launch

Her MTI was 1453 ft lbs..her PPI 1022...So when she came off the ways..she was fashionably showing a bit of bottom paint just below her DWL

So that's the relationship of weight to displacement...AND VOLUME I MIGHT ADD..If you bothered to read first lecture...LOL..you will see I describe the relationship in detail..as weight mirroring the concept of displacement...in detail since it's much more involved and exacting with ship stability..

Displacement belongs to the designer

Weight belongs to the customer..

My boat is a
40'ft.. displacement 23,500...Don't know the sail area ..around there."Someday I'll bother to check it LOL"

But I tricked out the stability curve..ability to carry sail..by giving her a 7 ft draft.....fin keel of course..fairbody shallow..795 Sq Ft

The result High performance..light displacement racer..but in seaway prefer my 23,000#..who needs the pounding at 64... AND 7 ft draft..but she could fly.....

PS...thanks for the plug...don't need it ...I'm retired from all that Jazz.. That's been on the web 8 years..look at it once a year maybe..