# Wide Transoms...A Discussion Thereon. (was Jeff-H)



## windship (May 4, 2002)

Will you please explain to me how a wide transom can NOT cause a fine bow to dig in. Could you also explain the wide transom thing? (one...more...time)
I''ve always been a ''traditional'' guy and I''m really trying to understand modern hulls.
Add anything else you''d like, to educate myself and others, if you will.
I will be moving up soon and I want a boat that goes well to weather and is fast.
Thanks,

Dennis


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

I am a little short of time but let me see if I can give a quick explanation. First lets start with a simple example. If you visualize a hull that was essentially a simple cone in shape balasted so that the point was at the surface of the water, you could spin it all day long and it would not change trim in a manner that would tend to force the pointy end down.

While the design process for a hull is obviously more complex, what allows a wider stern boat to heel with out going bow down, is that the hull is modeled so that the longitudinal center of buoyancy does not shift as the hull is heeled (at least through moderate heel anglee). Designers have simply shifted the longitudinal center of buoyancy aft but, of course, the longitudinal center of gravity has also moved aft in the hull the same amount as the longitudinal center of buoyancy. As a result the boat can heel without changing fore and aft trim at least through through small angles of heel (perhaps as much as 20-30 degrees of heel).

This of course requires careful modeling to maintain the same longitudinal center of buoyancy as the boat heels. Computer modeling becomes really critical to this process but most good modeling tools will show the center of buoyancy at various heel angles allowing the designer to move a little more buoyancy aft or forward to maintain trim with heel.

Although a very crude design compared to more modern designs, the pictures of my boat under sail demonstrates how little change in trim can occur with heel angle even on a boat with an extremely broad transom and fine bow. You can find a number of useful pictures on the Cruisers Forum Website:
http://cruisersforum.com/photopost//showgallery.php?ppuser=189&cat=500

The best picture to understand this is the one labled "Synergy Bearing away". Here she is heeled roughly 30 degrees and you can easily visualize that while any individual segment of the forward portion of the hull builds increased buoyancy slower than the transom area, the bows proportionately larger area and longer lever arm offsets the comparatively rapid increase in volume in any individual segment near the transom.

The following was exerpted from an earlier discussion of this topic:

"There seems to be a lot of discussion about why newer boats have wider sterns. There are a lot of reasons that modern boats tend to have wider sterns but increased accomodations is not necessarily one of them. More on that later. If we look a little bit of history, after the Fastnet disaster a lot of attention was focused on what makes a good seaworthy boat. Motion at sea became a popular research topic. Hull forms and weight distribution was studied in great detail. One of the trends that came out of all of that study was boats with longer waterlines and finer bows. Moving the waterline forward reduced pitching and making the bow finer reduced the impact with waves in a chop.

"As bows became finer the center of bouyancy moved aft as well. At first this produced boats that developed a lot of weather helm as they heeled and which tended to jack their rudders out of the water and wipe out easily. As designers got better at modeling hull forms this became far less of a problem.

"This combination of fine bow and powerful stern sections were found to offer exceptional upwind performance and reaching speeds that are substantially higher than theoretical hull speeds. So this fine bow, more powerful stern hull forms were really a win-win design trend that offered greater speed, coupled with better motion comfort and seaworthiness.

"In a recent issue of Sailing World (More than a year ago now) there was an interesting couple paragraphs dealing with theoretical hull speed which touched on the issue of theoretical hull speed as it relates to these new hull forms. I am quoting here:

"Waterline''s affect on hull speed is theoretical and not absolute. As a hull goes faster, the bow wave stretches to the point where the bow and stern wave become on wave cycle, whose wavelength is equal to the waterline length. This brings us to wave theory. "

"The speed of a wave (in knots) is equal to the square root of the wavelength (in feet) multiplied by 1.34. If your boat has a waterline length of 32 feet, the theoretical hull speed is 7.6 knots. The waterline length is thought to limit the hull speed because if the boat goes any faster the stern waves has to move further back taking the trough between it and the bow wave along with it. As the trough moves aft, it causes the stern to drop, making the boat sail uphill."

"Except for planning designs, sailboats typically can''t generate enough power to go any faster and climb their own bow wave. But a boat with extra volume in the stern can exceed its theoretical hull speed because the extra bouyancy prevents the stern from dropping into the trough. By the same token, a fine-ended design might not achieve its theoretical hull speed if buoyancy in the stern is insufficient." (Written by Steve Killing and Doug Hunter).

I do think that it is a bit of a stretch to say that these broader sterns resulted from trying to stuff in additional accommodations. I say this because as the stern gets broader, displacement is removed from the bow thereby reducing usable accomodations volume in the bow. If anything the accomodations are just shifted aft a bit. That is not necesarily a bad thing as the stern is generally a quieter area with less motion than the bow."

I need to get back to work!

Regards
Jeff


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## windship (May 4, 2002)

*Jeff-H*

Jeff,
Thank you for slackin'' off long enough to post. I understand better and agree.

Dennis


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## TSOJOURNER (Dec 16, 1999)

*Jeff-H*

Dennis,
It won''t matter what your hull speed is when big waves/whitecaps are lifting a big azz stern. Reserve buoyancy will lift the stern, increase speed and bury the bow or start a broach type course change. Spend a few hours sailing this way in storm conditions and it won''t be fun. Big sterns are not big wave friendly when running downwind. How big are the waves is the factor.


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## windship (May 4, 2002)

*Jeff-H*

Billpjr,
I agree and that is why I wouldnt want(though some would disagree)this type of boat for ocean voyaging but for here in Buzzards Bay, I think that I would rather have the performance to weather.
Two to four foot seas are quite common. Six footers, about three or so times a month. Eight to tens about mabey twice every six monthes and I''ve been ten to twelves once (you''d see those about once a year or so) and most of the time the seas are choppy.
What would would be you recomendations on a boat for these conditions?

Dennis


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

Billpjr, I really disagree with your statement,"It won''t matter what your hull speed is when big waves/whitecaps are lifting a big ass stern. Reserve buoyancy will lift the stern, increase speed and bury the bow or start a broach type course change."

I think that is an antiquated opinion. I just have not found that to be the case. The fine bows and narrow water planes on the better designed IMS derived newer boats can actually actually track quite well. By moving the center of gravity aft, the tendancy to bury the bow is greatly reduced even over more traditional designs.

In my own case sailing aboard more modern designs in heavier conditions, I have not experienced the kinds of broach problems that you mention, and certainly not as badly as I have experienced in more traditional water craft, and earlier CCA derived boats with their short waterline lengths, or IOR era boats with their comparatively blunt bows and pinched ends.

If you look at the extreme conditions experienced by the Volvo race boats, or even in the most recent Sydney Hobart, these newer designs are proving to be quite seaworthy and manageable even when pushed hard downwind in very extreme conditions.

That said, anything can be taken to an extreme and an overly broad transoms and beam found in cruising boats derived from the Open Class (Around Alone) boats, can be very difficult to handle in extreme reaching and running conditions.

Jeff


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## TSOJOURNER (Dec 16, 1999)

*Jeff-H*

JeffH,
We disagree on a lot more than this. You have a major bias toward racing and appear to hold the conception that the boat is always controllable. Under normal conditions this is true. Fine bows, calcs, crew, etc only offset the effects of wide transoms to a degree. My take is your idea about the size of a big wave and mine are different. Your idea of crew size and ability for an avg sailer must also be different. Sydney Hobart mega racers are apples and oranges to yachts sailed by normal people. Thinking wide transoms are better for sea keeping isn''t something I''d endorse as easier to sail or better for the avg jack.


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## PCP (Dec 1, 2004)

*Jeff-H*

Billpjr, I agree with you.

That''s why relatively small modern ocean going boats like modern Najads, Malos, Halberg-Rassys are less beamier and have a much more moderate transom than Bavarias, Jeaneaus and Beneteaus.

The first are heavier boats, designed mainly as passage makers, and made to withstand heavy seas. The others are boats that are used and designed mainly to the Mediterranean, taking in account the conditions you find there. Big waves are not one of those.

I am not saying that Bavarias and Beneteaus are not able to withstand heavy seas, I am only saing that the other type of boats are a lot better at it.

The Volvo ocean boats are 65f boats and comparatively to what Jeff calls "modern boats" have not wide transoms, nor have they large beams, considering the length.

Paulo


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## dman (Dec 25, 2004)

*Jeff-H*

I have to agree with pcp billpjr oh this one.I find alot of apple to orange comparisons.Formula 1 car and a 59 caddy.You can argue which does what better.Trying to compare a boat with another that are light years apart with different purposes goes nowhere.


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

Billpjr

To quickly touch on your points here.....

"You have a major bias toward racing and appear to hold the conception that the boat is always controllable."

"Your idea of crew size and ability for an avg sailer must also be different. Sydney Hobart mega racers are apples and oranges to yachts sailed by normal people."

I have a major bias towards easily handled boats and boats that offer good performance. I do not have a bias towards racing. I cited the Sydney Hobart race study because unlike many other forms of racing, the Sydney Hobart fleet that was studied was marked by high winds, huge seas (12 to 20 meters), and by a mix of boats from the most up to date go fast racers to very traditional 1930''s era boats.

I do not believe that a boat is always controlable, just that IMS derived designs with comparatively wide transoms seem to be proving quite controllable as compared to many so called cruising designs.

"My take is your idea about the size of a big wave and mine are different."

I do not know what your idea of a big wave is but my idea is somewhere between 12 and 20 meters.

Respectfully,
Jeff


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## dman (Dec 25, 2004)

*Jeff-H*

My take on all this is simply a wide transom on a displacement hull that does not come out of the hole does nothing to improve seaworthiness and would also hurt you in following seas.Actually with that setup you would slow down. In a design which promotes planing,it helps raise it out and if you are racing that is where you want to be.Now if seas are getting heavy and you need to reduce speed and thus loose the ability to plane I look at it being a disibility in a following sea. anyone else agree?


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## dman (Dec 25, 2004)

*Jeff-H*

Jeff When I read 12 to 20 I didn`t realize that it was meters! What you are describing is a mountain of water.I live in the North Atlantic where some of these exist but if ever hit with one I wouldn`t be writing about it after sailing in a 30 foot boat.It wouldn`t matter if my transom was 2 feet wide or 20 feet wide.I`m sure the other posts are trying to make the point of a 12 to 20 foot sea.And before someone writes in and says they did ,where there is 1'' 20 meter wave there will be more to follow and in the boats we are describing here, if you ever did survive such an event you must be living a church going lifestyle.


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## PCP (Dec 1, 2004)

*Jeff-H*

What is ideal for racing, is usually not ideal for cruising and even for ocean racing, wide hulls and transoms make only sense if you are limited by the rules and can not have a longer and less beamier boat, for the same weight..

Listen what Dave Gerr says about that:

"Wide, shallow hulls tend to pound upwind (and sometimes downwind). They can be difficult to steer because when they heel, the waterplane becomes far more asymmetrical than a narrow hull of the same parent form.

....The ultimate drawback of wide, shallow hulls is that their reserve stability is usually very poor.

Generally, a moderately slender hull (longer for the same displacement with a careful thought-out waterplane moment of inertia and a low enough vertical center of gravity ) will be a better all-around performer than a wide shallow hull.

The moderately slender hull will also be easier to manage and more confortable in a seaway."

Dave Gerr in an article published in Sail Magazine - 9/2004.

I think that cruiser/racers or racers are beamier and have larger transoms because they have to maximize initial stability (sail power) to a given length.

I think that passage makers are not designed thinking in racing, they don't have to maximize performance for a given length, they are designed thinking in seawordiness and overall performance and that's why they are less beamier and have more moderate transoms.


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

I basically agree with Dave Gerr that "Wide shallow hulls tend to pound upwind", but we are not discussing wide, shallow hulls. We are discussing moderate beam boats, which have had their center of buoyancy moved aft, resulting in comparatively wide transoms. More specifically these are precisely the boats that Dave Gerr is referring to when he says, "a moderately slender hull (longer for the same displacement with a careful thought-out waterplane moment of inertia and a low enough vertical center of gravity) will be a better all-around performer than a wide shallow hull. The moderately slender hull will also be easier to manage and more comfortable in a seaway"

The idea that racers and racer/cruisers are by definition "beamier and have larger transoms because they have to maximize initial stability (sail power) to a given length" is very much an outdated idea, at least in terms of the IMS derived performance cruising boats upon which my comments within this discussion are based.

Respectfully,
Jeff


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

Again, I have a problem with using anecdotal data on a small sampling to make a case. I have sailed traditional 26 footers that tracked well in a wide range of conditions (my folkboat for example), and a whole bunch of equally narrow traditional boats that tracked miserably. I am not sure what kind of boat that you own so it is hard for me to comment. I also want to point out that I have been agreeing that there is nothing worse than a poorly designed boat with a a lot of beam that results in wide transom and you may be unfortunate to own one of them.

But the original question was about boats with large transoms and how could they possibly handle well. It was not about about beamy boats that also had wide transoms.

Gerr says "moderately slender hull", he does not say extremely narrow. 9''8" beam on a 60 footer is extremely narrow. perhaps using a couple example to explain my point, I think that we would all agree that a late 1990''s era Hallberg Rassy 39 with a 12''-4" beam has a moderately narrow beam and a small transom. In comparison, the 40 foot Beneteau 40.7 which is at the racer and beamier end of the spectrum that I am speaking of, has a beam of 12''3. Similar beams. The 40.7 actually has a narrower beam to waterline length than the Hallberg, yet the Beneteau 40.7 has a much wider transom. Based on a conversation with an owner of a Hallberg Rassy 39 who delivered a 40.7 in heavy conditions, he felt that despite the short chord foils on the Beneteau, the 40.7 was easier to keep on course in a following sea.

While you are right that in a following sea, the water has a larger area to lift on a boat with a wider transom, the more aftward position of the center of gravity on a properly designed large transom boat means that there would not necessarily be a change in trim, and the finer bow would trick the water into thinking that this is a narrower boat helping the boat to track better, than a boat that has a fuller bow.

Respectfully,
Jeff


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

I think that we have gotten to the point where we are perhaps debating semantics rather than substance. I understood that the reference to the 9''8" beam 60 footer was quoted from Gerr and but I also understood that he referred to that beam to length ratio as ''extreme''. In the quote he contrasted the beam to length ratio of the Open Class 60 with a moderately slender beam that he says is more ideal for cruising. This dovetails with his other quote extolling the virtues of a well modeled moderate beam boat, which I still contend is precisely the boats that I am also advocating. The clue to that we are talking about the same thing his discription suggesting the importance of carefully modeling the waterplane shape of the boat.

I think that Gerr is saying that from his stand point the perfect racing hull is an extremely slender hull but that the perfect cruising hull is moderately slender. He and I are agreeing. What is not explicitly being discussed in Gerr''s quote is the longitudinal position of the center of gravity and buoyancy. The current thinking on seaworthy and seakindly design principles places the center of gravity and center of buoyancy further aft than they had been in the past. This results in larger stern sections than had been typical in 20th century designs.

With regard to the choice of boats to compare, I purposely chose the Hallberg Rassy 39 specifically because it is an older and highly respected offshore design. I chose this example trying to illustrate that these newer designs with larger transoms do not have to have to have an extreme beam in order to end up with larger transoms and that the transom size resulted from the aftward placement of the maximum beam rather than from an increase in overall beam of the vessel as been suggested in early discussion.

Lastly like so many things in yacht design, I am a firm believer in moderation in the design process. While extreme design may be justified for all kinds of very spicific applications, when designing a cruising yacht I feel that there is a need moderation in all of design decisions that a designer may consider. I believe that I am in agreement Dave Gerr and with the majority in this discussion that is not a healthy thing to carry to any extreme such key seakeeping factors as the amount of beam, overall displacement, transom size and shape, the distribution of weight and buoyancy, or the position of center of buoyancy and gravity, etc.

I think that we are now discussing the finepoints of our individual definitions of ''extreme''and I am trying to point out that within this discussion there is a range of transom size and weight distribution that may not coincide with historic norms but within any reasonable definition are still quite moderate and when incorporated with properly integrated and balanced design has been shown to successfully improve seakindliness, seaworthiness, load carrying capacity, and performance over more traditional hull forms which were conceived within the limitations of the materials available and the specific uses for which these vessels were being used.

Respectfully,
Jeff


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## PCP (Dec 1, 2004)

*Jeff-H*

This time I have to say that I agree with you. 
It is clear that in recent boats, even in passage makers, designers have also"place(d) the center of gravity and center of buoyancy further aft than they had been in the past. This results in larger stern sections than had been typical in 20th century designs".

But you do not need to have large transoms to do that. Large transoms that offer more surface to breaking waves are not a desirable thing in itself.

To see what I mean, go to the Malo site and take a look at the new Malo 40. Compared with the 10- year-old 39, it has larger stern sections. That, in the less expensive version results in a slightly broader transom, but in the Classical version (that, I think is the one that goes with the spirit of the boat) the narrow transom is maintained.

Being the waterplane the same in the two versions, they have similar sailing characteristics.

The Classic version has the added advantage offered by the small transom in following heavy seas.

Of course, it has also two disadvantages: the small increase in weight (that I don''t believe it has any importance in this type of boat) and the increase in price.

Respectfully

Paulo


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## TSOJOURNER (Dec 16, 1999)

*Jeff-H*

Jeff, I admire your patience. As an owner of a very beamy cruising tub, with a moderately fat ass, that, little known to most, has racing pedigree ( hull designed by Nelson Marek) I can attest that the long, but relatively light nose is easily controlled, even when running downhill.

If waves become 12-20 meters, it doesn''t matter what you''re driving, you throw a drogue out the back and slow down, or else you run the risk of digging in the bow, fat, skinny or indifferent.

For a good visual:

http://www.woodenshoemusic.com/Images/familypics/Forumshots/TopClimber.jpg

Oscar
C42 # 76 "Lady Kay" (Ex. C250 WB #618 )
Georgetown MD/Fort Lauderdale FL


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

Whatever patience I have comes from years of light air sailing and trying to explain and reach understandings about complex subjects over a medium that really is pretty ill-suited for that purpose.

While I basically agree with you about trailing a drogue in those conditions, I once talked to a fellow who single-handed a sistership to my boat from Capetown, SA to the Carribbean. He told me that he was in 30 to 50 knot winds for the first 10 days and was sailing in seas that built to what he estimated to be 40-50 feet in height (trough to crest)with occasional higher waves thrown in. He said he ran for days under just a jib or a storm jib with the windvane doing all of the steering. He said that he was at 16 knots long enough for that to show up on his GPS as his fastest speed run. I only mention that because no one would consider my boat to have a small transom, but she is not terribly beamy either. The newer designs have even better seakeeping and tracking ability than my boat which is more than a 20 year old design.

I do want to repeat my earlier comment that designing a boat with a largish transom and good seakeeping ability takes a lot more care in modeling than designing a boat with its center of buoyancy further forward and a narrower run. Done right, it is worth the effort. Modeled poorly, the boat can be a real handful.

Regards
Jeff


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## dman (Dec 25, 2004)

*Jeff-H*

Jeff did you ask this guy if he was crazy.50 foot wave ,surfing at over 16 knots!Sure he wasn`t on an episode of fear factor.Not to mention days of this activity.This is definitely scaring off wannabee sailors.This guy actually went to sleep.Now that sounds like a real family outing.


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## dman (Dec 25, 2004)

*Jeff-H*

I sent this message just to illustrate a point.I live in a small fishing village in the north east and there are no protected waters.Standing along the coast I watch the fishermen go out most every day of the year.Every family who lives here has lost at least one family member to the sea.Standing on a cliff I can feel the earth move from crushing waves ,on nice days not to mention stormy weather.I have left without a breeze and bobbed in large swells many feet high.Waves which have crossed an entire ocean.I think we take some of these stories lightly with some humor.The sea is and remains seductive,however, it is a killer waiting for another victim.We must never think of it as anything else.Whenever I leave to go out there I have butterflies.I think that many people get a false security listening to someones daring or foolish actions,depending on who you talk to.I just want everyone to be prepared and being afraid of the ocean is normal.Huge waves kill so do whatever you can do to avoid them.


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## Jeff_H (Feb 26, 2000)

*Jeff-H*

Amen....


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## PCP (Dec 1, 2004)

*Jeff-H*

Dman, I agree with you.

I have said that I had been in the sea in a 26ft boat with 7m waves and it is true, but it was only once and I was young and foolish (20 years ago).
The weather was not bad when I sailed out for a 100M passage, the meteo reports were not accurate those days (at least here) and I didn't have a radio. I was caught by the weather in a coast without safe ports and I had to endure it. I was scared (my boat was 60 years old) and I was lucky. I have to say that I also had a lot of fun...Stupid guy&#8230;.

It is my opinion that, if you don''t have one of those rare and very special ocean going 27fts, it is very stupid to be in the sea with 7m waves in a 27 footer.

Like you, I live near a fishermen's village in the west cost of Iberia''. The coasts are unprotected too.

I guess that the size of waves is not everything because generally, here we don''t have waves bigger than 10, 12 meters, and I can assure you that with a weather like that, along the Portuguese coast (in Spain you have the Rias) the vast majority of the Ports are closed, only the big ones, like Leixões or Lisboa remain open. I remember in the last years several cases of yachts (foreigners mostly) shipwrecked when attempted to enter closed bars. They are deadly places. Unfortunately in most cases it was not only the boat that was lost.

Here there are plenty of days when fishermen don''t go out, and they have strong seaworthy fishing boats, normally between 25 and 45 meters long with two motors, sometimes with a total power of more than 1000hp.

From Summer till know, along these coasts at least three fisherman boats were lost, one of them with all hands and several cruising yachts had the same luck.

I leave near Cape Carvoeiro .The name means "the one that works with coal" is a very old name and the one that works with coal (hell) is the one that it is not nominated (gives bad luck) ,the devil himself...You can imagine that there is a reason for that name, as there is a reason to name a coast , also a very old name, called "Costa da Morte", or in English, Death Coast .

Yes, I fully agree : "I think we take some of these stories lightly with some humor. The sea is and remains seductive, however, it is a killer waiting for another victim.

I think that many people get a false security listening to someone's daring or foolish actions, depending on who you talk to.

&#8230;&#8230;Huge waves kill so do whatever you can do to avoid them."

Paulo


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## PCP (Dec 1, 2004)

Why should I bring to life an old thread with 5 Years?

Well, it is an interesting thread, but someone should change the title, or at least *add (large transoms versus small transoms)*. The title *"Jeff" *doesn't make sense. But that is not the only reason, the main reason is that I don't subscribe anymore the same opinion that I was defending on this thread.

I have been learning and besides that, reality and evolution of boat design on these five years showed that Jeff was right.

So, I want to make some corrections:



PCP said:


> &#8230;
> That's why relatively small modern ocean going boats like modern Najads, Malos, Halberg-Rassys are less beamier and have a much more moderate transom than Bavarias, Jeaneaus and Beneteaus.
> 
> The first are heavier boats, designed mainly as passage makers, and made to withstand heavy seas. The others are boats that are used and designed mainly to the Mediterranean, taking in account the conditions you find there. Big waves are not one of those.
> ...


Time (5 years) has showed that new Najads, Malos and Halberg-Rassys have now much larger transoms than they had then, as all modern big production boats.

Big production boats cannot match in build quality small production expensive boats, but they are designed by the best world naval architects (the Bavarias are Farr designed now ) and certainly they can match them in design quality.

I believe that the reason why Najads, Malos and HS have taken more time to improve their design (in what concerns hull lines and transoms) is because their target public is a more conservative one. Basically they take more time in modifying their boats for commercial reasons, not to scare away conservative clients.



PCP said:


> &#8230;
> The Volvo ocean boats are 65f boats and comparatively to what Jeff calls "modern boats" have not wide transoms, nor have they large beams, considering the length.
> Paulo


Yes, and they are for their length the fastest ocean racing monohulls, but they require a large (11) and expert crew to sail them. Not the kind of boat that you leave safely on autopilot (if sailed fast). Even so, if you compare the old Volvo with the new one you will notice that they have now a broader transom.

The fastest boats conceived to go fast with a small or solo crew are the Open 60 and those have huge transoms. They are needed to provide the stability that makes them forgiving, much easier to control than a Volvo, and permits them to go fast and safely under autopilot.

Cruising boats are crewed by small and inexpert crews (some solo) and go on autopilot most of the time, so they will have more to gain from the hull development of the Open 60 than from the Volvo's hull development.



PCP said:


> &#8230;
> Listen what Dave Gerr says about that:
> 
> "Wide, shallow hulls tend to pound upwind (and sometimes downwind). They can be difficult to steer because when they heel, the waterplane becomes far more asymmetrical than a narrow hull of the same parent form.
> ...


Well, that's a good post . I am not going to say that what Dave Gerr says is not right, only that all sailing boats are compromises and that the design tendency on small cruising boats (less than 60ft) on the last 6 years has shown that the vast majority of the best naval architects have chosen another kind of compromise, for the design of the modern cruiser.

There are some cruisers (and naval architects) that have followed the direction Gerr is pointing, but they are just on the fringes of modern design. I mean, boats with a *"moderately slender hull (longer for the same displacement with a careful thought-out waterplane moment of inertia and a low enough vertical center of gravity ) will be a better all-around performer than a wide shallow hull. "*

I like those boats a lot. In what regards beauty, they are unbeatable (and that's important for me) but they are almost all on cruiser-racer territory and they aren't really " better all-around performers" .

The most we can say is that they sometimes can match the performance of more beamier boats, especially when racing under handicap, but they are not a match if it is an open race (considering only length, like on some Transats) and definitely they are not a match on solo or small crew ocean races.

Dave Gerr says that:

*"....The ultimate drawback of wide, shallow hulls is that their reserve stability is usually very poor."*

Perhaps that was true once ( some IOR designs) but after the 1979 Fastnet, with the IMS and IRC rating handicap system, with RORC and ISAF safety minimum standards for offshore racing, complemented by the even more demanding safety rules on stability from the solo racing classes (Minis, Class 40 and Open 60) and the minimum requirements on stability demanded by the EC ruling body, for class A boats, the truth is that today there is now no significant difference in the reserve stability (the positive stability that is not used for sailing, but for safety, on high heel angles) between the modern main stream production cruising boats and the more slender production modern boats.

There are exceptions on both sides, but the general rule is that they have similar AVS (LPS) and if the more beamy boats (because they have a bigger righting arm) tend to have more reserve stability than the modern slender boats, they also tend to have (for the same reason) a bigger inverted stability.

Dave Gerr says also:

*"They can be difficult to steer (beamier boats) because when they heel, the waterplane becomes far more asymmetrical than a narrow hull of the same parent form"*.

And that is certainly true, if we consider boats with a single rudder. Modern boats that have opted for a single spade rudder have it almost as deep as the keel, to solve that problem. But today modern designers are opting for a twin rudder system (that is a standard feature in all solo racing classes). That allows each rudder to be almost at the center of each asymmetrical waterplane .

The twin system permits smaller rudders and being the spade rudder the most fragile part of the boat (to underwater debris), having two adds to the general boat security.

I will post a picture to explain this better. It is from a 2008 article by Jean Marie Finot : (translated) *"why modern boats have large Transoms"*. It is a very interesting article, but it is in French. Go here: Groupe Finot, Architectes navals and look under: "Ecrits". You can "google" translate it and I can help with any difficulty in the sometimes "strange" translation.

On the picture you can see that asymmetrical waterplane, but also that a beamier and light sailboat has normally a smaller waterplane than a slender and heavy boat.









Finaly Dave Gerr says:

*"The moderately slender hull will also be easier to manage and more comfortable in a seaway."*

I tend to agree that it will be more comfortable in a seaway, but not in all sailing positions and I have many doubts if they would be more easily manageable.

The more slender boat will be more comfortable close against the wind in steep short period waves but, as Jeff has pointed out, the bow design and the forward entries are the biggest intervenients in boat pounding. All things being equal, the slender boat has an advantage. Better have a good look at that particular item while choosing a boat (Cruiser-racers have in that aspect an advantage compared with pure cruisers, that translates in a smother movement and less pounding).

But a modern mainstream design will have an advantage in what concerns a smaller heeling in all sailing positions, and it will be a lot more stable and safer while running and going downwind.

About a slender boat being more manageable, I think Gerr says that because such a boat needs smaller sails compared with a more beamy boat ( and also for the asymmetrical waterplane that I have already addressed above ). But today, with advanced furling and reefing systems you don't need to go out of the cockpit to do it and you can see that small women like Samantha Davies or Ellen MacArthur have no problem in managing alone the huge sails of an Open 60.

Bigger sails are not such a problem today, but stability going downwind still is, at least for some designs.

In a slender boat, going fast downwind , you cannot let the boat in autopilot and you need experienced sailors at the wheel and at the sails. The boat can roll a lot and you have to be experienced to stop that movement that can be dangerous if amplified by waves. On a large transom beamy boat (influenced in design by the Open boats) the large transom permits a much more stable motion, eliminating rolling.

The difference is so big that while you need an experienced crew to go fast downwind, on a large transom (Open type) you can leave it to the autopilot (if the sails are balanced and if the boat is not near its sailing limits).

All these positive aspects have made large transom boats dominant on the mainstream of modern cruising sailboats. On the choices and compromises modern Naval Architects have done to define the better boat to the job, there is another important factor: Price.

Slender boats are a lot more expensive to build. They need more ballast and that implies bigger stress on the hull junction with the keel. That means expensive reinforcement of the hull and a bigger grid to distribute the charges. But the bigger setback is interior space. The interior space of a modern slender 40ft is comparable to a 36/37 interior space of a mainstream boat. For having the space and the overall stability of a 40ft mainstream boat you will need a 42/43ft slender boat. And that makes that kind of boats very expensive.

Regards

Paulo


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## Stillraining (Jan 11, 2008)

Thanks for reviving this thread PCP it was a great read...and I agree a name change is in order...I would never have found it.


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## smackdaddy (Aug 13, 2008)

Great thread! Thanks for floating it PCP.


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## deniseO30 (Nov 27, 2006)

I declare this thread unfair to double enders! (not that I have one)


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## tdw (Oct 2, 2006)

*Name Change*

Name changed. Makes a bit of sense now.

Paolo....I'd think again about deleting those old posts. I think its pretty cool to have a thread of this age evolve to a point where one of the participants has the balls to admit that their views have changed over the years. Me, I think your original thoughts should stand.

Cheers

Andrew


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## PCP (Dec 1, 2004)

Well, if you think that way you can bring them back. I left what I thought it was relevant and I have deleted what seemed to me noise, but perhaps you are right.

The idea was to make the thread relevant and clear.

Regards

Paulo


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