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I was looking at Catamarans for sale, and recently found an interesting "Custom Wharram Design 37" that appears to be rigid.   Anybody know the story if this boat?   It can be found here at the link below.   location is  Arapahoe, North Carolina USA.   Note the bulkheads tied directly into the coach roof.   There are not enough photos inn the add to really put together a good picture.  If I lived on the East Coast, I would take a drive over and have a looksee just out of curiosity.

                                                    H.W.

https://www.sailboatlistings.com/view/78094 

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     Any designer / engineer gets hostile when people start making changes......... for good reason.     He has developed a sound reliable, and rugged boat, according to his own parameters, and someone is questioning design decisions , and making modifications which often have cascading effects, and may not take into account all the  structural factors that drove the original design process.   It always adds weight, and often has other unforeseen effects.   For example rigidizing a Wharram means whatever you are using for an attachment structure may not be built to sustain that kind of load without some give.  The lashings  hold the create an upward pull on the rail that extends along the length of the hull well below the beam.. It is a vertical tension load that is transmitted into the skin of the hull via this rail, and the beam troughs carry a compression load, as well as the load of the hulls wanting to lead or trail each other... a sort of lateral rocking moment, as well as a longitudinal rocking moment.  Locked in, the entire load is concentrated at the beam troughs, and through the bulkhead(s), and transmitted by this structure to the hull skin..... I'm not suggesting that this is a huge issue, but it is one that needs to be examined.  The outer rail now carries nothing, and the beam trough or whatever is taking it's place carries everything......... The better part of wisdom would be to look at boats by other designers, and how the loads are distributed.   I personally like the work of Bernd Kohler in many ways.... His boats use bulkheads that intersect, and furniture that is built in, rather ingeniously to create load bearing structures.  The interplay of the different components is structurally critical and changes absolutely demand and examination of the total structure, and how it works... The counter top in the galley, or a settee on the bride deck has a structural function. Ed Horstman  had much the same approach, and in fact most well designed boats use this design methodology to some extent.  I would not consider modifying a Wharram casually....... a look at load paths, and the interplay of structural elements is the first step.  This is NOT to suggest that boats as designed are "perfect", structurally or otherwise, only that one needs to get inside the designer's head, and see the little things... "now why did he do that?", and reverse engineer to a point where you can move forward intelligently with a good understanding of the "whys" .

     James said  something to the effect of "If I'd wanted a cabin, I'd have designed it that way"........ He didn't, I do.    The boat is built and has been sailed extensively, and at this point it is mine..... The unfortunate thing is that it will always have the name of James Wharram on it, no matter what I do to it, and he has zero control over the latter.   That has to be extremely threatening to any designer.  When things go tragically wrong, the press reports "Wharram Tiki 38" in all caps, and "modified" in lower case..... I have no trouble understanding where James is coming from.....  Out of simple respect and consideration, a modified Wharram should be called  a "Wilkerson 38)............But can you change the papers to expunge Wharram name?

                                  D.W.

Here is another rigidized Wharram.... a Pahi 42, that has been rather radically altered..... quite beautiful, but you will notice that they lowered the bridge deck under the bridge deck cabin, greatly reducing clearance.......  not  my idea of a good idea, presumably to make standing headroom without too much increase in windage. It is listed for sale at this website:  Pahi 42

42K Euros, and there are extensive very nice photos interior and exterior there.   

                                                                                        DW

      Looks like great boat.  Certainly could not build it for that price.  i agree the the lower bridge deck might be a problem. and I would like to know  exactly how the beams were reengineered. 

 

Yikes!  The more I look at this boat the more I like it. Still, wondering what the offshore effect of the lower bridge deck  would be. Probably pounding. But unsafe? 

A great "houseboat"........ I would love to have it for a live aboard in a place like Chesapeak or Puget Sound..... I would be reluctant to sail it off shore in either the Pacific or Atlantic, but it would be perfect on the intracoastal, or be a great boat for doing the great loop.  You would find the pounding unbearable when sailing close to the wind.   There are many cats out there that have this problem.  In the pursuit of standing headroom, the trade off between windage and clearance is a tough one, usually losing on both ends.    James understood this, and once retorted to someone's inquiry........  "If I'd wanted a cabin I'd have put one on it".....or words to that effect.  There is no solution to this dilemma except upscaling to ever larger yachts.  Most modern cats are never sailed close to the wind......... they just won't do it well.  I've yet to sail a Wharram, but I suspect they are well above average in this regard............ but at a cost.

                                                                                    

                                                                           DW

Arthur Gottschalk said:

Yikes!  The more I look at this boat the more I like it. Still, wondering what the offshore effect of the lower bridge deck  would be. Probably pounding. But unsafe? 

I did communicate with the owner of that boat. He admitted that pounding was a problem ad that he is selling because his wife found it uncomfortable. 

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