Plenty of all round view and visibility in our bridge deck cabin, see pic below.

Bern Kohler's 8m Maxi Cat details can be found on The Duckworks site under Bernd Kohlers designs. It is a very minimal 8 meter bridge deck catamaran. Pic below. It would be interesting to explore a junk rig option for this boat, but once again it is a mast aft design so there may not be sufficient buoyancy in the forward part of the hulls to support a junk rig. But Bernd does design bi-plane rigged catamarans, any of which could I imagine be fitted with a junk bi-plane rig. These boats all have the dory style flat bottom hulls which are quick and simple to build.

David:

    The Eco series are unique and innovative......... The Maxi  looks like kind of a freak to me.  An overgrown beach cat cross bred with the eco series.  Long slender low displacement  hulls, very light weight for it's size, not enough displacement or beam... sacrificed for trailerability........... That's my take anyway.  

       There are a number of naval architects who strongly believe that the center of effort on a multihull should be as far aft as possible, and there is really no reason except the location of the existing CLR on the boats people are converting to junk rigs that dictates the mast location be far forward.  That is one of the unfortunate aspects of junk rigs.  Almost nobody designs boats specifically to have a junk rig.     I have yet to see any articles about changing the CLR on a boat when installing a junk rig.... for obvious reasons.   Though far from impossible, it's easier to just move the mast forward to achieve balance.   I've often wondered about increasing the size of the skeg....when there is one, or altering the keel shape...... cutting away more forefoot and adding to the back.   These are things that are simply not done.   

       With the advent of the split rig and the forays into carrying greater balance area, it seems that it is quite possible to place a mast in the original location on a fractional rigged boat.   Like the Prouts, the aft mast on the Maxi is in a nice location, and a structurally strong one.   If I were building one with the increased beam as you suggest,  I would probably look at increasing displacement... Perhaps just by carrying the hull sides down a bit further, and setting the hull bottom down further.... Not much.   You are carrying more bridge deck and cabin area as well as the junk rig.  You might place a single free standing mast on the forward side of the cabin bulkhead instead of aft of it, and use a split rig with the max realistic forward balance... perhaps 30% or even a bit more.   I don't know what the practical limits are.   And during building put a skeg ahead of the rudders.    Another approach for a  cat might be to do what Kohler himself has done with the KD 860 since realizing that his anti vortex panels simply do not work, and install a single centerboard under the bridge deck.

     In any case I think the aft mast location is a good one in many ways, and that you will want more displacement if you are widening the beam and installing a junk rig, and that if you are building from the ground up for a junk rig,  it is probably desirable to design for it instead of setting the mast(s) forward. 

                                                                                H.W

Anonymous wrote:

That little boat of Sven's looks interesting, a sort of monohull version of the catamaran Miss Cindy which made an epic voyage down the west coast of Central America, traversed the isthmus and then sailed to Cuba and onto Florida. And Sven has done some incredible voyages on very small boats.

A friend of mine owns a 54 foot bi-plane rigged cruising catamaran on which I have done a lot of sailing including an ocean passage from New Zealand to Tonga. The rig is quite hi-tech having carbon wing masts and a fully battened mainsail only on each mast. But for a boat of the size it is very easy to handle and for a heavier cruising catamaran still has sparkling sailing performance.

I am always interested in 'thinking outside the box' small cruising yachts, and am actively looking for my next possible build. I am very happy so far with my Eco 6 catamaran and am planning some extended coastal cruising this coming New Zealand summer. Based on that cruise I will decide whether I keep the catamaran or go for something different, but part of this is that I actually enjoy a boat building project. The new Wave Rover 6.50 design interests me as it is a purpose designed junk rig yacht for offshore cruising, and a bit of a thinking outside the box approach. But maybe another small catamaran. Bernd Kohler's new 8 meter Maxi Cat but with an extended beam interests me, but it would also be good to have something on which I can get back to a junk rig, and maybe a bi-plane junk rig. Part of my problem is that I like to sail fast so I am always looking for more performance orientated boats, and because I cruise with my wife I also want a double berth and a semi private head compartment, so if going small a catamaran best provides those needs.

So many potential interesting small boats out there, and not enough time to build them all.

I like some of Kohler's ideas, and definitely his construction methods.  I wasn't aware of  his 8M Maxi Cat.... nor can I find anything about it except a page that seems to be in Dutch which I don't read, and is an advertisement for a boat .... sold:

https://www.scheepsmakelaardijgoliath.nl/de/schiffe-angebot-einzelheiten/171989/kOEhler-catamaran-8m/

 Kohler's construction methods are appealing... simple, and fast.   I like the dory hulls.   What I don't like is a cabin without full view........  Sitting height is fine, but why have a bridge deck cabin without windows all around where you can retreat when the weather gets bad.  

I hope you looked at Sven's current videos on his project boat built from very thick (70mm) divinicell......a very interesting  construction, and I'm looking forward to seeing how he fills the joints which currently have foam wedges in them... will he fill it in entirely with wedges with epoxy micro between?   It's at least as interesting as the Wave Rover project... actually  more so as I can really see the benefit in the very thick foam for thermal and sound insulation.... both would be nice on a voyage.

https://www.youtube.com/watch?v=4h3oao1Ozpo

I've toyed with various ideas for using ordinary blue XPS in very thick section for a boat hull encapsulated of course with fiberglass and epoxy.  Adhesion is an issue with XPS, though it is very strong.   I've played with roughing the surface in various ways, as well as cutting into "planks" with fiberglass on the edges , and joining the planks so that the scrim of glass along the joints provides connection between the two surfaces.  I've played with heat and compression, and even used a sewing awl / speedy stitcher to penetrate the foam with fiberglass thread in a pattern to give the surface fiberglass something more to bond to.   All with varied results, but I think it IS workable.... weather practical or not is another matter ;-)  When dealing with very thick foam.... say 2", the cost difference is huge.    The only real liability would seem to be the fact that it melts in the presence of solvents, but encapsulated, this should not be an issue.   I've been thinking of building a small boat using this material as an R&D.

                                          H.W.

Anonymous wrote:

Howard wrote

     You are right of course...........  The mast that appears on the opposite side is actually forward of the other one and smaller......... the perspective in this photo is weird... I found another photo on line knowing the name of the boat.   I was fooled ;-(

   I posted a photo of Sven Yrvind on one of his boats which has a biplane lug  rig plus a mizzen......  I posted this photo and a link to the Utube thread just today.   This guy in his 80's sails all over the world in very small boats and has for many years.   I have a deep appreciation for unconventional outside the box thinking and solutions.... probably because Buckminster Fuller was a childhood hero.. an engineer and philosopher that marched to the beat of a different drummer.  

     

                                                            H.W.

Actually there probably is no good reason why a bi-plane rig could not work on a monohull, provided there was sufficient beam to keep the sails far enough apart. Miss Cindy, an intrepid voyaging small catamaran had a bi- plane rig on a beam of around 2 and a bit meters. Footprints and Shoestring both have vertical topsides and with a beam of over 3 meters a bi- plane rig would be possible, the masts being able to be placed well out to the side of the boat. One of the reasons I sold Footprints was that I found the 53 sq m sail a bit too much to handle in getting the sail up. A bi- plane rig would be one way to divide the sail plan up into more manageable sails. During the time I owned Footprints I designed all sorts of alternative rigs, but never considered a bi- plane rig, but of course I was trying to work with the existing mast.

I don't see a biplane rig as practical on a monohull for the most part either.... but it's obviously not impossible....  Sven's boat has a very small rig on 3 masts.  It's not the only biplane mono I've seem photos of........ but I'm not having much luck finding them.  On one I recall, the masts were raked outboard very noticeably but I cannot find that photo.  If it were practical, I suspect we would see them.   Here's a puddle duck 8' "racing" scow with a biplane rig.... and a cartoon image of Sven with is biplane rigged boat.  

                                                              H.W.

Anonymous wrote:

Howard wrote:

I stumbled onto this interesting photo on Duck Duck Go..... which led me to Annie's blog.  It appears to be a monohull with a biplane junk rig and additional mast aft....... a biplane ketch?   Also appears to be flush deck.......... I'd love to know the story and description of this.  Are the masts raked outboard?    A very unique and interesting setup.   I love original outside the box thinking

                                                        H.W.

That is 'Shoestring' which is a sistership to the boat I owned, 'Footprints' It is not a bi-plane rig, I do not think a bi-plane rig would work on a monohull. Roger, the still current owner loves to experiment. That rig experiment was a result of having to cut down the length of the mainmast because of rot in the mast. So Roger experimented with different ways to get sufficient sail area. So, a foresail, mainsail, and mizzen. The mainsail was made from weed mat. The rig worked surprisingly well and 'Shoestring' still had comparable speed to my own boat. Roger has now gone back to a single mast rig having had a new mast fabricated out of steel, and is using the boats original HM flat cut sail. I suspect though that it is not the end of experimenting for Roger.

'Shoestring' and 'Footprints' were designed by Gary Underwood as low cost coastal and offshore cruising yachts. 10 meters in length, they have a simple sharpie hull form, plywood construction, shallow draft, flush deck, and very commodious accommodation including a double berth cabin under the aft deck. Both boats have an outboard motor in a well as auxiliary power. 'Footprints' has sailed offshore having cruised from New Zealand to New Caledonia in 2013. 

     You are right of course...........  The mast that appears on the opposite side is actually forward of the other one and smaller......... the perspective in this photo is weird... I found another photo on line knowing the name of the boat.   I was fooled ;-(

   I posted a photo of Sven Yrvind on one of his boats which has a biplane lug  rig plus a mizzen......  I posted this photo and a link to the Utube thread just today.   This guy in his 80's sails all over the world in very small boats and has for many years.   I have a deep appreciation for unconventional outside the box thinking and solutions.... probably because Buckminster Fuller was a childhood hero.. an engineer and philosopher that marched to the beat of a different drummer.  

                                                            H.W.

I thought a biplane rig was like what's at the top of this page:

https://pdracer.com/sail/unusual/

Doesn't look like the one you've posted the photo of.