Chris White Atlantic 47, MastFoil

Only CW can tell us how much Anna influenced his latest design. However, the notes here suggest that Anna might have been a design issue, ie. an inability to short handle a squall blow. This conclusion would be incorrect. At one time the Anna's log was posted. Careful reading of it showed that 95% of what occurred was Captain's error. He is very experienced, but is prone to Type 2 error - fixing the last thing done wrong. This, rather than anticipation of what may occur and sailing accordingly. The only fault in the design is fairly simple. The mains on 57's have three reef points when they need four. In CW's own review of the event he points out that little is lost from full to the first reef. That is because we all forget this is a PERFORMANCE cruising catamaran. So in reality, reef point one is full and full is really turbo (all things excellent or do not go there). And, below the current reef one, the 57's need three regular reef points. That is a very minor change and with or without it a Captain must anticipate the worst, factor in crew capability and adjust accordingly.

As for the mastfoil, I can follow the math (albeit I need days), but math does not show her sailing, test her in tight circumstances, prove her low maintenance, and demonstrate she is to be counted on. I look forward to the eventual sea trial. Until then, I trust Chris, encourage him to add a reef to the 57 main, and challenge him to continue to wipe away the symetry that has constrained his designs.

 

Anti-capsize Devices

I know what you are saying, but at some point I just don't want to reef down to the smallest size sail area I have every time I see a potential thunderstorm....I would be sailing way below my potential.

So I began to look at anti-capsize devices again...what might be new?...what might be an additional safety factor added to the skipper's decisions?... might even term it a 'back-up' device?

Here are 3 forums I posted on:
http://www.boatdesign.net/forums/multihulls/capsize-prevention-devices-41340.html

http://www.cruisersforum.com/forums/f48/anti-capsize-devices-66876.html

http://www.multihulls4us.com/forums/showthread.php?t=3959

 

Launched and sailing home...looks pretty good and sails rather easily.

Another mainsail-less, alternative design sailing rig that looks quite promising...

http://www.chriswhitedesigns.com/atlantic_cats/mastfoil/update_01-12.shtml

 

1925
Otto Mader invents MastFoil, calls it "Junkers Doppelflügel " ( double wing).

http://upload.wikimedia.org/wikiped...ip.png/640px-Junkers_Doppelflügel_Prinzip.png

http://en.m.wikipedia.org/wiki/Junkers_Ju_52#/media/File:Junkers_Ju_52-3mg2.jpg

http://en.m.wikipedia.org/wiki/Junkers_J_29


Anyone interested in the aerodynamics of Mastfoil , it's principle, may search with the keywords " Doppelflügel" , " double wing" or " Junkers Flap".

pogo

 

as someone who actually sailed next to the mastfoil boat I will testify that it seemed a bit sluggish and underpowered to me, albeit in relatively light air. If it was to live in a heavier air venue I'm sure the convenience would soon outweigh the lack of light air performance. It is a very pretty boat and looks extremely comfy and seakindly.

 

I would not have expected it to be a good 'light-air' boat. First of all, reasonable sail area, not excessive. Secondly lots of 'very stable' catamaran platforms don't allow their sails to drape into good foil shapes in light airs

 

But , after tacking in light airs such a soft forsail will "jump"into the new shape,
not so with a fullbatten main.
On monos, especially dinghies, one solves this problem with gravity--heeling, on a multihull ......

I like these self-tacking jibs w. boom.
Note that the boom's gooseneck is mounted about 15-20% of J --providing "automatic" fulness an little bit twistcontrol.to the sail.
In Germany the selfacking jib w. boom ( Baumfock" has never been furling.
The Jib has a high aspect ratio, partly furling, reefing, makes no sense.
So those jibs had hangs , were quickly set in strong winds and/or closed waters.
Nowadays bigger ships , up from 30' , having such a Baumfock have slab reefing.
This new generation of Baumfock is the one and only foresail , at least on cruisers. So they are bigger thru longer J.
Being slab- reefing implies that such a jib still has hanks, which work much better than a tuffluff.

Another way of improving the handling and performance of a selftacking jib is the camberspar by american sailmaker Bierig.
A batten , a half wishbone boom integrated in the jib, tensening the forestay and controlling twist.

I think the MastFoil has potential.
with a slab-reefing Baumfock , or a " Bierig" , smaller ( cruising) boats might be equipped with it , eleminating thhe disadvantages and avoiding patent troubles.


Jollenkreuzer ( non ballasted centerboarder) often use Baumfocks.
Here a steel 30er out of the late fifties ( and still goin' fast)
http://www.search4sailing.ch/Kleinanzeigen/news_images_large/300_2 Jollenkreuzer 10 m Klasse.jpg

Bigger and reefable on a Reinke:
http://www.reinke-yacht.de/images/2014-fotos/eu-109-sender-IDA-6-14-01.JPG

A Bierig Camberspar
http://www.sailboatlistings.com/sailimg/m/48709/main.jpg



pogo

 

MastFoil in the 70s

in the 70s Franz Xaver Wortmann , aerodynamic prof and well known for his laminar airfoils (FX types) for gliders, designed a 30' racing trimaran for lufthansa pilot Klaus Schrodt for taking part in the 1980 OSTAR. ( Today Schrodt is aerobatic world champion , euopean champion, red bull airraces...)
The boat was designed at University Stuttgart and benefitted from modern aircraft composites---it came out w. 700kg.
Most interesting was the rigg. Worthmann opted for a Junkers Doppelflügel--MastFoil.
The wingmast , one spreader only, has been positioned at about 60% of the boatlength, sporting a boom of about 1m with a tiny fullbatten main. The Jib was huge.
During seatrials and races in the med, the little boat achieved 25kn.
Unfortunately the boat was banned from OSTAR , cause of it's John- Westell- Principle.
At IMM 1995 i had the opportunity to see the boat.
It has very much comfort , room for it' s length, is unbelievable fast, and, easy to handle.
The boat really was ahead of it's time.

Unforunately i've found no pix in the www -----pre web aera.
The only pix i have are in my bookshelf.
"Single Handed" Ebnoy Press, London
It' a book about OSTAR , published 1984
Interviews w. Shuttleworth, Newick, Weld, Hasler ( Jester), tabarly, Jeantot, lots of info and grat pix

http://www.abebooks.com/servlet/BookDetailsPL?bi=12526299424&searchurl=tn=single handed

pogo

 

Can you scan that one pic from the book,...the one you speak about?

 

Just keep in mind that the bigger headsail does not gain in efficiency on its own. .....it gains as a result of the interaction with the trailing sail of foil.

I am quite familiar with that bierig jib,...we installed one on one of the Firefly trimarans we built. Client was single-handed for daysailing, and really liked it.

Don't be afraid to pay a little commission for a patented item....get the man some credit for going so boldly forward.

 

No, sorry, i,ve no scanner.
order the book please, it's cheap.

http://www.abebooks.com/servlet/Sea...&n=100121503&cm_sp=mbc-_-9780852234303-_-used

pogo

 

I just ordered that book

 

Flaps , flaps , flaps

How and why can be read here:

http://www.boldmethod.com/learn-to-fly/aircraft-systems/junkers-flap/





Flap and spoiler
Chris White:
"So the question becomes, what can be done to improve the efficiency of the hull fins to daggerboard level without making them excessively deep?

The answer: put a flap on the trailing edge of the fin. This makes so much sense. It is simpler to construct and maintain, weighs very little and is not vulnerable to damage. Yet a flap has the ability to dramatically improve the performance of the fin.

Let me explain: The typical symmetrical daggerboard creates zero lift unless the hull is sailing a little bit sideways in the water. In order for anything beneficial to result from the increased draft of the daggerboard it must go through the water at some "angle of attack" to the water flow. Normally a good sailboat going to windward will be "making leeway" of 3 to 5 degrees. This means that the boat is turned 3 to 5 degrees to the rush of water coming along the hulls, which is highly inefficient. Unless the hulls are operating at this inefficient angle to the water flow the boards have no angle of attack and cannot provide any lift to combat the sideways push from the sails. So in order to get "lift" from the board you need to accept an offsetting "drag" penalty from the hull.

What makes the most sense is to have an underwater foil that is adjustable so that it can provide lots of lift while the hull tracks nearly straight thru the water. By far the simplest way to do this is to install a flap on the trailing edge of a fixed fin.

I can see all sorts of beneficial uses for fin flaps beyond just sailing to windward. They can be used to balance the boat under different sail trim. They can be used to combat crosswinds in a docking situation. They can be very effective sailing down wind too. Flaps set at negative angles will reduce drag and help "push" the boat to leeward which is just what you want when deep reaching.

There is even the possibility for using the fin flaps as a built in drogue. By setting them in opposite directions at high deflection angles they will be very effective "brakes" and could be handy in conditions where you need to slow down. Each flap will have an independent control and will be adjustable from the helm station."
Source: http://www.chriswhitedesigns.com/atlantic_cats/a47/

More lift thru flap:
http://www.boldmethod.com/images/blog/2013/10/flaps-aoa/camber_dirty.png

Less speed thru spoiling flap and spoiler:
http://www.agapemodels.com/wp-content/uploads/2008/01/dive-flaps.jpg



Flap on keel in the sixties, named trim tab:
http://1.bp.blogspot.com/-qpbSF3zpB...oSoVckp1yk/s400/1952%2Barrangement%2Bplan.jpg


Alles gut !


pogo

 

Actually that's not quite so true,
....the soft foresails will not develop an airfoil shape when hanging vertically in very light winds.
....the full batten mainsail can at least be forced to take an airfoil shape on one side or the other.

 

Reading back thru this subject thread again and noted this posting

It made me reconsider how much more easily a jib or genoa sheet might be released in an emergency than a multi-purchase mainsheet. I made a notation of just such an incident recently when the new Gunboat G4 with its fathead mainsail capsized:
http://player.vimeo.com/video/125378004

Which Sail Cause the Capsize

http://www.boatdesign.net/forums/multihulls/gunboat-g4-uptip-foils-50397-7.html#post733511

I was seeking that same lower COE. If I remember correctly, my aft-mast ketch rig lowered the overall rig's height by 25% compared to a fractional rig sloop with the same sail area..