ATOA Expedition yacht

Hello, we just finished the long term project of design and building the aluminum expedition yacht ATOA, it takes about 3 years of hard works and sure that she is fine vessel.
I wish to ask the comments of members about this yacht and about concept in general, as I will proceed with new project of ATOA-50, therefore need to get some critics.
I make my concept based on own marine and boatbuilding experience and collection of wishes of clients, and commissioned Gabriel Heyman for design and built in Netherlands.

Some basic things in ATOA, not new, but included:
Aluminum yacht for live aboard and unlimited cruising worldwide.
The basic ideas in this project: safety and comfort in open seas
- solid hull for any conditions
- simple and practical layout and finishing
- high average speed (motorsailing) at minimum fuel consumption
http://www.atoa64.com/index.php?menuid=8
What do you think about her ??

 

Great blue water design. I like the hard bimini and transom extension also the amount of light you must have below. Are there more pictures available on line?

 

Awesome boat! Out of my league of course but..
Only one seaberth? For an expedition cruiser it's hardly enough.
I have also some doupts how that huge stern platform does work in heavy weather. I've been worrying about placing a 40cm platform in my 10m motorsailer.

 

The contruction of platform is rather solid and the decking with very solid teak boards. The platform is also place for RIB with aluminum bottom (not loaded on photo)

 

i like that aft platform, saw the first frame positioned on your boat at DYB some time back
good to see her back sailing on video now, great expedition boat, congratulations

 

thank you indeed, after finish with sale of this boat, will proceed with new very interest project - fast expedition yacht 50+ ft. Surely aluminum again, as I like it.

 

Alex,
There have been already a couple of favourable comments on ATOA 64 around in these forums.
I like very much the concept, although I find sail area/displacement ratio somewhat low. I'd prefer something at least in the 15-16 range
Have a look at:
http://www.boatdesign.net/forums/showpost.php?p=139790&postcount=221
Probably you can tell me if my numers are right or need corrections.

Cheers.

 

The sail area about 160 sq.m. of main sails (main, mizzen and jib), the actual displacement is vary depends of storage, as the boat has hudge storage capability. The sail area can be increased by using of vary gennakers/blazers/code0 etc. The moderate sail area was designed at the begining, to avoid extra works with sails when the wing is increasing, to have the later reefing as possible, for light wind you have the extra sails or motorsailing as option. You see on video and fotos the 9 knots of speed at 25 knots of true wind, with reefed main and full jib, but for better ballance the full jib and full mizzen was better, speed as a little less, about 8-8.5 knots in same conditions.

 

Alex
I like the style , you ask for comments so here are mine:

I'd be concerned about that aft platform in heavy weather too and would like to be able to remove it or fold it away before a storm.
The concern is not too make it strong enough to stop it being broken but to consider the effect of it NOT being carried away by a large breaking wave.
Draw the vectors of the forces of the heeled vessel experiencing the jet from a breaking wave, this jet will act of the platform like a pelton-wheel blade. To project this sort of area beyond the vessel is not very desirable at sea.

Interesting that you have gone to the effort of fabricating a low drag foil shape on such a low AR keel, such a keel can be hugely simplified as a simple section and a flat LE with the edges slightly rounded for the same lift/drag ratios. The design of such low AR (hydro) foils is not adequately covered in foil design texts.

You might want to consider a swing centre-board option for upwind sailing ?

Keep up the good work.

 

Ok, noted, thank you. The platform is heavy built, having in mind that back waves for sure. The design had options of side boards (as on Open60), but was rejected as the ATOA is designed and built for safety, comfort and low maintenance, so we avoided any complicated things below water. The tacking upwind is very reasonable and not worse then on any production cruiser. The long keel is reinforced for grounding, dryout, etc. and not for the best upwind angle. The foil form of low aspect long keel is for lower resistance in combination with hull form, which is good formed for soft motion in seas independs of wave direction. I aimed to high AVERAGE speed on passages (sail + motor-sailing + motor) with minimal fuel consumption.

 

For future reference, a low aspect ratio keel like this acheives no benefit from a cross section shape designed for wings and the whole idea lacks validity. You could use a much more easily fabricated keel shape with a wide flat LE.

The flow on a low aspect ratio 'stub' is not longitudinally oriented. the whole purpose of a wing section is to keep the flow attached for as far as possible to improve the L/D relationship and you simply cannot achieve this with such a short wing. It can be hard to believe this until you see the results in a model resistance test. Just as long as the leading edges are not sharp enough to result in vortex shedding you can use rounded edge flats, round sections, and the fabrication trouble of eliptical gives no advantage at all.

 

Yes, you right, but we had no problem with fabrication of profiled keel section, so we did it profiled.

 

Nice details on that craft.

 

You have a very pretty boat. Congratulations!

I agree completely. I prefer a small rig for the exact reasons you mention. Motorsailing is a much better option when there is light wind. A good downwind sail inventory is more important than a big overall rig. That's where I'd rather spend the money.

About the platform... MikeJohns' point is valid. If I understood it correctly, he means that waves can lift the stern, and even spin the boat and cause a broach. Maybe those teak plank sections could be removable?

 

The boat has long keel and balanced sail plan, the platform is rather high above the WL, so no much reasons for broaching. The teak planks are rather solid, but surely they can be broken in some extremal conditions, but in that case it is not the biggest lost indeed.