60'+ or - 20' Ocean Racing Monofoiler Design Discussion

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Probably be more help on the Cole 43 Rumrunner(TM)....

 

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Follow-up: In the latest International Hydrofoil Society Newsletter the guys were able to get a model keelboat on foils 100% both in a towing tank and then under sail!!
From the Newsletter:

Conclusions
"This project demonstrated that a 30m maxiyacht could achieve a speed advantage at higher speeds. However, implementation at full scale may not be easy; there will be problems with structure, control and berthing arrangements. Some of the problems can be solved relatively easily while others will be more difficult to address. However, canting keels were not without their problems either yet these are now firmly entrenched in high performance maxi yachts. It is the author's belief that when one enthusiast takes the plunge and fits hydrofoils to a full-sized yacht[designed for them dl]
, then the speeds achieved will convince more to follow."


Yes, they will!

 

crush space

>
Well, about broken bones and so on Doug can learn from the automotive industry. In order to get as many stars as possible according to the EURO-NCAP and US-NCAP a lot of research is on-going. Air-bags, increase of crush-space, pedestrian designed bumpber and hood. Especially dangerous to the human brain is rotation during crash events. Shear-stress are imposed on the connection between the brain-halves. There is possible to calculate values such as HIC (Head Injury Criteria) to ensure that Doug survives in his super-Moth.
Regards,
Booster

 

I did all the boat building work on M1 for the foil change. If you believe PA ( peter hull ) they got over engineered. In his view they had to increase the scale of everything to allow enough carbon. So in theroy the drag and weight went up. The system was very hard to keep in the grove, but did have it's moments reaching. If all the gear could have been 30% smaller it may well have had a better working window. But we will never know. They always talked about the resulting lift in three factors, righting moment ( a carbon rig would have provided better gains ) , dinamic lift ( you never realy ever felt or saw any gain ) , and windward lift - this was very inpressive at times. One winter race was a tight reach down the harbour, I was starting two divisions back, we watched many a yacht rounding up but M1 was off upright and in a ball of spray.

 

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One of those sketches looks like DSS-both appear to be instances of using
"foil assist" -great to see. The guys quoted by the Society Newsletter, on the other hand, have done outstanding, pioneering, work putting a keelboat on full flying hydrofoils.
Both are great examples of the appplication of hydrofoils on keelboats-something we will see a lot more of.

 

60' Moth

Here is a summary(more detail in post #1) :


Summary:
-LOA-60'---------------------------------------

-Beam-50'--------------------------------------

-SA 2500sq.ft.-----------------------------------

-Displacement:14,731lb.'s ; Max: 18502---

-Draft(off foils) max 18'-------------------------

-Foil areas-30 sq.ft. main foil; 15 sq.ft rudder foil-------
===============================================
COMPARISONS--------------------------------
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--D/L ratio- 60' Monofoiler: 30.4----------------D/L ratio- Orma 60 trimaran: 24.8


----------- --------- For what it's worth, the following comparison is between the 60'Monofoiler and the 60'ORMA trimaran. And I consider it one of the most important comparisons of all. The ORMA trimaran is presumed to have 70% of it's displacement supported by a "banana foil", with 30% of it's weight supported by the ama while flying the main hull. For this comparison the 60' Monofoiler is presumed to be flying on just two foils. The vertical fins of neither boat are included and both sides of the foils are included:

1)Orma 60 trimaran-estimated ama wetted surface 124 sq.ft; estimated foil wetted surface 32 sq.ft.(both sides) Total 156 sq.ft. Now this figure is divided into SA(3000sq.ft.) giving 19 sq.ft. of SA per sq.ft.of wetted surface.
ORMA SA/ws= 19/1

2) 60' Moth Mainfoil area(both sides): 60sq.ft..Rudder foil area(both sides) 30sq.ft.. Total is 90 sq.ft . Dividing SA(2500sq.ft.) by this figure gives 27.7 sq.ft. of SA per sq.ft. of wetted surface.
60'Moth SA/ws=27.7/1

 

Foil or ballast?

What is this? I saw it in Moreton Bay out of Manly. It was a lot faster than the cruising monohulls on the same tack (as any racing style boat should be), but it was also leaning over more than them.

 

Whatever it is, it appears to have the keel up to windward in that shot. Maybe instead of dynamic lift they have simplified the canting keel to a sliding keel and simply throw it up to windward instead?

On second thoughts - the appendage is located so far down that it must be intended for immersion rather than flying.

No doubt this will get the local frother frothing.

 

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Did the foil move? If it was DSS it would likely have been deployed to leeward.
Some early DSS R& D RC models had a fixed foil and there was a B23 outfitted with DSS on just one side in Australia.
DSS is one of the most promising applications of "foil assist" to monohull keel boats, developing vertical lift while at the same time increasing RM. It is fully retractable as well...
http://dynamicstabilitysystems.com/

http://www.boatdesign.net/forums/sailboats/dynamic-stability-systems-imoca-approves-34317.html

 

hehe. When I saw it I imediatley thought of this thread and yelled out "get the camera quick, the internet needs to see this"

I don't know if it slides. I thought there might be another one on the other side. But docking would be pretty hard. It looks like a very thick section so maybe it does have weight in it therefore must slide to work?

The boat was leaning much more than the cruising mono I was on and the other 3 or 4 cruising monos on the same tack beating to get out of Manly. In that pic they have moved out of the wind a bit and are closer to reaching. Maybe it has very little keel weight?

Anyway it should stir this pot a bit more in any case

 

60' Moth comparisons

More comparative info:


The area of the submerged part of a Hydroptere foil* at speed is approximately 2' X 6'= 12sq' or 1.12 square meter per foil( 24sq.ft. total/ 2.24 sq.m total) but, of course, both main foils aren't always in the water-just most of the time. That is at close to max speed and is one of the advantages of fully submerged foils since the nominal 1st run area of the monofoiler main foil is 30sq.ft.( 2.79 sqm); Hydroptere at speed has only 80% of the main foil area of the monofoiler.
But the monofoiler has one less surface penetration...
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If you read the first post( and post 141) there is a comparison
of SA/ wetted surface between the monofoiler and an ORMA 60 tri-quite revealing.
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* This is an updated correction to my estimate of Hydropteres wetted area at speed in the first post.
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You might be interested in these foil loading comparisons: (based on main foils supporting 80% of the load)
----Monofoiler: Light: 393 lb. per sq. ft. Ballasted:493 lb.per sq.ft.
----ORMA( main foil supporting 70% of the load):
450 lb. per sq.ft.+ (estimated)
---- Hydroptere: light @ takeoff: 171 lb. per sq.ft. / Ballasted,at speed estimated:684 lb. per sq.ft.
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An interesting correlation to the puzzle is that while Hydroptere has much lower foil loading at takeoff its est. SA/sq.ft. main foil area is 66 vs the Monofoilers 83.(Moth about 84)

 

What?

RM does not change with scale. For a cat or tri RM = Weight * 1/2 Beam.

If you scale a boat correctly, there are two common dimensionless numbers that do not change: D/L and SA/D another ratio that does not change is SCP/Weight.

The dashed red line in the graph is D/L showing three scaled boats, 20, 40, and 60 feet. The blue line is the SCP/W of about 36% For scaled boats the SCP/W ratio is EXCATLY the same ... until the crew becomes Smart Ballast(tm) and move to windward.

The red line shows the % of displacement that is crew. The ratio of crew to sail area is constant: 1 crew per 150 ft^2

Note that the crew becomes a smaller percentage of the total weight as the boats get bigger.

The green line shows the effect on SCP/W when the crew weight is 3 feet off the beam. Note that the 20 foot boat is much more powerful with the crew acting as Smart Ballast(tm) than the 60 foot boat. The small boat has a SCP/W of 57% when the crew is on the wire. The big boat cannot match that power.

So, if anything small boats benefit from scale more than big ones. What looks like a RM curve in favour of the large boat ignores the fact that to have the same SCP/W ratio the HM is larger also if the rigs are scaled. That line is flat.

Shifting ballast to increase performance does not add drag. Using a RM foil does. Added drag is the very last thing you want. Kill the tri idea. Cant the Tfoils out from a catamaran platform and cant the rig to weather. Now you can fly on the leeward foil have some lift from the canted rig and pay NO drag penalty since the weight of the boat is providing the RM. You also lose thw aero drag of the unused RM foil that you have waving about doing nothing half the time.

R

 

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Sail area varies as square of length; displ. varies as the cube of length and RM varies by the 4th power of length.
A Moth has the ability to sail in 1.36lb pressure per sq'SA w/o depowering with a 175lb crew aboard. If you scale up the Moth the
weight of the 60 footer is 39,000 pounds and the SA is 2558sq.ft..
But the RM is 827,253ft.lb--way, way more than required for a 60 footer to sail with 83% as much SA as a ORMA tri in the SAME PRESSURE. In fact, for the 60' Moth to sail in the same pressure(2lb per sq ft) as an ORMA tri it only requires an RM of 223,203ft.lb.-27% of the scaled up RM.
And with better numbers than the ORMA Tri, particularly SA/WS: Orma tri 19/1------- 60'Moth 28/1.
If you scale up a Moth without any real world constraints you have a heavy beast with way more RM than required to target an ORMA tri. Thats why the 60' (real world) Moth has these dimensions (For a rightable version requiring crew action) :
-LOA 60'
-Beam-50'
-SA 2500sq.ft
-Displacement: 14,731lb.'s ; Max: 18502---

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As to power foils I disagree: Both the Hobie Trifoiler, Rave and Osprey use fully submerged foils with dual independent altitude control systems(wands or planing extensions on the Trifoiler). And both are exceedingly fast in stronger winds. My "Power Foil " idea is to utilize the foils at the point where they do the most good and with their foil loading and section designed accordingly. Because lift varies as the square of speed these foils gain quite a bit in terms of efficiency when compared to any of the three boats because they are only used when the boat is already moving very fast-not from zero as in the other cases. The L/D of the whole boat is still exceptional when using these foils and the boat can carry more SA in light and moderate wind as a result of the availability of the foils in stronger winds.

 

Doug, when SA/D and D/L are the same and the rig dimensions scaled so the important ratio SCP/weight does not change. The HM scales at the rate the RM does, so looking just at the 4th power change in RM is misleading.

I've said all I have to say on this. I think think the dynamics that make a Moth work do not scale, because Smart Ballast(tm) does not scale. Waves that a 12 boat sails over, a 24 foot boat sails through, this dynamic does not scale either.

I honestly think that the decades that people have been trying to make hydrofoils work on sailboats have produced only two successful boats; The Moth and to a lesser degree Hydroptre. Doug, you might find the magic answer that has eluded all the others until I see something that works and is not a doodle on paper I remain a skeptic.

No one has found a way to make hydrofoils work in the ocean, including the US military. I think it is a dead end except for unique dynamic combination like the Moth.

R

 

Foilers(successfull)

-----You really should include Mirabaud, the R Class, the I-14(foil assist) and National 12(foil assist) and lets not forget "Brace, Brace, Brace" the Wellbourne designed DSS sportboat that beat 70 other sport boats in its first race......

PS Hydroptere set the record across the channel-does that count for "ocean"? And what about Groupama 3 using lifting foils around the world and Banque Populaire using lifting foils across the Atlantic, and the top three finishers in the Route Du Rhum, and the Open 60's starting to use lifting foils. Foils for foil assit are spreading like,ah, well wildfire-and its just the begining....

Thanks for the conversation -helps me to think it out. I appreciate it.