Faster then hull speed with a monohull cruiser?

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haydude

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How easy is it to go faster then hull speed with your cruiser?
At what point of sail, which boat, with what sails/rig, what wind speed? Can you do that normally or just on exceptional circumstances?
 
Usually manage when going downwind .... at which point it is easy to stay 'over canvassed' because there is less healing force. Anything from 15-20kt up.
 
haydude said:
How easy is it to go faster then hull speed with your cruiser?
At what point of sail, which boat, with what sails/rig, what wind speed? Can you do that normally or just on exceptional circumstances?
Click to expand...

Quite easily, when the beer is flowing!

More seriously, hull-speed is a bit of nebulous concept - it is simply "the speed at which drag forces start to increase rapidly". The constant in the equation is variable over a large range depending on hull form and so on. There is nothing to stop you travelling faster than hull-speed - it just needs a lot more power for every extra knot than it did below hull-speed.

I have exceeded hull-speed for long periods with a quartering wind, when I have done consistently over 8 knots in my Moody 31. That was a combination of a favourable point of sailing, surfing down waves, relatively sheltered water (the Hunterston Channel) and a wind that was stronger than I thought (as I found out when I turned back and was close-hauled!). But such ideal conditions are rare.
 
haydude said:
How easy is it to go faster then hull speed with your cruiser?
At what point of sail, which boat, with what sails/rig, what wind speed? Can you do that normally or just on exceptional circumstances?
Click to expand...

There are several reasons for exceeding 'hull speed'-

1. You calculated it wrong - yes, really. The 1.4 in the equation isn't a universal constant, it reflects hull form so for the same LWL two different boats can have different limiting speeds.

2. If you have a very fine-lined hull, hull speed doesn't really exist. That needs a length/beam ratio of 8+ which is why the phenomenon is common in multis, rare in monos.

3. You are getting onto a full or partial plane. Most modern hull forms have the flat after sections that allow planing given enough power.

4. Surfing. When you are on the front face of a wave the surface of the water is travelling forwards so your water speed is low compared to SOG.
 
Doesn't often happen to me with just boat speed, but given the right tide, you can get some pretty nice ground speeds.

Small sailing boat, last week on the south coast.
 
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haydude said:
How easy is it to go faster then hull speed with your cruiser?
At what point of sail, which boat, with what sails/rig, what wind speed? Can you do that normally or just on exceptional circumstances?
Click to expand...

To exceed the hull speed you need enough power to make the boat climb up its own bow wave and as the stern will sink into the trough, you are perpetually motoring / sailing uphill.

Not impossible but costly in terms of fuel.

I
 
with a spi above 25 kts wind, may end up in a mess...
easier with goose-winged main and jib or partially furled genoa (poled out) above 30 kts
 
A friend got caught out in a squall with spinnaker up. They hit 14 knots before they got it under control. It was a 15 ton 42 footer. He didn't get a chance to work out what the hull was doing at the time!
 
We kept up a steady 9.5 to 10.5kts over several hours in our 41ft SunLegende, broad reaching under full (roller) genoa and a single reef in the main, true windspeed around 25kts. We averaged 8kts on a 60ml Channel crossing that started with F5 and went up to F8 for several hours, again broad reaching. Theoretical hull speed allowing for greater immersed LWL at speed when the tail sits in rather than just over the water is 8kts, but to average it over 60mls and starting with a mere F5 meant we were really going some for long periods.

Our record in the Sun Legende 41 was 19.1kts. That was achieved in E6/7 off Poole with less than half the roller genoa out and no main and the log was set to show average speed over 10 seconds not instantaneous readings. Again this was a broad reach.

On our earlier W33 ketch (hull speed 7.2kts) we also had one trip where we averaged 7.5kts over 18 hours, so were regular up over 8kts for long periods. We had a downwind 110ml run too in 45/50kt true winds and did that in 15hrs despite being almost windless for the first hour and speeds went from 5kts in the troughs to 10.5kts down from the peaks!
 
Two best sustained speeds I've ever done were both in a J105.

The first was a very windy nationals (30kts+) where the speed never dropped below 14 with the kite up, and hit 19. The bow wave started about where the keel was.

The second was the complete opposite, 7kts of breeze or less, completely flat sea, close reaching just holding the (very) big spinnaker. Speed sat between 8 and 9 knots for 2 hours.

Theoretical hull speed for that boat is about 7 knots. But it does have a hull shape that helps it up onto the plane, and on the windy day once we were on the plane it was much more controllable. It was only if you made a mistake and fell off the plane that the loads shot up and crashes happened.

Complete contrast to the Elan I sail normally, which won't plane, but will surf. That boat is much harder to drive agressively with the kite up, and the 14 knot burst round the back of the island in 2008 was scary.
 
AntarcticPilot said:
Quite easily, when the beer is flowing!

More seriously, hull-speed is a bit of nebulous concept - it is simply "the speed at which drag forces start to increase rapidly". The constant in the equation is variable over a large range depending on hull form and so on. There is nothing to stop you travelling faster than hull-speed - it just needs a lot more power for every extra knot than it did below hull-speed.

I have exceeded hull-speed for long periods with a quartering wind, when I have done consistently over 8 knots in my Moody 31. That was a combination of a favourable point of sailing, surfing down waves, relatively sheltered water (the Hunterston Channel) and a wind that was stronger than I thought (as I found out when I turned back and was close-hauled!). But such ideal conditions are rare.
Click to expand...

Yes and no. It's the speed at which wave drag increases rapidly. Wave drag is only one of the three types of drag acting on a vessel and (as you would expect) can be minimised by minimising the generation of waves; this is why catamarans (particularly the higher performance variants) which have narrow bows with fine entry can easily exceed hull speed (some even while going upwind); whereas even the best monohulls struggle a fair bit.
 
haydude said:
How easy is it to go faster then hull speed with your cruiser?
At what point of sail, which boat, with what sails/rig, what wind speed? Can you do that normally or just on exceptional circumstances?
Click to expand...
Thankfully, I don't have the need for speed. The boat happly rolls along at 6.5 knots with a theoretical hull speed of 7 knots. I suspect I could go faster but that would mean working harder faffing with sails and would inconventily interrupt tea and good craic in the cockpit.
 
Sandy said:
Thankfully, I don't have the need for speed. The boat happly rolls along at 6.5 knots with a theoretical hull speed of 7 knots. I suspect I could go faster but that would mean working harder faffing with sails and would inconventily interrupt tea and good craic in the cockpit.
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I don't generally have a 'need' for speed but much prefer the motion of a boat that is fully driven, both on and off the wind. This doesn't have to be at full racing speed, but just the speed appropriate for the wind and sea states. There is nothing worse than that time when you have been sailing with a reef and the wind drops, leaving you rolling around without sufficient drive to counter the not-yet-settled sea. Just occasionally it can be rather satisfying to keep excess sail when the the wind pipes up, typically on a broad reach when the theoretical hull speed can easily be passed, if only for brief periods. My 10m boat can readily sustain 7-8kn and be quite comfortable, though my record was 11.5 on a couple of occasions, for maybe 5 seconds or so, with about 35kn of true wind on our tail.
 
Obviously, if we didn’t have a need for speed, we’d be in the wrong boat. The transition to planing you can only see by looking at the log and the stern wave such as it is. It turns into a sharply defined V at about 7.5Kn. At 12Kn you start to get a feather off the lee bow. At about 16Kn, the reefing alarm tends to go off. (OH‘s voice gets a bit shriller) How often? Every sail unless it’s as dead as a door nail. If you want to go fast, by far the easiest way of achieving it is a multi. We do it with 2 crew, and it’s comfortable, easy to manage. Of course there are drawbacks to the boat, but performance wise, she’s sublime.
 
Had a happy day once when the wind and waves lined up nicely for a surfing reach back over the Minch.
Well powered up with full main and genoa, if a gust and steep wave lined up we’d be off surfing. The trick was to head up a bit along the wave to keep the surf going. Over sheeting the sails slightly made it harder to catch a wave but kept you powered and on one longer. Bearing off straight down the wave gave less severe but similar results to doing the same thing if you were properly surfing..
The hull would start to sing then the bow wave sprayed out in line with the chain plates once you were up and going.
I wouldn’t like to try it in ‘proper’ conditions though.
 
pioneer_11 said:
Yes and no. It's the speed at which wave drag increases rapidly. Wave drag is only one of the three types of drag acting on a vessel and (as you would expect) can be minimised by minimising the generation of waves; this is why catamarans (particularly the higher performance variants) which have narrow bows with fine entry can easily exceed hull speed (some even while going upwind); whereas even the best monohulls struggle a fair bit.
Click to expand...
Considering that the OP asked the question 12 years ago , the moment may have passed. !!!
 
Not sure how but I seem to recall that Anderson 22's have the opposite problem ... they find it hard to do anything other than exceed hull speed :)
 
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