Best speed?

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chuzzlewit

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Bashing back from Lymington to Poole against force 5 in a Merry Fisher 805 at 8 knots felt safe enough but caused complaints from the admiral. 15 knots would have lifted the hull and lessened the spray. Would it also have smoothed the ride, giving the hull less time to fall into the troughs? Would a longer hull, say 38 feet have given a smoother ride?
 
15 knots would have lifted the hull and lessened the spray. Would it also have smoothed the ride
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Thats a difficult trick to pull off because you need to have a combination of hull length, speed, wave length and skill to find the right speed for the bow not to fall into the troughs and just kiss the tops of the waves. And if you get it wrong you are going to hit a wave with an almighty crash and that definitely won't please the admiral. IMHO better to find a speed that you and the boat feel comfortable at and put up with whatever spray is flying about. Yes a longer hull would generally perform better in a head sea partly because the extra hull length may bridge the troughs and partly because the extra weight is going to push through the chop easier

I can sense some man maths coming;)
 
As Deleted User said. If you can find the sweet spot the boat will be more settled. Only problem is then when the period / height /rhythm changes on the odd wave the slam can make you situp and take notice.
 
An SC35 can go upwind in an F5 at 21kts, but I wouldn't describe it as "smooth'.
Having said that, 8000kg and 11m definitely squashes waves better than 4200kg 8.8m does (previous S28).
Taking several massive steps up, Henry's 25000kg and 50ft would only see small ripples in the Gin.
 
I have had a similar experience in our MF 695 (very light by comparison) both to and from Poole to IOW and tried various speeds and angles of attack and really there is no "right" speed.. I tried faster which was quite hard going and lots of playing the throttle, it worked ok until there was a non-uniform/unexpected wave or trough at which point we felt more like a submarine for a couple of seconds.. Slower is definitely the more comfortable and less stressful way to do it even if there is lots of water over the bow, the wipers running overtime and the boat pitching and rolling all over the place.. At the slower speed my "commander" climbed down into the front berth with her blanket and went to sleep, I guess at least it was quiet rather than being shouted at at the boat slammed its way home.. :)
 
chuzzlewit said:
Bashing back from Lymington to Poole against force 5 in a Merry Fisher 805 at 8 knots felt safe enough but caused complaints from the admiral. 15 knots would have lifted the hull and lessened the spray. Would it also have smoothed the ride, giving the hull less time to fall into the troughs? Would a longer hull, say 38 feet have given a smoother ride?
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Did you make trip yesterday morning by any chance (Saturday 2nd). ?
 
Ah man maths! :D

As others have said, in theory the answer is yes but in practice the risk of getting it wrong is high!

Having spend most of my boating time in fast boats and ribs i have spent more than my share of time trying to get it right with mixed success. in my experience, the key is throttle control and its much easier on a small, light boat or one with an abundance of power to help. Best is of course small light boat with loads of power but thats another story.

Balancing the boat so the sharpest point of the hull when pushing through the wave gives the softest ride, if you look at the books on throttling i tells you to ease off as you reach the top of the wave (so you dont launch into orbit) and power on down the back of the wave to keep the bows up and avoid stuffing.

When you get to the point of clipping the tops of waves it gets more critical as you need to keep the power on to keep the speed up yet be sympathetic to keeping the boat level and to control revs when the prop(s) are in the air

any excuse to post this video again.... (sound up makes it even better)

Getting it right is an amazing feeling but needs a lot of concentration as getting it wrong gets wet and painful quickly! you also need to be aware that if you are getting the boat flying (and talking about single engine boats) you need to take great care to land the boat level. landing on the chine is very painful (for you and the boat) often a little flick of the helm as you start to fly is enough to counter physics deployed by the single spinning prop. (prop torque)

best boat we had for this... the Hunton with plenty of water line length, plenty of power and a very narrow hull...
 
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Hi

The last reply was great and I would only add one small point. On most boats 26 feet or under the biggest factor I have found for a good ride is as others have said power, concentration but also the balance of the boat is vital. A few months ago I was out in my rib following a MF out in the swells of troon. The MF was set up wrong so she was far to light at the front. 80Kg later the 1.5 M waves were fine at around 22 knots give or take a few. Before that it was a smoother ride at 6! I do accept that the skill of person is also has a factor but in this case my pal Jimbo simply did not have the balance right. We also had the advantage of being able to see how the boat performed when sitting in our redbay cruising along side him. So my tip is weight balance is a massive factor so its worth a bit of effort to at least trying to get it close to being right.

Dave
 
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