reeac
Well-Known Member
That 0.8 litre per hour figure looks dodgy, being so much less than the 4.5 lph. which only increases the speed from 5.5 to 6.4 knots. Possibly the fuel transducer has a bit of friction at very low flow rates.
your boat, and how fast she goes
- Thread starter benlui
- Start date
VO5
Well-Known Member
Yes, agreed.
However, on a flat sea ideally with no wind.
Additionally, this accurately verifies that component of the log that records the distance run.
To verify the speed shown on the clock the speed must be steady on both runs and the speed indicated by the needle or the digital disply noted and compared after all the calculation is completed.
Searush
Well-Known Member
Not interested in max speeds so don't know mine.
However, I was pootling along the Straits at 2k rpm in flat water at 4kts last week when I noticed that the speed had fallen to 2.5kts for the same revs. This startled me somewhat so I checked the engine, which was running fine, as were the prop & stern gland. Then I realised I was in a localised area of disturbed water. Sea Rush was bashing thro an area of wind over tide & that was what was slowing her down. Bashing into the waves knocked all her speed off each time. After we came thro the area the speed was soon back up to 4kts. At no time did the engine note change, but boat speed was severly reduced.
This is on a greatly over loaded 31' W Pentland with a new 29hp Yanmar 3YM30.
However, I was pootling along the Straits at 2k rpm in flat water at 4kts last week when I noticed that the speed had fallen to 2.5kts for the same revs. This startled me somewhat so I checked the engine, which was running fine, as were the prop & stern gland. Then I realised I was in a localised area of disturbed water. Sea Rush was bashing thro an area of wind over tide & that was what was slowing her down. Bashing into the waves knocked all her speed off each time. After we came thro the area the speed was soon back up to 4kts. At no time did the engine note change, but boat speed was severly reduced.
This is on a greatly over loaded 31' W Pentland with a new 29hp Yanmar 3YM30.
fireball
Well-Known Member
On port tack on Sunday in the Solent - fully sailed - relatively flat and with the tide against us - mostly top 5 and into the 6 knots ... when the wind dropped a bit we were down to 5's and when the wind got up to 20 knots+ we upped to mid 6's - at which point we were slightly overpressed and could have done with a reef in.
D
Deleted member 36384
Guest
I would add and repeated over a range of speeds. Instrument drift can vary at different readings, especially at the low and high ends. It could be considered an academic exercise, comparing accuracy at a range of speeds, simply because navigation is mainly EP with a spattering of fixes, unless one uses GPS, which makes the exercise more academic. Still having an accurate log is worthwhile in my opinion.
sailorman
Well-Known Member
Still having an accurate log is worthwhile in my opinion.
Im with you
if it isnt accurate why bother having one
flaming
Well-Known Member
An accurate log is a very useful tool.
How else are you going to do DR nav if the GPS fails?
And when your all singing all dancing integrated instrument system is all working, without an accurate speed reading all the other calculated information (TWS, TWD, tide, etc) will be out.
On the Elan 37 I race we have a target upwind speed of 7.3. We regularly achieve this, but this is with laminated sails and a full crew on the rail.
Interestingly, doublehanded racing (same sails but minus the crew weight) we find ourselves doing about 7 - 7.1. On delivery with the (really cheap) dacron sails we can get close to those speeds, but we lose about 5-10 degrees of height. We also have to reef much earlier.
Two sail reaching (where the sail cloth makes much less diference) which is normally after finishing, so crew lounging around the cockpit eating sandwiches, not hiking, we'll hit 8-9 knots in 15kts true.
To get the boat above 10, requires a lot of wind, and normally wave assistance. Only once have we broken the 10 barrier without wave assistance, when we were caught with a big kite up by a 35+ squall, but in flat water close to the lee of the Island. The boat took off, and one of the crew claims to have seen 13 on the log, but it ended in the inevitable crash and display of the keel to the rest of the fleet.... 37 foot, 8 tonne cruiser racers are not meant to plane....
It was not an experience I care to repeat, and we were very lucky not to break anything.
In contrast I've been hit by a similar gust on a boat that will just about plane, a J105, and we took off at 18 knots in perfect control with the crew whooping and hollering and the bow wave starting about level with the mast. Only the bottom mark brought an end to the fun.
I also spend quite a bit of time cruising on a Dufour 40. it's quite heavily laden in comparison with all the usual cruising clobber, and upwind it's definitely slower (if not always in straight line speed, but definitely VMG) than the Elan in race mode. Reaching and downwind it's probably about 5% faster in stronger winds, but of course slower in the light when the cruising weight really takes it toll.
How else are you going to do DR nav if the GPS fails?
And when your all singing all dancing integrated instrument system is all working, without an accurate speed reading all the other calculated information (TWS, TWD, tide, etc) will be out.
On the Elan 37 I race we have a target upwind speed of 7.3. We regularly achieve this, but this is with laminated sails and a full crew on the rail.
Interestingly, doublehanded racing (same sails but minus the crew weight) we find ourselves doing about 7 - 7.1. On delivery with the (really cheap) dacron sails we can get close to those speeds, but we lose about 5-10 degrees of height. We also have to reef much earlier.
Two sail reaching (where the sail cloth makes much less diference) which is normally after finishing, so crew lounging around the cockpit eating sandwiches, not hiking, we'll hit 8-9 knots in 15kts true.
To get the boat above 10, requires a lot of wind, and normally wave assistance. Only once have we broken the 10 barrier without wave assistance, when we were caught with a big kite up by a 35+ squall, but in flat water close to the lee of the Island. The boat took off, and one of the crew claims to have seen 13 on the log, but it ended in the inevitable crash and display of the keel to the rest of the fleet.... 37 foot, 8 tonne cruiser racers are not meant to plane....
It was not an experience I care to repeat, and we were very lucky not to break anything.
In contrast I've been hit by a similar gust on a boat that will just about plane, a J105, and we took off at 18 knots in perfect control with the crew whooping and hollering and the bow wave starting about level with the mast. Only the bottom mark brought an end to the fun.
I also spend quite a bit of time cruising on a Dufour 40. it's quite heavily laden in comparison with all the usual cruising clobber, and upwind it's definitely slower (if not always in straight line speed, but definitely VMG) than the Elan in race mode. Reaching and downwind it's probably about 5% faster in stronger winds, but of course slower in the light when the cruising weight really takes it toll.
Tranona
Well-Known Member
Very good illustrations of what happens at the margins.
You can break through the "theoretical" hull speed if you have enough power - but the overpowering brings with it other issues which may or may not be exciting depending on your point of view!
You can get sailing boats to plane with the right hull form and enough power.
If you want to achieve higher cruising speeds and potentially shorter passage times then there is no substitute (with a monohull) for longer LWL, but ensure you have the power to weight ratio to use the extra length.
Nothing new really!
You can break through the "theoretical" hull speed if you have enough power - but the overpowering brings with it other issues which may or may not be exciting depending on your point of view!
You can get sailing boats to plane with the right hull form and enough power.
If you want to achieve higher cruising speeds and potentially shorter passage times then there is no substitute (with a monohull) for longer LWL, but ensure you have the power to weight ratio to use the extra length.
Nothing new really!
alex33
New Member
Bavaria 39 cruiser, 2006...
8.3 kts on "white" sails, hull clean, but quiet loaded.
engine Volvo 55 hp, flat-out 8.3 kts, cruising 7-7.5 kts.
8.3 kts on "white" sails, hull clean, but quiet loaded.
engine Volvo 55 hp, flat-out 8.3 kts, cruising 7-7.5 kts.
DJE
Well-Known Member
Heckler
Well-Known Member
http://s434.photobucket.com/albums/qq70/skipper_stu/?action=view¤t=PICT0013.flv
What cant speak cant lie! Bene 381
Stu
Sojourner47
Well-Known Member
Under motor - SelwayFisher Simplicity 14, sail but not sailing at present -6mph on Breydon Water with full throttle - 2.3 hp Honda OB (when the carb's clean, see other threads) - but I can cruise all day on 2 litres of unleaded!!!
But not at 6 mph (inland waterwaysspeak - knots are for you saltwater guys)
But not at 6 mph (inland waterwaysspeak - knots are for you saltwater guys)
Juggler7823
Well-Known Member
Bene 393 heavily laden, Summer 09, North of Skye Bridge, 23kts true. Managed 9.5 kts on reach for more than several minutes with No3 genoa and 1st reef in main with wife on helm. Can manage 8kts under 55 hp VP engine but never tried full throttle yet. Can't load photo proof.
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Spud 7
Member
Broadblue 385 surfing a rather large wave mid Atlantic.
24.7 knts before I stopped looking!
(and yes it was
and I needed a Scotch afterwards!!)
24.7 knts before I stopped looking!
(and yes it was
and I needed a Scotch afterwards!!)gonad
Well-Known Member
speed!
carter 39
broad reach 9.5 on the gps well offshore
mid-atlantic surfing in a force 8 handkerchief foresail 15.8 on the gps
out of control!!
under motor perkins 48hp 7.5
carter 39
broad reach 9.5 on the gps well offshore
mid-atlantic surfing in a force 8 handkerchief foresail 15.8 on the gps
out of control!!
under motor perkins 48hp 7.5
