Just curious...what kind of boatspeed do people typical see when motoring? Last week we chartered a Catalina 30 and the best we saw on the speedo was just under 4 kt. SOG with the GPS was the same within 0.1 kt. There was no headwind. Under full sail in 25 kts of wind, we were doing right around 7 kt. I was a little surprised, because my wing-keel Hunter 23 will easily do 6 kt under power (8hp outboard, no headwind) and under similar wind conditions I have seen 7.6 kts on the speedo. Again, SOG with the GPS was within 0.1 kt. I know the whole "hull speed" thing is a little imprecise, but I still would have expected faster speeds from the longer boat. Both hulls were clean. Any ideas, or was the C-30 just underpowered/underpropped? Peter S/V Raven
How fast is your boat...really?
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Justin - O'day Owners' Web
Boat speeds
On my Catalina 25, I get about 6.1 - 6.2 through the water with an 8hp outboard - under sail I see about the same. Of course since the Daysailer will plane with its 8hp, is a whole different game. Justin - O'day Owners' Web
On my Catalina 25, I get about 6.1 - 6.2 through the water with an 8hp outboard - under sail I see about the same. Of course since the Daysailer will plane with its 8hp, is a whole different game. Justin - O'day Owners' Web
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Barry
Hull Speed
Displacement hulls generally go 1.34 times the square root of the waterline length.(if powered and proped correctly) That puts the C30 just under 7 knots. On rare occasions you get faster SOG surfing or running with the current. Like Justin said, your 23 must be starting to get up on plane based on the speed you report here. Barry
Displacement hulls generally go 1.34 times the square root of the waterline length.(if powered and proped correctly) That puts the C30 just under 7 knots. On rare occasions you get faster SOG surfing or running with the current. Like Justin said, your 23 must be starting to get up on plane based on the speed you report here. Barry
I'll take "Planing the H23" for 200, Alex...
I'll accept the planing explanation. Having sailed planing dinghies for many years, I just didn't think I was going fast enough on the H23 for this to happen, especially since all I had was the stock main and working jib (110). Thanks. Peter S/V Raven
I'll accept the planing explanation. Having sailed planing dinghies for many years, I just didn't think I was going fast enough on the H23 for this to happen, especially since all I had was the stock main and working jib (110). Thanks. Peter S/V Raven
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Jack Gilmour
Check Feb. Sail Magazine
There is an interesting article in Sail stating that D/L ratio can alter the 1.34 factor for hull speed. See page 82.
There is an interesting article in Sail stating that D/L ratio can alter the 1.34 factor for hull speed. See page 82.
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Les Murray
Looks like the Cat 30 was underpowered/propped
Peter, My vote is that the Cat 30 was underpowered or underpropped. A decent engine/prop combo should get it near hull speed. I read the article in Sail. Very good. According to that article, you either have a prop that is too small or you are not getting enough RPMs out of the engine. Les Murray s/v Ceilidh 86 C-36 #560
Peter, My vote is that the Cat 30 was underpowered or underpropped. A decent engine/prop combo should get it near hull speed. I read the article in Sail. Very good. According to that article, you either have a prop that is too small or you are not getting enough RPMs out of the engine. Les Murray s/v Ceilidh 86 C-36 #560
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steven f.
just fast enough
I've owned a H23 for several years and my true speed with a Nissan 5 hp was about 6.5, all conditions being ideal. I now own a H33 and there is a Westerbeke 21a with a fixed three bladed prop. My true speed is 6.5kts at crusing rpm's. Now like everyone else, I've had her up to the high 7's with a 25kt wind on a broad reach with nominal seas. She's surfed at 12 knots but that is a story it itself. good luck.
I've owned a H23 for several years and my true speed with a Nissan 5 hp was about 6.5, all conditions being ideal. I now own a H33 and there is a Westerbeke 21a with a fixed three bladed prop. My true speed is 6.5kts at crusing rpm's. Now like everyone else, I've had her up to the high 7's with a 25kt wind on a broad reach with nominal seas. She's surfed at 12 knots but that is a story it itself. good luck.
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Dave
Top Speed of 6.3 with 11 hp
I've got a 1983 C-30 with the Universal 5411 (11hp) diesel engine. I'm turning the stock 2 blade prop that came with the boat when I bought her new in the fall of 1982. I cruise at 5.3-5.5 and top out at 6.3. So, if that C-30 you chartered was newer than 1983, it has more than 11 hp (1983 was the last year for the 5411, it was switched in mid year)...it had the wrong prop on it or the bottom was really dirty...
I've got a 1983 C-30 with the Universal 5411 (11hp) diesel engine. I'm turning the stock 2 blade prop that came with the boat when I bought her new in the fall of 1982. I cruise at 5.3-5.5 and top out at 6.3. So, if that C-30 you chartered was newer than 1983, it has more than 11 hp (1983 was the last year for the 5411, it was switched in mid year)...it had the wrong prop on it or the bottom was really dirty...
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Mike Basham
Old 23' O'Day with Old 10HP Crysler
According to a GPS, I hit 7.8kts in pretty high winds, and 6.8kts with the motor at full tilt. At a more reasonable throttle position on the motor, it was closer to 5kts. Hope this helps!
According to a GPS, I hit 7.8kts in pretty high winds, and 6.8kts with the motor at full tilt. At a more reasonable throttle position on the motor, it was closer to 5kts. Hope this helps!
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Al Sandrik
According to my GPS unit...
...I've had my Hunter 28 up to 6.7 knots. Now I believe her LWL is 25 feet. 1.34 x SQRT (25.0) = 6.70 I'll be darned either the hull speed equation works or my scientific calculator is screwed up from too much balancing of the check book to pay for the boat! :^) Al Sandrik s/v Miss Julia's Money
...I've had my Hunter 28 up to 6.7 knots. Now I believe her LWL is 25 feet. 1.34 x SQRT (25.0) = 6.70 I'll be darned either the hull speed equation works or my scientific calculator is screwed up from too much balancing of the check book to pay for the boat! :^) Al Sandrik s/v Miss Julia's Money
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hp
charter boats
you did not say what rpm's you were operating at but could it have been that there were intentional cut back so that the engine was not operating at full throttle? a lot of charter companys do this to save the abuse of wide open engine speed. A 30 catalina should do alot better then 4 knots!Just a thought !
you did not say what rpm's you were operating at but could it have been that there were intentional cut back so that the engine was not operating at full throttle? a lot of charter companys do this to save the abuse of wide open engine speed. A 30 catalina should do alot better then 4 knots!Just a thought !
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Dick Carey
SOG vs Knotmeter
The boats knotmeter is measuring to speed thru the water. The GPS is measuring the SOG (speed over ground) If your boat is going 6 Kts thru the water and the water is moving 1.2 Kts (current) in your direction, then your boat is moving 6 + 1.2 = 7.2 Kts over ground (a GPS reading). Contrarily if the current is from dead ahead, then your SOG is 6 - 1.2 = 4.8 Kts over ground. With current from any other directionit will be in between the above two examples and you can determine it with vectors (ugh!), or just beleave the GPS and use that as your SOG for plotting your DR & Fix on your chart. (You do do that, don't you). Regards & Good Winds, Dick Carey S/V Puffin H-33.5
The boats knotmeter is measuring to speed thru the water. The GPS is measuring the SOG (speed over ground) If your boat is going 6 Kts thru the water and the water is moving 1.2 Kts (current) in your direction, then your boat is moving 6 + 1.2 = 7.2 Kts over ground (a GPS reading). Contrarily if the current is from dead ahead, then your SOG is 6 - 1.2 = 4.8 Kts over ground. With current from any other directionit will be in between the above two examples and you can determine it with vectors (ugh!), or just beleave the GPS and use that as your SOG for plotting your DR & Fix on your chart. (You do do that, don't you). Regards & Good Winds, Dick Carey S/V Puffin H-33.5
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Mitch Witt
Of course you know.........
Amigo, you mentioned SOG and hull speed. SOG is just that, hull speed has to do with speed through the water. Hull speed error's are minute, not enough to consider for pleasure applications. With our First 42(WL of 39'3") and a hull speed of just over 8 knots we have done over 11 knots heading north in the gulf stream-SOG. In dead calm water, motoring with our perkins 4108, a 2 blade prop,Even with the extra push of a 15 hp dinghy motor we would be doing very good to hit 7.5 kts. The prop selection is critical. So is it's drag. Use a max prop? They are good but just not as reliable as a fixed prop. If you are outfitting and cruising on a fixed budget there is no room for experimenting with different props. Go with old reliable. One more thing ! if you go with a max prop make sure your motor mounts can handle the added torque ! Mitch & marie-ellen witt sv Private Dancer 7,500 nm - Caribbean: 96,97,`98 yachtprivatedancer@yahoo.com www.bbafloat.com
Amigo, you mentioned SOG and hull speed. SOG is just that, hull speed has to do with speed through the water. Hull speed error's are minute, not enough to consider for pleasure applications. With our First 42(WL of 39'3") and a hull speed of just over 8 knots we have done over 11 knots heading north in the gulf stream-SOG. In dead calm water, motoring with our perkins 4108, a 2 blade prop,Even with the extra push of a 15 hp dinghy motor we would be doing very good to hit 7.5 kts. The prop selection is critical. So is it's drag. Use a max prop? They are good but just not as reliable as a fixed prop. If you are outfitting and cruising on a fixed budget there is no room for experimenting with different props. Go with old reliable. One more thing ! if you go with a max prop make sure your motor mounts can handle the added torque ! Mitch & marie-ellen witt sv Private Dancer 7,500 nm - Caribbean: 96,97,`98 yachtprivatedancer@yahoo.com www.bbafloat.com
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