benlui
Well-Known Member
hum
I always use my handheld GPS and onboard chart plotter for speed not my log.
Truth be told, my log hasn’t worked for a while despite doing everything i can to try fix it.
I understand that SOG and thru water are completely different, so don’t try explaining please.
Because this is simply what it reads. Often 7knt and slightly above if the wind and sea state are suitable.
Once, caught out with a squall of 55knt wind and a full main sail, the boat surfed at 10knt. Debate this all you want, there was 4 of us and all witnessed it. I wouldn’t do it again for the world. Lets just say, brown underpants moment.
I’m interested to know how accurate the speed formula is. I.e., how can lets say a 30ft race yacht vs a 30ft cruiser that is also geared out for racing, be compared? Obviously the race yacht is faster for many reasons but at the end of the day, still has the same LWL.
There are many other things such as ballast, sail types, SAIL AREA, deep keels, as already mentioned, etc etc etc so therefore one can only assume that the speed formula is in fact a guide only, and not gospel.
Ie, you have to calculate the LWL when heeled to be precise, not the LWL when standing still. I don’t know what my boats LWL is when heeled, but at a guess its surely an extra 1-2ft at least, considering her overhanging stern , and her oval shaped hull,all in the water more when heeled, similar to a contessa 32 i think.
So, Using your formula of my boats LWL, and correct LWL of 23'4" not 22' and weight in gross tonnes of 3.75 not under 3 as stated earlier in this thread, and taking into account her extended LWL while heeled, it is quiet possible from what you are saying to achieve 7kts on fastest point of sail.....
Thanks to those of you who replied to the question at hand, as I am quiet keen to learn about design/boat speed and I think this thread was a good start.
I guess one of the reasons for this thread is I will eventually upgrade to something bigger, and although I want to travel further a field in something very sea worthy, I don’t want it to be a slow snail either. I want a good compromise of both.
I always use my handheld GPS and onboard chart plotter for speed not my log.
Truth be told, my log hasn’t worked for a while despite doing everything i can to try fix it.
I understand that SOG and thru water are completely different, so don’t try explaining please.
Because this is simply what it reads. Often 7knt and slightly above if the wind and sea state are suitable.
Once, caught out with a squall of 55knt wind and a full main sail, the boat surfed at 10knt. Debate this all you want, there was 4 of us and all witnessed it. I wouldn’t do it again for the world. Lets just say, brown underpants moment.
I’m interested to know how accurate the speed formula is. I.e., how can lets say a 30ft race yacht vs a 30ft cruiser that is also geared out for racing, be compared? Obviously the race yacht is faster for many reasons but at the end of the day, still has the same LWL.
There are many other things such as ballast, sail types, SAIL AREA, deep keels, as already mentioned, etc etc etc so therefore one can only assume that the speed formula is in fact a guide only, and not gospel.
Ie, you have to calculate the LWL when heeled to be precise, not the LWL when standing still. I don’t know what my boats LWL is when heeled, but at a guess its surely an extra 1-2ft at least, considering her overhanging stern , and her oval shaped hull,all in the water more when heeled, similar to a contessa 32 i think.
So, Using your formula of my boats LWL, and correct LWL of 23'4" not 22' and weight in gross tonnes of 3.75 not under 3 as stated earlier in this thread, and taking into account her extended LWL while heeled, it is quiet possible from what you are saying to achieve 7kts on fastest point of sail.....
Thanks to those of you who replied to the question at hand, as I am quiet keen to learn about design/boat speed and I think this thread was a good start.
I guess one of the reasons for this thread is I will eventually upgrade to something bigger, and although I want to travel further a field in something very sea worthy, I don’t want it to be a slow snail either. I want a good compromise of both.
