Originally Posted by brucehawsker
Been thinking of range issues for Farfetched in last 24 hours. The global average figure off the smartcraft gauge (to date since new, now 54 hours) is 1.1 - I think that is nm/l.
Tank is a nominal 160 ltres, although Kev at Solent told me that I should assume 20 l are effectively inaccessible.
So how do I calculate a safe figure? Lots of the usage so far has been blasting around having fun at close to WOT. I unfortunately did not take the numbers before and after Littlehampton cruise.
Firstly look at the manual for the smartcraft guages and establish whether your 1.1 figure is nm/l or l/nm. It makes a 10% difference & you need to know.
Secondly, a fair assumption is that 20l of your tank is not useable.
Thirdly, calculating a safe range should be based on cruising rather than blatting around. Its the distance travellign where its more important anyway.
Assuming you have 140l of useable capacity and do 1.1nm per l. In theory you have a range of 154nm. However a 20% reserve is a sensible precaution so a range of 123 nm is more realistic. But, and heres the important bit, be sure to factor in weather and seastate when planning trips. You will burn significantly more fuel in bad weather - working the throttle more to maintain a comfortable ride as you burn fuel to lift the bow, accelerate down waves etc etc. Think about it this way, you have many more humps to get over than when the sea is flat so you are travelling further to go the same distance if you see what I mean!
You should also do some fuel burn tests at a comfortable cruising speed. Unless conditions are dead calm and your wallet is bursting, you are not going to be travelling any significant distance at WOT. If you did your range is probably going to be 70nm not 123 nm! If you cruise at a comfortable speed say 25-30kts you will probably get max range. The smartcraft guages can help you with this IIRC. You can look at litres burned per hour and range at different speeds and set your speed and trim to maximise fuel economy.
HTH, Nice article in RIBLINES btw. I rather suspect I was one of those that told you to just get on a buy a bloody boat. Glad you are enjoying her now!