Message 4 of 4
Posted by member Steve on Tuesday 5 December 2023

Hi Steven, Hi Peter

Peter, your figures are extremely useful and I offer mine by way of comparison. To compare them we need to note the following differences in equipment and usage:

I have found a note within the files left to me by the previous owner, that my Hardy 27 was originally supplied with 16/16 props. This note also says that 16/15 props are recommended, (as per Peter's boat), but also says that mine has been fitted with 16/18 propellers. I will need to check whether these 16/18s are what are actually fitted as of today when I get the boat out for its winter refit.

I have experimented with the use of trim tabs, but tend to only use them above hull speed - below this I find that they reduce speed at any given RPM and, as I mentioned in my previous post, we use the boat in the Solent where the choppiness and powerful swirling tides makes comparisons in performance rather complicated. Mind you, I have made a note for next year to try again with smaller angles of trim and try to recall my very limited racing dinghy experience; although this will be coming from much further back in time than I care to think.

As for measuring fuel consumption - the sender in my tank is quite unreliable so I regularly get into the lazarette with a dipstick and tape measure. I also, mostly for the fun of it, make a careful note of speed, rpm and timings of the engine usage. Peter's figures are also appear to be quite detailed so I am in no doubt that his are also highly reliable.

I have prepared an image which should be attached to this message to tabulate a comparison between Peter's figures and my own measurements.

Two trends seem to stand out - the first is that my revs top out at 3000 rpm - perhaps this is to be expected by the coarser pitch of the props, but my top speed is far less that that of Peter's boat. My fuel consumption does seem to be kinder on the wallet at most speeds, especially at sub- hull speed ranges.

A winter project that I have set myself is to map the power consumption, HP, %prop slip etc to the engine performance curves and when I have done all that.....

I will go and find a real expert and ask them!

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Message 2 of 4
Posted by member Tarka 2 on Sunday 30 July 2023

Hi Steve

I too have a Hardy 27 - a beautiful boat with twin Yanmar 100s. I have started to wonder about the pitch of my Propellors as the revs at full throttle peak at less than the 3000 odd rpm quoted in the handbooks. I have never achieved anything like 13knots, even with the trim tabs in use. That said, we use her in the Solent where the sea becomes choppy at the slightest excuse. The disruption to a smooth passage through the water will impact on the top speed of any boat, powered or sailed. Even 'glassy calms' in the Solent means a swell that gets her gently pitching just enough to prevent that ideal laminar flow we all dream of. We also usually have the water tank half to fully full and never less than a quarter tank of diesel. Add in the tools, spares, dinghy, clothes food, supply of beer yet to be drunk, me, (occasionally with beer recently drunk) and the laden weight will significantly exceed whatever condition the boat was in when the marketing department did their trials. Obviously they would have ensured the hull was very freshly anti-fouled too.
Her hull profile aft appears to be less designed for planing than that of the smaller 25s, so perhaps we should not expect too performance much beyond that of a beautiful displacement craft. I also have conducted Revs v Speed over Ground and Fuel Consumption trials and have every incentive to plan all journeys at 'Hull Speed'.
After 17 years with a smaller 30knot boat, (where we got wet every time it rained), I have had to simply accept that the journey is as important as the destination and a more intense focus on working the tides is part of the fun.

We keep her on the Hamble are you local to us?

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