This does seem a little slow, if my math is right. My Hunter
27 (1978) was getting between 4 and 5 kts GPS
in the ICW
and the St. John's River (Florida) this last spring as I brought her home from purchase
, and when we hauled her out in August from the freshwater river, the three inches of barnacles
were hollow shells (fresh water
apparently killed them and the minnows and bluegills cleaned them out of the shells!), and mussels and other marine
life were there too. We used a pressure washer which pulled the vast majority of the growth off (as well as a ton of sponge creatures) and eventually we got to the bottom paint
, and then even it was falling away.
We then sanded and chipped until the hull
was clean, and then started applying bottom paint
. I do have a 3 bladed fixed prop, and it was not moving (engine had a broken valve spring so was not running), and I also used a sailboat shaft outboard
(also an 8 hp motor
like the Yanmar
SB-8 inboard that is in there still) to propel her because the PO or his PO had removed the running rigging
(which along with the dorm fridge, microwave, AC unit, sail suite, etc., was all still on board for the transit, along with something like six full 5 gallon gasoline cans on deck).
So even with the extra outboard
drive shaft submerged and lots of cavitation (as the bracket is mounted just a touch too high and the outboard was not precisely enough angled, AND mounted to one side!), tons of bottom growth, extra weight within the cabin
, two 300+ pound 6 foot new "sailors" (hey, we are working on it!) in attendance, and odd currents along the way that took us up to 5.2 knots at a high and down to 4 knots at a low outside of the St. Augustine area (Matanzas Inlet is a booger at tidal change) at varied times in increments of tenths of a knot
, we were not far from the hull speed
of theoretically 6+ knots on our 22 foot waterline length.
You SURELY should be getting better
than that. Sailboat Data shows you have a 32 foot waterline length. You can paste the link below into your browser in another window and it will show some stats in case someone thinks the numbers I am giving need recalculating.
HUNTER 386 sailboat specifications and details on sailboatdata.com
My math shows about... 9 knots and change... for your theoretic hull speed
and maybe closer to ten, I think. I have to do the exact
math, but the square
of the cube root
of hull waterline length
should give you the answer for "guessing" about the correct fluid dynamic solution for your hull speed maximum. If you get to 9 knots
, you are definitely approaching where you
SHOULD be, approximately, at max motoring speed (and theoretically the upper potential limit for your sailing speed, if you are not surfing a wave).
Of course, it also depends how close to wind
you are sailing, etc., hence the motorized nature of this test, which should limit the windage variance issue to an extent. This formula is an approximation, and I don't recall
precisely where I first heard it, but it was in a book on building boats, I am fairly sure, and I have seen it here on these forums
as well. You can also find it online in various sites related to how vessels achieve their motion through the water
without planing (this math is for displacement
hulls like most
I will post back when I manage to get Equinox
back into the water again from the yard, if you like, but I bet I am at 6 knots solidly
by then, maybe a tad more (7? 7.5??). My theoretical hull speed maximum is something like 6.8 or some such. It will be interesting to see how much each engine
affects this, and even what happens if I try to run both engines at once. I imagine I will get to hull speed then plant the bow firmly into the water and just be wasting horsepower and tranquility at that point rather than climb over my bow wave. But we shall see!
All that said, this mathematical tomfoolery only gets us an approximation, because I don't think it fully takes into consideration density of the medium penetrated, volume of hull under water (wetted area), our three bladed fixed propellers, my extra outboard shaft running down beside the rudder
, my bent rudder
post, the difference between keels (I have a shoal keel), etc., and those may be close enough to negligible to partially cancel out, but accuracy of it is
negatively affected by drag caused by growth of critters on the hull, and that drag, as others noted, will make a difference.
Your mileage may differ slightly
, that is my unsolicited opinion, worth precisely three times what you paid for it (or is that a third??).