Can I Sail/motor upriver in 5 to 7 knot current if hull speed is less?
- Thread starter scott hall
- Start date
In 2015, I left Industrial Lock on The Mississippi River west bound, and turned downstream for Algiers lock- the old Muddy was honking!!. It's a five mile trip, and my 5.6 Knot hull speed boat did it in 36 minutes!!
Conversely, before I knew about Algiers, I brought my 35 foot tri out of Industrial and turned UP STREAM for Harvey lock. Again west bound. Took us 6 1/2 hours to do 5 miles to the lock
Also, motoring against a current over in the Carolinas ( forget which river) in the boat with 5.6 hull speed, snapped this pic-GPS said we were doing 1/2 knot over ground!! Some times running against a stream is like beating your head against a wall
Cumberland won’t have 7 knots current, but 1.5 knots might be more like it. Will depend a lot on the release rates at Old Hickory Dam.
Why not go a half to a mile past the dam and motor back. That would resolve the question. Better to have a 9.9 than a 5 anytime. Then you will know what folks are talking about
Regardless of the actual current you determine to be normal in the Cumberland River (1.5 knots or 5 knots) make sure you have an anchor that can be deployed quickly if you routinely sail or motor in restricted waters like rivers or channels. Even at 1.5 knots things can go very badly in a river very quickly if you lose your engine and you don't happen to have your sails up to manage the situation (they might not help much either if in calm winds). You will be surprised at how fast you are screaming towards that river bank or small island even at 1.5 kts. It can be a real "pucker factor" for you and your crew (don't ask how I know)
for you and your crew (don't ask how I know)
Sorry... that was confusing. Let's see if this quote makes any sense;
In this simple diagram.. the COG/SOG can be gps data... whereas the Heading/Speed is info gathered by compass and water speed transducer. A comparison between the two sources will give you current drift and set... allowing you to make navigational decisions .,, crossing the gulf stream, for instance, it would be important to know how this works. Modern chart plotters that are networked with the appropriate transducers can calculate and display this type of data.
"Hull speed" isn't theoretical, it's a definition and always refers to speed through the water. Different from boat speed which is actual, which you can measure over ground or through the water, your choice but they aren't the same either, so be clear about which you mean. Your question was a great one to ask. It shows your head is in the right place.
The Hunter 23 has a nice wide stern and flat bottom. You should be able to exceed hull speed with a motor of the right size. 9.9hp can probably push a hunter 23 over hull speed but it is unlikely to get her up on a plane. This means you won't likely exceed hull speed by much until you actually do get up on a plane. I don't know how well the transom are built on the hunter 23s, you might think about stepping up to a 25hp motor. Your weight will have a lot to say about how hard it is to get over hull speed.
Just imagine anchoring in 7, 8 or 9 knots of current. If your anchor holds, your boat is exceeding hull speed. Getting towed by a big enough boat will do the same. There is a lot of force involve to push a boat up her bow wave to get up on a plane. Have good cleats.
However, it sounds like we have moved into the realm of theory because your river isn't really moving at 6-7 knots. It's still an interesting exercise and worth experimenting with. Use a GPS and measure your speed thru the water, both under sail and with motor. Get to know your boat. It will be fun.
- Will (Dragonfly)
Absolutely. Having an an anchor ready at an instant saved my boat at least once. Coming through a draw bridge into the St John's River in Florida once, against a full incoming tide. Had cleared the bridge, tender had lowered, and started Traffic across,, when my engine quit.. He was sounding emergency siren and trying to clear bridge, I raced to bow and dumped anchor and already cleated off scope, from when we had anchored earlier. Wound up standing in cockpit, looking up at bridge tender, from about 20 feet shy of bridge.Regardless of the actual current you determine to be normal in the Cumberland River (1.5 knots or 5 knots) make sure you have an anchor that can be deployed quickly if you routinely sail or motor in restricted waters like rivers or channels. Even at 1.5 knots things can go very badly in a river very quickly if you lose your engine and you don't happen to have your sails up to manage the situation (they might not help much either if in calm winds). You will be surprised at how fast you are screaming towards that river bank or small island even at 1.5 kts. It can be a real "pucker factor"
Note to self- when wife asks- think we should add some fuel to tank, DO IT!!!