designing a fast rowboat

apologies

Did the Snow Row on Sturday. The Nordfiord is going to be very good. Waterline fell right where anticipated. The thwarts are 2-1/2" too high, which also was sort of anticipated. 12o pounds of stone brough us down enough to have the stablity we needed to row confidently. We got whalloped: 6 minutes behind first place. Still, all in all, happy as we're totally out of shape and couldn't row as well as the boat requires. A very smooth passage through the water: almost no stern wave at all, especialy as compared to the Nordvind. I was so busy trying to figure out ballast VS no ballast that I didn't realize that one of the folks from this thread was talking with me. I dodn't recognize him, and was impolite to not speak with him. Again My apologies for being inconsiderate.

 

Good for ya. Curious what the water/air temperature was. We still have plenty of ice/snow pack but we are suppose to be in the 50'sF the rest of this week for highs. Good for me, but their will be flooding along our rivers with a thaw this fast. Reminds me of March.

 

weather

Conditions for the snow Row were: air 45 degrees, sunny, water 36 degrees with a chop about 18" high. The lead boat in our class came in with a 41:56 time. we were 5 boats behind with a 46:09. most of the other boats in our class were around 43:30 +- . overall average time for all boats (107) was 49.21, so we were faster than average time. There were a lot of surf skis, multi-seat sliding seat boats and competition kayaks, 4 and 6 person gigs and other fast boats so I don't feel too bad. Look at the Hull Lifesaving museum site for pictures and race results. We have the only translucent boat. The specs on Nordfiord are O.A. length 20'3" waterline beam 29" waterline length 19' 5", weight estimated to be about 180 pounds

 

Hi,
Sorry if this has been discussed yet, but I'm growing lazy seeing 65 pages to read ...

I was wondering why most rowing or paddling hulls are designed with narrow stern ?
Would we benefit from a design such as tri or cat ama's ?
The question came to my mind while seeing pics of the extreme design of bmw oracle tri, so I'm referring to this kind of hull :
Some hard chine look (even if the edges are rounded), with an abrupt, "square stern".

 

It has been discussed and explained (in short here) that since a rowboat has very limited power it's most important to minimize drag from friction (wetted surface) and wavemaking (make it narrow). That leads to more or less round bottoms and narrow ends.

 

OK.
Although I understand the narrow and long hull, in order to minimize the wave making, I don't get how the narrow stern is better than a blunt one ?

 

A blunt stern, like a transom, must be above water, or it will create suction and eddies and drag. Try to push your hand through water.

 

So, why do sail boats have a transom ?

 

A transom increases width at the stern and provides space for the helm, mainsheet attachment etc. The stern of a double-ender can get crowded. Not all sailboats have transoms however. Since this is a rowboat thread, lots of rowboats have transoms too - handy for seats.

 

Try to load some heavy passneger at the stern
As soon as the transom is submerged more than a few cm you can feel the drag.
You need speed to make the water flow freely under a submerged stern,

1/2V^2 = gh

 

Some sailboats are "double enders" and sharp at the stern, some have transoms which are above the waterline, and some have transoms which extend below the waterline. If the transom is above the waterline then it doesn't cause added resistance.

Some sailboats are designed to plane, some are not. Boats which plane work best if there is a sharp edge at the stern to aid the water flow in separating from the hull. Transoms which are partially submerged at rest and at slow speeds work well at planing speeds, as do sharp chines near the stern. At slower speeds a submerged transom causes added drag as do sharp chines (unless aligned with the flow).

Rowboats don't go fast enough to plane so they don't benefit from a submerged transom.

 

Snow Row

I was up at the Lake Champlain Maritime Museum this evening where the students my wife works with showed off their latest gig (the tenth!). Nick Patch of the museum said he had rowed in the Snow Row. Harvest Moon, Crouching Lion, and Wind Rose are DO/LCMM boats. Couldn't miss your translucent boat in the pics! You should come up for the Basin Harbor race at the museum (usually around July 4).

 

That's great.
In a few sentences you all got me to understand fairly well the why and how about stern shape - at my level, not pretending to graduate in naval arch. -

seriously, I'm glad this forum exists on the internet, it makes me feel more clever every time I take a look at it.

Thank you folks for your time and patience !

 

Less wetted surface.

 

Snow Row

Dick T, Afer the race, I spent some time talking wit a couple of guys from your program up there, didn't get their names. We spent time talking about how many boats the kids have built. I enjoy seeing the kids get all revved up about the race.