Pros/Cons - weight distribution

[SFLDBT]

Hey all! First things first, I'm representing my dragon boat team (Suen Feng Loong, based out of San Francisco) and know VERY little of the finer points of traditional boating. With that said, I figured this place would have some great, expert advice to offer!

My question is: Considering straight-line speed is a critical part of dragon boat racing, what is the best weight distribution to have in the boat? (eg heavy paddlers in the back to bring the bow up, even distribution of weight front/back)

Info on our boats:
- boats have 10 benches holding 20 paddlers, a steersman in the back and drummer on the front
- boat length 12.49 m
- boat width 1.16 m (at the middle)
- max wt 250 kg
- some info on materials/etc can be found

http://www.dragon.de/184-International-Racing-Boat.html

 

[rbh]

Re: Pros/Cons - weight distribution

The less boat in the water the less drag you have, but the strokes have to be the same
OK then heavyer short armed people to the back, skinny long armed people to the front
had to take a guess
rob

 

[SFLDBT]

Re: Pros/Cons - weight distribution

hmm good point. pretty sure the bottom of the boat is symmetrical front to back (as in the deepest point of an empty boat is the middle). Assuming it is, would it have less surface area in the water if back-heavy?

 

[QC]

Re: Pros/Cons - weight distribution

I am not so sure that less boat in the water applies here . . . I am not positive about the energy required to reach "hull speed", but with a displacement hull (non-planing), hull speed increases with the waterline length, so potentially (only potentially) you want the weight centered to maximize waterline. There are obviously some limitations to this as I don't believe that you could row a 1000 ft. container ship faster than your Dragon, buuuuut if the weight is the same, I think you actually want the longest waterline combo. You'll need to read-up on this one . . .

 

[SFLDBT]

Re: Pros/Cons - weight distribution

aha...
After a shoddy self-education, I'd classify our boats as having displacement-type hulls. QC, I don't know what the waterline length would be exactly, fully loaded, but I guess we should try for max'ing the waterline length as you suggest?

Equation for max efficient speed of a hull (v) = 1.34 x (waterline length)^1/2

thank god for wikipedia

so what exactly DOES max efficient hull speed mean?

 

[QC]

Re: Pros/Cons - weight distribution

I think it means that above that theoretical speed it becomes less efficient . . . Soooooo, if you can exceed that speed then you are wasting some power as opposed to applying that same power to a slightly longer hull. Buuuuuttt I did NOT stay at a Holiday Inn Express last night!!!!

 

[RickJ6956]

Re: Pros/Cons - weight distribution

I would do some tests. Add a couple hundred pounds of weight to the bow and note the speed. Move it to the center, then the stern, then distribute it evenly. Note the speed after every change.

 

[Mischief Managed]

Re: Pros/Cons - weight distribution

I think the skills and strengths of the paddlers, along with even side to side weight distribution, would be more important. You are likely going to be paddling at well above hull speed, so hull efficiency is going to be less important than getting power into the water efficiently.

 

[QC]

Re: Pros/Cons - weight distribution

That may be true ^^^^^, but it would seem though that if the total weight is the same that a higher theoretical hull speed would be faster below planing speeds . . . There are people that know this stuff, I am just not sure who that is here.

 

[SFLDBT]

Re: Pros/Cons - weight distribution

I agree that skill goes a LONG way...but I'm not really sure about us traveling over hull speed. I (more like my math-oriented teammates) crunched some numbers to see how our speed-length ratio stacked up and we estimated it to be about 0.7 vs the 1.35 where the water resistance curve takes a trip to the moon.

Our calculations where probably off considering we didn't know the exact waterline and moment-to-moment speed of our boat. We estimated using the total boat length and average speed from our fastest race this season....

An interesting side note, we've noticed that we can practice in some much heavier and longer boats and keep up w/ teams in smaller boats. While it's much harder to accelerate the heavy boats off the start, our top speed is very close to the lighter boats. Both boat models have similar build styles. Perhaps the heavier boats have a longer waterline that makes this possible?

Thx for all the help so far everyone!