Cardboard canoe challenge

Yesterday we participated in a canoe race in the pool with the canoes made out of cardboard and duct tape.
I have compeleted 5 achievements.
I compeleted the build it achievement where I built the canoe with my team. Our canoe had a v bottom shape which fills the v bottom achievement.
For the feedback achivement, under the positive sign we stayed up for a long time and the canoe was easy to build. Under the change sign I think we should build a flat shape bottom and we should have built our paddle better so we could have gotten faster. I was surprised that it floated as long as it did and that water came into the canoe.Some questions are that if we would have done better if we had a flat bottom and why the v bottom succed inn the water.
In the how low did it go achievement, our canoe went a couple of inches down in the water when it floated. The density of the boat was less than the water's density which is why it floated.
I also compeleted the redesign achievement. I think next time we do this project my group should build a flat bottom canoe so it would float better and we could win.