Dear Carla and János,
Thank you for your questions and sharing your ideas and interesting project with us.
In general, I would say you are on a good track to tackle your problem. Here are a few comments:
- It does make sense to look for materials with a low density (you don’t want the paddle to drag you down while paddling). However, think about the fact, when the material is too light and the swimmer has to use a lot of energy to push it into the water to hold against it’s high buoyancy. So I suggest finding a good compromise.
Since you already mentioned that most hand paddles are made out of PP or PE you can use those as a reference point. You can also consider general paddle material such as carbon and glass fibre reinforced plastics.
- You have also done some good thinking about the additional constraints, such as durability. Here I would also refer back to your reference materials. I noticed that setting durability regarding UV radiation at excellent also results into even loosing your reference materials. Go ahead and explore what their durability regarding UV radiation is. Keep in mind that there are good reasons for specific materials to be used most commonly for certain products; i. e. PE might only have “fair” durability regarding UV radiation, but the paddle might be coated for extra protection. Plus the paddle is not constantly exposed to sunlight (i.e. when stored somewhere and not in use), so it does not necessarily have to have excellent durability.
- I would keep the stiffness-limited design as you want to have low flexibility of the paddle, so that the energy transfer is most efficient (muscle energy put into paddle is transferred into propulsion)
What have you formalized as your goal for this material selection project? What are you trying to achieve by finding an alternative material to the one usually used? So WHY are you looking for a different material?
I.e. Do you want it to be more environmentally friendly? Do you want it to be cheaper?
Try to find constraints around those questions to narrow down your choices and to achieve what you are looking for. (e.g. restrict to only recyclable materials)
By the way, it was not wrong to start with those constraints, such as UV radiation. This is all part of the process. Sanity checking the results, comparing with the reference material, finding reasons for results that seem to be unrealistic, and repeating the process with adjusted conditions to achieve your goals.
The more constraints are added, the more difficult is becomes to find an optimal pool of candidates.
Hope this helps. Good luck with your project!