Forgive me if this question has been covered already. We have a free-form pool and I would like to extend our NE swim season with a solar cover. I figure a rectangular solar sheet could cover roughly 80-90% of the surface. Would I get 80-90% of the insulating value if that is all that is covered or do uncovered areas have a disproportionate effect on overall heat loss? In other words, should I go to the trouble of buying oversize and cutting a perfect fit for 100%? I'm trying to trade off the convenience of being able to reel it up easily in one step versus getting most of the value of having the pool insulated during the early and late months of the swim season. I understand that one can fold the eccentric areas up and make it into a rectangle before reeling, but I'm trying to be honest with myself about how many steps I'm likely to undertake to take before doing a few laps before and/or after work (Yes, I'm kinda lazy). I know myself, if it is too much of a hassle, I'm less likely to do the folding and rolling. I suppose I could also have separate small pieces that I could pull out to cover the non-rectangular bulges...but will they stay in place when the reeled rectangle is in place?
The cover would probably only be used during the early and late months of the season. Thanks for any thoughts/experience that can help.