Question about flexwatt and wattage

Ok so I will be building a new rack soon and plan on using 12" sections of the 11" flexwatt. However, I also want to make a couple of the shelves with the 3" 10 watt flexwatt but I know your supposed to use the same wattage flexwatt so that the heat being release is equivalent. My 12" sections are 20 watts each and the 3" section is only 10 watts per foot, if I were to get a 24" section would it work out the same. Not sure if it works this way?????

1' of 3" FW = 10 watts so two feet should = 20 watts. Correct????

It doesn't work that way. Good try and sound logic. Ok so lets look at 17" FW @ 10 watts per foot it maxes out at about 88ºF But the 4" 8 watts per foot hits over 125ºF max. To use one t-stat you need that same heat out put per length of flexwatt. Look at the power per sq inch if that is the same you MIGHT be ok. (17"@10w=0.59 4"@8w=2) The four inch gets about 4 times more power per sq inch than the 17 so it gets hotter.

I would stick to the smaller flex watt, yes the wattage is the same, but the 3 inch is going to stay hotter than the 11 inch. kinda like how hot a 60 watt standard light bulb gets vs how hot a 35 candelabra bulb gets.... lower wattage not any cooler because they have the same rate of heat transfer and the smaller has less surface area to dissipate heat so it is more concentrated. The 3 inch flex watt provides me a hot spot for everything from my baby balls all the way up to my female burm. You wont ever get all temps stable with one thermostat on several sizes of flex

Ok I understand how it works now. So a 10 foot roll of 11" FW would stay around the same temp as a 1 foot roll of 11" fw.

Yes give or take it varies a bit but basically.