Originally Posted by busbus
I feel like these are not intelligent questions but I am confused about these things since I am really new at this. I also tend to over think things.
Nothing wrong with being new and asking questions
1. How heavy is too heavy for a fly? By that, I mean how heavy is too heavy for, say, a 3wt vs a 5wt vs a 7wt? I have no way of knowing but it would seem to me that a 7wt will certainly be able to cast a fly that is too heavy for a 3wt. At least it seems it would be able to cast it better: more accurate and farther.
A 7wt will cast heavier flies better than a 3wt. In terms of weight limits, that will vary from rod to rod and depends on who is casting the rod. Perhaps someone will chime in with a great formula.
2. On the flip side, how light is too light, for the same reasons? Or is this, too, a moot point? Can a 3wt cast a lighter fly better than a 5wt? Than an 8wt?
Tippet size can effect this. If you have a 5wt I wouldn't feel the need to get a 3wt just because you'll be fishing small flies. Rods don't only vary by weight but also action can impact how a fly is presented. However, if you learn to cast your rod well you can do a lot of fishing with a 5wt rod.
3. I see reels that say they can be used for, say, 4-5-6wt or 6-7-8wt. I would assume this is only because of the weight of the reel? So it balances with the corresponding rod correctly? I would assume the weight of the line has nothing to do with a reel and everything to do with the rod--or am I completely wrong?
It also has to do with how much room there is for the line and backing to be spooled on the reel. A 7wt line takes up more room on a spool than a 3wt does so you get a bigger reel for a 7wt than a 3wt. However if a reel is rated for a 3 or 4 wt rod you can likely use it for a 5wt. Just have to see how much backing you can fit on the reel with that line.
4. Speaking of rods, is it "possible" to use different weight lines on a single fly rod efficiently and effectively? In other words, can you use a 5wt line on a 4wt rod and make it work okay? I would think trying to use a 5wt line on a 6wt rod would not work well but maybe I am wrong. I guess I am asking if you can overlap line weights and, if you can, do you use the same line on lower weight rods or higher weight rods?
Yes it definitely is possible to use different lines on the same rod. There are threads on the forum discussing rods that are rated for one weight by the manufacturer but perhaps should be rated a different weight. That aside, I have a rod that I like with a 5wt line, but if I know I'm going to be fishing very close in I sometimes put on a 6wt line because it loads the rod better with less line out of the guides. It might be made to cast 30 ft of 5wt line well, but if I'm only fishing 10 or 20 feet of line I might enjoy fishing it better with a 6wt line.
5. Finally, does the length of a rod only limit the casting difference? For example, if you had an 7-foot 5wt, you may not be able to cast as far as the same rod that is 9-feet long, right? Or are there different reasons other than simple distance as to why you would use a longer or shorter rod? (Well, you use a shorter rod whenever you fish in constricted areas--are there other reasons?)
Yes, confined spaces are a good reason for a shorter rod. I also like them because they can be very compact. A longer rod can also help you hold your line above multiple current lanes to get a dead drift, this can be effective on open streams and also on confined streams where there isn't much room to cast even a short rod. The extra foot or 2 of reach can sometimes be the difference between drag and dead drift.