I have not been flyfishing for many years, but when I started I was told that a fly rod is able to cast a line that is one wt. up or down from the rod wt. Hence, a 5wt could cast a 4-5wt line. However, after an experience this morning, I am starting to doubt this advice.
Normally I fish in moderately swift, skinny rivers with trees on either side so the cast is not going too far beyond about 25 feet. In addition, I usually have the line and rod match. This morning I fished a small still pond, so I took my 4wt Scott A2 along with spools of WF-3F and WF-4F. Starting with the 3, I had all kinds of trouble shooting line--it seemed like I could only get it so far before it ran out of steam and piled up on itself. Later on, I switched to the 4, and all of my problems went away. I was able to shoot line almost any distance and my accuracy seemed to return. So the hopefully not-stupid question is, must the line and rod always match, and if not, is the technique for casting a lighter line more fine?
Here are my thoughts. Graphite rods are marvelous things and some will cast a large range of lines. Some rods do seem to have a sweet spot and they only want to cast one certain line. That line may or may not be the line wt that the rod manufacture recommends. Sometimes the manufacture seems to miss the target.
The most important aspect of casting a rod over/under lined is the caster. I believe that over/under lining a rod has lot to do with the ability of the caster to slow or speed up his timing to accommodate the line and rod dynamics. When a rod is underlined the caster has to compensate for the reduce wt of the line out of the tip. So if a 5wt rod cast a 5wt line very well then a 4wt line will have to have more line out of the tip to compensate for the reduce line weight. Saltwater fishers do this all the time. In high wind the saltwater caster may go down a line size to reduce the line diameter with less wind resistance. The saltwater caster then increases the line out of the tip by 10' or so to compensate for the lighter line. The caster must be able to carry the additional line in the air. When you over line a rod you have to compensate for the additional line weight out of the tip by reducing the amount of line out of the tip.
Along with adjusting the amount of line out of the tip when you under/over line you may have to slow or speed up your timing. This is why I think that over/under lining a rod should only be down with accomplished casters with a good deal of experience. An experienced caster can feel the cast and understand what is needed to match the rod action and line weight.
There is one other consideration when lining a rod. The manufacturing of fly rods does not allow the lay up of graphite to be absolutely the same with every rod. Lefty Kreh states in "Lefty's Little Library of Fly Fishing". This is a direct quote from his book: "...I would be willing to bet that if you took 20 rods from any top-line manufacturer, all designated as 6-weight, there would probably be at least one 5-weight and one 7-weight rod in the batch. The rod manufacturers will tell you that". So it is understandable that some people find certain rods work better over/under lined.
So Patrick, getting back to your question about your 4wt. It is not surprising that on very short cast that the 4wt line worked better. If you could have extended more line out of the tip with the 3wt line, it would have cast better. In your situation the 4wt is a better choice but that doesn't mean the rod cant cast a 3wt quite well in certain conditions.
Thanks Frank, your comments are very accurate. I did have to noticeably adjust my casting with the 3wt, but due to the surrounding flora, could never get the right amount of line out to compensate without landing branches. I also think that rod length plays a small role in this, but this particular rod deos seem to have a "sweet spot" when loaded with 4wt line.
You know I would bet that if you tried a 5wt on your rod that it would work very well on those shot cast. One problem is you may not be able to make as soft a cast as you could with the 4wt. If you opened your loop a bit a 5wt may be great.
My 4wt is an 8', but I also have a 9' 5wt rod (with a different reel). I tried the 5wt reel and line on the 4wt rod yesterday when I was practicing. I was hitting my target fairly well at a range of distances, both into and away from a stiff breeze, but I did not try this rig on the water. Now it would appear that I have another excuse to go to the local pond!
So Patrick, getting back to your question about your 4wt. It is not surprising that on very short cast that the 4wt line worked better.
Hi Patrick---Frank hit it on the head
The air temperature might have something to do with how your line acts on a certain day also---i grabbed a rod and went steelheading and realized i had a tropical saltwater line on it and spent the day stretching my line ---the same nice supple line in ohio wont shoot on a hot day on the florida flats
I'm not sure if you guys covered this, but I don't have much time to read this on my break. I was having problems for a couple of months casting with 5wt line in my 5wt rod. I was told by my buddies father-in-law to try 6wt line instead, So last yesterday I bought some and it made a big difference. I was able to feel, control, cast farther, and make a good presentation with the line. So You could try and go one up on your line weight.
The reason the 6wt worked better than the 5wt, would have to be because all fly rods (except Orvis and Winston WT 2-5wt) are rated for DT lines, not WF. To get the same flex and feel, if it is a 5wt rod, that is a DT5F or WF6F, hence why some rods are labeled 5/6, 4/5, etc. Also, the casting feel is a completely subjective thing. Entirely up to the caster.