I know that wrap lengths vary from guide to guide and that each guide wrap is directly proportionate to the size of the guide and this proportion is maintained by making the wrap in front of the guide the same on all guides.

Is there a rule of thumb in determining the length of the wrap in front of the guide? How does the professional rod builder determine the length of the wrap in front of the guide?

It is the builders choice! No set rule or practice, as some prefer only a very few wraps, while others like more. Additionally, some like to make all the wraps the same length regardless of the guide foot lengths.

If weight is a concern, obviously, the shorter the better.

I build only fly rods, with size "A" thread, and do 4 wraps before the guide foot. If putting a trim wrap on, it is in addition to the 4 wraps.

I try to balance aesthetics with durability and performance. I don't really have a formula that determines a specific wrap length.

They need to be long enough to achieve the aesthetic design goals with keeping in mind that extra unnecessary thread and finish adds weight to the build which robs performance. To speed the layout I do use a 3x5 "story card" for each guide frame and size ring. Along the edges of the card I have marks for variations in wrapping and trim like one or two trim band colors. I created the cards one day by looking over my personal rods and choosing the guide wraps that just looked and felt right to me. I just transferred the trim color transitions, wrap length, and center of the ring to the cards. The whole process took me about an hour or so to make sets of cards for the three frames I use most often. I don't deviate from the cards unless I'm trying to do something out of the ordinary from what I usually do.

So to answer your question, for me anyway, I have no rule of thumb.

I wrap starting from the tip top of the rod I will wrap the first guide from the top ( the small ones are a pain ) making the wrap as small as I can Then measure with a compass and do the tip top a tad smaller Then as i go down the blank depending on the taper I make each guide a little longer Maybe the first several the same If it looks good
I found that when the blank gets wider with the thread the same size the butt guides looked a lot shorter then they were To me it did not look pleasing

Bill - willierods.com

I generally make all of the wraps about 1/8th inch longer than the guide foot.
Be safe

I usually make my wrap 3mm each end longer than the guide & maintain that through the guide train .

Regards Baz

Bundeena
NSW Australia

That's helpful information. Thanks.

I do three wraps.
just enough to create the needed tension so the thread will hold itself in place while wrapping the rest, regardless of the length of the foot
I build for performance and anything unnecessary hinders that performance.

Steve is right On a 3 wt fly rod you want the least amount of weight possible On a heavy saltwater rod it may not matter ??

Bill - willierods.com

No reason to have any more than a minimum amount of wrapping before the guide foot. The purpose of the thread is to hold the guide in place on the blank. If the thread is not wrapped around the guide, it is not serving any useful purpose except to keep the thread wraps tight and to form a finished end to the guide wraps. More than that is unnecessary.

I like shortest wrap, one to three turn and I'm on the guide foot.
I'm with Roger, wrap on the blank desserve no purpose (aesthetic aside).

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Eric
[www.emfishing.fr]