Hi folks. I hope everybody is staying safe in these interesting times.

I am building my second fly rod. Don't look too closely at the material for this blank**, not relevant to this discussion . I'm using Flex Coat High Build epoxy for the thread finish on this rod. I put on one very thin saturating coat and let that cure and then was planning on putting another thin finish coat on. But it occurred to me, do I really need to? The picture is representative of what the wraps look like so far. Thread texture can be felt at some spots. If the additional coat would just be cosmetic I might not bother and save the weight.

** The blank is a graphite Batson Rainshadow Revelation 10' 5wt 2-piece, if anybody is interested.

Thread finish has two purposes. The one we spend the most attention to is the aesthetic - thread wraps are more attractive with a nice finish.

More importantly, the finish keeps the wraps from moving. The finish glues the wraps together so they act more like a tube of nylon holding the guide instead of acting as individual strands. The combination is stronger that the parts.

Functionally you need enough finish to glue the stands together. Second, a smooth finish better protects the wraps so individual wraps aren't bumped and separated. I like brockton's description of "fused into one element". Once you feel you have satisfied those two things, any additional finish is simply for looks.


Tom

Well explained. Enough to fill and smooth the wraps. In epoxy finish, best result for that goal is with "low-build" finish types, which are closer to the finished appearance of spar varnish, which is inherently "low-build" unless dramatically over-applied. The "thin" nature of each coat may be different from type to type, but with any one of them, another "thin" coat for that finish type is better than an extra-"thick" coat just to avoid doing another one. Yours looks good, and the last coat will level it. Remember to start each wrap with less finish to spread, because you won't have the absorption and flow to the underside as with the first coat or two, so the wrap will require less.

High Build, Low Build, those terms are actually pretty stupid to label a product.
They should be labeled High/Standard Viscosity or Low Viscosity.
You can get a “low build” application with a High or Standard Viscosity product, just don’t apply as much. When you look at someone’s finish work whether it be a hobby/pro or factory job, and you have a “football” appearance, they are applying to much finish, regardless of the viscosity.
Like some others have stated, apply just enough to cover the wraps with an even finish that results in not being able to see the thread ridges. It should look like the wraps are incased in glass.

I like the way wjude put it. From a manufacturing and formula standpoint, the "football" finish (high viscosity) formula does allow more latitude and (other than shape) maintain good durability and clarity if applied too thick. It is formulated to work thick. With the other products, varnish especially, the thinner the better. Putting a lower viscosity on too thick will result in a finish that is more likely to be soft, or to cloud, peel, and check. Their beauty and resilience is brought out best in thin coats as described. An additional benefit is that they are easily refreshed 10 or 15 years later on that original finish with one more coat--still without a bloblike, soft outcome.