I am building a dipsey diver 8-6 M I feel it’s a tad light. I have done a static deflection test and have a layout that is close enough but not perfect. I’m using boat rod style guides. I’m wondering if there is a way using thread to do an extended underwrap or some other method to stiffen up the blank a bit. It will be a conventional wrap not a spiral wrap. Btw.

All suggestions are welcomed

Adding thread, or anything else, will make it softer, not stiffer.

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Build it and let her fly......

What Tom said. You are thinking backwards. Using "boat rod style guides" and an under wrap is making matters worse, not better. Going to a spiral wrap should allow you to use less guides which would also help. Those guides could also be smaller and lighter.

Added all together you might be surprised at how much difference it makes.

Russ in Hollywood, FL.

Buying a stiffer blank is the best way to stiffen a blank.

About the only option you have at this point if you are going to use the blank is to consider trimming and/or extending the blank, but that will change the action as well as the power of the rod. If you find that you want the tip slightly stiffer, mount a single foot fly guide on the rod and slide it around until you have the stiffness in the tip you want. (Don't cut until you are sure you want to cut, you can't put it back and tip trims can kill a blank in a hurry.) I've done it in the past when I had a blank that just needed a small tweak to fit the bill. If you need more power in the butt section, an over-sleeve over the butt of the rod can be used lengthen the rod from the rear and increase the power of the rod. Trimming a blank will make the action slower. Extending a blank will make its action faster.

Right, at this point you can't make it any stiffer, but with wise component choices you can keep it fairly close to being as stiff as it is in its naked form.

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Use the lightest guides you can find, like the PacBay Minimas.
Norm

Using guides that really hug the blank, and a few more of them will decrease the tongue placed on the blank perpendicular to he blank. This will decrease the bending force a bit, in effect making the finished rod stiffer. Also, and I don't even know if this is possible, but from an engineering point of view, running a flexible nylon threads lengthwise along the (spine, not belly) top, from tip to but, securing it it in place with a few, tight spiral wraps, and then giving the whole rod a rod coat will create a composite. That will make the rod stiffer, but increase the weight of the rod. Using the strength of the composite will also make for a stronger rod. But that is what is built into the rod in the first place. To get a stiffer rod, you have to purchase the proper blank. Using guides that hug the blank is probably the best strategy. Just make sure you space the guides so as to not let the line touch the blank under load. The advise given is sound, from an engineering standpoint.

Any counter-arguments are welcome, and encouraged. This is the place to share what we know.

Tight Lines and Frisky Fish

RJF

Adding guides of any sort will make the blank softer. This is easily proven by simple wrapping a bunch of guides, stiff double foot guides if you like, and then trying the blank. You will find it terribly softer and slower in response.

Nor will you make the blank stiffer by application of lengthwise threads. And coating that and the rod with epoxy will make it softer, yet. You're simply adding more weight the blank has to carry and since what you have added does not begin to approach the modulus of the blank itself, the end result should be obvious.

The only way you can make the blank stiffer is to add more layers of carbon prepeg, effectively creating a larger, heavier walled blank. For obvious reasons, this isn't very practical.

Some have experimented by injecting foam into the rod blank interior, reckoning that this will tend to resist the tendency of the blank to oval when flexed and therefore increase stiffness. Actual results are mixed and this method is rarely bothered with nowadays. Best to start with the correct blank.

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Lighter guides never make the blank stiffer, they just makes the rod less soft then using heavier guides.
Norm

Bradley,

The solution is at the end of your fingers.

Go to your favorite on line vendor and buy the rod blank of your choice that has the exact amount of flex, power, speed, and stiffness that you like.

The softness, or stiffness is part of the blank design.

Do, not ruin a great blank by trying to mess with the over all blank design and manufacture of the blank

Best wishes.

Keep cutting back the tip until you reach the stiffness you desire - or buy another blank.