Powell ABC Spey taper

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StePhDen
Sport
Posts: 87
Joined: 02/20/20 13:21

Powell ABC Spey taper

#1

Post by StePhDen »

Hi All,

I've been playing around in RodDNA working on a 12' 5/6 Spey taper (penta cross-section). I'm combining an A tip, B mid, and C butt. I know I'm probably not the first to do something like this. Being my first taper I was hoping someone would double check my math. I calculated stresses using a 6wt line and set the casting distance equal to the line length (assuming I am casting the entire shooting head). It looks like I've got the stresses in an appropriate range for a 6wt. It might be a little heavy for a 5wt. I started with a 0.1" tip diameter and used an Powell #8 with a 0.002 rise. At the 48 inch mark I kept the deltas the same to 96 inches and then used a 0.002 decline through the butt. I had to increase the tip/mid diameter by 0.008 to bring the tip stresses under 220000. I then converted the hex Powell to a penta cross-section and changed the station increment from 6" to 5". I then smoothed the transition between butt and mid section. In the end the dimension chart doesn't depart very far from linear but the stress curve looks pretty smooth.

I appreciate any input Y'all have. This is the first taper I've designed, let me know if I've got any fatal flaws or if I could tweak some things to make it better. Like I said if anything right now it might be a bit heavy for a 5wt shooting head.

Cheers,

Stephen

Here's the taper:

0 0.1180 0.0000
5 0.1330 0.0150
10 0.1480 0.0150
15 0.1635 0.0155
20 0.1790 0.0155
25 0.1950 0.0160
30 0.2110 0.0160
35 0.2270 0.0160
40 0.2435 0.0165
45 0.2605 0.0170
50 0.2770 0.0165
55 0.2945 0.0175
60 0.3110 0.0165
65 0.3290 0.0180
70 0.3455 0.0165
75 0.3607 0.0152
80 0.3763 0.0155
85 0.3926 0.0164
90 0.4090 0.0164
95 0.4255 0.0164
100 0.4403 0.0148
105 0.4566 0.0164
110 0.4729 0.0163
115 0.4892 0.0163
120 0.5055 0.0163
125 0.5217 0.0162
130 0.5378 0.0161
135 0.5535 0.0157
140 0.5690 0.0155
145 0.5690 0.0000



Image

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henkverhaar
Master Guide
Posts: 700
Joined: 07/02/16 15:37

Re: Powell ABC Spey taper

#2

Post by henkverhaar »

Don't know, but it looks like pretty much a straight taper to me (the delta's are almost identical over the length of the taper), and more like a 10-11 weight...

Image

Note, this is for a hex taper with these dimensions, but I don't think it would change the general picture that much. Should've taken more care reading though...

User avatar
penta-spey
Guide
Posts: 187
Joined: 06/20/12 11:44

Re: Powell ABC Spey taper

#3

Post by penta-spey »

Some thoughts based on my empirical design-build-cast testing cycles (hard work).

The overall slope tip to butt is roughly equal to B10, so appropriate for a 12 foots rod. Less than B10 overall for a rod of that length is going to be too noodle like IMO.

I suspect you might not have enough taper convexity (taper roll-off) in the butt. Butt may be unnecessarily stiff depending on what the designed flexing of the rod is intended to be.

I agree with Henk; you are way over a 5 weight, my guess is somewhere 8-10 weight (AFTMA spey line weights).


Other than that ... Pretty good job for a first though!

StePhDen
Sport
Posts: 87
Joined: 02/20/20 13:21

Re: Powell ABC Spey taper

#4

Post by StePhDen »

Thank you both for your input. I thought it was a bit heavy, didn't realize how much I over did it. I looked up the AFFTA line specs and I realized where I was going wrong. I'm working on making a rod for a guy who already has a 5/6 wt, but it's ferruled and he wants a spliced rod. He told me he was using a 400 grain Scandi line and 450 grain Skagit. In my original post I said shooting head and assumed those lines were 400-450 grains in the head as opposed to the whole line. So I see how I was way off/a bit confused.

When I finished entering the deltas I noticed it really didn't deviate much from a linear taper. I guess my rise/decline values weren't aggressive enough. I'm going to go back to the drawing board and probably start with a linear B10 like penta-spey suggests and then start adjusting from there.

Cheers,

Stephen

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BigTJ
Bamboo Fanatic
Posts: 3475
Joined: 06/04/06 18:00

Re: Powell ABC Spey taper

#5

Post by BigTJ »

400 scandi 450 skagit is 6/7 not 5/6.

Google up sone Spey tapers U think you’ll find a tip in the high 80 to low 90 thou range is where you want to start. The overall taper should be a moderate C If you want more of a scandi tod speed up the last 20” of the tip. If you want a skagit rod beef it up. Or make two different tips. Good luck.

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penta-spey
Guide
Posts: 187
Joined: 06/20/12 11:44

Re: Powell ABC Spey taper

#6

Post by penta-spey »

BigTJ wrote:
04/06/21 20:50
..... The overall taper should be a moderate C .... Good luck.

... Google up sone Spey tapers ....
Yes agree!; moderate C would be a good way to describe an overall spey taper shape. .... would imagine other types of tapers work too but I'm not there yet.

Careful if you are going to build down loaded spey tapers ... check that the rod taper has the speed and flex you are looking for, there are some noodles out there ... if some rod makers had only 50% of the time back spent on building spey tapers that have ended up being not so hot - they'd be able to solve world hunger.... ::)



And remember Your-Milage-May-Vary (YMMV) and "it must be true cause I read it on the internet" 8) Cheers

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