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Topic: Kaskazi Marlin, another Dorado killer...< Next Oldest | Next Newest >
Capn Jimbo Offline
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Posted: Oct. 17 2007,19:35

Some at a certain Simian website call my beloved Disco a Dorado killer.  In a way it is.  But if you disagree, you might consider the Marlin.  Lighter, faster and still a very serious fishing machine.  Here's some pics to whet your interest...









:capn:


Edited by Capn Jimbo on Oct. 17 2007,19:36

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Capn Jimbo

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kreidel Offline
Minnow




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Posted: Jan. 17 2008,07:39

Is the Marlin truly faster than a Dorado? I have read and reread reviews and opinions but I still can't determine which would work for me. I am trying to decide on whether I want a composite kayak at all since speed is not a factor for me. But I really like the idea of a lighter kayak, and maybe the "bling" element fiberglass has. I own a Native Magic 14.5 which is the family mini van but it works fine for most things I do.
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amhirsc0 Offline
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Posted: Jan. 20 2008,11:30

A while ago I used the KAPER program, which estimates the drag resistance of kayaks, on several kayaks for which the necessary input data (LOA, beam, waterline length and beam, displacement, wetted surface, and several other coefficients) were easily available. Data for the Marlin and several other kayaks were available, but not for the Dorado.  The output of the program shows estimates of drag resistance for various speeds (2 to 7 knots). The drag resistance is what a paddler needs to overcome to maintain speed.  

A review of the kayak data shows clearly that wetted surface area and waterline length are the two parameters that influence the estimated drag resistance most.  Wetted surface affects frictional resistance most, and waterline length affects form resistance most; the two of which are additive.  Frictional resistance increases uniformly with speed, but form resistance is relatively low until the yak reaches 'hull speed' ( in MPH about ------ 1.5 TIMES THE SQUARE ROOT OF THE WATERLINE LENGTH), at which point the form resistance increases substantially with increasing speed.

After looking at the results for several kayaks, wetted surface area decreases with a decrease in beam. The easiest way to decrease beam, and thereby reduce frictional resistance,  is to increase length, which works up to about 18 feet.  The easiest way to delay the increase in form resistance is to increase length.  

While this has been a long way to get to your question of which is faster is to look at the length and beam of each. According to Kaskazi the difference in length between the Dorado and Marlin is about 2 inches and the beam about 1/2 inch. Thus, it is likely that there is little difference in the drag resistance between the two is not significant, nor would its corollary --- speed ---- be.

Just as an aside, the Kaskazi website lists the weight of the Marlin at about 55 pounds, and the Dorado at about 63 pounds in the standard fiberglass layup. Other lighter layups are available on special order and the Marlin can be built to about 45 pounds with a different layup (e-mail communication with Kaskazi).

With respect to the Magic 14.5 (Length), which has a beam of 32 inches, compared to about 24.5 inches of the Marlin, and has funny hull shape with a partial tunnel amidships, the Marlin will be substantially faster than the Magic.  I've paddled the Magic and have described its performance as 'awful' when compared to my Kestrel 14 SOT (14' x 26").


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KayakAl
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Capn Jimbo Offline
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Posted: Jan. 20 2008,17:46

Although at first glance, and based on simply length and width, one could easily assume there is little difference between the Dorado/Pelican-Marlin. It's a shame that Kaskazi no longer publishes the hydrodynamic data they once did.  Accordingly I have taken note of the published weight capacity, which states that the Dorado can carry 88 more pounds than the Pelican/Marlins.

That is significant.

It implies to me that the hull form/shape is different enough that the Dorado can carry this significant additional weight.  As an interesting experiment I used Kayak Foundry v1.5 to compare the Dorado vs the Pelican/Marlin.

With a 200 lb paddler:

Pelican: wetted surface 20.8 sq ft, waterline 14'-1.9".  Force required at 4 knots = 3.54 lb.  With an additional 88 lb the force required is 4.35 lb.

Dorado: WS 21.5 sq ft, WL 14'-4.3", force required = 3.8 lb.

Now remember the Dorado is designed to carry an additional 88 lb, so with 288 lbs aboard:

Dorado: WS 25.4 sq ft, WL 14'-6.9", force required = 4.67 lb.


Bottom Line:

I also compared the performance for 3.5 knots (a more realistic cruise).  In all cases the Pelican showed about a 7 to 8% advantage, ie.  can go about 7 or 8% faster or maintain the same speed with 7 to 8% less effort.

And this is with about the same hull shape.  Keeping in mind that the Dorado is designed for an additional 88 lb. I wouldn't be surprised if the hull differs from the Pelican.  I'd have to say the Dorado is definitely slower than the Pelican (which is reported to be more agile as well).

Personally I'd recommend the Marlin any day except for those who simply must have the additional 88 lb capacity, additional room and intend to do a lot of live baiting.


:capn:


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amhirsc0 Offline
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Posted: Jan. 24 2008,14:01

Since our last posts on the subject of the potential speed difference between the Marlin and the Dorado, Jimbo and I have bounced several e-mails back and forth.  When I read his response to my post, I was, and still am, concerned that the use of the FOUNDRY computer program in the way it was used was inappropriate.  The Marlin, indeed, may be faster and have less drag resistance than the Dorado, but it’s not the conclusion that concerned me, it’s that the results of a misused program were offered as proof.

Specifically my concerns include:

1. The FOUNDRY program calculates drag resistance from hull design.  Jimbo used the generic hull design, changing it only to conform with the LOA and beam of the two hulls.  First, its unlikely that any specially designed yak conforms to a ‘generic’ yak.  Specifically, the generic hull is not as full at the ends as the Kaskazi’s and the wetted surface area, which is critical in calculating the frictional resistance, was more than one square foot more in the program than provided by Kaskazi previously. Thus, the program’s estimate for the wetted surface of the Dorado becomes questionable, as well.

2. According to Kaskazi, the maximum load of the Dorado is 88 pounds greater than that of the Marlin.  I failed to appreciate that in my post, and that may in fact suggest that the hull designs for the Dorado and Marlin are different, because a 2-inch difference in LOA and a 1/2- inch difference in the beam is unlikely to increase the maximum load by 88 pounds. My guess that the ends of the Dorado are fuller and/or the hull is deeper.  But, in any case, utilizing the same hull design by changing only the LOA and the beam, as was done, is subject to question.

3. Jimbo’s post shows that the performance of the Dorado is 93% of that of the Marlin both at the maximum load of the Marlin and the maximum load of the Dorado.  When overloading a yak the performance will deteriorate, but a simplified program such as FOUNDRY or KAPER does not generally calculate the effect of overloading.  I question whether the performance of the Marlin will remain 108% that of the Dorado when over-loaded, and if it does not, then the predictions of the program are in error.

4. Unfortunately, the outputs of computer programs are too often assumed to accurate to the Nth degree, rather than reporting a margin error, which is inherent in all computer outputs. Outputs are subject to accuracy, and the output can be no more accurate than the inputs and the simplifying assumptions of the program.  In addition, just because a program gives, in this case, drag resistance or speed to two decimal places does not mean there is not substantial error that should be reported.  Too often we measure with an axe, record with a crayon, and report with a sharp pencil.   In my opinion, it would not be unreasonable to assume an error of plus or minus 5% in this case, because the inputs to the program are gross assumptions for all of the necessary input parameters.  If this is the case, then an 8% difference is with the margin of error and there may be no difference in performance.

Again,  I don’t argue with conclusion that the Marlin is faster than the Dorado ---- only that the results of the FOUNDRY program do not substantiate the supposition.


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KayakAl
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Capn Jimbo Offline
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Posted: Jan. 24 2008,21:33

It is true my first run through used the generic designs provided by Kayak Foundry.  I did this being fully aware that the Dorado and Pelican appear to be a bit fuller toward the ends.  It was not my intention to duplicate the Dorado or Pelican, but rather to see what a similar change in length/width would have on the two generic designs.

The result was that the slightly shorter/narrower generic design had superior KAPER performance figures.  I assumed that the similar changes between another set of similar designs - the Marlin and Dorado - would likewise favor the shorter/narrower version - the Marlin.  

Based on our correspondence, I then modified the generic designs so as to more closely resemble the Marlin and Dorado, ie with fuller ends.  The result: the Marlin lookalike design still outperformed the Dorado lookalike (though not as dramatically). Whether my theory was correct or whether I was just lucky is for the reader to decide.

I wasn't surprised, since over the years I've played with a bunch of similarly modified designs and found that the slightly proportionally smaller kayak seemed to always outperform the larger in the cruising range (3.5 to 4 knots/hr.).  

Why?  Because the two designs are proportional, the main difference is in wetted surface, as all other hydrodynamic variables and ratios remain the same.   For most cruising kayaks the slightly smaller version will demonstrate less drag at lower speeds.  At a point approaching hull speeds the drag curves will finally cross and finally the longer version will prevail and show lower drag.

A fair generality is that for cruising, less wetted surface favors the slightly shorter/narrower version.

It is also important to note that Foundry does indeed allow you to "overload" the design by raising the waterline to match your target (overloaded) weight/displacement.  Doing so is essential for an accurate KAPER result.  

Bottom line:

The best that can reasonably be done is to try to recreate the Dorado and Marlin designs.  Both my original run through using the generics, and my subsequent run through with Kaskazi lookalike designs compared the two versions at both design weights and overloaded (additional 88 lb).  In all cases the shorter/narrower, generic or lookalike, demonstrated less drag at cruising speeds.

This was not at all unexpected.  


:capn:

ps. Al and I both agree that the additional 88 lb of additional weight capacity for the Dorado remains a mystery.  The old owner of Kaskazi swore the Pelican/Marlin and Dorado were basicly the same hull form, with the Dorado being slightly longer and wider. Accordingly I think the additional 88 lb is just plain marketing...


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Capn Jimbo

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kreidel Offline
Minnow




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Posted: Jan. 25 2008,06:44

I did my best to keep up with all the tech talk, I think I understand the bottom line. I was able to purchase a used Kaskazi Pelican which I can rig up to my needs. I would have liked the Marlin's compartment in the console but I think the amount I saved buying this Pelican offset and regret. Thanks for the input and your website, alot of good info.
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6 replies since Oct. 17 2007,19:35 < Next Oldest | Next Newest >

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