Return to Hobie.com
Hobie Forums
It is currently Mon Dec 17, 2018 10:47 am

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 109 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8
Author Message
PostPosted: Mon Nov 12, 2018 5:30 am 
Offline
Site Rank - Old Salt

Joined: Wed May 11, 2016 1:27 am
Posts: 380
The premade fins being discussed in this thread are canted anyway as they are perpendicular to the hull surface they are attached to, which is curved.

When banking/edging a kayak in a regular turn it is edged to the outside, not the inside, as you would a surfboard


Top
 Profile  
 
PostPosted: Mon Nov 12, 2018 7:17 pm 
Offline
Site Rank - Old Salt

Joined: Sat Aug 16, 2014 4:00 pm
Posts: 503
Waverider, I look forward to your fin size experiments, just like I appreciate your other findings. The reason I first posted in this thread was because you and staktup talked about trying bigger fins. Big fins can help reveal if they are tracking due to drag alone or if they are aligned to be slippery.

There was a photo in this thread with massive toe-out, which is the opposite to what the triangle kayak or surfboard suggests. Like you said, even a dragging stern line can help keep a kayak paddling or towing straight, but at what cost dragging big fins at possible wrong angle. You pointed out the difficulty of finding adjustment space, but you seem to have the adhesive challenge solved enough to cut off part of the restrictive flange.

I am naive about kayaks - I never saw anyone else kayak for decades after I built and helped to design 2 kayaks. I feathered the paddle at a ridiculous 90 degrees because that's what fuzzy photos looked like. I may have edged turns backwards. But I do have a lot of familiarity on aircraft aerodynamics, and how countless little fin-like protrusions are faired in on military aircraft. Off center antenna, sensors, weapon fairings, etc tend to flow counterintuitively and not go either straight or parallel to taper of the fuselage. Always interesting to find out what airflow drives this, like for the lookalike F102 to F106 aerodynamic transformation I marveled at as a kid who knew such a pilot.

So I am not challenging the gurus here, but just warning to be aware of needlessly giving higher drag to achieve better tracking. And to clear away contradictory clutter in my mind. For instance this thread moved me to track down why yachts hook drogue chutes only to the stern. If I deploy a makeshift one from my kayak bow, will I get in trouble? Yes, it turns out, if the drag is low enough so I can tail slide down face of a wave. The rudder or skegs or even bare stern can get misaligned and promote a broach and flip. Only large sea anchors should be bow mounted they say. Alternatively, little drogues can even used when autopilot sailing at night, to mellow wave action for sleeping.

P.S. at 6 min and 30 seconds, the following new video which I subscribe to discusses how displacement stern flow can be more important to drag than bow flow. I don't follow, but does the extra transverse pressure get resolved by diverging wake (and vertical upwelling) which may suggest toe-in side fins?


_________________
My Hobie i12s... sailboat in a suitcase!


Top
 Profile  
 
PostPosted: Tue Nov 13, 2018 11:40 pm 
Offline
Site Rank - Old Salt

Joined: Wed May 11, 2016 1:27 am
Posts: 380
daft wrote:
You pointed out the difficulty of finding adjustment space, but you seem to have the adhesive challenge solved enough to cut off part of the restrictive flange.



The issue here is that the flange is flexible in a side to side axis, so this can follow contour of hull. It is not flexible front to back due to rigid effect of the fin base itself, hence you can't really toe them in or out as it would be required to mold to the hull curvature to do this, which it can't. A surfboard is flat so not an issue in that application.


Top
 Profile  
 
PostPosted: Tue Nov 13, 2018 11:52 pm 
Offline
Site Rank - Old Salt

Joined: Wed May 11, 2016 1:27 am
Posts: 380
As a side experiment to aide paddling I tried a piece of timber wedged across the footwell at a distance to suit me and profiled each end to fit the side foot scollops. This becomes a foot rest/bar. Surprisingly big improvement. Paddling power substantially improves as you push down with your foot. Also given the hobies have open cockpits, being a bar rather than foot pegs when you try to edge the kayak you can shift your entire "uphill" foot and leg over for weight transfer which you cant do with pegs or if you have a center consol. Really helps when you want to lean the kayak to counter a constant cross wind

Being just wedged there I can quickly remove it if I want to pop the drive in. Much better, simpler, and cheaper, than previous ideas I had of rigging up hinged foot pegs. Handy bit of lumber to have as a fish pacifier too..


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 109 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
© Hobie Cat Company. All rights reserved.
Powered by phpBB® Forum Software © phpBB Group