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What affects turning?

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foam-n-fibre
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What affects turning?

Postby foam-n-fibre » Mon Jun 25, 2018 4:18 pm

Maybe this is a huge question, but I have a few basic questions and am hoping for of the DIYers have played with different parts on foils they have built. It's one thing to compare the feel of two different foils which I'm sure many people have done, but unless you change only one part at a time its hard to know what effects what.

My setup does not seem particularly turny. I have a twin tip style fin under the the back of the fuselage and rear wing. Would making the fin smaller or getting rid of it completely change things? What about moving the rear wing and fin forward on the fuselage?

Also, my board is still a butchered old surf style board that I have made smaller, but it's a bit bigger than average. Would a smaller board change the swing weight and make more or less of a difference? What about having a board with a flat or concave deck rather than slightly domed, does that change the foot feel much?

For the record I can ride back and forth on all points of sail, but very rarely complete a transition. I can carve to toeside but don't feel very stable toeside. Larger turns like a carve to toeside is OK, but smaller turns carving around on small wind waves feels pretty stiff.

Suggestions???

Thx,
Peter

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Re: What affects turning?

Postby TomW » Mon Jun 25, 2018 4:44 pm

From what I've read, the vertical fin at stab is creating yaw stability. make it smaller.
From my own experience, board size, overall weight and swing weight have huge impact on foils performance. So I would change the board first if it's too big or heavy

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Re: What affects turning?

Postby jumptheshark » Mon Jun 25, 2018 5:16 pm

Flat wings turn easily... as in yaw.

The vertical component....an or di hedral in the wings or vertical tail fins. The more of it, the more directionally stable.

Wing area and wingspan determine roll. The bigger the wing, and the longer the wingspan the harder it will be to roll.

Pitch is mostly the size of the tail wing and the length of the fuse, with bigger wings and longer fuse being more pitch stable.

Turning is mostly yaw, quite a bit of roll and barely any pitch, but carving can be a much more blended combination the three.

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Re: What affects turning?

Postby foam-n-fibre » Mon Jun 25, 2018 6:45 pm

Cool thanks for the replies. Although I do plan to build a smaller board, I think I can throw together a much smaller rear fin faster! :)

If a longer wingspan is harder to roll, which makes sense, does that make it harder to bank and turn too?? I have a 56 cm wingspan and about 3cm of curved anhedral. It's moderately swept back, with a chord of about 13 to 14 cm until the wingtips. Not huge, but I think a bit above average. My thinking is that a flatter wing would make the foil a touch more stable, but I'm not sure of the turning would change much - or would it?

Peter

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Re: What affects turning?

Postby SaulOhio » Mon Jun 25, 2018 8:02 pm

foam-n-fibre wrote:
Mon Jun 25, 2018 4:18 pm
Maybe this is a huge question, but I have a few basic questions and am hoping for of the DIYers have played with different parts on foils they have built. It's one thing to compare the feel of two different foils which I'm sure many people have done, but unless you change only one part at a time its hard to know what effects what.

My setup does not seem particularly turny. I have a twin tip style fin under the the back of the fuselage and rear wing. Would making the fin smaller or getting rid of it completely change things? What about moving the rear wing and fin forward on the fuselage?

Also, my board is still a butchered old surf style board that I have made smaller, but it's a bit bigger than average. Would a smaller board change the swing weight and make more or less of a difference? What about having a board with a flat or concave deck rather than slightly domed, does that change the foot feel much?

For the record I can ride back and forth on all points of sail, but very rarely complete a transition. I can carve to toeside but don't feel very stable toeside. Larger turns like a carve to toeside is OK, but smaller turns carving around on small wind waves feels pretty stiff.

Suggestions???

Thx,
Peter
I'm in pretty much the exact same situation as foam-n-fiber. My board is home built from an old windsurfer with the tail broken off. I put in extra fin boxes because I was thinking of using it as a regular race board, and it came out VERY heavy. I have plans on building a much smaller, lighter board as I improve.

The deck of my board is domed, too. Once I have a new board, I am thinking of keeping this one, just gutting it from the top, removing those extra fin boxes, then giving it a flat or convex deck.
34268600_1574912712632205_5660066855113457664_o.jpg
https://www.youtube.com/watch?v=gkuUa175-9Q

Can anyone answer how reshaping the deck can help? I would think it would make turning easier to control.

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Re: What affects turning?

Postby jumptheshark » Mon Jun 25, 2018 10:21 pm

Sorry, board makes a really big difference. I have had two boards with the same foil, both the same weight, one six foot, the other just under four foot.

There is a huge difference in the agility due to the lower swing weight of the shorter board.

My first was a converted surfboard with a domed deck, I eventually chopped it down to 4 foot, but can't really abide riding it. Once I got used to the flat, low volume deck of the skim, it ruined me for any kind of domed and floaty board. Feels very direct to be standing pretty much directly on the plate. Reshaping would be nearly as big a job as simply building what you really want from scratch. That DIY in the pic has loads of nose rocker and float. Learn what you can for the first season on that, then move on.

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Re: What affects turning?

Postby TomW » Mon Jun 25, 2018 10:44 pm

The board makes a huge difference. I'm talking about huge difference between a moses T40 and. Slingshot 4-6 dwarfcraft. These are pretty good production boards.
The boards you guys are using may be even more. It's more than you realise.

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Re: What affects turning?

Postby foam-n-fibre » Mon Jun 25, 2018 11:43 pm

Thanks for the input on the board. Mine is not as big and chunky as SaulOhio's, but I'll make it a priority to get a smaller, lighter, thinner flatter board sorted out too.

What is the difference between the Moses and Slingshot boards... as in can you relate the feel of them to certain physical characteristics like weight or length or width?

Peter

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Re: What affects turning?

Postby SaulOhio » Tue Jun 26, 2018 10:05 am

I just recently remembered I started a thread on mast placement relative to the wing and its affects on turning ability. The farther back on the fuselage you put the mast, the more turny it is.

viewtopic.php?f=196&t=2396850&p=981376& ... ng#p981376

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Re: What affects turning?

Postby plummet » Tue Jun 26, 2018 11:34 am

Back the stab aoa off. That will make it less stable and more responsive.

Shorter fuse.
Shorter mast
Wider foot stance.
Smaller vert and horizontal stab.
Lower aspect smaller wings.


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