Quad fin placement on midlength - help!

I'm making up a mid length 6'10"x22 for smaller surf and want to set it up with a fin box and quads. I'm guessing rear quads at around 6" and front fins at 12" but haven't done quads on a board this long before. Any comments, ideas or help would be great.
Thanks Bill

Im going to call you the "anti mac".

Gets boards you can afford. Makes them work
Loves to experiment.

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termite said..
Thanks Hydro! Heaps to think about there.

I really like the idea of extra plugs. I'm now thinking of a plug in front of the forward quads so that I can set them forward enough to act as side bites for a 3 plus one set up.

How good is the Carbon Jet! I rode one and am now up to making my 7th version with some minor and more substantial tweaks (all vast improvements of course). I owned that exact Webber but sold it because I preferred riding the Carbon Jet.

I found the Mckee formula for their quads and will probably use that for the basic quad placings www.mckeesurf.com/?page_id=267

Thanks again. I hope your new setup goes well.

Pic below is CarbJet copy #3 built in polystyrene and epoxy.

Bruce McKee website,VERY informative

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termite said..
Thanks Hydro! Heaps to think about there.

I really like the idea of extra plugs. I'm now thinking of a plug in front of the forward quads so that I can set them forward enough to act as side bites for a 3 plus one set up.

How good is the Carbon Jet! I rode one and am now up to making my 7th version with some minor and more substantial tweaks (all vast improvements of course). I owned that exact Webber but sold it because I preferred riding the Carbon Jet.

I found the Mckee formula for their quads and will probably use that for the basic quad placings www.mckeesurf.com/?page_id=267

Thanks again. I hope your new setup goes well.

Pic below is CarbJet copy #3 built in polystyrene and epoxy.

Yeah I love my CJet but everyone else baggin me out because it's a tainted pop out. Screw them I say.

I recon a guy like Beau Young would have some idea of what works and doesn't, besides it's his name on the label and at the end of the day he's a dual world champ, Webber isn't. No slight on Webber, it's just that Beau's cred is stronger to me.

So you recon the CJet goes better than the Webber? Wow, that confirms I made the right decision then. I was inspired by some aspects of the Webber but wanted the fin variability that the CJet gave, and which I could then even tweak further.

I've been all over Mckee's site and downloaded and his tables, I plugged them into excel and graphed the relationship of spacing to board size and found it was a linear relationship, so a formula can be easily derived for any board size and tail width based on this.

But as you likely have discovered there is a lot of conjecture about exactly what is happening with the Twinzer dynamic. One article comparing them to the forward canards on a jet fighter and slip stream effects etc. All well and good if they align with the trailing wing but Twinzers do not do this, so I think it has more to do with energy distribution and release through delayed winglet / canard stall angle due to pressure distribution between the fins in close proximity. Way too complex to explain the full dynamics but this would allow the fins to punch through the normal stall angle of a wing and hold / delay the slide or pressure release. Hence feeling more grippy than a traditional quad but just as zippy.

So the key is likely the proximity of one to the other in the fin placement, but likely for other reasons than people think.

Which is why I'm gonna punch holes in my Cjet, need to have a couple of new plug locations to get the fin proximity. But before doing that I will simply try the swapped quad arrangement and see how it "feels", good old fashioned scientific and engineering based experimentation ;-)

That copy you made is a ripper, I love the wide swallow tail. That would be a sweet shape for a dedicated twin with trailer or quad, the swallow would bite nicely and give you some added hold on the rail.

So do you actually shape these or model them and get them shaped and glassed third party?

Unfortunately Hydro its just me making a mess in the garage.

I've gone with the swallow on most of them to help hold that wide ar@e tail in. I set it up with Simon Anderson's quad placings with same cant on front and rears and it goes like a twinny with a bit more drive and hold.

Bit of a stretch from the CJ but I tried a few blunt nose rounded pin versions. This one is 6' reportedly fat, flat, fast and fun

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Cuttlefish said..

Hydromann said..

termite said..
Thanks Hydro! Heaps to think about there.

I really like the idea of extra plugs. I'm now thinking of a plug in front of the forward quads so that I can set them forward enough to act as side bites for a 3 plus one set up.

How good is the Carbon Jet! I rode one and am now up to making my 7th version with some minor and more substantial tweaks (all vast improvements of course). I owned that exact Webber but sold it because I preferred riding the Carbon Jet.

I found the Mckee formula for their quads and will probably use that for the basic quad placings www.mckeesurf.com/?page_id=267

Thanks again. I hope your new setup goes well.

Pic below is CarbJet copy #3 built in polystyrene and epoxy.

Yeah I love my CJet but everyone else baggin me out because it's a tainted pop out. Screw them I say.

I recon a guy like Beau Young would have some idea of what works and doesn't, besides it's his name on the label and at the end of the day he's a dual world champ, Webber isn't. No slight on Webber, it's just that Beau's cred is stronger to me.

You left out the part about Beau Young being a longboarding dual world champ.
Carbon jet isn't exactly a longboard.
I lived at Bondi from 81-84 while going to Uni. That's where Greg and his brothers are from. They all ripped.
Greg Webber has shaped shortboards for many of the best pro surfers in the world since the 80's and his designs have been very often groundbreaking and ultimately influential.
End of the the day carbon jet is a forgiving funshape.
The search for the Holy Grail is good fun and morphs as age, injuries, locations and water time dictate our directions in board choice.
Carry on.

Yeah I did, but a 6'10" is a long board to me ;-)

I grew up riding 5'7" boards and a 6'4" single fin gun. Did have one mal which was a ripper but ended up trashed and waterlogged.

Besides you seen him rip on some of the smaller boards as well?

Yep Webbers pedigree is not in doubt, I have been emailing him recently about some bits and pieces and he knows his stuff and is a straight shooter.

Like I said not dissing Webber, just the look and feel of the CJet (as well as the price tag) spoke louder to me. I couldn't make my own for what I paid for the Cjet, and looking around seconds of the Webber Diamond or the Miller SubX all cost over $200 more, and that was without fins!

Yeah the elusive perfect board, perfect break, perfect curves sitting on the beach waiting for you after a long day in the water....

And the bite of reality that smashes that illusion to pieces ;-)