Moon Tails! (don't moon me-haha)

I’m starting to design my next board & need some advice on a moon tail (which I have never done before). This will be another Kite surfboard for light wind days used mostly in mushy waist to chest high beach break. I’m anticipating the board to be 6’ x 20-1/4" x 2-5/8". Nose at 14-/2"; tail @ 16-1/2". 5 future fins so I can ride either as a thruster or a quad (Though I’m guessing I will mostly ride as a quad. I like how “loose” they are in the wave).

As I have never done this type of tail before ( though i try something new on all my boards to expand my knowledge) , I thought I would put this out to you all for advice.

Is there any formula/ratio for the design of the width/depth of the “moon” versus just “make what looks right”? My thoughts are to extend the line of the rear side fins of the quads all the way to the tail and make that the “points” of the moon. What do you think? and How deep should I make the arc of the moon?

It really is more about what “looks right”.   Although the deeper and greater the “Arc” the more rail to rail and angular your turns will become.  Very much similar to a Fish with a deep butt crack wide tail.  Same theory behind it.  I did one for a guy, but that’s it for me.  I personally think you can get a smoother turn out of a wide Diamond Tail or Round Tail.  Just my 2$.

Hey Lowell-Thanks for getting back to me. My design thought on this board is that it will be a “hybrid” fish in concept. If you’ll remember my build last fall, I built a “tomo vanguard style” board that had a swallow tail.That was my 1st with that tail too, but I had alot of problems laminating & finishing in the “butt crack”. I was lucky that John Mellor came over & helped me laminate the board. I figured the moon tail would be easier to make & yet offer similar ride characteristics to a swallow tail. Plus it gives me a chance to try another “new” type of tail for me.

Chris,

I can generate the arc for the Machado Moonbeam as seen in this thread.

https://www.swaylocks.com/comment/549112#comment-549112

Then I can scale it for whatever tail width you choose.  Let me know.

Bill

Bill.

Thank you so much. This is exactly  the kind of information I was looking for. I reviewed the machado moonbeam and your blogs on proportional scaling & that is exactly what I was thinking.

Last week I started designing the outline in BoardCad, but wasn’t real happy with it. I got busy with work & stepped away from it & somehow accidentally deleted it, so with this new information, I can start up again. My next couple of weeks are  pretty busy, but I’ll get back to you with the info in a couple weeks (or do you want me to send you a copy of the boardcad file?).

Again, here’s what I’m thinking. Do you remember the “Vanguard style " board I posted here last fall? It had a swallow tail & I had aligned the rear side fins with the “points” of the swallow tail. Out in the water, when I look down at the tail, the flow coming off the tail is real smooth with no apparent cavitation. Since the moon is similar to a swallow tail, I’m thinking of using the same fin layout & extending an imaginary line from the rear sides all the way to the tail and that would become the “points” of the moon or should I pick the tail width (12” from the tail, let you scale the moon tail and then I adjust the fin layout accordingly. What do you think?

Chris

You get the same hard corners with a square tail or an arc tail, and without the fragility of the points.    

Not saying that the crescent/arc is better.  But the physics of fluid flow will be different.

Chris,

I’m not the person to ask about quad-fin position/placement.  I would go with the advice of Sways resident gurus regarding fin placement.

Regarding Board.cad.  I don’t use it.  My medium is PowerPoint 2D-CAD.  I would recommend developing a planshape template you like with a squared tail.  Then when you know “end-of-board” tail width, I can create a tail-crescent template to overlay with.

Regarding the Machado Moonbeam, I was not necessarily suggesting that shape.  Mostly just pointing to it as an example of Crescent-Tail arc that could be easily duplicated for any tail width.  For that matter, you could add a crescent tail to your previous Vanguard inspired template.

Either way, happy to help with a crescent-tail template.

Bill

Bill,

Of course, the shape I have in mind is slightly different than the machado. I just meant that it is very similar to my design & will be a good “starting point” for mine. I thought of using the vanguard fin layout for the same reason you mentioned. I’ve also got the McKee Quad fin design chart that I can look at (If I can figure out how to read it).

I specifically don’t want to use my vanguard template because the outline is alot straighter and with how wide that board is, I think it wouldnt work (I let one of my friends ride it and he complained that it was so wide that he couldn’t sink the tail enough to “stick” a bottom turn).

Thanks again for your help.

Chris

 

Stoney was a big help when I did my “moonbeam”.  Laying out things dimensionally like that puts it in perspective .   Especially when you don’t have a template or board to refer to.  In the end for me the hardest part was getting that point to point Arc right.  I know it looks easy.  I was thinking things like;  “I’ll use a gallon paint can or a frisbee for a template”.  But finding the right Arc and using it to connect the two corners was harder than I thought it would be.   Clint said; “A man has got to know his limitations”.  I should just stick with what I know.  But it was a nice challenge and I learned a bit.  Later on I was able to look at one in a shop and it was quite a revelation.  Good luck with it Chris.  Lowel 

Clint also said “I know what your thinking.Did he fire 6 shots or only 5? Well to tell you the truth, in all this excitement I kind of lost track myself…”

Lowel. Thanks for the encouragement. Bill has offered his help and i  went back & read your post of a few years ago when you made a “Machado Moonbeam” and also saw a Youtube interview of Rob discusssing what went into his design. They’ve all helped me greatly and I’m pretty “close” with the design in my head. Now I just have to find the time to finalize it and make a template.

I’m looking forward to the challenge. Chris

 

Use the bottom of a GIbson Les Paul for a perfect moontail.

Hey-I’d love to, but Eric Clapton never returned the one I loaned to him!

Wow!  Nicely done.  Perimeter Stinger, Concave, Tail and fin placement;  all very well done.  You thought that shape out.  You saw the board in the blank before you ever fired up the planer.  Was it EPS or one of US Blanks Poly with Perimeter Stringer?  Lowel

Lol!  Yeah, back in the day;  I loaned him a pick and a $100 bill.  Never got 'em back.  Lowel

A Les Paul would be nice.

But a simple circle/chord and the Moonbeam template will work.

Specific arc dimensions can be adjusted relative to surfboard width or length.  My inclination would be to adjust dimensions relative to surfboard width or end-of-tail width.

I bought an old and cheap Stretch tl2. I like how it works in head high waves. 

Yeah Stretch is da man.  No stringer either, huh?

That was a few years ago and wa my daily driver for a long time,  Love that board.  It’s also held up well but is just too small for me now.  

Perimeter stringers with polyurethane foam on the rails, EPS center.  It had Innegra/S glass deck , s glass bottom, vacuum bagged on.

 

 

Thanks. That was a few years ago and wa my daily driver for a long time,  Love that board.  It’s also held up well but is just too small for me now.  

Perimeter stringers with polyurethane foam on the rails, EPS center.  It had Innegra/S glass deck , s glass bottom, vacuum bagged on.