Surf setup 2015 242LS

[Scuba_ref]

I'm no Hydro Jet Propulsion Engineer and I also did not stay in a Holiday Inn Express last night, but I wonder what this shape would do?

 

[Scuba_ref]

Or some variation of it like this?

 

[swatski]

Or some variation of it like this?
View attachment 51637

Hah! THAT I did not consider, yet.
But I am toying with a couple of quick flap mods, and definitely redoing the brace at this point.

As far as the flap size, will need to go down by about a 3rd of the total surface.
As far as the flap shape, I'm leaning towards almost the opposite (of the one above) -- with the trailing edge angled/protruding out.
Why? Because I research this. I use garden hoses and scrapers to study properties of various shapes on jet stream deflection angles.
(Just don't try it at home. Your wife may leave you.)

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[KXCam22]

For cutting rubber what works is to grind the side teeth off of a new hacksaw blade. Side teeth are the parts that protrude from the sides of the blade to widen the cut. I have used this in the past for cutting tires and it worked well. Possibly you could do the same with a sabersaw blade. There are also some saber saw blade that have no side teeth and also might work. They are called "clean" wood cutting blades with 2 rows of teeth that point inwards. They are all I use since they cut nice. Cam.

 

[Rod5]

Shouldn't it be about the same size and shape of a right & left wake wedge installed together as a good starting point?
Just a thought...

 

[swatski]

Shouldn't it be about the same size and shape of a right & left wake wedge installed together as a good starting point?
Just a thought...

I am working of the OP's plan but wanted to test a longer flap since I could not find anyone doing it, and I was just curious what it would do with the water at speed. Frankly I was hoping the jets would force a longer and flexible flap to conform into somewhat of a water funnel. Unfortunately, that does NOT happen.

Back to the drawing board today, was a very busy day. I changed the size/shape and the brace angles and got those fabricated, AND did some more testing, will post later when I catch my breath.

The flap will not work like the Wake Wedge, which is rigid and mounted on one side/sideways. That pushing water to the side is the Wedge's way of generating delayed convergence effect (on the non-surf side). That is a very clever design that (to be completely clear) CAN NOT be replicated with a flap of any size/shape.

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[swatski]

So, my kids did not have school today and I needed to stay home... which gave me some time to advance the flap project!

Anyway, I did two things:
1. changed the size (and shape)
2. changed the braces to angle the flap

Here is the new flap (16" is the apex, in the middle):


And here are the new braces, angled at ~30deg (down from 90 - or strait down). I only tested the new 30deg brace with the new flap today, will post below - VERY encouraging. I still need to test the strait (90deg) brace with the new flap, and may fabricate another brace at 45 degrees.

I'm sure there are better ways to design those, but I used a rod to aid the fabrication - ended up using a .5" rod for the 30 deg brace, see below (the welding process made the 0.5' diameter pretty close to the theoretical 0.647" and therefore 30 deg angle).
I was also tired of drilling stainless steel, so went back with aluminum.

Here is the back of the envelope calculation produced by my son (who took about thirty sec to write this out and text it back to me... kids are so smart these days, LOL):


And here is Brandon of Gerling Bros Welding, these guys are seriously AWESOME.



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[swatski]

Here are some pics of the setup I ended up testing today.

First, the new 30deg braces - mounted to the hull (this is all in need of cleaning up, of course):


And the new flap:


The ladder is still completely usable:


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[swatski]

Here is the wake at about 9-10mph, no ballast.
Left is the NO flap (from yesterday), the right is WITH the 30 deg flap (today):

There is a very encouraging (I think) trend in the way the wave forms here (with the flap).

The wave with the new 30 deg flap at 18-20mph (I don't know exactly) also looks interesting, it still shoots up a bit in the middle, almost like it is pushed down by the flap and then tries to pop back up, but down the wake it cleans up real nice.
LOTS of testing remaining though this is trending in the right direction, I think!


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[Glen]

I just have to say it @swatski, brother, you are amazing!

 

[Mainah]

Quick thought on the 30 degree angle. If one were the leave the flap attached out in hot temps for an extended period at any angle that fights gravity the horse stall mat may develop a bend. My selfish interest in this is for knocking down spray at wakeboard and tubing speeds with something that I can leave on all the time. My secondary intrest is improving the wake if possible. That said I will likely stick to straight down mounting angle when I get around to this.

Still glued to this thread to see what does and does not work.

 

[Bill D]

@swatski I love the work you're doing here! I don't know if I would get too carried away with the way the wake looks, especially for surfing, until you get some ballast on board.

The profile of the boat changes a lot with 2k+ lbs of water towards the stern. When my boat is loaded up enough to make a decent wave, the water is about halfway up my calf on the lower swim deck. I think that changes the attitude of the boat (points the jets downward) and listing to the surfside also points them away from the lip of the wave a bit.

For wakeboarding, the list isn't there, but I would imagine that some ballast would still sink the jets in the water a bit.

 

[swatski]

Quick thought on the 30 degree angle. If one were the leave the flap attached out in hot temps for an extended period at any angle that fights gravity the horse stall mat may develop a bend. My selfish interest in this is for knocking down spray at wakeboard and tubing speeds with something that I can leave on all the time. My secondary intrest is improving the wake if possible. That said I will likely stick to straight down mounting angle when I get around to this.

Still glued to this thread to see what does and does not work.

Yes indeed! "set-it-and-forget-it" is my motto, too.
I am keeping both braces for now as I have not tested the smaller flap with the downright brace, yet. And this is all going to change with ballast, anyway.
The flap (either size) does not completely beat the spray down, not sure what it would take (short of diverters).

EDIT: @Mainah I don't know if my new flap is small enough to drag it behind the boat all day long mounted strait down, will have to see. The large one is NOT, that's for sure. It wanted to stop the boat!

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[Scuba_ref]

@swatski if we all sign a note excusing you from work, would that help?

 

[swatski]

@swatski For wakeboarding, the list isn't there, but I would imagine that some ballast would still sink the jets in the water a bit.

Yes, a loaded and/or ballasted boat is a different beast all together.

Don't know if the flap will work at wakeboarding speeds. There is this annoying plume of water droplets that I see all the time (without the flap):


With the flap, it seems to subside somewhat, maybe -- you still get the spray but it seems more "concentric". I hope this is going to hold, and is not my wishful thinking, LOL.

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[swatski]

One issue with this current setup, as I see it, is the difficulty in mounting/dismounting on the water. That of course is all relative, but with the weight, mounting position, being submerged in freezing water - becomes a limiting factor especially if testing various shapes, sizes and flap angles.
From what I have observed thus far, it is unlikely one can design a flap that helps with the wake AND is compatible with cruising (any significant distance), short of some actuators' help.
One can jump in and it becomes a lot easier in the water, but I would still prefer something that can be dismounted from the swim platform (without getting into the water). I'm trying to think of ideas for quick release braces/attachments.

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[Mainah]

Good point on affecting the wake but what if the "acuator" was simply filling ballast? Is there a size and shape that does not have any negative impact on cruising but once the boat is ballasted then has an impact on the wake?

I bet showering in cold water for the next couple of months would acclimate your body to being in freezing cold water so the rest of us know what works.

JK ... Keep up the great work but don't risk hypothermia.

 

[jcyamahariders wife]

I think you need to go pro the polar plunge !

 

[swatski]

Good point on affecting the wake but what if the "acuator" was simply filling ballast? Is there a size and shape that does not have any negative impact on cruising but once the boat is ballasted then has an impact on the wake?

Yes, that is the idea!
BUT
based on what I have seen so far I would most likely not be comfortable cruising around with anything hanging back there at any cruising speeds, going over 20mph or so, certainly not with a vertical flap, LOL.

I keep coming back to this picture (courtesy of @Williamsone46 ? I think):



As far as further flap testing, I may just install a semi-permanent square tube back there, and then figure out a way to latch-on flap constructs of various shapes/angles. If I can swap those on the water it would speed things up considerably.

I'm sure @Scuba_ref can come up with some really cute flap shapes to test! LOL.

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[swatski]

I think you need to go pro the polar plunge !

No kidding...
I actually used to do this ritual back in the Meramec Marina every year - the New Years Day plunge...
But that was back in my drinking days, LOL.

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