Beyond the Rectangle. Surfmats.

[ULTIMATS]

Good find of the Australian company, thanks.
There's a bit of conjecture about how to bond plastic sheets together, ive seen some traditional mat makers use an electric welding bar/table, industrial plastic sheets are welded with a portable air/gas machine and the local inflatable surfboat builder uses 2 part glue.
In the end I think its going to be a case of trial and error to find what works best for me. I've tried the 2 part glue and never had a problem over a few years except for the local boat builder ripping me off with exorbitant markups when I buy it from him. Last time I found the manufacturers label on the can so I will be bypassing the middle man and saving a small fortune.
I think the glue is easier to use when there are awkward corners and fiddly angles to bond.
I'll ask the company in Tasmania for some samples.

[ULTIMATS]

Building the frame... I'm putting it together in sections so that each piece has the grain aligned for the strongest shape.



There's a central beam that I could build higher or lower to make a concave or convex hull or a mix of both.

I dont believe that a floppy mat is a sign of how it rides, even if you take most of the air out. Once you lay on a mat the pressure increases and how much it increases is determined by your weight. Pressure in a volume is the same at all points so the hull is as solid as the deck. I'll see if I can find a pressure gauge and do a few experiments to show the change in pressure.

[ULTIMATS]

Material samples arrived...
There's enough here to make 3 mats.



Nylon, polyurethane backed, all sorts of colours and weights. The lightest I'm not going to use because I want the robust nature of a stronger material. And I want colours that will show up in pics and video so I'm going with the red and yellow. I will do a few compatability tests first.

Just had a thought about puting a frame inside a mat... As the mat is inflated its perimeter shrinks and grabs the interior frame. The mat still has I- beams but it has an internal flexible frame for better direction control and stability..... Certainly sounds like an interesting concept so i might make one of those after I finish this first one.

[ULTIMATS]

I found a highly accurate pressure guage this morning so this evening i will link it up to a few different mats and check the pressures.

I will check what amount of pressure is registered for each mat that is/has
1/. almost completely deflated
2/.a 90 degree bend
3/. fully inflated up to an arbitrary maximum.
4/. and the increase in pressure when different weight riders are on top.

it will be interesting to see what pressure difference there is between an empty , 1/2 full and full mat and if a rider increases the pressure beyond the levels that can be reached by oral inflation.
Potentially a heavy rider increases the pressure higher than you can blow it up so a lighter rider can ride an inflated mat and get the same performance as a heavy rider on a deflated mat...

More info and pics in a few hours.

[ULTIMATS]

Ok, here's the pressure gauge, its used in operating theatres to measure subtle changes in respiration, I wouldn't know where you could find a more sensitive gauge...



Even if you speak into the inlet port it registers an increase.

So, the first test is an almost empty mat, folds onto itself...



It registered zero.

Next is a 90 degree mat.....



It registered just under 2..



Next is a totally max full mat, as hard as I could inflate it.



It registered a 30.



Then a 60 kg rider on the full mat. It registered a 50.



Then an 80 kg rider on the full mat. It registered a 60.

[ULTIMATS]

So the next test was to try the 90 degree mat with a 60 kg rider, it registered a 20.
And the 90 degree mat with an 80 kg rider, it registered a 30.

That's worthy of some thought. Anyone ?

[ULTIMATS]

I'm posting to myself here so I'll finish the mat and post it up then.

[chrisb]

Firstly I don't intend to be rude - just asking a question.

I had a surf mat when I was a kid, many years ago, and they were fun, except when they got punctures.

But after that the bodyboard was developed.

I'm thinking that a hard side surface on a surf mat would really be replicating what the bodyboard does already.

So is there a place today in the lineup for the surfmat and why

[ULTIMATS]

Chrisb, mats haven't really advanced like other surfcraft and there's room in the lineup for a modern mat.
Great ideas Matticus and if I had the time I'd try them all.

I'm amazed that no one is interested in the pressure numbers ??
If mat riders use low inflation mats...but when they lay on the mat the pressure goes up and beyond any high inflation number....then what's all the hype about low inflation on a mat ?
An almost empty mat feels supple and conjours up images of magical floating rides but a rider of average weight takes the pressure on an almost empty mat to equal of a full inflation pressure.
My belief is that low pressure for a mat is only important on the smallest of waves where the forces are subtle and a mats unique performance is a result of a balancing act of the gentle forces and gravity because mats have no projection unless the wave allows it with an angled face to allow acceleration.
Beyond this small wave realm, higher pressures are essential as the mat needs to maintain a consistent shape to perform, especially with respect to form drag or straight line speed. Mats have a poor ability to grip a wave of any size especially with their 5 inch round rails and youtube videos show riders on decent waves using their inside arms/hands\fins to provide resistance and maintain position on a wave.
Other surfcraft use hard surfaces and sharp rails to provide speed and grip so there's room for a mat- hybrid that utilises the unique high speed acceleeration of a soft hull and high bouyancy mat and add the control of rails.

[ULTIMATS]

Interesting post Matticus,
Re: posts Vs Views... I wonder how people can read, come back again and again, and yet have nothing to say, no questions, no advice, no encouragement, not even abuse.... It's a mystery to me !!
The conversation could develop into something amazing with everyone's ideas and the best ideas come from outside the box, but no, its just a voyeuristic sideshow for so many.
So I thank you for your comments.

The pressure is the same whether you're lying on concrete, grass, sand or water.
Forward velocity wouldn't change how much you weigh but the pressure would increase when turning but only when you're accelerating during the turn. But that acceleration could triple the internal pressure.
I've met Cpt. Caveman a few times he's a decent bloke and an excellent surfer. We'll have to arrange a Sydney mat-meet and get out there !
Here's a few of the mat build...

[alakaboo]

The inflation numbers make sense, maybe that is why there weren't any comments on them.
If someone inflates fully then gets on it, then they can't bend it easily to turn, it will skip out etc.
If they inflate it partially, then their body weight only takes it to a point where it still works.

So, I know you've done a heap of tests of different designs etc.
I'm wondering how much of the 'performance advantage' of a mat is purely due to the buoyancy, and not due to the flexible hull at all. It would seem that from a performance perspective every other feature of the mat is a negative. Certainly in boat and kayak hulls they try and remove the flexibility as much as possible.

So, have any of your designs been hard shells/skins on both sides, but hollow? With or without an internal frame. Not like the pontoon one on the previous page, but just like a hollow bodyboard. If you had a bike valve you could then change the internal pressure, or even put in different fluids of different densities (making sure it was full, so they didn't slosh around)

I like the orange mat in the last post, it is starting to make more sense to me now.

[ULTIMATS]

The numbers make sense but what they reveal is amazing... the idea that mats are a floppy ride isn't true, the riding pressure is quite high with the rider adding pressure that takes a floppy mat to a point where its as hard as a fully inflated mat. So the numbers show mats work at a fairly high pressure.

The greatest assets a mat has are bouyancy and the flexible hull,the bouyancy reduces the displacement to the lowest possible level and the flaxible hull yields to the irregular wave surface instead of flattening every peak and ripple like hard boards do. With such minimal displacement, mats or any board with a flexible hull have the potential for instant acceleration and a massive top speed.
But because mats are unable to generate additional speed they are a slave to gravity.
From the various boards/ mats Ive made I would say an inflatable hard hull isn't likely to better a mats performance.

[MrMik]

Very interesting topic, I just came across it recently, hence no earlier replies.

...
The pressure is the same whether you're lying on concrete, grass, sand or water.
...

I wonder if your above statement is correct. Did you test it or is it an assumption?
What is the volume of the surf mat? I'll take a guess, using the picture you showed of the fully inflated mat: Maybe around 33 litres, assuming a radius of 6cm for the three tubes and a 1m length?
With the density of a surfer being around 1kg/l, the 80kg surfer + mat will have a volume of 110l and a weight of about 82kg.
Therefore, the mat will sink and the relative pressure in the mat will be reduced by the water pressure at the depth to which it is being submerged.
The gauge you use displays cm of H2O. For every cm submersion, you would need to subtract 1cm H2O from the gauge reading to get the relative pressure in the mat in the water.
The surfers relative weight will also be reduced when in the water, because all submerged body parts (legs) become effectively weightless and this might reduce the pressure in the mat.
I assume that - particularly with a partially inflated mat - the firmness of the mat with a person on it will be very different in water compared to the firmness on firm ground.
On/In water, the mat will be floppier.
On/in water, the surfers weight will have less impact on the pressure in the mat.

I can't quite wrap my head around it theoretically, but I'm convinced that you will find some interesting differences if you test the pressures in water.

Can you r gauge get wet without being ruined?

[ULTIMATS]

MrMik, thanks for your reply, Im not certain that a mat actually sinks at all ?
In motion I tend to see mats skimming lightly on the surface rather than being a displacement hull type of craft.
There would be a reduction in mat pressure due to the feet and fins being off the mat but most people ride with their fins/flippers skimming the surface or gliding just above the surface to maximise speed.
Overall, there will be circumstances that increase or decrease the pressure momentarily but its not going to change a whole lot without the mats performance changing a lot.

[MrMik]

What do you think is the approximate volume of the mat?

I will need to take out that surf mat and get some real world experience...

I bought one recently, the large version of the "Redback" available in some Ozzi surf shops. Don't know how it would compare to what you are building.
I have not surfed an inflatable surfmat since about 1987, when I was backpacking and used one as a rather short and uncomfortable mattress, as well as my only surf-craft. I did not have fins and did not know what I was doing in the surf, but it was fun!

Mik

[ULTIMATS]

MrMik, Im not sure what the final volume of my mat will be but I will take a few measurements tomorrow and give you a close estimate.
Considering that serious mat riders never fully inflate a mat to its full dimensions so I think mats could be a lot thinner...
Are you in Australia ?

[MrMik]

I bought one recently, the large version of the "Redback" available in some Ozzi surf shops.

Where did you get it MrMik? I'm thinking I'd like to get a mat once I've paid my rego in a couple of weeks but the $200 price tag puts me off, especially for what I'm wanting it for.

I bought it from the Cabarita Surf Shop for $50.- .

[alakaboo]

On the topic of posting the obvious, a thinner mat is going to be less buoyant.

I'm still interested in this idea that a flexible hull is better. It doesn't make sense to me.
The mat can knock out the influence of a choppy surface, but this has to come at the expense of friction and downwards suction, surely?

It is a long time since I rode a surfoplane, but isn't the advantage mainly that the lack of grip and control forces you into lines that draw more of the energy from the wave?
A bit like the way a McCoy board likes to sit high and tight in the pocket. It is fast, but you have to surrender to it in order to get the most out of that design.

i.e. When mat riding you are maximising the gravitational and kinetic energy available by having the mat flat on the surface of the wave rather than trying to exert your own directional desires.
Once you try and change the application/direction of one of those forces you are going to be needing stiffness in the fins or rail to transfer the energy.