has anyone looked into a carbon fiber/kevlar weave fabric? a friend of mine who is a dogsled builder uses this to cover thin wooden runners to make them lighter but stronger and safer than aluminum runners. there are a few fabrics out there from different suppliers with tighter or looser patterns.
example:
Ignore the seatpost- that is dependent on the angle I set the angle adjustment at. It is irrelevant. I should have removed the seatposts from the diagrams to avoid confusion.
What I’m trying to show on both diagrams is the flat section at the back of each seat (because that is the widest part of the seat, and where you want to place your ischial tuberosities). In both diagrams, they’re at about the same angle.
You can see that on the NNC seat, you can almost draw a line from the back of the seat to the front. On the Nimbus flat seat, there is a 45 degree bend midway through the seat, which is right where you would place all your squishy bits.
Very commonly used in kayak construction (which is where most of my experience in composite construction comes from - most of the work I’ve done has been in repairing them!) The idea is that the kevlar is tougher than carbon, so better at withstanding impacts. Combining the two in a single weave give you a happy combination of the properties - stiffer than kevlar fabric, but not as stiff as carbon fabric, tougher than carbon fabric, but not as tough as kevlar fabric (though my understanding of the way that bit works is that you get close to the toughness of the kevlar fabric but a lot better stiffness). I’ve had kayaks made from all 3 types of fabric, but I can’t compare like with like - my kevlar/carbon one is a lot stiffer than the plain kevlar, but then it’s also a sandwich construction which makes more difference to the stiffness than the fabric used. The only one I’ve owned with a plain carbon weave was a totally different type of boat - was kind of fragile, but then I used it in competitions where you bounce off rocks.
As I mentioned above, I’ll almost certainly be building in plain kevlar, but that’s more a cost issue for me, as I have plenty of that available, rather than having to spend real money on carbon cloth. Will be more flexible than carbon, but a bit tougher, though I’ll almost certainly overbuild (especially given the fabric I have is fairly heavy weight) so it’s unlikely to be noticeably flexy. You’d certainly not have any major problems building with kev/carbon if that’s what you want to do, though the problems with building something like this for the novice is getting the fabric to drape into the required shape.
I placed the riders contact point on the widest part of the seat, and that is at the same angle in the two pictures. You can see the 45 degree angle that the Nimbus Flat seat turns upwards midway through the seat.
I’ve also increased the pelvis size (because someone pointed out the scale was slightly off). Hope this is closer.
I’d stay away from kevlar for a seat base. The main advantage with Kevlar is its abrasion resistance, which is why it is used in places that would rub against something else or take a direct impact, which is not the case with a unicycle seat. The best would be to use unidirectional carbon fiber for most of the layers, laying it from front to back. This provides the most strength when pushing and pulling on the seat. You could then either have a few layers of the unidirectional carbon fiber going diagonal each way, or having layers of a bidirectional carbon fiber, to help it be stiff when twisting the seat. If you are making bumpers for the seat, then that is where you would use kevlar.
Both kevlar and carbon fiber are expensive, so if you are just trying many things to get the shape right, use fiberglass. Hardware stores sell cheap repair kits that contain fiberlass cloth and resin that you could experiment with.
Hi All, just a brief description of how I do the NNC bases.
I made the plug from extruded polystyrene as it is easy to shape and you can get a good finish on it sanding wet. I looked at the possibility of flattening a plastic base but the shape is too complex to expect a usable plug.
I then made a mould from the plug, this was an internal mould, to make the base I needed an external mould so I laid up a new mould, from the first mould that was exactly the same shape as the polystyrene plug (I hope this makes some sense).
To make a base, the mould is waxed then mould release is applied, once dry I cut out the carbon shapes, so far I have been using 10 layers of 200 gram twill carbon with doublers around the post mount.
Steps for the lay up are, wet out the mould with epoxy using a 50mm paint roller, then lay a piece of carbon, roll on more epoxy, another layer of carbon etc until all the pieces are applied.
Then the mould is covered with bleeder cloth and an absorption material (I use paper towels, there always seems to be some in the kitchen :)) then it goes into a vacuum bag which compresses the lay up and bleeds out the excess resign, that’s why it weighs 120 grams.
I could post a heap of photos but I can’t work out how to do that, or Gizmo Duck could put them up?
I have had a fair bit of experience with glass, carbon and Kevlar and for this carbon is going to achieve the best strength and stiffness to weight ratio, also the most expensive.
I was thinking of trying one for MUNI, not sure if it would be suitable, I can make one for you to try but we are currently packing up to move house so it woul’dn’t be for a month or so.
Not suitable because of the light construction or too flat?
So are your seats much more comfy than say KH freeride? I was just curious if you would sell a beefed up carbon fibre base made stronger for muni- I don’t know if I would buy one Say if you were to make a stronger base for muni how much would you charge?
This raises the question of why, if flat bases are so much more comfortable, why has every single manufactured saddle to date had so much curvature?
Incidently, thanks to all those who are experimenting with these kinds of things- seat discomfort is the bane of unicycling and if this results in a saddle that reduces or removes that, then that would be brilliant.
if someone needs a test person for a flat muni saddle, I’m right here!
I’ve tried a bike saddle for muni with a “stick” from the seatpost to hold on, it worked pretty well, but in the front the saddle was to narrow, hard to control…
Pete- thanks for contributing to this thread! You did an amazing job of the carbon base- I’m loving mine. For those people who are wondering why it’s called the NNC seat, it stands for ‘No Nut Crush’
My theory is that there was a slight curve in early saddles because they did not have adequate handles. Also many freestyle riders ride hands free for tricks, which means the need to be wedged into the seat for crotch control. They also didn’t spend hours on the saddle at one stretch, until long distance unicycling started becoming popular.
Seat bases became more curved when the KH seats came out, because they use more or less the same plastic molds, and the molds are expensive to make.
As mentioned, Miyata seats were popular about 10yrs ago, and has a slight curve, but nothing compared to the 45 degree bend of todays seat bases. I still like Miyata seats, apart from the handle.
I’m intending to use mine for XC MUni, and I have been wanting a flat MUni seat for years. We haven’t tested the extremes of pulling and pushing forces yet, so not sure if it more carbon layers are required or if Petes 10 layer base is strong enough. It probably will be for me, but I weigh less than 60kg.
I have done a lot of different saddle testing and modifications. I agree that most saddles is to much curved. I also made a nearly completely flat saddle. But that didn’t work for me. Here is some thing I have found out:
The riding position has more to say than the width of your sit bones. If you ride a upright position (some does - like Chuck Edwall) you can ride width a wider saddle.
I have much less control on a narrow saddle. For me i noticed that i got problems when doing long rides. (Over 60km - 36").
I have much less control on a flat saddle. For me i noticed that i got problems when doing long rides. (Over 60km - 36").
I need a softer saddle when riding Muni and gravel roads. The saddle must have some suspension, but not be a spring.
You may have 1000 bicycles saddles to chose from. And they are made in all styles. There are not many unicycle saddles to chose from. I think there are place for a couple more
The result from my unicycle testing, finally, was that I changed the saddle on my bicycle (mtb) from a flat and narrow (Selle Italia SLR) to a curved wider (Fizik Aliante)!!!
I agree, there is room for a saddle that is not molded on the same base as all the others, esp one that seems to crush the jewels.
I have played around with foam cutting, mocked up a KH base with minicell foam trying to get a flatter and more comfortable seat. What I found was that the KH “dual denisty” Freeride foam is really tough to beat for comfort. So if it were to be combined with a flatter seat profile, that could be nice.
I’d buy a flattened carbon fiber base built to muni specs.
Say if you were to make a stronger base for muni how much would you charge?
