Flatfish NNC CF Base

For background on how this seat base was developed and brought to fruition, see this thread: The worlds best unicycle seat

How long riding: 4.5 years
Primary riding surface: Single track
General riding style: Rolling, minimal hopping, small drops 1-2’
Preferred wheel sizes: 26, 29, 36
Stats: 6’, 200#
Uni used in review: Nimbus Oregon 26", KH Moment 150mm cranks, Vee Rubber Devist8or 4" tire
Reason for choosing this seat base: Discomfort in the “nether” regions

First things first:
The wait and the cost, the seat base is kinda pricey, but it’s the only game in town and Pete lays up some mean CF, so three weeks later I arrive home from work to find a lovely little bag covered in Kiwi stamps.

The hardware:
CF bases don’t generally come outfitted with hardware, so there’s the matter of picking the hardware, mapping out your mounting, drilling the seat base, gluing the hardware in place, all before you can consider the foam. Unfortunately, here in the good ole US of A, we are still working on the metric conversion, so I had too choose between metric zinc coated T Nuts or SAE stainless T Nuts. I wanted to use the factory 6mm bolts from a KH seat, so I chose the zinc coated T Nuts.

Selecting a donor seat:
I had two choices, a KH Freeride and a Nimbus Gel. The Nimbus has thinner foam and it is a less expensive seat, so it won the contest. To access the foam on a Nimbus seat, you have to pull out a ton of staples, then peel back the cover, then carefully peel the foam from the seat base.

The mess:
Yes, I need a work shop, even a garage would do, but not anytime soon…

Preparing the base: (Do Not Fear, the Force is with You!):
Yes Dorothy, you will have to mark the holes and drill that seat base. Follow the old adage, measure fifteen times and drill once. You may be able to get your base pre-drilled, which I’d strongly suggest if you are not handy. Make your marks, punch your marks, use a smaller bit to make a pilot hole, then finish with a bit that is sized for your T Nuts.

Installing the hardware:
Pete recommends Gorilla Glue, which is what I used, it works well if you follow the directions: WET THE SURFACES! Yes, with water, because Gorilla Glue is activated by the water. Now you don’t need to soak it, dampened will work fine. In order to get good clamping pressure, install the seat post and bumpers, make me snug, this will get the hardware set at the correct angles. Wait a few hours before disassembling or the T Nuts may not be stable.

Tap those nuts:
What? Okay, so they have these things called taps, not the Taps they play when someone dies, but the taps that are used to clean up threads. You should consider running a tap through your T nuts so they don’t bind when you assemble the seat. If you are going to run a tap through the T Nuts, do this BEFORE gluing the foam onto the base; just in case the T Nuts spin.

The foam:
This is a biggie, mostly because you will be adapting foam from a seat that is molded to match a curved base. The foam will be curved and have varying thicknesses, in order to make the foam flat to match the seat base, you will want to do some cutting and filling. I use minicell grey closed cell foam in 1/4" and 1/2" to fill low spots. I filled in the depression over the seat post mount so that it was level with the seat base. I also added a wedge of foam at the rear of the seat to level the back of the seat.

The Carve

The Layup

Attaching the foam to the base:
You will need contact cement, it will be sprayed/painted on both the foam and the base, there are a lot of contact cements available, each has its pros and cons. I have tried quite a few over the years and the best one by far is the Loctite Spray Adhesive, medium bond, high initial tack. This glue is awesome, it sprays out fine so no clumping or over-wetting the surfaces, it is quick to become tacky and has a long working period in case you lose track of time.

The Glueup

The cover:
Now that you have the hardware installed in the base and the foam cut to fit, there is the matter of a cover. Again, like the foam, you will be adapting a cover that is designed for a curved seat base and thicker foam. I stated with a KH FR vinyl cover. First I tried restitching the cover (fail), I tried installing grommets (fail), the cover just wouldn’t pull tight enough. In the end I did it just like a bicycle seat: I glued the cover to the base. It worked and it is very clean. I even could have used the discarded Nimbus cover…

The final product:
I went for a slightly different profile, preferring to keep a “bicycle” style with a slightly higher position at the rear, with a slight tapering down to the waist, then flat out to the nose.
The cover is glued along the edges at the waist and nose, I did not glue the cover across the flat “sitting” area or the along the rear edges so that the foam could move and breathe. The rear portion of the cover is held in place by the rear bumper.
I had to modify the KH stiffener plate, both shortening and re bending the plate so that it would fit on the flat base. The aluminum is easy to bend using a hammer and a block of wood.
The handle and brake were swapped straight across from my KH Freeride seat. The handlle ends up being a tad lower than with a KH Freeride, so it feels akward. I will be making a revised handle in the Spring, with a upward bend to compensate for the lower nose on the Flatfish base.

The ride:
I was tight on time, so the first ride was an hour single track circuit near home, a mix of climbing, flats, and descending, some moderate tech with roots, rocks, water crossing, and mud. I adjusted the seat base a number of times looking for the ideal angle. I also worked on finding the ideal seat height as the thinner seat foam required a taller seat post setting.

I finally settled on ~12 degrees of seat angle which gave me the best ride feel and placed my sit bones in the best position possible. I would like to have been able to adjust the fore/aft position of the seat (like you would on a bicycle), as the ideal sit bone position was +~3/4" rearward, but I could not hold that position without rearward overbalancing the uni.

In terms of ride comfort, I’ll say this: On the drive home after riding it suddenly occurred to me that I had just gone for my first uni ride EVER during which I didn’t once reposition the jewels.

Well, nothing is perfect, and even though the Flatfish is loads better than any other seat I have tried; and I have tried a few, there a few things that would make it better:

Pete essentially “flattened” a KH seat base, so the resulting base is slightly longer than it’s curved cousin. I think the base flattening alters the dynamics of the seat base such that it brings the pelvis forward relative to the balance point of the uni. This is not a big deal by any means, just a fine point that should be discussed as this style of seat evolves.

A slightly different base shape, one that shifts the widest and most padded portion of the seat area forward 1/2-1", possibly by shortening the waist rearward of the seat post mount. It is also possible that rails/rail adaptor would make sense on a flat seat; which would also work with the existing base.

Final Comments:
Two Thumbs Up!
Top Honors for Most Innovative Product 2013
A must have for serious unicyclists.

Thanks for the writeup Ben! You’ve gone through some great lengths with the foam and bolt hardware. I like your stiffener modification. Was it hard to weld on?

Also, can I ask how well your handle works? It must be the most phallic looking thing I’ve seen on a unicycle in a long time. Have you tried angling it upwards? :smiley:

Interesting point about the increased seat length. I’ve actually found it useful for shifting your weight around on the seat. I think Pete mentioned lengthening the seat further at one stage.

Regarding saddle rails- I’ve never been a big fan of them- it adds extra weak points, and for short people, stack height which is an issue on a 36".

I’ve also thought about this a bit, and I think on a unicycle angle adjustment is all you need, because it compensates for forward/backward rail adjustment. Perhaps what we need is more angle adjustability rather than being able to slide back/forths?

Did you notice any difference in pulling power with the lower seat handles?

The handle is designed for a KH Freeride which has a upward angled nose, so on the Flatfish it is angled down too much, so much so that my back is a little sore today from having to reach further. The handle is usable for now, but I will have to make up some custom handles soon.

The handle mount is simple to make, you need a KH plate, an old MTB bar, and a R or L long bar end. Drill a hole through the plate centered between the bolt holes, cut off a 2-3" piece of bar, weld the bar stub into the hole on both sides, then install. The auminum bar stub does wear over time, so the next version will be made with stainless tubing and stainless plate.

I like this style of mount better than the KH T bar because it doesn’t flex much and it is very simple and lightweight. I want to make a variety of bar ends to fit the mount; a triple handle trident, a couple long ends, some straight ends, but first I need to buy a TIG welder; having stuff welded is pricey!

So you think the KH rail mount is too flexy? I have not seen one in a while and I have never used one, but I could see how it would be a clearance issue and add some weight. I do think the seat angle helps reestablish the balance point, but it was not enough for me even when angled excessively, so I ultimately picked the angle that handled the best. If I could slide the seat forward 10-20mm, I’d be golden! I am thinking that a custom low profile short rail adaptor made from an old bike seat might be a good start…

Now I need to order another seat base…

Ok, I was wondering why you had such a low riding position. I’ve found the plain plastic handle works great because of the lower angle, but I had to angle my KH T-bar upwards somewhat to get the same comfortable.

With rails, it wasn’t flex that was the issue, it was strength and added height. My experiences of the rail seats was with an early version (circa early 2000s), and on the Nimbus T7 Bar- I’ve seen 3 or 4 breakages, two of them on my Unitours. They always fail at the rail welds.

Probably only relevant for people like me with short legs- it adds stack height, which limits adjustment when you don’t have much seatpost on a 36". One of the reasons I wanted a flat seat was so I could get rid of excess foam and still have a flat seat (which is one reason the KH Freeride never worked for me).

Your bolt system looks really clean on the Flatfish- I might do that with my new bases (I bought two more).

The new base looks so much tougher than the prototype! I had problems with flex on the prototype- have you noticed any on the new base?

I presume most people won’t be using a stiffener plate with a flatfish - but I’m working on making a flat seat by bending a standard base*, so need that plate is I want to use a T bar. I was wondering how I was going to make a standard plate fit, so thanks a lot for the info.

  • not yet finished, but I’ve got far enough to be confident of success - will be rather heavier than a flatfish, but a lot cheaper!

On my prototype base- I used the KH plate to line up the holes for drilling.

It should easily fit- but you might have to cut the proximal end and drill a couple of holes to align the base.


The base is stiff, not sure how much the stiffener adds, but when I flexed the plain base, it was at least as stiff as a Gem. When I ride, even with pulling up hard, the base is stiffer than a KH with a stiffener plate.

The T Nuts still want to spin, even when glued; I had one spin out when I was doing the final assembly :frowning:

I think there is an answer, but it would involve changing the mold slightly. There are T Nuts that have a rectangular T, so I was thinking that if there were depressions made on top at the mounting holes, then the T Nuts could be held in place more securely.

Imbedded T Nuts would be cool, but if they spun or reduced the strength of teh base, then that would be bad.

I was also wondering if maybe there is a better glue, something more shear resistant, like what is used to glue concrete benches to a sidewalk or to glue reflectors to the street, maybe a semi firm setting epozy that relies less of bond and is better able to hold the T’s in a “floating” position…

@ Aracer,

The plates are easy to bend, so much so that I wonder if they really add that much structure to the seat…

To get the plastic base to flatten, you’ll have to cut off all the edging or make a series of pie cuts. Do you have a spare base to sacrifice?

Have you considered building a base from aluminum or SS? I think a piece of flat stock cut in the preferred shape, left entirely flat, then weld an strip perpendicular to the edge of the flat stock. The hard part would be building the ramp for the mount.

I think a metal base is a possible answer, though a good CF base is available…

I’m not getting any spin. Are you using old bolts from another seat? I bought brand new ones so the threads are perfect. I also used a little bit more glue and glued a bit over the top of the nuts them sanded down the excess. I lefts mine to set overnight with longer 6mm bolts and washers to set the t nuts as tight as possible. In fact, the 2 of the front t nuts have bent to conform to the base a bit and my seat post bolts are cut to fit with each other to reduce spinning.

I haven’t performed my final assembly but I really don’t see them spinning.

I was very surprised, in fact I was really quite miffed and I’ll admit, some words were said that would not be considered polite in mixed company :angry:

So I had to pull up the foam and reglue the T Nut, it appeared that the glue simply separated; there was residue on the nut and seat, so I I roughed them up and dampened them, then reglued and it was fine.

I had clamped them and left them overnight, so they were as cured as they can get.

Hey, what are you going to do with the handle Bryce made, does it fit?

The handle I have been using goes into a KH t bar set-up. It’ll fit, I am going to modify the front bumper to get the right angle. I’m going full custom with the foam. I’ll be using dense closed cell foam that I use for kayak outfitting. I’ll post pics.

The trick to T-nuts is having an interference fit, that is, the hole is 0.1mm smaller than the T-nut, you then pull them in using the glue as a lube, the glue dosn’t stop them from spinning it is the tight fit that does it, I have not had one spin yet. I do not use water with the Gorilla glue, it sets just fine with the moisture in the air, if you do use water I would sugest only applying to the carbon and wiping away excess as to much will weaken the bond.

My understanding is that it’s not designed to need a stiffener, hence you could have just cut yours off behind the holes where it mounts, rather than having to flatten in and drill new holes to make it fit. That or made yourself a new smaller plate and fitted the tube at an angle to make up for the change in angle of the handle…

It doesn’t need to be resist bending in order to stiffen the seat. I’ve only taken apart an old seat, but I presume the new ones are similar - the reinforcing plate in mine is a steel sheet which you can bend by hand. The thing is, a plastic base sandwiched between a steel sheet one side and an alu sheet the other (all bolted tightly together) should make a nice stiff structure no matter how little resistance to bending any of the parts has on its own - by using the plastic to separate the metal sheets, the bending load on the seat is taken in tension and compression on the metal sheets, something they’re good at resisting. Rather like a composite sandwich construction. Bending stiffness is only required to stop buckling (one reason for needing a thicker alu sheet on the bottom - the thin steel sheet on the top is prevented from buckling by the foam and cover).

I’ve already flattened a plastic base without any cutting. Just a pan of boiling water to heat the plastic to the point where it softens enough to plastically deform. I need to redo it as I didn’t work out the best way to do it first time - hopefully in the next couple of days.

I might still try and make myself a composite sandwich base - the current experiments should help me a bit with that (the original plan was just to sculpt the foam on the old seat I have - not until I took it apart I came up with the boiling water idea).

NNC CF Review

How long riding:
5 years as a kid; 30-year break; 9 months as an adult on a KH 36
Primary riding surface: Paved, off-road, single track
General riding style: singletrack + mud = :smiley:
Wheel size: 36
Stats: 6’, 170#
My uni: KH 36, Nimbus Nightrider, KH Moment 150, Magura HS 33 rim brake, 8-panel padded bike shorts

I do a 20-mile ride every week http://robsride.com with more experienced, faster riders. During the last 5 miles or so of every ride, I have been experiencing a lot of crotch pain. Naturally, this thread caught my attention, and I ordered a NNC CF base from Pete. He was very helpful, and sent me a base with the hardware already installed. It only took 8 days to reach the west coast of the US. It looks very well-built and sturdy. It is much lighter than my original KH base.

I sacrificed my KH Freeride for the foam and cover. I like the “flat” look of the Flatfish, so I fashioned a wedge of foam from an old yoga block in such a way that made the seat as flat as possible. Not sure if this material was the best choice for the wedge, but it is something I had lying around. I have not yet modified or glued the cover, so it doesn’t fit perfectly at this point, but it is pretty close. The handle of my Magura HS 33 rim brake no longer fits quite perfectly with this base - I am not worried, as I plan to adapt to a handlebar and different brake solution soon.

After building the seat, I rode around my house with an allen wrench and experimented with a variety of seat heights and seat angles. Like Ben, I landed on something close to a 10-12 degree angle. At this angle, I can feel a different part of my gluteus bearing a lot of my weight, and there is more open-space up front. YES!!

I set out on the 20-mile ride with the gang.

I like the seat a lot. While I ended up in some pain at the end of the ride, I think the seat helped to delay the onset of pain. Also - I think I need my body needs to get used to the new pressure points. The flat seat handles beautifully. I can climb sitting or standing, ride technical parts, etc. just as well as with the old seat. Jump starts will take a little getting used to. The old seat provided a bigger, more well-defined target to land in. Now, I need to be a little more precise, but I am already learning to trust myself with jump starts with this saddle.

While this saddle did not ultimately “solve” my pain issue, I have some strategies to manage my continuing pain:

  1. Get used to this saddle, and dial it in
  2. Become a faster rider. In comparing Strava data with some other riders, I see that my riding time is 20-30 minutes longer than their times. They get longer rests to recover during the ride. Most ride with geared hubs. I like the idea of a lower cadence on the long flats. I hope to get a geared hub soon.
  3. Experiment with a handlebar.

Final thought:
Two thumbs up for the NNC CF base.
Thanks to all who contribute time, talent, and experience towards a more comfortable ride on the unicycle :slight_smile:
Time to go


Hi Kev,

I’m curious why you chose the KH Freeride foam, and as much foam on the seat as on the regular KH Freeride?

The reason KH made the Freeride saddle was to create a relatively flat saddle, but in order to do so, he filled in the curve with excess foam.

It doesn’t make sense to me to get a flat base, and then use just as much foam as you get with the KH Fusion Freeride. You end up with a similar shaped saddle.


Hi Ken -

My original Freeride base has over 50 degrees of curve in it, and the original saddle was nowhere near flat. When initially placing the foam from my original saddle on a flat base, I ended up with a saddle that was slightly concave down towards the rear (as a result of all that excess middle-foam you describe). Adding a small amount of filler material at the rear only made the resulting saddle completely flat - not concave-up like the original. My current working prototype is completely flat - again - very different from the original. I guess you are asking me why I didn’t shave foam from the middle in order to achieve flatness. That option did not occur to me and my sore arse, yet would be an easy second-generation prototype to test. I must admit, I am in no hurry to shave foam at this point :slight_smile:


Hi Kevin,
I had a similar problem with my brake and to fix it I made a new clamp half from steel so I could slide the brake further forward on the KH mount



@pete what did you use to make your spooner?

how can i buy one in europe?

I cut the shape from plywood, 3mm I think, then layed up CF on both sides using the brake lever as a mould, then I coated the top half including the lever with mould release, then I put 4 or 5 layers of carbon over that.

When dry I was able to remove both halves from the lever and shape and put in the bolt holes, it fits on the lever really well.

I am amazed how much abuse it has handled :smiley:

A trick I learned from riding dirt bikes works well here, leave the clamp slightly loose so you can still twist the brake on the handle bar or in this case the KH brake mount, that way when it hits the ground it can rotate instead of breaking :sunglasses:

Hi Turtle,
Send me an email to peter@gilbarr.com if you would like to purchase a flatfish.

They cost $175.00NZD including rear bumper and rear bumper bolts and a transfer for your frame.

The base is pre-drilled and has marine quality stainless steel threaded inserts pressed and glued in place.

Post to Europe including paypal fee is $21.00NZD.

Let me know if you have any questions.


Pete :slight_smile: