Need Help Drilling out CF seat base

Heyo everyone.

I just got a CF seatbase from Bedford. I was just wanting to know how far back to drill the holes for the SH/ Kingport rail adaptor. I have never really played with CF at all so I dont want to Fudge it up too bad if I can help it. If anyone out there has some pictures of their seats I would appreciate it. Or any other advice for doing the whole airseat conversion project.

The other question would then be are there any good techniques to drill out Carbon Fiber?


Carbon fibre drilling

I drilled mine last week. James has some pictures of it, but I don’t have a copy of them yet.

While in the carpentry workshop at Polytech, I held the CF base sideways and marked a line on a scrap peice of wood tracing the inside curved edge. Bandsawed it out and then sanded it to fit (on a belt sanding machine). Copied the design onto a large block of wood, bandsawed and sanded it to fit underneath the seatbase for support. I drilled the hole for the valve first, to get some practise. I did it smaller initially, then bored it out to 8.5mm and did a bit of countersinking to smooth out the glass edges. I might make another valve hole further back because I put it right in the middle of the back part, just in case it would interfere with the bumper. I am thinking it should go quite close to the back in the middle, because rear bumpers (I’ll get one soon maybe) have a gap in the middle to allow valves. The reason I will make another hole is to make the back part of the tube fill out to the edge better.

As for where you locate the Kinport, it doesn’t really matter as long as it is near the middle, because it is on rails it can slide back and forth. I got my KH saddle and put the CF one next to it, and marked (in pen) where the middle of the seatpost was on the KH seat onto the edge of the CF base. Then I drew a line across the Kinport, where the bend is in the middle (to make it easier to see). I lined it up vertically with a couple of marks too, and then did some dodgy marking by dangling a pen into the holes and drawing a circle. Then I scratched the marks in with a scriber so they wouldn’t rub off. My fasteners are 6mm so I drilled out some smaller guide holes, maybe 3 or 4mm, and then did 6mm holes. I was wearing safety goggles and a dust mask just in case, while drilling on a drill press with my curved bit of wood underneath the base for stability. I didn’t use any clamps because the woodworking ones were a bit heavy duty for the task at hand.

The holes were not too badly out of line, even though I am a bit useless when it comes to practical things. All the bolts fitted into the kinport adapter afterwards, so I am happy with the results.

I found it difficult to mark the holes for the Reeder handle, in hindsight it might have been easier to get someone to hold it for me. I just held it on myself, and tried to guess where the ideal angle might be, not really knowing because you have to try it to find out. I based the angle on ones I had seen in pictures, trying to make it point out to the front a bit.

I rode in the rain during my morning break to a local tire company, and asked them for some innertube. They told me to help myself in their rubbish bin, so I went and cut up some big strips of tractor tube. My friends wanted some for under their skateboard trucks, so they were stoked when I returned with heaps. I cut some patches to fit underneath the Kinport and Reeder handle, with a little bit poking out the edges to soften the sharp edges from stressing the carbon fibre. I also rounded the corners of the Kinport with a file but I doubt that is needed with the fat rubber risers.

After riding with the seat a bit, it was making some awful squeeking sounds when I went up hills, so I pulled it apart and added some normal bike innertube underneath the washers on the top of the seat. The washers were cutting into the glass a little bit already, so I thought a bit of rubber should help. I also put a few rubber bands in to try to hold the (air filled) innertube in shape better, it was twisting to one side more than the other.

Now the seat doesn’t squeek, and it is very rigid but still has a slight amount of flex due to the tractor tube. Hopefully it will last longer than my KH seat. I am thinking of replacing the KH seat so I can put it on top of the Thomson seatpost/kinport adapter to compare to the airseat.

I found it helpful to have a reversible drill. The drill bit I was using kept getting stuck in the hole, and I had to reverse it a few times to get it unstuck. Also I vaguely recall using drill bits of increasingly larger diameters, starting out with a very small bit to get the holes started. If you have access to a drill press, I would probably use that instead of a hand-held drill.