Hi All,
I'm just posting a brief description of a tail box I made for my V20 in case it helps anyone else to do something similar. Of course Cruzbike make what looks like a great option in the race case, but where I live it was rather expensive to get it delivered to me, and I was stuck in a COVID lockdown looking for a project, so I decided to try my hand at making something out of carbon fibre.
So here is the finished product:
The main carbon box is about 500gms. The aluminium mounting is about 200gm. Similar in weight to the Brain bag (with mounting) I had previously... but for me , the brain bag was in the wind above my shoulders and this should be more aero. On that note... I was not attempting to make a rear fairing. I just wanted a box that could carry hydration (bladder with tube going down left side of seat) and some food/clothing etc. in a way that does not have an aero penalty like the Brain bag did for me.
So the first challenge was working out a way to attach something to the back of a standard V20 seat. Unlike other high racers, the top section of the seat where you want to mount the box is just tubes with no seat back. I decided to use some 19mm hose seperator clamps to mount the 19mm head rest to some 19mm aluminium tube that is bent to form a panier rack of sorts. The pic below shows the mount system:
I'm new to carbon fibre so watched lots of youtube videos. The main thing is that you need a mold in the shape of what you want to make to layup the carbon on. I decided the simple option was to use some styrofoam to make the shape I wanted and then lay the carbon onto that. You end up with a fully enclosed box with the styrofoam inside. But the great thing about sytrofoam is it dissolves in Acetone... so you can just cut the hole for the lid and pour in some Acetone and dissolve the foam out of the inside. I made a hot wire foam cutter and cut piece of foam close to the shape I wanted and then sanded it to the final shape. Here is the foam piece in place:
Now before laying up the carbon, I covered the foam in packing tape. Packing tape is great because epoxy resin does not stick to it, so you can easily remove it from the cured epoxy... and it seals the foam so the epoxy does not soak into it.
I ordered a couple of metres of carbon fibre fabric (200gsm, 3K 2X2 twill) and an Epoxy resin kit (slow cure time for a newbie!!). I also got some breather material and perforated release film. Now I decided to try vacuum bag it using a vacuum storage bag the department store. The idea was to wet lay the carbon, then cover in the release film and then the breather, and then into the vacuum bag. The benefit of this being that the vacuum bag applies pressure to the layup which squeezes the excess epoxy through the holes in the release film where it is absorbed by the breather material.
I ended up doing this in two stages as I was not confident of doing it all in one go and handling it all when the entire mold was covered in wet resin. So I did the underneath first followed by the top and sides seperately being careful to overlap for strength. I went with 4 layers which is around 1mm thick. I cut the carbon to size before mixing any Epoxy. It almost turned into a disaster as the first time was on a hot day and I think I got the resin mix wrong and it was starting to cure after only about 10 minutes. I was lucky to resurrect that by working in smaller batches with less hardener. It ended up working out pretty nice. Here is the vacuum bag:
That was the first stage. I worked out that it pays to smooth out the bag as much as possible to save finishing work later. Here is the box out of the back with some minor cleanup:
Now because of the way I did it, the outer finish was pretty rough. So there was a lot of finishing required. I ended up sanding it down to the carbon, and then coating in Epoxy again followed by sanding... rinse and repeat a few times. I think there a good 8-10 hours not including the cure time of each coat. If you could make a nice split mold, it would save a lot of finishing time! But it came out pretty nice:
At this point I decided that I wanted a lid that was larger than the opening hole, so I could not just use the cutout for the lid. So I covered the top in packing tape again and used the box as a mold for the lid and made a new lid piece using a similar process with another 4 layers of carbon. Now the lid is perfectly shaped to the top.
Next stage was to cut the opening. I used a dremel cutting wheel to do that. Then it was time to remove the foam. Here is the cut box with little acetone thrown in:
After you dissolve all the foam, you can peel off the packing tape, and the finish inside was actually much nicer than the outside.
All that was required was to drill some holes for mounting the mounting system with some bolts and also for the hydration tube. I got some nylon hinges from a hobby store (for RC places), and added some small magnets to hold the lid down (but I use a rubber band also to make sure nothing falls out on large bumps.
I'm pretty happy with the result. It is not perfect. I did sand through the epoxy in a few spots which you can see as it loses the gloss. I may one day give it a clear coat which would sort that out, but I want to use it a bit first and see if I need to make changes.
I hope this helps anyone thinking of doing something similar!
I'm just posting a brief description of a tail box I made for my V20 in case it helps anyone else to do something similar. Of course Cruzbike make what looks like a great option in the race case, but where I live it was rather expensive to get it delivered to me, and I was stuck in a COVID lockdown looking for a project, so I decided to try my hand at making something out of carbon fibre.
So here is the finished product:
The main carbon box is about 500gms. The aluminium mounting is about 200gm. Similar in weight to the Brain bag (with mounting) I had previously... but for me , the brain bag was in the wind above my shoulders and this should be more aero. On that note... I was not attempting to make a rear fairing. I just wanted a box that could carry hydration (bladder with tube going down left side of seat) and some food/clothing etc. in a way that does not have an aero penalty like the Brain bag did for me.
So the first challenge was working out a way to attach something to the back of a standard V20 seat. Unlike other high racers, the top section of the seat where you want to mount the box is just tubes with no seat back. I decided to use some 19mm hose seperator clamps to mount the 19mm head rest to some 19mm aluminium tube that is bent to form a panier rack of sorts. The pic below shows the mount system:
I'm new to carbon fibre so watched lots of youtube videos. The main thing is that you need a mold in the shape of what you want to make to layup the carbon on. I decided the simple option was to use some styrofoam to make the shape I wanted and then lay the carbon onto that. You end up with a fully enclosed box with the styrofoam inside. But the great thing about sytrofoam is it dissolves in Acetone... so you can just cut the hole for the lid and pour in some Acetone and dissolve the foam out of the inside. I made a hot wire foam cutter and cut piece of foam close to the shape I wanted and then sanded it to the final shape. Here is the foam piece in place:
Now before laying up the carbon, I covered the foam in packing tape. Packing tape is great because epoxy resin does not stick to it, so you can easily remove it from the cured epoxy... and it seals the foam so the epoxy does not soak into it.
I ordered a couple of metres of carbon fibre fabric (200gsm, 3K 2X2 twill) and an Epoxy resin kit (slow cure time for a newbie!!). I also got some breather material and perforated release film. Now I decided to try vacuum bag it using a vacuum storage bag the department store. The idea was to wet lay the carbon, then cover in the release film and then the breather, and then into the vacuum bag. The benefit of this being that the vacuum bag applies pressure to the layup which squeezes the excess epoxy through the holes in the release film where it is absorbed by the breather material.
I ended up doing this in two stages as I was not confident of doing it all in one go and handling it all when the entire mold was covered in wet resin. So I did the underneath first followed by the top and sides seperately being careful to overlap for strength. I went with 4 layers which is around 1mm thick. I cut the carbon to size before mixing any Epoxy. It almost turned into a disaster as the first time was on a hot day and I think I got the resin mix wrong and it was starting to cure after only about 10 minutes. I was lucky to resurrect that by working in smaller batches with less hardener. It ended up working out pretty nice. Here is the vacuum bag:
That was the first stage. I worked out that it pays to smooth out the bag as much as possible to save finishing work later. Here is the box out of the back with some minor cleanup:
Now because of the way I did it, the outer finish was pretty rough. So there was a lot of finishing required. I ended up sanding it down to the carbon, and then coating in Epoxy again followed by sanding... rinse and repeat a few times. I think there a good 8-10 hours not including the cure time of each coat. If you could make a nice split mold, it would save a lot of finishing time! But it came out pretty nice:
At this point I decided that I wanted a lid that was larger than the opening hole, so I could not just use the cutout for the lid. So I covered the top in packing tape again and used the box as a mold for the lid and made a new lid piece using a similar process with another 4 layers of carbon. Now the lid is perfectly shaped to the top.
Next stage was to cut the opening. I used a dremel cutting wheel to do that. Then it was time to remove the foam. Here is the cut box with little acetone thrown in:
After you dissolve all the foam, you can peel off the packing tape, and the finish inside was actually much nicer than the outside.
All that was required was to drill some holes for mounting the mounting system with some bolts and also for the hydration tube. I got some nylon hinges from a hobby store (for RC places), and added some small magnets to hold the lid down (but I use a rubber band also to make sure nothing falls out on large bumps.
I'm pretty happy with the result. It is not perfect. I did sand through the epoxy in a few spots which you can see as it loses the gloss. I may one day give it a clear coat which would sort that out, but I want to use it a bit first and see if I need to make changes.
I hope this helps anyone thinking of doing something similar!
