+x

 

Andrew R - 1/21/2021 1:15:44 AM

+x

 

Warren (Staff) - 1/20/2021 9:50:20 AM

For the final layer, use a 2x2 twill fabric with the overlap/seam on the underside out of sight.  Most decent epoxies will go to around 80C with a post cure which should be fine for a cold air pipe like that in an engine bay.  That way you can use a good quality coating resin on the surface to give a smooth finish.  The resin can be sanded then polished or lacquered much like you would with skinning. 

Thanks that's what I ended up doing, putting the seam more on the underside.  Frankly it looked better BEFORE I wet it and bagged it - maybe it wasn't even necessary to vacuum bag it ?   FWIW the smaller end of the pipe is millimeters away from a turbo charger, which will get very hot so I do have some heat to consider. 

Tacked down, perfectly smooth:

After bagging, with some mild veins/wrinkles.  How can I improve?  Not enough resin?  Poor vacuum? 

+x

 

raygun - 1/31/2021 4:27:03 PM

+x

 

Andrew R - 1/21/2021 1:15:44 AM

+x

 

Warren (Staff) - 1/20/2021 9:50:20 AM

For the final layer, use a 2x2 twill fabric with the overlap/seam on the underside out of sight.  Most decent epoxies will go to around 80C with a post cure which should be fine for a cold air pipe like that in an engine bay.  That way you can use a good quality coating resin on the surface to give a smooth finish.  The resin can be sanded then polished or lacquered much like you would with skinning. 

Thanks that's what I ended up doing, putting the seam more on the underside.  Frankly it looked better BEFORE I wet it and bagged it - maybe it wasn't even necessary to vacuum bag it ?   FWIW the smaller end of the pipe is millimeters away from a turbo charger, which will get very hot so I do have some heat to consider. 

Tacked down, perfectly smooth:

After bagging, with some mild veins/wrinkles.  How can I improve?  Not enough resin?  Poor vacuum? 

Side note: the cold side (compressor housing) of a turbo really doesn't get that hot. I'd be really, really surprised if it got anywhere near 80C (176ºF). The incoming air as well as the cooling system block between the turbine and compressor keep that side relatively cool.
Now, the hot side (turbine) is another matter entirely. That thing will literally glow under the right circumstances.

+x

 

Hanaldo - 2/1/2021 2:05:16 AM

+x

 

raygun - 1/31/2021 4:27:03 PM

+x

 

Andrew R - 1/21/2021 1:15:44 AM

+x

 

Warren (Staff) - 1/20/2021 9:50:20 AM

For the final layer, use a 2x2 twill fabric with the overlap/seam on the underside out of sight.  Most decent epoxies will go to around 80C with a post cure which should be fine for a cold air pipe like that in an engine bay.  That way you can use a good quality coating resin on the surface to give a smooth finish.  The resin can be sanded then polished or lacquered much like you would with skinning. 

Thanks that's what I ended up doing, putting the seam more on the underside.  Frankly it looked better BEFORE I wet it and bagged it - maybe it wasn't even necessary to vacuum bag it ?   FWIW the smaller end of the pipe is millimeters away from a turbo charger, which will get very hot so I do have some heat to consider. 

Tacked down, perfectly smooth:

After bagging, with some mild veins/wrinkles.  How can I improve?  Not enough resin?  Poor vacuum? 

Side note: the cold side (compressor housing) of a turbo really doesn't get that hot. I'd be really, really surprised if it got anywhere near 80C (176ºF). The incoming air as well as the cooling system block between the turbine and compressor keep that side relatively cool.
Now, the hot side (turbine) is another matter entirely. That thing will literally glow under the right circumstances.

Mmm no, it most certainly can get very hot. Ive got logs from my race car showing the intake charge out of the turbo gets as high as 170° C, this is why we have intercoolers. Just because the turbine side can get up over 700° C doesn't mean the compressor side isn't also very hot.

The intake pipe going into the turbo doesn't get quite so hot, but it will still see up over 100° right at the inlet. Ive got a carbon pipe on mine that I made with pre-preg cured at 100°, and it has done fine but is severely yellowed on the last 50mm next to the turbo, and you can see the pressure from the hose clamp on the silicone joiner distorted it a bit. So definitely still gets hot.

+x

 

Hanaldo - 2/1/2021 2:50:18 AM

Yeh I would definitely use pre-preg, but for several reasons not just the temperature resistance. Pre-preg is much easier to get a good result with, and very consistent. I've actually just sourced a higher temp curing pre-preg than X-Preg because I make charge pipes which do see a lot of heat pre-intercooler, and the 115° capability of X-Preg meant I had to make the pipes a lot stronger than they really need to be just so that they could cope. 

I understand pre-preg is a massive investment for people as well, so if you aren't in this for the long haul where pre-preg would be worthwhile, then I would recommend atleast using a high temperature laminating epoxy like Easy Composites EL160. You could use that resin in the process you are doing now, though if you are making more than one then a mould is a great idea. Moulds are not hard or expensive to make for components this size, and there are several ways to incorporate the bungs. Ive just finished some tooling for some reasonably complex piping myself: 




I say 'reasonably' complex because each pipe was still only a 2-part split mould. Some pipes may require being more pieces if its own geometry becomes a lock. Buts its all quite simple and certainly this first pipe you've done would not be an outrageously difficult mould to make.