If I do use spray adhesive, I go VERY lightly and press more.
Doe…nice Tig welds by the way ! Let me know when you want to knock out a few for me ( De-gass and pot chambers), 
Well I made the real thing finally, but unfortunately I had some issues with the finished part.
Anyhow, here is the process.
-
Scribe trim line into mold
IMG_5610.jpg by Kevin_Doe, on Flickr -
Wax the mold, 4 coats of Meguiars Max Mold release.
-
Lay in 1.2 oz/yd fiberglass, plain weave. The idea for this was to provide a finer layer on the surface. The glass can also be sanded easier if necessary.
IMG_5615.jpg by Kevin_Doe, on Flickr -
Lay in two layers of 5.9 oz/yd 2x2 twill weave carbon fiber, first at 0/90 then at -45/45.
IMG_5616.jpg by Kevin_Doe, on Flickr -
Place 1/4" divinycell foam core mat. I drilled 3/32" holes on a 2" grid. This is a slightly tighter grid than I used on the all glass test panel.
-
Lay in 4 additional layers at 0/90 for additional stiffness on the mounting flanges.
IMG_5617.jpg by Kevin_Doe, on Flickr -
Lay in two more layers of carbon, at -45/45, then 0/90.
IMG_5620.jpg by Kevin_Doe, on Flickr -
Peel ply
IMG_5621.jpg by Kevin_Doe, on Flickr -
Infusion media
IMG_5622.jpg by Kevin_Doe, on Flickr -
Spiral Tubing and Vac bag
IMG_5623.jpg by Kevin_Doe, on Flickr
IMG_5624.jpg by Kevin_Doe, on Flickr
IMG_5625.jpg by Kevin_Doe, on Flickr
The infusion seemed to go great. No real issues. Yesterday I pulled off the vac bag and consumables. The part looked great. Then when I demolded today the surface has a lot of porosity and dry spots. Looks like the dry spots are only in the glass surface layer but its hard to tell for sure. The dry spots are 2" apart, meaning it certainly had something to do with my hole spacing in my foam core.
I cannot just toss this piece and start over, since I’ve gone way over my anticipated budget already. What is the best course to fix the spots? I have a few ideas.
- Sand through the fiberglass down to the carbon and hope the carbon was fully wetted out. If that is the case, I will just clear coat part and all will be well.
- Paint on some epoxy and use a heat guy to help it flow into the voids and pull out the air bubbles. I’m not confident this method will work. There is wax probably transferred to the surface, plus I don’t know how well the resin would wet out the cloth.
- Fill in with glazing putty and paint. I’d rather showcase my hard work, so this will be a last resort.
Any ideas, I’m open!
Or another option. Sell it as is, and make another.
Most importantly, what went wrong?
Looks like your infusion was a bit quick, how long did it take to infuse? There a several ways to do this, you can either crimp the line slightly (meaning don’t fold it over) there are line breaks/pinchers you can get, I wish I had a picture…I am at home and they are at the shop, they basically pinch the line to reduce the amount of flow. I picked them up from Princess Auto in Canada (where I am).
Edit: http://www.princessauto.com/pal/product/2990414/Engine/2-pc-Hose-Pincher-Set
^ I use those to slow the flow down when needed. The other method is to create resin breaks in the flow media, this is where you would leave a section intentionally without flow media, I never go bigger than 1.5" when I do it, on a part like yours, I might put 3 in evenly spaced. Thats another option but I have found it can cause small bubbles where it traps.
Last option is to reduce your resin infeed line, are you running 3/8" or 1/2" lines? Others will post come recommendations as well…Mould looks nice by the way! 
I used 3/8" resin inlet, pinched down significantly to slow the resin down. The total time for infusion to complete was about 40 minutes. The part with flow media over it took approximately 10 minutes. Went pretty slow. I did have a small hole in the bag that took a few minutes to find. It was right near the resin inlet line and was distributing air bubbles throughout, which made it tough to find the source. I ended up finding it and plugging it, then all the air was removed and all seemed well. I suppose this could be the issue, but not sure.
The dry spots look focused to one end of the part based on the pic, is that case?
The dry spots are concentrated in one area.
I fed with a manifold of spiral hose down the middle. I placed an additional strip of flow media along the center, about 4" wide to help distribute. The spiral manifold was 3/8" OD, a bit smaller than I’ve used before. I noticed that the resin did not flow across the manifold/media all that quickly. I expected the resin front to flow from across the manifold quickly, then spread evenly from the center outward. What I saw was a teardrop shaped resin front. Hard to explain, but you can see it in one of my pics if you look closely.
Yea, I see what you mean now…may I ask why the manifold? Just run a spiral line the width of the part on one end and sprial vac on the other…easier that way KD, plus it is a controlled flow in one direction. Your issue with the dry spots was based on saturation, we know you had good vacuum, no holes (even the one mentioned won’t cause that), a slow enough infusion, your lay-up was not an issue, but the resin did not saturate through the laminate skin layers.
It is plausible the manifold method allowed the resin to run quick through the center of the part, only to cause traffic for the subsequent feed of the resin so to speak. The key is maintain an equal and always consistent feed rate that saturates the laminate skins (fabric) at the same rate from the beginning to the end.
On your next one, try just running vacuum from one side, feed line on the other, lay-up as usual, flow media from one side to the other on the entire part (minus the flange), pinch your line 1/4 the way of width and see if it results in a better infusion.
Why feed in the center and draw vac on the perimeter? I’m not sure what exactly lead me to that decision. I was thinking that it would yield a nice even flow front, from center outward.
When you say pinch the line 1/4 of the way of width, what exactly do you mean? You’d pinch off the feed line before the resin reaches the other side?
Would you say it would make sense to feed from one flanged end, across to the other flanged end. That seems like it would be quite a long path for the resin to travel, but maybe that’s better than what I’m currently doing.
Kevin…is there ANY chance that fiberglass has a coating of some kind ? If it did…saturation may be inhibited if the resin of choice is not specified to THAT coating.
Just a thought. Your off to a good start.
Save the part by sand blasting the voids with quartz sand. Clean well and carefully apply resin in the low spots, let dry and flat-stick sand then clear coat the whole exterior with good quality automotive clear. Wetsand and polish to rave reviews !
I think you may be onto something. I looked at it closer and there are undersaturated spots even where there is no core. Seems like the fiberglass just didnt want to wet out like the carbon did. Seems like the carbon is fully saturated but the glass was more resistant to the resin flow. Could be from it being a plain weave or maybe a coating. The glass i used was over 10 years old. I had it leftover from a project i was working on back arould 2000. No idea about any coating applied. I think i will go without it on the next try.
The finish on the glass definitely has a life span. Glass finishes that are “spent” will show a reduction in wet-out ability and a reduction in interface strength between the fibers and the resin. It’s best to store the glass in sealed plastic to extend the shelf-life of the finish.
I don’t know if that was the problem though.
I sold this carbon one with the blemishes. I’ll get another chance to do it right. I’m happy.
Thats great news! all this work, you deserve a nicely finished piece!
Keep us all posted!
Success!!! Thanks for all the help everyone. I’ll post an update as to what I did different as some point later on.
For now, just a quick camera phone pic. Now one question: Do I need to have it cleared? The Adtech 820 resin says that it is UV stabilized.
Nice! It would probably be best to clear-coat it.
BTW, you were wondering how to calculate the thickness for a given amount of fiber and Vf. Here is a thread where I posted the math.
Here is what I did different.
- Holes, 1/8" dia, 1.5" square grid, offset. Previous was 2" square grid.
- Grid scored the mold side down surface of the foam, to create flow channels.
- Double foam thickness on long edges. This was to stiffen up the part in that direction. 1/4" thick foam on entire top surface, and 1/2" total thickness on edges. I blended them in to help the fabric lay out easier.
- No fiberglass cloth on surface.
- Degassed resin until no more bubbles, approx 40 minutes (premix).
- No spiral distribution on resin inlet. I just used three layers thick flow media as the “manifold” down the middle of the part. This was to avoid the print of the spiral manifold.
- Semi perm release, Frekote 770NC.
Infused perfectly, nice slow and even flow. The part came out with extreme ease. Previously I was using all 10 of my wedges and a lot of force. This time one wedge and it nearly fell out of the mold.
I cleared it and wet sanded and buffed it. I’m super happy with how it turned out. I can’t wait to delve into my next project.
IMG_5781.jpg by Kevin_Doe, on Flickr
IMG_5783.jpg by Kevin_Doe, on Flickr
IMG_5862.jpg by Kevin_Doe, on Flickr
IMG_5869.jpg by Kevin_Doe, on Flickr
IMG_5872.jpg by Kevin_Doe, on Flickr
Very nice. Are you guys degassing your epoxy before you add the hardener? Main reason I ask is my epoxy Artech 820 doesn’t give me enough time to degass after mixing.
I am using the medium hardener. I also don’t have time to degas after mixing. I degas the resin and the hardener separately, then mix. I have tried degassing again after mixing, for about 10 minutes and didn’t get any bubbles so I assumed that mixing didn’t really introduce any bubbles. I mix manually with a stir stick and try to avoid creating any bubbles.