Problems with bridging on intricate mold

[20_rc51_00]

I have a mold of my chain guard and I have spent some time practicing the infusions with glass, but I am having difficulty eliminating the bridging near the really curvy parts ie. around the mount bosses. I tried to pull partial vacuum and then massage the glass layers into the curved parts by hand but it still seemed to have bridging issues.

I am using a old fridge compressor for my vacuum, and it is doing a real nice job of evacuating the air and maintaining a good vacuum. I had 4 layers of ~3oz glass, peel ply and the red resin flow media, I’m thinking that all this stuff when finally in the mold creates quite a bit of bulk and prevents the bag from properly pulling the layers into the tighter areas.

Any suggestions on what to do to solve this problem?

[luisn]

well first off… you need some sort of surface coat / gelcoat … something much smoother then what your putting which is just either epoxy + fabric, or ES resin and fabric. if using epoxy, find a good surface coat, if ur using ester then find a “tooling” gelcoat. then when applying in tight areas… find out how thicken your resin in some areas then lay fabric… or add some chopped fiber glass, NOT CSM and moosh it all up to create a good colgate type consistancy… then lay it on good.

[riff42]

Really, more bagging material and more pleating (slack)…
Bridging is normally caused by areas where the bagging material is pulled tight around a negative area. If you have more material that will suck down into said negative area, it won’t bridge.

at least from my experience…

[system]

also lay your peel ply in strips, that may help as well because most peel plys don’t strech and that could cause it as well

[BazNos]

Preventing bridging is all down to getting the first layer in the mold in perfect contact with all the mold surfaces.
I use various little tools to do this but you must make absolutely sure this layer is perfect. Dont try laying all other layers in one piece but rather use smaller pieces this way you wont run the risk of pulling the first layer off the mold. Do the same with the peel ply and make sure this goes into every part of the mold using whatever tools needed. Dont rely on the vacuum to move all the layers of fabric and peel ply into all parts of the mold as this will not happen, use a little tac spray on all layers including the last layer before the peel ply. Make absolutely sure the bagging film is not bridging, i can pull and release a vacuum several times before i am happy i have achieved this. I will also run my finger around any awkward parts just to make sure i have full contact of the bagging material. You can also use a heat gun on these awkward little places just to make sure the bagging is in there but go easy with it if you use this method as you dont want the bagging forming around the infusion media and preventing resin flow.

Follow these steps and bridging will be a thing of the past.

Baz

[hybridracers]

First off let me say you chose a really intricate part as a first part…so congrats you got that far!

I still get problems with bridging and it drives me nuts but I too through process of elimination, have ended up doing the sectioning and the extra slack in a bag.

Youll find that it works much better…

The next thing youll have to tackle is what I go thru…finding the best place to lay your inlet line so you can get proper infusion.

I did some triumph parts the other day and they were a disaster the first time thru the mold. We shall see later on.

[luisn]

what i have also done, is worked in layers. 2-3 layers when molding. i KNOW ill get briding and what i usually do CAREFULLY is take a dremel and cut so the hole is exposed. the next layers i had a goop of resin + fiberglass (which i cut with sissors really small and fine ) and make it into a puddy + CSM in those holes. fills in good, strong and i can then pop the part out later. the mold is strong and can take a good hit.

[system]

interesting, I am going to have to give that a try

[luisn]

be careful not to hit your surface coat / gel coat.

[20_rc51_00]

thanks guys some excellent tips!

As far as extra pleating goes, I’m pretty sure that it wasn’t the problem, I REALLY went nuts there!

anyways, good tips!

[fz1gpt]

Preventing bridging is all down to getting the first layer in the mold in perfect contact with all the mold surfaces.
I use various little tools to do this but you must make absolutely sure this layer is perfect. Dont try laying all other layers in one piece but rather use smaller pieces this way you wont run the risk of pulling the first layer off the mold. Do the same with the peel ply and make sure this goes into every part of the mold using whatever tools needed. Dont rely on the vacuum to move all the layers of fabric and peel ply into all parts of the mold as this will not happen, use a little tac spray on all layers including the last layer before the peel ply. Make absolutely sure the bagging film is not bridging, i can pull and release a vacuum several times before i am happy i have achieved this. I will also run my finger around any awkward parts just to make sure i have full contact of the bagging material. You can also use a heat gun on these awkward little places just to make sure the bagging is in there but go easy with it if you use this method as you dont want the bagging forming around the infusion media and preventing resin flow.

Follow these steps and bridging will be a thing of the past.

Baz

+1
for bag bridging you can also use the stretchlon bagging film, but make sure you get the thicker stuff (pink/orange) if you use PER or VER.

[Fastrr]

I have a mold of my chain guard and I have spent some time practicing the infusions with glass, but I am having difficulty eliminating the bridging near the really curvy parts ie. around the mount bosses. I tried to pull partial vacuum and then massage the glass layers into the curved parts by hand but it still seemed to have bridging issues.

I am using a old fridge compressor for my vacuum, and it is doing a real nice job of evacuating the air and maintaining a good vacuum. I had 4 layers of ~3oz glass, peel ply and the red resin flow media, I’m thinking that all this stuff when finally in the mold creates quite a bit of bulk and prevents the bag from properly pulling the layers into the tighter areas.

Any suggestions on what to do to solve this problem?

Yeah… give the finished chain guard part to me That would fit my CBR900RR beautifully