Infusion Questions

[weldandglass]

I've been wet bagging all of my parts to date but I'm about to make an order of infusion materials so I can make the switch.

I'm infusing a 18' by 5' hull and cap mold for a little skiff. I've got a hull that's near completion that was wet-bagged. I'm going to experiment with infusion on the remaining bulkheads and sole of the partially complete boat to get a feel for infusion, then start another hull and cap and do them fully with infusion. All parts are biaxial e-glass skins with H-80 divinycell core. When I'm wet-bagging, I'm using Proset LAM239 epoxy with the extra slow cure speed hardener. I'm in Texas so during the warm months I need all the extra working time to get the parts wet-out prior to pulling vacuum. I'm going to switch to the Proset INF114 resin for infusion. My gut tells me to keep working with the extra slow hardener so that I can have the luxury of maximum working time. Other than a slower cure cycle and having to wait additional time prior to demolding, are there any disadvantages to using an extra slow hardener for infusion?

Also, all the core panels in the mold are developable. With all the wet-bagging I've done, I just used plain H-80 and perforated the core myself. Switching to infusion, I'll need to order perforated H-80 but I have two areas of core towards the bow that will require perforated and scored core because there's a little bit of curvature. If I use perforated only in most of the layup and have two core panels that are scored and perforated, will this result in two different infusion rates? I want to minimize use of the scored H-80 in order to reduce resin uptake by the core and minimize weight, if possible, but if this creates issues for an even infusion I may need to look at other strategies.

Any advice would be much appreciated.

 

[fallguy]

I am a wet bag builder who wished he had done infusion. I am a limited resource at best.

A couple thoughts. Generally, xslow would be runnier and would thus flow faster which could mean areas would be harder to wet. Also, xslow often requires post curing. Hope you are aware.

I used xslow Silvertip and we had to cook our hulls. This is a bit unnerving, but we did it in a 40' ship container.

I think you need to double check on the perf only because I was always under the idea that perf alone was insufficient and you always need scoring or mesh for flow. My core was all perfed and someone told me it would NOT work for infusion two sides or without mesh or both.

I apologize for leaving you with more questions than answers and I'm curious to see if I am wrong.

 

[Chris Rogers]

Good idea to start with small stuff - infusion has a learning curve! I think you'll want a slow-ish hardener, but because viscosity is reduced as temperature goes up, the same infusion will fill faster in warm weather unlike wet layup where you need working time. Too slow a hardener with infusion tends to amplify problems like leaks and trapped volatiles so there is a down side to having a full part sit there for hours before gelling. Still, having it gel before it's finished infusing is no fun! The Proset is nice and definitely likes warm to get that viscosity down.

The curved area with the grooves is manageable, but it will behave differently. Could you thermoform it? Probably only a good idea with thin-ish core - you in the 1/2"-5/8" range?

Even if you have some varying flow rates throughout the infusion, it should be manageable with good resin breaks and a vacuum perimeter that is segmented into a few zones. Vacmobiles has a good post about it: Enhancing resin infusion with peel ply resin breaks https://www.vacmobiles.com/peel_ply_resin_breaks.html

And not to flog my own half-finished and un-edited-down article but it may be helpful - though it hasn't got any pictures yet: Introduction to Vacuum Infusion | Explore Composites! https://explorecomposites.com/articles/lamination/introduction-to-vacuum-infusion/

Good luck! Infusion is more pleasant than wet layup - but more stressful too.

 

[weldandglass]

Chris and Fallguy:
That's all really good info, thanks for the feedback. I am planning on using flow media, so hopefully perforated will work. I hadn't though about thermoforming, given the high cost of the scored core and the very small amount of curvature I need, that may be the best solution.

Regardless of all of this, I'll do some test pieces before I jump into full-scale infusion of finished parts. The main problem (and the reason for me asking in advance) is that I can't order a single sheet of perforated or perforated and scored core, 15 sheets is the minimum. As such, it's good to have some idea of what might work before I spend a couple of thousand on core material. I'll probably go ahead and perforate a couple of more sheets on dimensions that match the factory perf'd core (as I've done i the past), experiment with thermoforming and then run some test infusion before I order any more core. I have about 15 sheets of 1/2" plain divinycell sitting in the shop so I'll make some test pieces and go from there. Thanks for the input.

 

[fallguy]

15 sheet minimum? How about Noahs in Toronto?

where on the gulf coast?

I might move there.

 

[weldandglass]

I'm in a small town close to Corpus Christi, Texas.

 

[Dejay]

I've recently heard CSM helps has a spreader medium. I've also seen you can order scoring down to 0.7mm which I assume works for infusion. But I have no experience either and would love to hear how your experiments turned out.

I'd also be curious if "extra resin" trapped in scoring and perforation add enough to stiffness and toughness to be worthwhile and not a waste.

EDIT: Looking at Chris Rogers videos sample #28 the scoring added 1.5kg/m² resin! While sample 7# worked fine without scoring and just flow mesh on one side and perforations. Thanks for those videos, they're is awesome!