Infusion vs. Open Mold (for a Novice)

General Composites Discussions Composites Talk
#1

Hello Everyone-
I am a complete novice, and new comer to this forum. I have done some basic, in the garage type, of fiberglass work, with good success. Lately, I have become enthralled with the idea of vacuum bag infusion. I have read and watched videos extensively on the process and have learned a great deal. After watching many videos, and seeing how effortlessly some of you pull parts I am left with what I am afraid is an unrealistic level of confidence that I can replicate the process.

I have this project in mind that involves carbon fiber. I do plan on practicing on some small components to get the technique down, but after pricing everything out I am realizing that the startup costs are quite a bit higher than what it would be to just open mold cast.

Which leads me to the following question…

Although an infused product is superior to an open mold cast (assuming the infusion is successful) how much better is it really?
The reason I ask is I am about to plop down the money to purchase enough material a few practice runs and then my project, which is a big piece. I would really hate to find out that I had failed at infusion for one reason or another with that much money on the table. At the same time I of course want the best possible finished product.

I am not trying to sell my finished product. I just want a strong light weight finished piece. If you were me, would you take the gamble with infusing, or would you go with open mold?

Thank you in advance for your response and time.

#2

A proper made infused part is to prefer to a contact lay up for the following reasons:
On a same weight basis, the infused part is stronger because you have more % of fibre and no voids.
It allows you to make sharp corners and intricate details without the need and the risk of resin rich areas (on thin laminates).
No smell around.
Cleaner.
Maybe more but that’s what I have in mind now.

#3

Are you going to be vacuum bagging your hand layup?

#4

Thank you for the responses.

No, I was not inquiring about vaguum bagging the hand layup.

I am now realizing the error in my questioning the difference. I’ve done more research since I posted this. I now know for certainly I do want to vacuum infuse my product. I am just afraid of botching it when I get to the big piece.

Hopefully when it comes time to to pull the trigger I could query you fine folk for some advice during the process.

#5

Infusion is a learned talent. I did various dry run tests, first learning how to do pleats and bagging on a piece of acrylic, dealing with hoses and clamping, etc., until I was able to do it and have no leaks. Then I did the same with a piece of reinforcement. Learning how to weigh, mix and manage the epoxy. I did a couple of these. Each with a different objective. Some I did with my acrylic “mold”, others in the live mold with it’s curves. It gets really expensive really quick if you don’t take these baby steps. I think I’ve made every dumb mistake there is to make!

The marvelous thing about the infusion process is that you must get everything prepared before you finally commit to the infusion, but that preparation must be near perfect if you want near perfect results. --And practice makes perfect!

#6

Benefits of vacuum bagging - Thinner part, stronger part, better resin to fiber ratio, neater part, better chance of even weight distribution, lighter part overall, less pin holes if any, far less air in a part.

Benefits of wet layup with no vacuum bagging - Its fast, easy, and that’s about it.

However, I believe the cons of wet layup with no bagging far outweigh the benefits of fast and easy.

For example, we have some colleagues that manufacture sport cars. The company that manufactures the body panels use a wet layup. As a result, when the car is being assembled, every car has to be corner weighed in order to adjust the suspension to be even. Each car is different, each corner is different.

#7

Vacuum bagging a hand layup does nit make sencse. You have the same work than with infusion and your result wil never be perfect!
By vacuum bagging you will always have pinholes and voids and it is hard to controll the fibre to volume ratio (VF).
By a classic wet layup without compressing/bagging it you can get very good optical results ( if you have years of experience) but never a light and stable part. You wil have a max VF of about 40%, realistic is 30-35%. No sharp corners can be made ( but if possible never make sharp corners) and you will have voids in the laminate.
It no clean work and you are not able to stop and drink a coffee if you started once.

With infusion you can get perfect results, that is not impossible and you will get a lot of help here.
By infusion you can laminate sharp corners, reach a high VF of up to 60%, most times you will get 50-55%, get a void free laminate, a strong part, have time for a coffee, work clean and get a perfect finish.
An wet layup part can be stiffer because of the bigger laminate thickness but not stronger.
A small example. I have been consulting a small company producing jet ski. They had been made by wet layup and vacuum bagging before. The weight of a hull was 12,5kg. Infused with the same layup it was only 8.5 kg abd because of the stronger laminate and in combination with the goemetry it was also stiffer and stronger.
Our product the MTI hose helps to get a good quality by infusion, at least for people who started with infusion. You can find all informations in the MTI thread in product talk.

If you have questions just ask.

#8

^ The MTI hose is a great product. I use it in small amounts when I infuse. For example, if I infuse a set of Corvette door sills, (13 inches wide by 27 inches long) I will infuse with a 3/8 inch hose in between the two door sills, and vacuum through a 8" strip of MTI hose at the other side. We’ve noticed that we get less air bubbles and a stronger vacuum.

#9

Thank you all so much for the advice and help. I will be practicing quiet a bit before my “big project” and I am sure I will have a lot of questions a long the way.

Thanks again, and I am looking forward to giving this a try.