Vacuum infusion problem in corners

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#1

Hi to all,

Last month i infuse a 10m hull rib.
I use about 12 layers fibre like csm and triaxial.
When i start to set up the first layers in the mold were ok. In the middle of the fibres i can’t adjust very well the triaxial in the corners with result in the last layers have big problem.
The problem became bigger when i vacuum the bag, the layers adjust in the flat points and in the corners was empty because of the traction.

Any idea how to solve this ?

Thanks

Regards

George

#2

Yes, this is a lay-up problem. Few options you could do:
Be more careful placing the layers into the corners
If its difficult cloth to manipulate, design ply sizes differently so that you arent putting the cloth into two consecutive corners.
Cut plies and locally re-inforce
Ensure there is no bag bridging
Use intensifiers

Any photos?

#3

If I understand, you are getting bridging in the corners? Do you have CSM in those corners?

#4

Thanks findhan,

Yes the problem is the fibre bridging in the corners.

I send some photos in about two days

Thanks for your reply

George

#5

Dear ASB,

The fibre reinforcent is about 60% csm. (225,300,450matt)

Ι have put only 2 layers of 900 triaxial between these csm’s

I’ll upload photos during the week

Thanks

#6

It is difficult to get CSM to sit tight into sharp corners when you are drystacking. If you put a stitched fabric or cloth over the CSM it will naturally bridge the corner because the CSM will stop it from sitting tight into the corner.

#7

As i can understand ABS it’s better to use cloth fibre than csm ?
Also the csm matts are not suitable with vacuum infusion

Am i right ?

You thoughts about what kind of fibre can i use than csm ?

Regards

#8

Which resin are you using?

#9

I use simple polyester resin for vacuum infusion, not vinil , not epoxy

#10

Is the polyester resin anything special? Isn’t it too thick and doesn’t it cure too quickly?

#11

I thought you couldn’t infuse chop strand mat to begin with? Or am I wrong.

#12

You are using a high tech method ( resin infusion ) that requires considerable expense in equipment and consumables, and a great deal of experience to infuse large hulls. But CSM is the lowest cost, and lowest performance reinforcement. On top of that CSM has some drystacking issues as already mentioned. It is hard to go past Biax and Double Bias. Triax and Quad are fine for big flat panels, but can be challenging to drystack in hull panels with strakes and chines. a 600 biax and a 600 double bias are generally easier to drystack than one 1200 quad, with the same resultant fibre orientation.

#13

That depends on the kond of stitch. I have a 1100 Carbon IMS65 NCF that is very easy to drape and a 400 biax that is nearly undrapable.
His problem is a leak in the setup, first it was ok and then he had air in the corners. Boat builders call it spring back, but it is simply a leak and poor vacuum setup.

#14

DDC. That is not what he said in his first post. I’d suggest you read it again.

#15

It’s a simple polyester not something special.
Of course is too thick to vacuum

regrads

#16

Dear ASB,

For your opinion it’s better to put a 1200units infused quartaxial than 2 times biaxial 600units ?

Thanks

#17

You can make silicone RTV 90 degree angles or tight round angles to use in the process to properly push the fiber down tight prior to bagging or infusing?

#18

He wants to say that it is easier to place two layers of 600biax than one 1200 quadraxial. CSM is always hard to place and fix in the corners, if possible try to use wooven or non crimped fabrics.
Have you used spray adhesive to hold the fibers in place?

#19

Not in my experience George.
I make a lot of test panels before I build a new boat. One of the purposes of those tests are to determine how the proposed laminate schedule with stack and infuse. I have test moulds that replicate areas of the hull mould that has corners or overlaps. Eliminate unforseen problems during your tests.