Infusion Help needed (

[jestah]

I would really like to try resin infusion as i feel this will be a positive progression and help reduce my exposure. I am a self taught back shed board builder so please bare with my limited knowledge.

I have read over most of the reading i can find around the web and am confused about the use of uni in infusion. Some say that the fiber can compact closer together and hinder resin migration and this is combated by using CSM backings But in others suggest that uni can also be a good way to move resin along its length.

I am also unsure as to WHEN you should use flow media. One part of me thinks its a good way to get resin across a part quickly or it is used to move resin to a line from which a resin front will move outward from.

Here is what i would like to infuse by late july:

http://www.boatdesign.net/forums/sho...042#post143042

While it is quite simple i think i should start with something a little simpler. My first infused board will be flat nose to tail with 8mm of concave rail to rail. I plan to make a simple mold by carving a thick sheet of mdf and then glassing with some cloth and sanding fair. These are just prototypes and i am not expecting any thing more than a peel ply finish on ether side so cheaper/faster mold suggestions are welcome.


The board will be from deck down:

Fiberglass uni 0 degrees
12mm Balsa core 1.05*0.260m
400g Fiberglass double bias
Fiberglass Uni

The core is mostly balsa but it has a 15mm rail of marine ply that it is set into. It is also cut from nose to tail into 2 long pieces and between these a layer of uni is "woven" over the first under the middle and back up over the second forming 2 12mm tall fiber "stringers" (as in a surfboard. is this the right term?)

The part is no wider than 260mm so I'm hoping to be able to infuse across the width of the board by using spiral tube wrapped in peel ply run down each side. I have accounted for a thiner laminate and added 2mm to the core. Should i use some form of transfer medium over the laminate or should laying the spiral tuble onto glass that will be trimmed away later be sufficient. The balsa core says it is treated to reduce resin intake but is there any way i can reduce it more? How should i be perforating the core to make sure i get an even resin flow on both sides of the core as i am very worried that the uneven skin lay up could see one side being much more restrictive that the other. Now if this works should i expect similar results if i change to carbon fiber?

Now for the real kicker... How much vac do i need to be pulling as right now im using a fridge compresser riged up to a vac switch that cycles it on and off. I know that this cycling will not be good for the infusion so i have tested a pump to run continiously at 26-27"mg for 8 hours and its fine... hot but fine.

thanks in advance
Jestah

[JRL]

Cant really help you much on the contruction part. But just some advice.

Continuous Strand Mat will aid in resin movement. Chop Strand Mat will kill it.

Use as much vacuum as you can possibly get. Theres no such thing as to little. Ideal would be 29". Ive had no problem infusing small parts with 25".

I also recomdend using a resin in the 400 to 200 cps (viscosity) range. I infused some radome covers that looked like a top hat using 8 layers of 8.8oz satin weave E-glass (very tight weave). In some places it was upwards of 13 plys thick. The parts came out air free. That was with epoxy that was 350 cps. Ad-Tech 820 with medium hardner. Love the stuff. Its solvent free also.

Use flow medium almost every where you can get it. Try not to use it on joints. And dont overlap it. Overlapping will create a lot of very small bubbles and disperse them through out the part. Found this out though a series of trial and errror. The elimination of overlapping was the only thing that made the small bubbles disappear.

Ive been using green flow medium from Airtech. Enkafusion is the "fastest" flow medium available. Its also the most expensive. There is another brand that sells this blue medium thats pretty quick also. If I remember Ill edit this and put it at the bottom of the post.

A lot of guys speak against using Stretchlon 200 bags for infusion. The problem is that its not VE/Poly friendly. It does work well with epoxy. I personally like it because it pulls itself between the flow medium, which to me means less voids, more pressure. Thicker nylon/poly bags tend not to. Stretch 800 works well if you have a strong pump....I dont.

For your core I would look into infusable cores. Like Diabs Dyvinimat. Or scored balsa. Your gonna need something to get the resin past/over/around the core.

And to avoid a resin rich part cut your resin off when your part is about 75 to 80 percent infused. Its a little scary the first time you do it, but the resin will keep flowing. If you wait to long to clamp the resin line you will loose the clamping/pressure from the vacuum. Plus you risk sucking resin into your pump.

Vacuum plays an equally important role in which way your resin travels. On my top hat looking radome covers I put the resin inleat on the top of the dome. And surrounded the base with a loop of spiral wrap. The resin was pulled from the center, out.

Ultrasonic leak detector is a gift from god. Untill you use one, you dont know what your missing (leaks).

[jestah]

What about uni cloths... do they aid resin flow? and if so is the flow sent along the length of the strands or parallel?

What is flow media supposed to be used for? I was guessing it was used to move a resin quickly to the edge of the fabric to make an even resin front that would then be pulled across the fabric but by you saying i should cover the part as much as i can i don't think i was correct. Can you please explain why you want to cover lots of the part as to me it seem this would create an easy path for the resin to skip over the part.

Here is a quick drawing of the cross section of my board:

http://farm1.static.flickr.com/200/5...984b53.jpg?v=0

have i got this right? should i kill the flow media before the resin outlet? I can also see that introducing the resin in the middle of the board and pulling it to the outside will cut the resin travel distance in half but wont it leave an imprint on the board? I have seen a shop using peel ply as flow flow media once to make a very tall stack of glass (30-40 layers of 200g dlb bias i think) they put peel ply from the resin inlet up over the edge of the stack then took it to about 30mm from the opp edge. Then on the under side another strip ran from 50mm UNDER the glass stack out and then to the vac line. Can some one explain why they did this

Thanks for all the tips, its pure gold to learn from others than have to remake LOTS of board and then later on find out the expensive way If i cut the resin off TOO soon can i reopen it if the pot has not gelled yet?

Thanks once again
Jestah

[jestah]

What about uni cloths... do they aid resin flow? and if so is the flow sent along the length of the strands or parallel?

What is flow media supposed to be used for? I was guessing it was used to move a resin quickly to the edge of the fabric to make an even resin front that would then be pulled across the fabric but by you saying i should cover the part as much as i can i don't think i was correct. Can you please explain why you want to cover lots of the part as to me it seem this would create an easy path for the resin to skip over the part.

Here is a quick drawing of the cross section of my board:

http://farm1.static.flickr.com/200/5...984b53.jpg?v=0

have i got this right? should i kill the flow media before the resin outlet? I can also see that introducing the resin in the middle of the board and pulling it to the outside will cut the resin travel distance in half but wont it leave an imprint on the board? I have seen a shop using peel ply as flow flow media once to make a very tall stack of glass (30-40 layers of 200g dlb bias i think) they put peel ply from the resin inlet up over the edge of the stack then took it to about 30mm from the opp edge. Then on the under side another strip ran from 50mm UNDER the glass stack out and then to the vac line. Can some one explain why they did this

Thanks for all the tips, its pure gold to learn from others than have to remake LOTS of board and then later on find out the expensive way If i cut the resin off TOO soon can i reopen it if the pot has not gelled yet?

Thanks once again
Jestah

[JRL]

On your part you would want to infuse it exactly like your cross section picture.

Resin moves REALLY slow when its not aided with flow medium. If you were going to infuse with out it you would have to carefully layout several resin inlets instead of just one.

Your definition of what FM does is right. The reason I say to cover as much of the part with flow medium as possible is that it eliminates any chances of resin not traveling to that area. If you use AirTechs green flow medium you wont have any problems with the resin moving too fast.

You can eliminate flow medium in certain areas after you learn how well resin travels to them. Like if one area is moving way faster than the others you will want to cut back the FM in that area. Last thing you want is resin hitting the vacuum outlet when there is still un-infused cloth. And definitely end the flow medium before your vacuum outlet. Resin will have no problem traveling the final 2" unaided.

And yes you will get a pressure dent on the part if you put the resin inlet on the part itself. The only reason I did that is that it was the most effecient way to infuse those parts I was making.

Heres a couple videos. The airtech one in my opinion is overkill.

AirTech

http://www.youtube.com/watch?v=noRRQ_1BMtQ

This one was done by the former owner of Compositesfab.com
He achieved the same results with much less flow medium, and noticed how he had completley different vacuum/resin line setups. I emailed him about this video due to all the bubbles in the close up shots. He said the resin he uses is very gasey. Im still not convice he didnt have some kind of leak. None the less his method still works well.

http://www.youtube.com/watch?v=Bzi-IMiu_J0

[jestah]

What about unis... do they aid resin flow? and if so is the flow sent along the length of the strands or parallel? im asking as i was wondering if it is more effective to put the double bias above or under the uni.

Ok i think i have clicked to what your saying about the FM. Im planning to make this laminate:

http://farm2.static.flickr.com/1155/...e328d0.jpg?v=0

The board is 250-270mm wide so I hope that i should be able to go from one side to the other to avoid the pressure dent. The board is going to be around 950mm long so do you think i will need more than one resin feed into the spiral wrap that will run the length of the side of the board?

As for my mold i was planning on making a FG mold but then realized that i will only be taking one or maybe two pulls from it so what about surfacing some mdf forms with a sheet of acrylic plastic then wax and mold release that?

[JRL]

Uni's will aid in resin flow. Like you said, the resin will travel the direction of the cloth. And have less flow in a perpendicular direction. But thats what flow media is for. To aid resin movement in EVERY direction.

I really cant see why the resin wouldnt be able to travel a yard. Most hoods are around 950mm long. They normally use one inlet and one outlet.

I could see your cores slightly disrupting the resin flow though. Your gonna have to do several practice runs to get your resin flowing right.

As for your plug it sounds like it would work. I use MDF and Marine filler on a lot of my plugs. White melamine is nice for flange material. Dont forget to make large flanges....6" or so.