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 Post subject: Re: Carbon fiber lay up
PostPosted: Sat Apr 12, 2014 11:59 am 
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Joined: Sun Feb 12, 2006 8:16 pm
Posts: 389
Location: Kettle Point Ontario Canada
Thanks Johnny.. you are right on about the mix ratio and the percentage of resin... too much is not good , not enough is not good.
A lot of people do not measure the weight of the material before mixing the resin to get the percent of resin needed.

I am going to do a wet prepreg layup for the molds.

The resin I use is forrest epoxy. It starts to flow nice at 105 degrees.. So I will have my caskets in the press with the layups.
Heat them to 105 for 15 mins and 30ton to get a nice flow, then at the 15min mark will take it to 180 for 45mins and 60ton . then step it down over an hour for cooling stage.

I hope I put enough weeping channels in the molds. In the model airplane world they always put a channel lead edge and trailing edge of shape pieces so
you can finish out a sharp profile.

I am the type of person if someone says I can't do something I am going to give 110% and prove that I can. Then if I fail I can say at least I tried.


Terrie
www.jellyfishboards.com


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 Post subject: Re: Carbon fiber lay up
PostPosted: Sat Apr 12, 2014 1:24 pm 
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Joined: Wed Nov 20, 2002 1:00 am
Posts: 917
Location: rhode island
@TPink
one additional thought that no one has mentioned.

how secure is the joint between top-plate and your strut?
(...or the way its secured to the wall, or the wall panel itself ?)

you may have lots of deflection in this region which negates or hides any proposed improvment to your strut layup.

for comparison purposes, you could repeat your experiment with the strut 'simply' supported at each end and the weight placed in the middle. the new deflection should be 1/16 of the initial test.
If the new test is much different than predicted, you should look for the cause.
both tests will help give an experimental estimate of E*I
defl (cantilever)=PL^3/3EI
defl (3point-bend)=PL^3/48EI


...just a thought
-bill


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 Post subject: Re: Carbon fiber lay up
PostPosted: Sun Apr 13, 2014 3:55 am 
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Posts: 324
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tkettlepoint wrote:
I am going to do a wet prepreg layup for the molds


gotcha most of the goo can be pre-squeezed out....

Still Not quite sure how you're pressing the part though
1. You keeping the mold halves open (2 parts)
2. or overfilling both halves slightly putting the halves together and squeezing the shit out of it till it oozes out enough to be perfect(ish)
3. something else,

Looking at your mold and weeping channels, I suspect 2?
I guess to control resin content you could pre squeeze your prepreg to shoot for a 40%-50% Vf or whatever is attainable, then whatever oozes out of your mold after the layup is bonus.....

I like this process

tkettlepoint wrote:

I am the type of person if someone says I can't do something I am going to give 110% and prove that I can. Then if I fail I can say at least I tried.


......You can't do it......IT'LL NEVER WORK :wink:


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 Post subject: Re: Carbon fiber lay up
PostPosted: Sun Apr 13, 2014 8:29 am 
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Joined: Sun Sep 04, 2011 5:37 pm
Posts: 1765
TPink wrote:
...

Bille, I would NEVER rude you!

I should have paid more attn to you though. The rods look sweet and less expensive than i thought.

I'm not gonna strip anything off my foil, cause that would be more work than building a new one. But would
be interested in adding some vertical rods down the strut.

So how many? do you suggest anchoring the ends? What's best to use to fair them into the foil shape?

Thanks!!


YEA-- i know ,
It was NOT you, but thanks for the concern !!

The rods kinda need to be added IN the lay-up, right from
the onset ; on a wooden shaped wing, they can be added before the outer skin is
put on.

The strut is where the rods mostly need to be .

From out of a female mold ,
Use + - 45 carbon fibers on each side of your rods , to distribute
the rod's strength to your lay-up. That's the direction Ya need to counter
the twisting moment anyway , so your not adding much, to what should
be there already.

For a wooden wing that needs fibers to stiffen it , the rods or rectangles,
can be stuffed in a groove made by your router ; coat them with a bit
of epoxy & high strength filler, ( the span-wise stiffening, is Done). Remember
that the closer to the outer skin you place your rods, the stiffer the spar structure
becomes, ( stiffness increases by the cube of the thickness) . So much added strength
as a mater of fact, that to get to optimum , Ya kinda need a shear-web now , but that's
what the wood shape just became. In other words, a foam core is not strong enough
to be a shear-web !

Put your outer skin at a (+- 45 deg) , to control twist.

Bille


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 Post subject: Re: Carbon fiber lay up
PostPosted: Sun Apr 13, 2014 12:19 pm 
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Joined: Sun Feb 12, 2006 8:16 pm
Posts: 389
Location: Kettle Point Ontario Canada
Johnny. you are right #2 it is..will but index pins in all the holes do the molds stay together (alined in the x/y/z)
Do my prepreg wet layup. ( was thinking of putting a thin layer of epoxy in the molds first ) lay them in to roughly 1mm above the molds ,
put them togethers and press the shit out of them like you said. If 60 tons isn't enough will take it too 70tons.

I don't like the idea of bonding two pieces together afterwards a full heat cure cycle. It won't be as strong down the center as the rest of it.

I had a brain frat a while back where I was thinking of trying to do infusion and press at the same time but couldn't figure out how to suck epoxy 850mm across the mast well under the press. So I went with my first plan.

Molds are being cut right now... ( mast mold is 9 hours worth of gcodes just to cut it.) I need to buy my own cnc if I want to make different wings.. My free cnc deal might end if I keep going to him with big cuts LOL.

Terrie


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 Post subject: Re: Carbon fiber lay up
PostPosted: Sun Apr 13, 2014 12:23 pm 
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Joined: Sun Feb 12, 2006 8:16 pm
Posts: 389
Location: Kettle Point Ontario Canada
Billy knows his shit when it comes to wings and spars.... My friend is a crazy man that flys like a bird all the time even after his accident
He builds his own high end gliders and his own legs. If he says the spars will work... I am 100% sure they will.

Brotha keep up the good work and one of they days I will get down there so we can kite together

Terrie
www.jellyfishboards.com


Bille wrote:
TPink wrote:
...

Bille, I would NEVER rude you!

I should have paid more attn to you though. The rods look sweet and less expensive than i thought.

I'm not gonna strip anything off my foil, cause that would be more work than building a new one. But would
be interested in adding some vertical rods down the strut.

So how many? do you suggest anchoring the ends? What's best to use to fair them into the foil shape?

Thanks!!


YEA-- i know ,
It was NOT you, but thanks for the concern !!

The rods kinda need to be added IN the lay-up, right from
the onset ; on a wooden shaped wing, they can be added before the outer skin is
put on.

The strut is where the rods mostly need to be .

From out of a female mold ,
Use + - 45 carbon fibers on each side of your rods , to distribute
the rod's strength to your lay-up. That's the direction Ya need to counter
the twisting moment anyway , so your not adding much, to what should
be there already.

For a wooden wing that needs fibers to stiffen it , the rods or rectangles,
can be stuffed in a groove made by your router ; coat them with a bit
of epoxy & high strength filler, ( the span-wise stiffening, is Done). Remember
that the closer to the outer skin you place your rods, the stiffer the spar structure
becomes, ( stiffness increases by the cube of the thickness) . So much added strength
as a mater of fact, that to get to optimum , Ya kinda need a shear-web now , but that's
what the wood shape just became. In other words, a foam core is not strong enough
to be a shear-web !

Put your outer skin at a (+- 45 deg) , to control twist.

Bille


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 Post subject: Re: Carbon fiber lay up
PostPosted: Mon Apr 14, 2014 1:33 am 
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Joined: Thu Dec 04, 2008 1:50 am
Posts: 324
Location: No fixed address
tkettlepoint wrote:
Johnny. you are right #2 it is..


If keeping things organized during the lay up goes for shit then you can always do two open molds as a running back up plan....
I meant to ask what's up with the high temp epoxy, However, I'm now seeing the benefit.....lot's of working time to screw around getting a clean lay up before kick off. and makes for easier pre-preg....which makes sure you don't have frayed kitty hair all over the place.....you thought this through better than I did.

Smart fella... :thumb:

Once again, so you stay motivated,........It'll NEVER work :lol:


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 Post subject: Re: Carbon fiber lay up
PostPosted: Mon Apr 14, 2014 2:10 am 
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Joined: Sun Feb 12, 2006 8:16 pm
Posts: 389
Location: Kettle Point Ontario Canada
JR thanks once again...

I started my topic herehttp://www.kiteforum.com/viewtopic.php?t=2384372&p=837297

and yes this is a reason for the epoxy that I am using.. long time for a perfect layup..(hopefully)

prepreg carbon is even higher heat and I not sure if I want to go there just yet. the press will do it but 250+ degree for 6 hrs is pretty scary to me. \So this
way I know I have the working time and a great product

Terrie


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 Post subject: Re: Carbon fiber lay up
PostPosted: Mon Apr 14, 2014 8:02 am 
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Joined: Sun Feb 24, 2008 6:15 pm
Posts: 240
Location: France
T K wrote,

"Billy knows his shit when it comes to wings and spars.... My friend is a crazy man that flys like a bird all the time even after his accident
He builds his own high end gliders and his own legs. If he says the spars will work... I am 100% sure they will." :thumb:

I agree 1000%!
I will surley use these ideas in my next build! :idea:
And talk about a guy with integrity, Bille bleeds it! I say this after reading a touching pm from him, whata guy!
If I lived anywhere near him I would make damn sure he would fly with me, kiteboardhydrofoil that is, he already knows how to fly like a bird!
It is a pleasure to know that there are just GOOD guys living amoung us, rock on BILLE!
R H


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 Post subject: Re: Carbon fiber lay up
PostPosted: Wed Apr 23, 2014 6:43 pm 
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Joined: Tue Nov 09, 2010 10:00 pm
Posts: 79
update...

Got some heavier (8.9oz) high mod uni CF, and layed up two layers each side of the strut, one on the 45 and the last (outer) layer straight down the strut. Much better!

strut thickness 14mm (was 11)
flex 28mm (was 85)
torsion 18mm (didn't measure before)
all up weight......... 1.7kg !! (was 1.3kg.)

I checked out the french foiling thread again and noticed a post for the spotz foil measurements and the flex was 25mm, so i'm happy to be in that neighborhood. I'm not planning on racing it anyway...

Only downside is the uni is slightly less appealing look wise than the cloth, but still looks pretty cool...

Time to finally shoot the vid..

stay tuned.


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