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Selfmade fiberglass fins

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
A friend and expert in composite technologies recommends an infusion technique or even better an RTM technique.

I've found an example of infusion on the youtube:
[ame=http://www.youtube.com/watch?v=k1v9sFfufQc]YouTube - Infusion moulding a kite-board[/ame]

It requires special resin with lower viscosity, but the results are promised to be far better than using standard lamination.

Regards,
Zmago
 

a perforated membrane with a absorbent layer on top or peel ply is needed to remove the excess resin . in water a ruff surface is not always a bad thing .it is a common practice to ruff sand the bottom of a surfboard to make it faster , and jet ski racers will drag a new ski around a gravel parking lot without a trailer to ruff it up .the reasoning is that the ruff surface traps tiny are bubbles that reduce friction. and that it prevents a constant water friction acting on the entire surface . smooth surfaces just look better to the consumer .
i have friends that have mads fins with a food saver bag and then clamped in a mold . to keep it flat and give it angle.
the infusion method is cool but is very wasteful with resin if you look in your vid you will see the large surface under the board its there because you need to use a large amount of resin because if a spot is starved there is no way to get in and add it
phil
 
Well I decided, to use the same mould, a bit modified to allow (normal) vacuum bagging.
A friend also took notice that rough surface should perform better in water. Why then commercial fins come out all shiny???

However
I will put a peel ply over the laminate and also additional paper towels on top of it to soak the excessive epoxy. Then everything will be top covered with breather, pvc foil and then vacuum bagged.

Any coments here?

There is also a debate pending about the fiberglass layers. Would it be better to use an UD (unidirectional) fiberglass layer in the core of the fin, covered with biaxial just on the surface layers?

Zmago
 
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Peel ply works a treat but I dont know if you need a vacuum?
Perhaps you can use more pressure on your mold - loads of G clamps might do the trick?
 
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foxfish said:
Peel ply works a treat but I dont if you need a vacuum?
Perhaps you can use more pressure on your mold - loads of G clamps might do the trick?
Click to expand...

I think that vacuum provides much more equal force distribution over the mould area.
Well I will try and see. I got some advice from a friend who really rules in composite model planes hobby.

Will post everything...
ericvrp said:
Great projects like this might get a lot more exposure and comments when (cross)posted on makezine.com: MAKE: technology on your time
Click to expand...

I know that magazine, it is great. I just have too many forum accounts... If someone wants to link the threads, please do so.


Zmago
 
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Zmagoj said:
I think that vacuum provides much more equal force distribution over the mould area.

Zmago
Click to expand...

I am sure a vacuum pump system would give great results but not a cheap option for just a few products!
Maybe you can borrow the equipment?
 
Reactions: spaghetti
foxfish said:
I am sure a vacuum pump system would give great results but not a cheap option for just a few products!
Maybe you can borrow the equipment?
Click to expand...

The complexity is what I tried to avoid, but if it can output a much better result...

Anyway, a fridge compressor can be found on any scrapyard.


For our purpose it even doesn't need any pressure regulation.

Zmago
 
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Zmagoj said:
The complexity is what I tried to avoid, but if it can output a much better result...

Anyway, a fridge compressor can be found on any scrapyard.


For our purpose it even doesn't need any pressure regulation.

Zmago
Click to expand...

you can also get a venturi vacume "pump" very cheap just put a valve in the lime so after you have the vac you can seal it off.
Harbor Freight Tools
phil
 
An alternative cheap solution would be putting the fins on while they are fresh and diving with them to 100m - that pressure would be better than the vacuum you can achieve with a common pump.

OK, OK, so not diving with the fins, but perhaps you could simply sink the blades on a rope to couple of tens of meters
 
I've thought about using pressure (instead of vacuum) before, but would it still pull out the excess epoxy? It seems like if you use uniform exterior pressure, then the only thing that "motivates" the excess epoxy to move is the wicking action of the peel ply and breather fabric / paper towels?

This is different (in my head) from applying pressure with clamps. In that case, the epoxy flows out to the sides, or wherever the clamping force is less?

I have almost no practical experience here, so don't take this as anything more than a thought experiment on my part!
 
Joking aside, I believe vacuum is better than pressure, since it it forces the bubbles to grow and merge, and hence to escape easier from the material. When exposing to pressure, the bubbles are compressed and easier locked in the material. The best would be both external pressure and vacuum in the same time. The pressure is good for removing excess resin, while the vacuum for removing bubbles.
 
I also dont know much about vacuum bagging but from what I see on Utube the vacuum system seems to actually extracts the resin into a catchment vessel?
You better help us Phil?
I think you might need slow curring resin as they seem to leave the pumps running for 12 hours!
 

It is not so difficult really.
It is always better to use slow curing resin/hardener thus have more time for the lamination and later the compression.
The vacuum must be provided over the whole curing process, that's why the pumps run for a long period.

I will post the whole procedure.

Zmago
 
So, I have tested the blades and the third iteration performed quite well.
There were some problems with the Omer footpockets, thats why the string on the blades.
Don't look at my kicking, I am a beginner here!
[ame=http://www.youtube.com/watch?v=JpK7HIo1ldQ&feature=channel]YouTube - Testing 2 and 3 version of the freediving fin[/ame]

I also made some progress at preparing for the fourth iteration for which I've chosen the vacuum injection technique. The mold is covered with 4mm glass to get air tight surface. The UD glass fibers are still on the way. When I get it I will make the fourth blade.


Zmago
 

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there are lots of ways to vacuum laminate . it sounds like you saw the infusion process, you can also just hand lay the glass and then bag it . the important part is that you have a incredible amount of even pressure acting on the object ,and at the same time since the all the pressure is removed all the bubbles expand to the point where they pop (if you used pressure instead of vacuum you would end up with highly pressurized bubbles in the matrix)
you can run the pump the whole time or cycle it with a pressure switch if you have a leaky system ,or if you have a tight bag just use a valve



its looking good
 
Here is the fourth iteration of the freediving fin:
[ame=http://www.youtube.com/watch?v=B44CO_5J9pM&feature=channel]YouTube - Homemade fiberglass fin-part 4[/ame]

I had some problems with the infusion process. A leak occurred at the end, when almost the whole volume was filled with resin. However, I just made some changes and continued with normal vacuum bagging.

And Phil was right. The vacuum process resulted in a much better product.
The blade is very close to the carbon one in performance. I also used UD cloth instead of twill, what probably contributed to very good spring effect.

Bottom side of the blade is glass shiny, whereas the other has a rough peel ply structure, but looks good also. It has an uniform thickness (1.2mm) and weight 350g (untrimmed).

Thats it. The performance fulfilled my expectations. I could have stopped the development, but I have another idea and want to try the RTM process.

The advance will be slower due to time consuming learning curve, but I have the will. In the continuing I will use the polyester resin to cut down the costs and get some skills. At the end I will switch back to epoxy.

I also made a rough cost list for one blade:
epoxy 200g -> 7 eur
twill 200g/m2 0.5m2 -> 2 eur
UD 600g/m2 100mm 4x700mm -> 2,5 eur
flow media, peel ply, pvc -> 5 eur
---------------------------------------------
SUM 16,5eur
The costs can be cut in half if buying bigger quantities.

Zmago
 
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Reactions: nz676
Very well done - you have created not only a good product but a great thread too
 

Does that include shipping to Chile? I'll have 5 pairs please :t:t:t

haha, only joking, but to be honest, you have invested so much time in this, why not set up and sell a few pairs for a nice profit? I'm sure you would do well.

Congratulations on the project, very cool DIY
 

polyester resin doesn't do so well with the vacuum process , so any experience gained my not cross over . there is also the issue of running a flammable vapor threw a compressor . i would just stick with epoxy , if you need to cover your cost i'm sure you can sell your protos they might not be perfect but the have to be at least as good as plastic
phil
 
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