Making Skins #74 - Brisbane Australia

[Surfcnc]

Hi Russell

I ripped a slot out of some plumbing pipe on my table saw and made the "C" clamp fitting you mentioned.
It worked really well after I rounded over the cut edges (first time it cut into the bag sliding the clamp on).
Cobbled together some old brass fittings and made a bag entry point and even with out gaskets it made a surprisingly good seal.

My "test" vinyl bag did not have a single leak so I was able to vac down a few layers of ply over a form.
Thanks for your input and I have visited all the links you were kind enough to put together for me.

Regards
Ross

[Surfcnc]

Hi All

I just love the Mechmate, it is a uber creative tool.

Last time I made a skateboard deck, it was cut from a single 12mm ply and epoxy glassed on the underside.
This time I cut a 3mm 2400 x 1200 sheet of thin plywood and vacuum laminated 5 individual plys together for a stronger and slightly thicker deck.
One of my beef and bacon fed mates is going to be the new proud owner and he has made me warranty my work (it's a freebe in truth but none the less he will want a new one if it breaks!)

MM #74 with the raw product
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Used a clothing storage bag for the vac press - worked very well
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Vacuumed down hard and squeezing the excess glue out of the laminates.
Going to be a bit of tidy up by the look of it as I forgot the peel ply in my rush to put it in the bag.
Note my $20 plumbing parts frankenbuild breach unit, it is always a pleasure to use things in ways they were never intended
IMG_2389.jpg

Regards
Ross

[Regnar]

Ross I think we have given you enough time to take pictures of what your boards looked like after coming out of the bag. Did you use anything to keep the boards from moving on you under the vacuum bag? How well did the zip locks work for you? I have been thinking about using some of them for quite some time but never have gotten around to it.

[Surfcnc]

Hi Russell

It worked very well. Apparently it got Skippy's mind ticking over as he was asking about using the zip lock bags as vacuum bags.

Out of the Bag
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General Shot
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My Alignment Method - With the screws in place once the vacuum was on it is impossible to make a mistake.
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I am short of epoxy to finish the deck and have a resupply trip planned for later in the week.

While on the subject of adhesives. The vac bag was still wet with glue after 8 hours.
Given the amount of energy put into the system to keep it vacuumed down I will now switch to a chemical set epoxy for lamination and it will only take two hours max to set up.
Despite the quality of the glue it can never match the properties of the two part expoy.
I keep on learning !!

Regards
Ross

[Surfcnc]

Russell - the vac pump cycled on every 10 - 15 minutes.
Obviously there was a leak somewhere but I was not able to detect it (no audible hiss).
At that point I decided to just let the machinery do the work and not bother with achieving a perfect seal.

Regards
Ross

[Gerald D]

Two thoughts: A 5 layer deck will benefit from glass cloth under the outer layers. To save on glue, the inner 3 layers can be a single cheap 9mm ply.

[Surfcnc]

Hi Gerald

While the decks remain flat this laminating process is really quite wasteful in terms of time and effort.
The process uses a lot of glue and it is not cheap given the small supply quantities (500ml) at our hardware stores.
It is only once some bends are put into the picture that the thinner laminates are worth the time.

The home made laminate did seem to have a much snappier return when I loaded it up but it should be at 2.5 mm thicker than the previous one.
I expect the deck to become even stiffer once the epoxy and fiberglass is applied on the bottom of the timber laminate.
My next project will be to try to put a slight concave lengthwise down the deck by sucking it down onto a rigid curved former.
I will post up some pics once it is set up.

Regards
Ross

[Regnar]

Ross thanks for the pictures. I always like seeing other people projects come together.

I also bought what looks to be the same bags as you from Harbor Freight. I vacuumed down my wife towels and and was suprized on how 5 fluffy towels turned into sheet of plywood.

Just incase others are interested in the bags here they are. http://www.harborfreight.com/3-pack-...ags-95613.html

Mine actually came with 5 bags, 3 of them have vacuum ports and the other 2 are just large bags.

[Surfcnc]

My mate made the terrible mistake of giving me artistic license.
Green going one way, orange going the other and lilac epoxy glass on the underside.
Teamed with some huge 90mm diameter yellow wheels it becomes my "Stealth Model".

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Regards
Ross

[zumergido]

ha.. my eyes are sad.

[Pixelated]

Apologies if all this is obvious but some of the flex characteristics of a longboard (or skateboard) derive from the width and/or lengthways curves added in the press during the lamination stage.

Some of the options which will affect the ride are:

• Concave - downwards curve across the width of the deck.
• Camber - upwards curve along the length of the deck.
• Rocker - downwards curve along the length of the deck.
• Drop - the deck drops between the trucks for a lower platform.

And to get more fancy you can add a kick to the nose and tail.

I imagine the MechMate has enough Z-travel to carve beautiful and accurate male/female moulds (remembering the offset for deck thickness), plus you have the welding skills to make a simple hydraulic press using one or more bottle jacks.

(From someone who wishes they had the space, cash and skills to build a MechMate)

[Surfcnc]

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My vacuum bending jig a very simple device. The rail outline was offset outwards and inwards by 10mm and cut using the Mechmate,
This support is then screwed to a flat board and 5 x 3mm plys are aligned with two screws and then the whole jig loaded into the vac bag.

The vac bag easily pulls the middle of the deck to the jig floor and gives 15mm of concave side to side.

Additional Vacuum Storage

IMG_2400.jpg

I'm certain this will get some tails wagging but it can and has been done safely.
Due to the nature of what could potentially happen, my only suggestion is to buy new bottles untouched by gas.

The gas "everyone" smells from used bottles is actually mercaptan residue that is probably the smelliest thing on the planet.
Mercaptain can easily be detected by us humans at concentrations of 100ths of parts per million and that is why an empty used gas bottle smells of "gas".
Propane gas is actually odorless so smelling gas itself is by definition quite incorrect.

As the bottles come on special at the hardware warehouses, eventually I will slave another three bottles together to give a total of 120 liters vacuum storage.
I have been thinking about slinging the bottles on their sides up under the table and making them a fixture.

All this really achieves is to limit the cycling on and off of the compressor.
If your bags make a perfect seal or you are unaffected by noise, it is quite unnecessary to add any storage volume.

Regards
Ross

[HomeMadeCnc]

Thanks for posting, I'm about 3 steps behind you at the moment on a similar setup,

Cheers
Tim

[Red_boards]

Ross,
Looking good. Interesting bending jig. I suggest cutting yourself a full jig.
Temperature is key for epoxy. Over 20 C required otherwise you have a loong wait (8 months +).
Innegra cloth might be worth a look in this application (but it is so flexy that it's a bit "sloppy".
I'm hearing good things about CET Epoxy made in Queensland. Again it might not be appropriate for your application.
I used to use window screen to help airflow in the vac bag, but I got too much stuck to the resin. I bought a bunch of release cloth that seems to work well as breather ply. I hear you can use any nylon cloth from the fabric store, but haven't tried it.

Forgive me if I seem to be teaching you to suck eggs.
Red

[Surfcnc]

Hi Red

All information is appreciated as you just don't learn as much or as quickly without taking other peoples ideas on board.

This afternoon I started my next experiment at bending compound curves into the 5 x 3mm laminates.
Used an epoxy layup this time and today it is still a good curing temp at 25+ deg C.
Part of this test is to start to release the vacuum as quickly as possible, so I might easily end up with wreckage.

I'm sure you know this but for any others that may not know...
To speed up the resin set time leave the full volume of mixed resin in the cup for ten minutes before using it as it starts the exothermic reaction off more rapidly.
Should not tell you this but I also microwaved the resin to recover as much from the bottle and this also speeds up the gel time.
Cheers for the resin tip, it seems to be distributed from Warrana on the North Coast.

Experiment in progress.
IMG_2404.jpg IMG_2401.jpg
IMG_2402.jpg IMG_2403.jpg

Regards
Ross

[Surfcnc]

After 3.5 hours released the vacuum and it straightened completely back up.
I realise that it should be in there much longer but the breach unit had a small leak and the noise and energy used under that condition is just not worth it .
I need to investigate better bag sealing and maybe (shock) buy a breach unit.

The deck itself seems quite usable though - just not bent

Regards
Ross

[PEU]

why not bend at lamination time?

[timberlinemd]

to speed up drying times a small oven would be needed. Temp effects the resin alot.

[TechGladiator]

Ross,

Excuse if this may already be repetitive but a buddy of mine uses this technique to make the bags and vacuum system, I don't think it can hurt..

http://www.joewoodworker.com/veneering/makingbags.htm

[Surfcnc]

Hi All

Pablo - my mold would point load the fiberglass layup as it bends from a single edge on the sides.
With a better mold design as Red suggests laminating and bending would be quite possible.

Steve - you bet.

Miguel - cheers. I have already made one bag that way and it worked pretty well but it got very badly damaged (my fault).
To construct the bag I used some .3mm PVC, a strong solvent and plumbing glue.

Next try will use a breach unit and tacky tape and I might just make up a new bag too!
Here is hoping it all seals - perfectly this time as that vacuum needs to be on for a looooong time.

IMG_2405.jpg

Regards
Ross

[Red_boards]

Hi Ross,

I use the tacky tape on all my bags and used to on my breech fittings (I had these fancy plug in/ quick release fittings). Now I just push the pipe into the open end of the bag and put tacky tape on both sides. If you do this, it's important to stop the bag sucking into the pipe. I use a folded muslin cloth around the end of the pipe and link it to the breather ply. I've also made breech units from the top of plastic bottles, complete with screw-on "fitting" (i.e. the tube fitted to the original cap).

Sounds as though you need a resin with a faster set time. Resin Research has a 20 minute epoxy. Tricky to find RR in Australia, though.

Regards
Red

[Surfcnc]

Thanks Red

I can't picture the fitting using the bottle cap but the rest is clear (a pic for me maybe?).
Played with the tape already and it really seals, so it looks like a winner.
Feral Dave is using the RR Quick Kick and recommended it to me.
They can flip a board in something like 30 mins to layup the other side !!!
I like his work by the way, very innovative and involved in everything.

Regards
Ross

[Surfcnc]

The tape worked best of any method.
It sealed so well I was able to disconnect the vacuum and let it sit without any further assistance.

IMG_2406.jpg

Regards
Ross

[ger21]

You might want to try laying an electric blanket over the bag for additional heat, to speed up the cure.

[Surfcnc]

Greetings Ger

A good suggestion so thanks.

Regards
Ross

[PEU]

Ross, check this site: http://users.telenet.be/Toothless/To...ess/press.html

That press can be done on the MM in no time once you have the plans, the CAD model looks like the kind of 3D work Fabrice does. Pay special attention to the green base of the press, always needed

Cheers

[Regnar]

Heat lamps will also speed up the cure time as well. Like the ones used in food areas and plants. Just need a good size reflector to get the whole area.

Pablo I liked the link. That jig and a few vacuum bags would make a easy production work.

[MAC2009]

Years back when working in a shop that did plastic laminate (Formica).
Steve and I build a press using compressed air less trouble then (vac).
Built similar to the MechMate 3 posts on each side of a 4 x 8 table with cross beams under posts extended above this by about 3 feet. Then a another
4 X 8
with beams on top this is adjustable in height under that another 4 X 8. But in between these length wise were hoses sealed at the ends and manifolded together lower on top of project and apply pressure. It was used mostly for flat work we did do some shape WORK WITH A UPPER AND LOWER PLUGS. WE HAD IT IN THREE SIZES (caps lock off) and can be made in any size with easy disassemble. We used fire hose but any hose that will go flat and hold 75 to 100 PSI would work. It is surprising how much pressure is applied to to project.

It work so well we talk of making a large one with steel and heating it, never happened though

Any way brought back old times

MAC

[Surfcnc]

Major success on the vac bag - fired it up and it sucked down one time and that was it, 24 hours later it was still holding the vacuum. Win.

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Pulled it out of the bag - total mess with resin, taffeta and paper towels everywhere

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Back under the machine for a trim using a 3mm inset cut on the outside and a .3mm offset on the inside.
Cleaned it up nicely considering the state it was in.

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My alignment screws glued in and then I snapped the laminate "hammering" out the screws.
Yes I know, now it does not seem like the hammer was such a good idea

Regards
Ross

[melissa]

Originally Posted by Surfcnc

My alignment screws glued in and then I snapped the laminate "hammering" out the screws.
Yes I know, now it does not seem like the hammer was such a good idea

Regards
Ross

When building my stitch-and-glue dinghy, I used a soldering iron to remove the wires. The epoxy next to the wire heats up and loses its bond, making it easy to pull out. The rest of the epoxy still holds the workpiece together.

Perhaps a similar approach could be used to remove the screws.