Vac pumps

[Adam_melb]

G'day,
looking at purchasing a vac pump. Have my eye on these two.
anyone have any opinions?

http://cgi.ebay.com.au/VACUUM-PUMP-A...ayphotohosting

http://cgi.ebay.com.au/ws/eBayISAPI....m=290029213480

would they be capeable of bagging an i14?
also, the ads say they are rotary vane pumps, however, they do require oil, so i presume thay are rotary oil vanes? ...correct?
Cheers adam

[wet feet]

There are several factors to take into account.Firstly,how long do you intend to run the pumps?This will be determined by the resin system and its cure rate so it might be a good idea to ensure that the pump will run for that length of time without overheating.This part is particularly pertinent from my point of view as earlier this year,I had an oil-free pump that had seen years of service die on me during a job.I now feel that it would be good insurance to run a pump,connected to a vacuum bag for as long as the cure will take,prior to the job.A failure at this stage is an annoyance,the same thing with a mould full of carbon and epoxy is a disaster.
As for the suitability for bagging an i14,a vacuum is a vacuum.The only manner in which the pump comes into the equation is connected to the speed with which it can evacuate the bag.Your post gives no indication of your experience with vacuum bagging and if you don't have much it might be a good idea to begin with a small project to gain experience and confidence.
A quick Google search for rotary vane vacuum pumps will find several references together with descriptions of how they work.Good luck with the project.

[Adam_melb]

thanks mate,
yeah, i have couple of smaller projects in mind before i go ands blow $5000 worth of carbon/foam/resin.
any other opinions appreciated

Cheers adam

[Buckle]

Hi,

If you spending 5k on materials, it isnt going to cost not much to infuse the moulding. I'm sure someone across the pond would give you a hand FOC.

[Adam_melb]

Thanks buckle,
what real advantage is infusion going to give?
cleaner?
More time to lay up cloth?
slightly better resin/fiber ratio?

but isnt there the risk of the resin not reaching all extremes of the laminate?

Cheers adam

[yokebutt]

Adam,

Infusion won't give you a better laminate, but the risk of botching a part is higher. Just use a very slow epoxy and post cure it well afterwards. (Black plastic wrap and a bit of sunshine is cost effective, invest in a IR thermometer)

[Adam_melb]

thanks guys,
in that case ill give it a miss untill I'm profficient in vac bagging,
cheers adam

[Jimbo1490]

I recomend the EMI 24 catalyst. Works in anybody's epoxy and like using MEKPO in polyester, the ratio is variable. I usually use 5%. You get about 5 days working time (viscosity doubles in about 5 days at ISO Std. temp). But with even modest heating to 120*f (not very hot, really) full cure in 6 hours. Higher temps give faster cures and better cured sate properties. EMI 24 typically gives a Tg 50*C above cure temp, which is generally more than adequate for any boat part. It can be post cured at any time after cure to increase Tg if needed. The max Tg acheivable with this catalyst is really high, over 300*F.
One caveat is that EMI 24 tends to make cured resins a bit brittle. Not real bad brittle, but a bit more than ideal. But any of the mono-epoxide modifiers (thinners) has the opposite effect and is generally desirable to reduce viscosity anyway. Most every commercial resin that is nice and thin for hand laminating already has one or more of these thinners so brittleness won't be a problem with EMI 24. But it could be if you are using a straight resin like Epon 828 or such. West and most others have the modifiers.

Jimbo

[Herman]

As for the I14:

Buying a pump without having it seen first is a bit tricky. I bought a small pump (6 m3/h) for euro 300 over here, new.

This pump should have you go for at least the rudder and dagger first. That way you can practice closing vacuumbags, laying up etc.

When it comes to the hull the capacity is somewhat low. However, when you put an ordinary vacuum cleaner on the bag first, to empty 90% of the bag, you should be able to do with a 6m3 pump.

About infusion: It is possible.
* Plenty of time laying up your fibers and core
* Other consumables needed
* Some knowledge about infusion strategy needed
* Some tests needed to see how your laminate performs.
* Laminate quality not dependant on laminating skills

However, wetbagging a I14 is not too hard. Get yourself an epoxy with a long open time, and relative low viscosity. (400 mPa.s mixed or so). This will speed up the process, yet will not drain out (at least not with the materials you will probably use for a I14).
Do not forget to perforate your foam.

When your foam is not fitting too well, pull a vacuum after installing the foam. This gives you the opportunity to repair some foam spots / missing pieces etc.
If your foam is perfect, and lays down well, you could do the inner laminate in one go as well.