Model Forum / General / Models / December 2006

All you are doing is consolidating the layup, won't stippling with a
brush and use of a metal washer roller suffice?  You will of course
end up with a layup heavier than it could be and of less strength but
does it really matter?  

When professionally producing items using prepreg (essentially pre
catalysed resin soaked fibre in "dry" form) it's normal to aim for a
minimum of 29" of mercury, or 30mb absolute, but unless you are aiming
for an ultra thin low resin fraction layup and curing in an autoclave
then much less will be ok.  

You do realise that vacuum bagging will require a release layer/peel
ply, bleeder cloth and the vacuum bag ?  None come particularly
cheaply, minimum orders for these could easily be approaching the
price of a reasonable (aircon service) vacuum pump.

Another approach is commonly used in wood veneering that uses an old
fridge compresssor producing around half an atmosphere of "suck" with
an air bleed to avoid stall,

Forgot to mention, another problem with the vacuum cleaner approach is
the motor usually relies on airflow for cooling.

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have got a new good quality vacuum pump if you need to borrow not being used
brought as its going to be useful one day

Depends - if you are trying to get excess resin out through a peel layer
into an absorbing layer then you don't need or want a very high vacuum,
about 8 psi is okay - if you are trying to get air out of and consolidate
prepreg then a high vacuum is needed.