Anyone had experience looking for cabin rain leaks by pressurizing with
a shop vac?
Dick

Richard Lane wrote:

Anyone had experience looking for cabin rain leaks by pressurizing with
a shop vac?
Dick
be ***** careful!!! Ive done dinghy tanks with a foot pump before and it
works ok but we were VERY careful to keep the pressure really low.
Leaks were located with the aid of a 25% solution of washing up liquid
and a paint brush.

A quick calculation assuming a vacuum cleaner can reach 3 PSI and for a
deck 24' by 8' gives a force of over 40 tons on your deck/hull joint.

I guestimated the pressure with info from the Fermilab website where
they were getting 8 PSI differential using ordinary vacuum cleansers,
some on suck, some on blow to clean out a *really* expensive bit of high
tech kit. http://www.fnal.gov/pub/today/NuMIhorn.html

If you do decide to go ahead with this, *Please* record it on video for
posterity. If my predictions of doom are valid, it should be well worth
watching.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:
'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed,
All varnished hot moulded wooden racing dinghy.

Richard Lane wrote:
Anyone had experience looking for cabin rain leaks by pressurizing with
a shop vac?
Dick

I'd just let it rain on it, and look for leaks....

Ian Malcolm wrote:
I guestimated the pressure with info from the Fermilab website where
they were getting 8 PSI differential using ordinary vacuum cleansers,
some on suck, some on blow to clean out a *really* expensive bit of high
tech kit. http://www.fnal.gov/pub/today/NuMIhorn.html

From the website:

"It takes well over a year to build one, and I'm glad we were able to
fix it without breaking it."

nice thought!

basskisser wrote:
Richard Lane wrote:
Anyone had experience looking for cabin rain leaks by pressurizing with
a shop vac?
Dick

I'd just let it rain on it, and look for leaks....

The tough thing about many cabin leaks is learning just where the water
is coming in.
Where it is coming out will be rather evident. Water can run a long
ways behind upholstery or veneers, so the entry point into the cabin
may or may not be in the same place as the breach of the
superstructure.

Fortunately, the vast majority of cabin leaks occur around a fitting.
Rail stanchions, vents, hatches, etc. That makes it a bit easier to
begin to isolate the probable source points.

Ian Malcolm wrote:
Richard Lane wrote:

Anyone had experience looking for cabin rain leaks by pressurizing
with a shop vac?
Dick
be ***** careful!!! Ive done dinghy tanks with a foot pump before and it
works ok but we were VERY careful to keep the pressure really low. Leaks
were located with the aid of a 25% solution of washing up liquid and a
paint brush.

A quick calculation assuming a vacuum cleaner can reach 3 PSI and for a
deck 24' by 8' gives a force of over 40 tons on your deck/hull joint.

I guestimated the pressure with info from the Fermilab website where
they were getting 8 PSI differential using ordinary vacuum cleansers,
some on suck, some on blow to clean out a *really* expensive bit of high
tech kit. http://www.fnal.gov/pub/today/NuMIhorn.html

If you do decide to go ahead with this, *Please* record it on video for
posterity. If my predictions of doom are valid, it should be well worth
watching.

Ian, the boat is a Nonsuch 26 in Port Townsend WA and I am in N.
California for the winter. I calculated that for a 3psi stall pressure
from a Shop Vac that there would be 90Klbs lift on the deck area, this
would be distributed around a 67ft hull-deck joint periphery giving
about 120lbs/inch separating force. The joint is thru-bolted every 4ins.
However I doubt that 3psi would be achieved because of air leaks to the
chain locker etc and was going to include a manometer U tube in the
dummy hatch board. My boat yard foreman refused to conduct the
experiment for the reasons you stated and said it would blow the mast
out of the boat (I figured a 300lb lift on the fat catboat mast which
also has a 200lb wishbone boom hanging on it and a restraining tie down
to the step). He is going to remove and re-bed the grab rails and Atkins
& Doyle hatch (known problems on these 24 yr old boats) but there is
also a "Charlie Noble", Dorade box and bull's eyes penetrating the cabin
top and I was hoping to pinpoint all leaks before he got started.
Thanks for your interest,
Dick