Pressure Buildup In Hulls

I noticed some time ago that when the hulls are sealed up (drain plugs and inspection ports closed) when it's cool outside and then opened again when it's hot outside there is quite a bit of pressure built up in the hulls. I have wondered whether this pressure is enough to do damage to the hulls. For the last couple of years I have made a point of keeping the inspection ports cracked open when the boat is not being used and closing them when sailing as a precaution. Am I worrying about nothing here? Does anybody else do this?

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Dave

The hulls are designed to be vented, so I would add a vent hole to each. You could drill a VERY small hole in each hatch lid as long as the cooler area is venting... If not, I would drill a small hole in the cooler area up high and inboard.

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

At least you'll know they're water tight.

what about just opening the aft plugs; will this keep expansion damage at bay?

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Jerry Malone

I would guess not. Only because you have the boat out all hot in the sun. You close the plugs before sailing, drop the boat into cold water, air temp drops and you have a pressure difference between outside and inside which could cause a hull to buckle in....

I'm curious to know how much pressure we are talking about. My TI amas do the same thing. I typically pull the drain plugs after a day of sailing (never had any water come out) and I always get air escaping. I wouldn't say it's more than a few psi. and definitely not enough to cause any type of hull deformation.

Sent from my SPH-L720T using Tapatalk

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2015 Hobie Tandem Island Hibiscus
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Just people overthinking and worrying about nothing.

I'm confused by this. If they are designed to be vented, what's keeping them from venting? Is there a clogged vent somewhere?

I am curious about this also. Matt, can you go into more detail on this?

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Dave

I'll have to ask the factory what the current vent is intended to be. They used to drill a small hole inboard at the front or rear crossbar as I recall.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Factory reply:

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Matt, then I am confused.
At times there is a rush of air when I remove the plugs.
should I look for a clogged hole?

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Jerry Malone

Yes... if not present... you can always drill a hole.

Venting is not as critical on the rotomolded hulls as was with fiberglass, but could be an issue in hull deformation if pressure changes are enough... altitude changes while trailering, for example, could cause issues.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

I checked the hulls on my 2006 and found holes on the inside top about half way back (near the storage box drain holes). But they had a white plastic plug in them. These would work more like a burst disk than a vent hole. Matt, I'm wondering if this is something the factory did back in 2006 or maybe a previous owner added the plugs?

The holes were large, somewhere between .125-.250", so I'm reluctant to just take the plugs out. I'm thinking about drilling a .032" hole in the plugs to get some venting. Matt, what do you think?

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Dave

Those would be panel rivets plugging a brass molded-in fitting... not the vents.

It is always possible the factory failed to drill the vents or the vents are plugged or not drilled deeply enough.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)