So while doing the leak test this morning with some soapy water to reveal the exact location of a fin box leak I have discovered my vent plug is leaking almost as bad as the fin box crack. Never been a fan of over tightening the screw with fear of pinching the O-ring but from firm to over tight (in my opinion) it still leaks. O-ring is fine but seating area is questionable.
Any advise on refurbishment of seat area, larger O-rings or maybe a smear of grease to guarantee seal?

I've reworked a vent plug on one of my boards Steve with success. Basically: drill out the vent hole. Fill it with epoxy. Retap it. With my job you can't tell the difference before and after. Let me know if you need a hand. It's fairly easy and I have a taping dye.

OT but was wondering the other day why no-one has manufactured an after market Gortex vent plug that you can screw into the standard vent hole. It would more than likely have to sit proud of the deck but with the deck scoops nowadays that shouldn't pose too great an issue.

I have had sucess with one that had a bit broken off in the seat area (where the o-ring sits)

I just put a dab of metal filled thick epoxy (JB Weld, Devcon etc) on the broken bit. Then a vent screw bolt with mould release wax (shoe polish wax is fine) was screwed in to jussst touch the seating area. I smidge of epoxy on the underside edge would not hurt.

Remove next day and you have just re-moulded a nice perfectly flat seating area.

Key is to not have too much or too little epoxy - you want enough to make a new flat seat, but not so much it flows into the threads. You also need to be confident in your application of mould release lest you glue that vent screw in permanently :)

I have had problems with vent tread leaking in the past.

After every sail I remove the plug which creates a nice hissing noise, always a good sign, I then clean vent plug then I wrap Plumbers White tape 2 or 3 times around the tread and once or twice around the O ring,

I then place my plug in a small plastic bag ready for the next time. I find it a good habit to get into and have never had a leakage again since.

Thanks for the tips everyone, some good ideas there.
Been thinking also about getting a spade bit the right size and gently trying to reface the oring seat area, let you know if I go that way and if it works or fails.

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sausage said..
OT but was wondering the other day why no-one has manufactured an after market Gortex vent plug that you can screw into the standard vent hole. It would more than likely have to sit proud of the deck but with the deck scoops nowadays that shouldn't pose too great an issue.

I've done it, by drilling out existing thread and tapping to goretex plug size, but it's only possible if there's enough thickness to accommodate the bigger hole. I went off goretex vents though, while testing them I discovered that if you get water on both sides, it stops breathing altogether! So it's fine while the board is dry, but if you get a ding and suck water in, there's a very good chance the vent will stop venting.

www.carmo.dk/products/valves/relief-valve/03-374/

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decrepit said..

sausage said..
OT but was wondering the other day why no-one has manufactured an after market Gortex vent plug that you can screw into the standard vent hole. It would more than likely have to sit proud of the deck but with the deck scoops nowadays that shouldn't pose too great an issue.

I've done it, by drilling out existing thread and tapping to goretex plug size, but it's only possible if there's enough thickness to accommodate the bigger hole. I went off goretex vents though, while testing them I discovered that if you get water on both sides, it stops breathing altogether! So it's fine while the board is dry, but if you get a ding and suck water in, there's a very good chance the vent will stop venting.

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choco said..
www.carmo.dk/products/valves/relief-valve/03-374/

I can confirm the reduced performance of the PTFE valve when wet. The reduction in performance is more than 90% when the membrane is wet on the inside, which can and has resulted in catastrophic failures. Choco's PRV would work in this scenario.

My most recent board build included a Gore PolyVent XL



Although its a very robust IP68f I recess it into the deck so its flush, and below it I have a removable silica gel cell with 150ml capacity. The cell is readily replaceable and the silica beads turn from dark blue to pink when saturated, so if the board has been compromised it performs 2 essential functions. Primarily it keeps the PTFE membrane dry, secondly it is a moisture indicator to help maintain the integrity of the board by constantly removing residual moisture.

Naturally if the board has taken on water, every effort needs to be made to mechanically remove the water ASAP and I' not going to advise 'best practice' for that at there are too many variables.

Its about 70mm across, retail price would be $50(vent and back-nut only) and for me to buy them in I need to procure a minimum or 20 units. I'd need to have orders for 15 units to break even..unlikely

The system works well for me but then I'm quite fastidious about chasing any leaks on my own kit in any case and lie to include a couple of vents to facilitate draining and vacuum purging.

This is what it looks like fitted

I have the plastic PMF 100391 in stock in WA.

Do take note: for those of you that like to use grease or oil on the treads of vent plugs, the standard plastic plug supplied to the SUP/Windsurf industry is Non-Oleophobic(it will block with oil/grease residue)

The Metal Vent is Oleophobic - repels oils. As is the XL vent.

I've tested this unit for 2 months in Seawater and am satisfied that when soaked, rinsed and dried - their rate of air transfer is full restored. It is true of all PTFE membranes that if they are wet on both sides of the membrane they can stop breathing, so if a board has any moisture in it the vent needs to be cleaned and dried before it can be relied upon to breath automatically as per specification.

To differentiate air exchange rates(at 0.3bar for 30sec), the small plastic vent is 2.5lt, XL vent is 16.0lt and metal vent is 1.7lt.

Here is the Metal Vent in use - only sits 4-5mm above the deck. The benefit of this vent is it has raised writing around the outside edge providing grip for finger tightening and removal. The O ring is plush and the M12 thread has two flattened sides so with a half turn you can manually equalise similar to the manual Wind Tech vent, for those that remember it. Its too tall to retrofit into a standard M8 vent screw unless the vent is very close or integral to the mast track. Again I'd need pre-orders for 30 units to be able to supply them at Retail $35. If there is enough interest I'll start taking orders and can post them out Australia wide.

Guys,
thanks for the handy info on breathable vent plugs.

MOB, does the metal vent fit a standard vent or do you have to retap it larger / smaller?

Metal vent is M12 1.5 thread and will fit straight into the Gore Polyvent found on sailboards and SUP's as discussed above. If you have a Chinook or most boards out of Cobra the standard thread size is M8, so tapping is required and pretty straight forward.

An easy fix for std vent plugs (provided the thread is ok) is to toddle down to your local bearing supplier and get some different O'rings

The Std Orings are Ø8mm x 1.5mm NBR(rubber type)

You can get

Ø8mm x 2.0mm
Ø8mm x 2.5mm

They cost next to buggerall so grabbing 10+ will not dent a fiver

The larger cross section of the O'ring now will now contact the inner edge of the Vent plug hole so when you screw down the plug you will not just have the oring seal between the plug and seat it will also seal against the inner edge of the hole.

The reason why you get the 2 sizes (you can also get 3mm cross section) is that there can be a difference in the inside diameters of the plug holes and you want the O'ring to be a snug fit going in.

It should be noted that if the plug is removed the O'ring can quite often be left in the bottom of the recess, but can be quite easily hooked out.

I've found that with this method even with sand ingress there is little damage to the O'ring and I've yet to have one shred as is the want of the std O'rings.

Only Issue I've ever noted is that the plug can sit slightly proud of the deck (1mm) but I have had my mast base cover the plug on a number of occasions without any problems.