Mylar flap for transom drains

If you've all finished your dinners, here's a photo of a section of my transom as it is at present. The pink foam is what I stuffed into the pipes to prevent water entering...

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...I'm sorry, but you were warned, earlier.

It's a rotten job of fairing and finishing, because late in the summer, I was much more concerned with sealing the drain-tubes into the transom, so the rear compartment could stay dry and I could launch, than how she'd look. So, lots of Sikaflex got in there, lots of thickened epoxy, and a fair bit of paint in a weak attempt to hide the hideousness.

The nasty brittle yellow layers of epoxy-overspill need scraping off, and those ply rectangles need either sanding smooth or re-covering with a shiny smooth, thin, rigid outer facing which the Mylar flap can snap shut against when I pull a length of light shock-cord from the cockpit.

The whole hull wants several careful days' work with rubbing compound to shift stains and tyre-marks. That photo is just a specially nasty bit, and one which most urgently needs finishing because when the pipes are opened, the sea cometh in. Not all the time - the transom drains are several inches above the working waterline - but it still comes in.

Worth remembering that I hope to spend a few calm nights aboard this summer, weather permitting. No fun waking up in a wet sleeping bag. I'll keep the foam squares for stuffing in the cockpit ends of the tubes.
 
Cheers Andy. At least I'll have good before-and-after pictures when I'm finished, because whatever I do, it's going to look better than it does right now!

That said, inside the rear deck cavity, it's all pretty good. Sealed up tight and looking quite neat from the front end, with two small dry-storage lockers I can reach from the cockpit, and probably 1000 Newtons of buoyancy stuffed in there too. Much better than the gaping green hole she had when I bought her!
 
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dancrane said:
Daydream Believer, please don't take offence, it's just that several earlier threads I started were blatantly, irksomely hijacked by people who were determined that I go out that very day and practice capsizing. I know it's a vital thing to feel confident about, so there'll be a day for it. But I doubt it relates very closely to Mylar flaps on transom drains!
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But it does- you still not have said ( & I agree you do not have to, its your thread) is whether you have filled the boat with water to see if it will then float high enough for the drains to work if the boat is flooded
Your buoyancy tanks aft are under the side decks not in the floor like my dinghy so may well float low down
i do know of a boat where they were fitted & all was fine until they capsized & they could not stop water running back through the transom
The floors of my last 2 dinghies drained aft , not level
I have seen dinghies where the flaps have been taped shut as they are more agro than help
But if you have thought of that & checked then all will be fine
But if not & you get into trouble you will not be able to get going again
As for capsizing - you do not have to capsize to get big dollops of water on board in a few seconds so perhaps I am at fault for not phrasing it as " have you tried filling the boat when afloat to see if the drains will work"
 
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Daydream believer said:
...perhaps I am at fault for not phrasing it as " have you tried filling the boat when afloat to see if the drains will work"
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Ah. That is indeed a relevant question, which I hadn't even begun to consider. But I don't need to test it to feel fairly certain of what will happen...

...at present, a good deal of water (perhaps 80 litres) sits in the great concave 'basin' of the Osprey's floor, without even getting close to the inside end of the transom drains. Which isn't very helpful, except that in various windy Osprey videos, I've seen the bows pointing quite far 'uphill', so I hope lots of the water would slosh aft under gravity and down the drains.

I realised while I was building drains into the new rear bulkhead, that the standard GRP version of the Mk2 (which mine is) had no drains at the aft end...I assumed that MY drain holes had been clumsily cut into my transom by a crew whose experience had led them to see the benefit. Hence I retained the drains, albeit without the horrendous holes in the bulkhead and transom.

If I were to launch the boat and leave a hose running into her, I'm confident she'd take about 100 litres (22 gallons), maybe more, before the incoming water was deep enough in the cockpit to start running out of the transom drains...

...my own weight and SWMBO's in the boat doesn't even nearly put the outside end of the drains under water in a calm, so I assume the hull's buoyancy would make the cockpit self-drain of water, once it gets deep enough to overflow into the drains. It's very irritating that the curving cockpit floor reaches its lowest point far from the transom...that'll be why most Mk2 Ospreys have self-bailers too.

I hope that answers the question. I reckon the rear drains may be beneficial in some situations, but a water-tight flap is vital to prevent water sloshing in, particularly during launching.
 
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dancrane said:
Actually Humbug, I'm stunned to observe that your Osprey also has the rear cockpit-bulkhead missing, just as mine did when I bought her! I say stunned, because I'd always assumed my boat had been ruthlessly butchered for a last-hurrah cross-Channel trip, during which the planners foresaw capsizes and floodings, and wanted the water in the cockpit to be able to run aft and out of the transom...as the pic suggests...

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The design of the Mk2 Osprey seems to have enclosed the cockpit, making this rearward escape for water, impossible. I suppose I have inhibited its escape by rebuilding the bulkhead, though I think the square drains will still shift quite a lot quickly, assuming the bows point upward on the plane...they don't drain anything with the boat level...

Newrearbulkhead_zpsf736d699.jpg
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I did something similar when I built my International 14. I ran a length of plastic 4" soil pipe through the aft buoyancy tank. I shut off the outer end using a plastic funnel of diameter slightly more than the pipe and ran a piece of bungy from the sealed narrow end of the funnel through the pipe to a hook. In the event of flooding I could just slack off the bungy.

On my cat I have some large drain holes through the cockpit sole. In choppy conditions it meant anyone sitting near the drains got cold sea water up their trouser leg. I cured it with a flap of car inner tube on the underside, secured on 3 sides.
 
Dan
If you are going to have a bulkhead you will have ample buoyancy
You would also stop water getting into the aft end if you did away with the flaps altogether
You have already said that the drains do not get rid of a lot of water
If you had no drains & did away with pipes etc which all add to potential leak points
The main cockpit will fill up with water in a capsize or in a big sea but you will immediately loose half of it when the boat heals & that half is the same as what is left with the tubes in place
This means that the tubes & flaps are worthless & you are just wasting your time
Only a suggestion
Sorry to mention the "C" word again
 
Daydream Believer,

I have owned and cruised ( Chichester - Cowes ) an Osprey; as long as the tubes are closeable when Dan wishes, I think they'll be well worth having.

I am a little dubious about the mylar though Dan, I presume you were thinking of simplicity but I have my doubts about mylar compared to hinged perspex, funnels on a chord etc; maybe you could glue thin wooden strips to the mylar, like battens, to help them act as desired ?
 
Interesting thoughts, and I am grateful for the input. :encouragement:

Daydream believer said:
If you had no drains & did away with pipes etc which all add to potential leak points

The main cockpit will fill up with water in a capsize or in a big sea...

This means that the tubes & flaps are worthless & you are just wasting your time...
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Hmm. I was certainly free to seal the transom holes, and leave the rear bulkhead without any holes in it, when I rebuilt it. I retained the drains, lest I wished later that I had the option. I agree and admit, they've only been trouble so far - although packing that pink foam into the rear ends has effectively sealed the drains. The Mylar flaps were just meant to be a slicker way of letting out-going water out, while preventing incoming. So...worthless and a waste of time? That's a bit harsh. Let's say, "Superfluous so far." ;)

As to your remark, " the cockpit will fill up with water", I don't think that is likely. I've found footage of an Osprey being righted, and she's hardly brimming. Advance the vid to 2 minutes 10 seconds:


I certainly haven't had the misfortune of getting more than about 50 litres of water in there, yet. I really don't think it's likely to get much deeper, either...yes, in the event of a capsize I'll get an unpleasant amount in the bottom of the cockpit, but any more than that will drain out of the pipes under gravity, because the boat's buoyancy keeps any deeper contained water above the boat's waterline, and it'd be high enough in the cockpit to escape down the pipes.

And if the bows lift while planing, lots of the water which doesn't drain normally, may flush aft. If not, I'll probably have bought new self bailers by midsummer...and I'll always have my hand-pump. :rolleyes:

I wish I could find the thread where somebody assured me that Mylar was the answer to the transom drain question. He was very persuasive. I had tried fitting nice little hinged flaps made of rigid plastic, but they let so much water into the cockpit while launching, I gave up on that 'engineered' solution. Mylar sounded simple and effective.
 
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Dan,

did you try ' Hatchseal tape ' ? Sold in rolls in hang-up packs in chandleries, not that expensive considering it's incredibly useful; self adhesive ( under paper ) one side, then soft squashy neoprene about 3-4mm thick by an inch wide.

Probably not relevant now.
 
Thanks Andy, that almost certainly WOULD have made my hinged flaps waterproof...

...pity I didn't know of it. Ah well, at least the Mylar solution will require a glossy-smooth finish surrounding the drain-outlets...so I'll have no choice but to make a neat job of that rough transom area. :rolleyes:
 
Well I can see your desire for the mylar jobs to be fully automatic as soon as the boat rights after a capsize or otherwise collects a lot of water; I suspect it might take a little playing with glued stiffeners and maybe even something like hatchseal tape on the lower outside edges as weight, but it will work in the end.

Any auto anti flooding device must be good, you might get disabled by a mackerel or something leaving SWMBO at the centre of the next Hollywood blockbuster...
 
Dan

The curl of the Mylar is not an issue. See here...

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For this to work you need a fairly decent overlap. Don't make the mistake of overlapping a few mm. But you will need to make the surface much fairer. These do not work as hinged doors, more like those drain plugs you get in cars, or those thingies in the top of shower gel bottles...only open when there is fluid trying to get out.
 
Thanks Iain, the shiny smooth surface against which the Mylar will press, was top of my priorities. The protruding screw-heads are indicative of my hurry to launch late last summer...but I reckon it'll be easier to plate-over the roughness with some kind of shiny veneer, rather than rub down the unevenness.

Photos, in due course... :encouragement:
 
I haven't made any progress yet but here's a secondary, fairly irrelevant question to which somebody may know the answer...

I was thinking of blanking-off the rough ply area around the drains, by attaching one piece of smooth Mylar, and using another equally smooth piece as the flap, hence no leaks...

...so, hoping to find a waterproof adhesive which I could use to affix the Mylar, I Googled "what sticks to Mylar?"...

...and straightaway I found a site called UK420.com...which certainly sounded as if this question had been raised by dinghy crews, before...

...but apparently these aren't International 420 dinghy sailors...they're cannabis-addicts. Isn't that odd! In fact the top two entries under the Mylar search, lead to drug-fora.

Whatever is this Mylar-stuff? Why is it favoured by grass-smokers?
 
dancrane said:
Whatever is this Mylar-stuff? Why is it favoured by grass-smokers?
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Possibly something to do with growing it, rather than smoking it? Left behind in a student house I once found a proper published book on the subject, it seems to have become quite technically advanced. There were graphs of carbon dioxide partial-pressures, discussions of the best rate at which to move the lights (apparently a moving light source to simulate the sun results in better growth), chemical concentrations of different feed mixtures, all sorts.

Pete
 
Thanks Pete. I was only curious. If that damn wind would stop blowing so hard, I might go down to the boat, measure the transom-panels and start cutting the Mylar.

Any bets on which month I'll launch, this year...? :rolleyes:
 
dancrane said:
I ordered and have rapidly received the Mylar flap which I'll use to prevent water sloshing back up my transom-drains into the cockpit...
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Where did you get the Mylar? *

I'm doing the same in the limber holes in my bilge; tried silicone rubber sheet, but can't get it to stick easily.

* The large images above make it virtually impossible to look in this thread for the answer.
 
The Mylar panel (50cm x 30cm) came from people called "sailboats.co.uk".

Their prices were good and the delivery was extremely brisk. Their range seemed very wide too. I'll certainly order from them, again.

Sorry if any images I've included, weren't possible to view. I generally post pictures from the laptop and I know smaller devices don't give the clearest view of thread pages.
 
Pretty boat.
I learn't to sail in a 'Fish' which I believe was the wooden (Clinker build) prototype... sail No 5
Great boat but needed a fair bit of wind to get her moving and 4 people to lift her!
will try to find a photo
 
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