Weed Hatch Mods

[gwinsk]

The top and baseplates of the weed hatch on my trad are fabricated from 6mm steel plate; I suspect less to do with what is needed than what is available. The top is clamped on with a small girder. Lid is fastened to baseplate with a 1" square tube spacer bar.

To reach the hatch I have to lie across the top of the engine casing and reach, at full stretch, through a one foot high gap and try to lift this lot, vertically, at armslength. A coronary bypass left me with a sawn up rib cage that doesn't take kindly to this abuse.

To reduce the problem, I'm thinking of making a lighter top plate and separate bottom plate, from 1/4" ply, sheathed in GRP. To ensure the bottom plate doesn't float, before the top plate is clamped down, I'll retain a metal box tube as spacer, fixed to bottom plate and also sheathed.

Has anyone else tried to lighten the weed hatch components and does my intended mod sound feasible?

 

Regards,

Gerry

[Paul Evans]

I would have big doubts about building the weedhatch base of something as flimsy as 1/4" ply, even if it were sheathed in GRP. The prop creates a considerable amount of turbulence just below the plate and is capable of smacking lumps of wood and other debris into the plate with considerable force. You must have heard the odd almighty CRUNCH-CLANG-CRASH as something gets swept up under the boat! I think you would be into constant repairs - without the possibility of finding your engine hole filling rapidly with water.

 

I have a similar arrangement on my boat and have thought of having a hatch put into the top side of the counter so that I can get a straight pull on the weedhatch assembly. That would involve some potentially expensive steelwork for which I am neither equipped nor skilled so it's down to money. Would this would be an alternative for you?

 

The other route would be to find yourself a nimble, strong and willing weedhatch slave but they are few and far between (Unless you can arrange to pick up stuff on your prop only when Clevett is the vicinity ) and might lead to gossip!

[gwinsk]

I would have big doubts about building the weedhatch base of something as flimsy as 1/4" ply, even if it were sheathed in GRP. The prop creates a considerable amount of turbulence just below the plate and is capable of smacking lumps of wood and other debris into the plate with considerable force. You must have heard the odd almighty CRUNCH-CLANG-CRASH as something gets swept up under the boat! I think you would be into constant repairs - without the possibility of finding your engine hole filling rapidly with water.

 

I have a similar arrangement on my boat and have thought of having a hatch put into the top side of the counter so that I can get a straight pull on the weedhatch assembly. That would involve some potentially expensive steelwork for which I am neither equipped nor skilled so it's down to money. Would this would be an alternative for you?

 

The other route would be to find yourself a nimble, strong and willing weedhatch slave but they are few and far between (Unless you can arrange to pick up stuff on your prop only when Clevett is the vicinity  ) and might lead to gossip!

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[gwinsk]

Another possibillity, though not DIY, would be to construct the two parts from 1/42 aluminium plate. I'd still need to sheath the bottom plate in GRP, to avoid galvanic corrosion. Perhaps a rubber based deck paint would achieve the same objective.

The separate, alloy, top plate could be insulated by a rubber gasket.

As to a slave; SWMBO isn't sufficiently malleable!

On a Trad, the rear deck hatch leaves you with a fairly long reach, down to the prop?

[Paul Evans]

How thick is 1/42 aluminium sheet? If that's 1/42" it seems incredibly thin - about 0.6mm. But aluminium might be a real aternative to steel if you can overcome the potential corrosion problem - after all Sea Otter boats are built of marine grade aluminium and they must have weedhatches on their inboard engine versions. Perhaps they might be able to give you some advice about thickness and construction. Their website is http://www.seaotterboats2.co.uk/

 

The long reach on traditional (or in my case semi-traditional) boats is another of the things that has put me off doing anything about the problem Fortunately, I'm still bendable enough to get down the hole with only the minimum of cursing. But with a straight run down, you can use the boat hook to catch sheets of oily, muddy plastic - they are always oily and muddy and you never pick them up in clear water.

 

As for SWMBO, I have the same problem. In the lady's opinion, anything under the rear deck or water is my province. I did persuade her to lend me the vacuum cleaner once to suck up some leaves and general muck but it cost me a dinner out. I was thinking (...dreaming?...) of an additional crew member with the requisite qualities but am sure that a foot would come down very firmly indeed!

[gwinsk]

How thick is 1/42 aluminium sheet? If that's 1/42" it seems incredibly thin - about 0.6mm. But aluminium might be a real aternative to steel if you can overcome the potential corrosion problem - after all Sea Otter boats are built of marine grade aluminium and they must have weedhatches on their inboard engine versions. Perhaps they might be able to give you some advice about thickness and construction. Their website is http://www.seaotterboats2.co.uk/

 

The long reach on traditional (or in my case semi-traditional) boats is another of the things that has put me off doing anything about the problem Fortunately, I'm still bendable enough to get down the hole with only the minimum of cursing. But with a straight run down, you can use the boat hook to catch sheets of oily, muddy plastic - they are always oily and muddy and you never pick them up in clear water.

 

As for SWMBO, I have the same problem. In the lady's opinion, anything under the rear deck or water is my province. I did persuade her to lend me the vacuum cleaner once to suck up some leaves and general muck but it cost me a dinner out. I was thinking (...dreaming?...) of an additional crew member with the requisite qualities but am sure that a foot would come down very firmly indeed!

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[gwinsk]

How thick is 1/42 aluminium sheet? If that's 1/42" it seems incredibly thin - about 0.6mm. But aluminium might be a real aternative to steel if you can overcome the potential corrosion problem - after all Sea Otter boats are built of marine grade aluminium and they must have weedhatches on their inboard engine versions. Perhaps they might be able to give you some advice about thickness and construction. Their website is http://www.seaotterboats2.co.uk/

 

The long reach on traditional (or in my case semi-traditional) boats is another of the things that has put me off doing anything about the problem Fortunately, I'm still bendable enough to get down the hole with only the minimum of cursing. But with a straight run down, you can use the boat hook to catch sheets of oily, muddy plastic - they are always oily and muddy and you never pick them up in clear water.

 

As for SWMBO, I have the same problem. In the lady's opinion, anything under the rear deck or water is my province. I did persuade her to lend me the vacuum cleaner once to suck up some leaves and general muck but it cost me a dinner out. I was thinking (...dreaming?...) of an additional crew member with the requisite qualities but am sure that a foot would come down very firmly indeed!

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Sorry; that should have read 1/4" but the shift didn't work.

[John Orentas]

Gwinsk.

 

This is a problem I have always meant to sort out, but so far havn't got round to it.

 

On my traditional boat, I have to slide along the counter alongside the engine to get access to the weedhatch, this gets more difficult as the years go by. The hardest part as you imply is actually lifting from a awkward angle, the dead weight of the weedhatch / cavitation plate assembly.

 

This could, without problems be replicated as an aluminium fabrication, 6mm thickness would be ok for both plates but stiffen the edge of the hatch (top) plate with a 25mm strip all round, and continuously welded to fit outside the hatch flange. 4 lengths 25 x 25mm square box section to separate the 2 plates, the assembly needs to be quite rigid to prevent the cavitation plate from vibrating against the counter.

 

A significant weight saving will be accomplished, there should be no problems with corrosion as long as it is well coated with bitumastic paint.

 

John Squeers

Edited November 14, 2004 by John Orentas

[gwinsk]

Gwinsk.

 

This is a problem I have always meant to sort out, but so far havn't got round to it.

 

On my traditional boat, I have to slide along the counter alongside the engine to get access to the weedhatch, this gets more difficult as the years go by.  The hardest part as you imply is actually lifting from a awkward angle, the dead weight of the weedhatch / cavitation plate assembly.

 

This could, without problems be replicated as an aluminium fabrication, 6mm thickness would be ok for both plates but stiffen the edge of the hatch (top) plate with a 25mm strip all round, and continuously welded to fit outside the hatch flange.  4 lengths 25 x 25mm square box section to separate the 2 plates, the assembly needs to be quite rigid to prevent the cavitation plate from vibrating against the counter.

 

A significant weight saving will be accomplished, there should be no problems with corrosion as long as it is well coated with bitumastic paint.

 

John Squeers

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John,

I hadn't thought of using four square section spacer tubes, to make the cavitation plate stiffer. Good idea and, in aluminium, unlikely to increase the weight significantly. I'd intended to have the spacers welded only to the cavitation plate, with rubber pads on top, to fill gap between spacer and top plate.

Re top plate stiffening. Do you mean a 25mm strip welded to the top of the top plate, or extending downwards from it, around the hatch walls?

 

I'll see if a local fabrication shop, who've done bike bits for me, will quote.

 

Gerry Winskill

[John Orentas]

Gerry.

 

It depends on the original design, just copy that as far as you can, my top plate has such a stiffener around the edge going downwards. The cavitation plate does need to be rigid, there are a lot of forces transmitted through the water from the prop. only inches away, vibration can be a problem. Also, as has been said it needs to withstand, say a log getting jambed between it and the prop. the two plates welded together via 4 post will make a tough unit.

 

Remember this an important item, weedhatch problems are one of the few ways that a boat can sink.

 

John Squeers

[gwinsk]

Gerry.

 

It depends on the original design, just copy that as far as you can, my top plate has such a stiffener around the edge going downwards. The cavitation plate does need to be rigid, there are a lot of forces transmitted through the water from the prop. only inches away, vibration can be a problem. Also, as has been said it needs to withstand, say a log getting jambed between it and the prop. the two plates welded together via 4 post will make a tough unit.

 

Remember this an important item, weedhatch problems are one of the few ways that a boat can sink.

 

John Squeers

 

John,

One of my reasons for not having the spacers welded to both plates is weight, though aluminium should be about one third the weight of the current steel fabrication. The other is that not having spacers welded to both plates, just to the bottom but long enough to touch the top plate, eases the problem of alignment. If welded to both plates, then any inaccuracy in spacings, welds, etc could result in the top plate being out of line, when the cavitation plate is located on the bottom edge.

Gerry Winskill

[Paul Evans]

I can foresee a problem with having the cavitation plate and spacers separate from the top plate. Your current bottom plate is likely to drop into a hole and not sit on a lip. Unless you know you have a lip, the bottom part of your fabrication will simply drop into the cut. I think you might be best advised to take the current assembly and ask your fabricators to replicate it in aluminium - at least you will know it will fit and that you are using a tested design.

 

If you decide to go ahead - keep us informed because it sounds as though there are several of us out there looking for a solution to the problem.

[John Orentas]

Paul.

 

I think you misunderstand the point of my reply. Most weedhatch assemblys are manufacured in the way I described, I have advised to beef it up a bit for the lighter material by using 4 connecting pillars rather than the one that is currently fitted in Gerrys boat, they are to be welded to the hatch cover AND the cavitation plate to form a robust and rigid unit.

 

You are probably thinking in terms of a separate 'drop in' cavitation plate which sits on a flange built into the swim-plate that type is uncommon these days. I would not advise having two seperate units.

 

John Squeers.

Edited November 15, 2004 by John Orentas

[Richard Bustens]

Hi John

Would it cost a fortune to have one cast in alloy, coz they are hard to remove and i havant got the rear panal in place yet, not sure i will be able to lift the dam thing when all the panaling is there to restrict access.

[Paul Evans]

John - I don't think I missed your point. In his last reply, Gerry said "one of my reasons for not having the spacers welded to both plates" and went on to set out a number of reasons. I'm agreeing with you - a single unit would be stronger and withstand (I hope) the pressures created by the prop and the occasional lump of debris.

 

Richard - I doubt that Gerry is looking to have his unit cast but is thinking of having it made from 1/4" aluminium sheet with square profile spacers between the cavitation plate and the top plate.

 

Gerry - Having thought about it a bit more - should the top plate be strengthened across the centre as well as round the edges? The screw down fixing - essential to ensure a good seal and stop water entering the engine hole - exerts a considerable force on the centre of the top plate. Would that cause distortion in an unstrengthened top plate?

[gwinsk]

John - I don't think I missed your point. In his last reply, Gerry said "one of my reasons for not having the spacers welded to both plates" and went on to set out a number of reasons. I'm agreeing with you - a single unit would be stronger and withstand (I hope) the pressures created by the prop and the occasional lump of debris.

 

Richard - I doubt that Gerry is looking to have his unit cast but is thinking of having it made from 1/4" aluminium sheet with square profile spacers between the cavitation plate and the top plate.

 

Gerry - Having thought about it a bit more - should the top plate be strengthened across the centre as well as round the edges? The screw down fixing - essential to ensure a good seal and stop water entering the engine hole - exerts a considerable force on the centre of the top plate. Would that cause distortion in an unstrengthened top plate?

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Paul,

I'd wondered about that possibillity and was considering a 1/4" alloy cross, welded to the uper surface of the top plate. I guess another option would be to seek a heavier gauge for the top plate. Could finish up with the same weight as now!

To get around the alignment problem I could get it initially fabricated in two parts, then offer it up, with something like plasticine, no the top plate underside, before marking and getting the two sections welded together. Can't take the obvious route of giving the shop the existing unit, as we live some way away and I don't fancy leaving the boat with hatch exposed.

Gerry

[John Orentas]

1/ There is no reason why you can't use a piece of 1/2" ply to close of the weed hatch as a temporary measure.

 

2/ I doubt if the hatch would need much beefing up, but depending on the design of the clamping mechanism, perhaps a 6" square of ally could be welded in the cantre. Beware of distortion, intermittent welding is often better.

 

 

John Squeers

[Paul Evans]

I agree with John - there's no problem with taking the weedhatch assembly away from the boat as long as you don't try to move it. To be on the really safe side, disconnect the starter battery and put a notice up to remind yourself. That way nobodyelse can start it and sink the boat for you.

 

And the square of alumnium on the top side looks good too....

[Pinkatpole]

I have just solved the problem on my trad by having the quick access panel cut in the back by a set of local fabricators. Dont use boatyards, to expensive. They made a new rear floor panel from 6mm steel, grooved it to match the floor grooves, square frame for it to sit in, cut the access hole out, grinded it square, welded the frame to the under side of the new access hole. New floor panel now sits perfectly in its support frame and clamps with 4 recessed square key 90 degree catches. All for £190. Boat has yet to be painted, but touching up on a painted but should be minimal. I can take the panel out and the hatch is 1ft below the hole. No more boating yoga.

[Paul Evans]

Now that sounds a very reasonable price. Can you post name, address and telephone number of the people who did it for you?

 

But.... how do you cope with extra foot when reaching down the hole?

[gwinsk]

Now that sounds a very reasonable price. Can you post name, address and telephone number of the people who did it for you?

 

But.... how do you cope with extra foot when reaching down the hole?

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A friend's boat is fitted with one but that's a semi trad. I had a good look. Access is OK but mainly because, having lifted the large engine cover, inside the rear door, he can stand down in the engine compartment, so that he leans directly over the weed hatch. My setup would involve wedging feet either side of the hot gearbox. Less attractive.

Gerry

[Paul Evans]

I know that problem - currently I have to place my posterior very, very close to the exhaust pipe. Stripes on the bottom are a clear danger!

[Pinkatpole]

Now that sounds a very reasonable price. Can you post name, address and telephone number of the people who did it for you?

 

But.... how do you cope with extra foot when reaching down the hole?

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Paul

 

Will get the contact number for you over the weekend

 

Once the panel is removed, I can sit in the hole, with both feet either side of the weedhatch, undo the clamp and list it out with a straight back. Saves the abuse I gave the back during the fit out, lol

[John Orentas]

I deliberately ordered my boat WITHOUT a hatch on the deck. I worked out that I would need arms like a Gibbon to reach down to my prop. from above the deck.

 

A word of caution

A boat on my mooring was sunk a while ago because the owner left the weedhatch off. The marina owner needed to move the boat for a legitimate reason. In the process two burley chaps stood on the rear deck of the boat, unknown to them water poured through the hatch to such a degree that even when they stepped off, the trim was so affected that water continued to flow.

 

By the time they had broken into the boat in an attempt to do something about it, it was too late, it settled gently on the bottom.

 

John Squeers

Edited November 16, 2004 by John Orentas

[Paul Evans]

So that's why my surveyor suggested extending the weedhatch sides upwards - something else I haven't done! I guess I'll just have to ban big burly people from my boat - apart from me of course!