flush plywood hatches

[BrianP]

Has anybody made, or seen a method, for making flush ply hatch covers which seal well and do not have the dogs sticking up. Trying to think how to make a ply seat top access hatch which sits on it's sealing ring and is held down with a flush catch of some kind. Want it to be comfortable when sitting on it.

If I can solve this then I can use the same system for below cockpit floor storage. Not too expensive please, need 6 hatch covers all together.

Thanks,

Brian

[BrianP]

Just found this thread on the WBF for a clever flush ply hatch you can sit on - lots of cutting to do though.

http://forum.woodenboat.com/showthread.php?102513-Wee-Rob-Bulkhead-Hatches&p=2474378#post2474378

Brian

[Timmo]

Nice idea, but looks complicated and not sure how the twist on and off will work with a grippy rubber seal resisting the turn..

Some more ideas here:

http://www.clcboats.com/shoptips/fitting_out/hatches_no_toggles.html

And here:

http://www.orcaboats.ca/howtopdf/MagneticHatches.pdf

I like the magnet idea, not tried it yet. The rare earth magnets cost a fortune from places like Axminster but can be found much cheaper through a Google search.

Tim.

From: "BrianP

Just found this thread on the WBF for a clever flush ply hatch you can sit on - lots of cutting to do though.

http://forum.woodenboat.com/showthread.php?102513-Wee-Rob-Bulkhead-Hatches&p=2474378#post2474378

[Jeremy]

I've bought some really powerful neodymium magnets from eBay, much cheaper generally than other places.  Here's an example of some fairly easy to use ones, with countersunk holes to make them easy to fit: http://cgi.ebay.co.uk/14-D1-2-Countersunk-Ring-Magnets-NdFeB-Neodymium-/370213657446?pt=UK_Collectables_WeirdStuff_RL&hash=item5632741b66

These things are seriously strong.  I have some 20mm diameter ones and it's near impossible to prize two apart that are stuck together.  I think they'd hold  hatch down against a neoprene seal very effectively, but you'd need a good purchase to get the hatch to open.


Jeremy

[BrianP]

Any idea how far away a compass would have to be to be unaffected, or could you swing the compass with all hatches in place and just make sure you only sail a compass course with the hatches in place?

Brian

[alopenboat]

On 1 Mar 2011 at 12:03, BrianP [via UK HBBR Forum] wrote:

> Has anybody made, or seen a method, for making flush ply hatch covers
> which seal well and do not have the dogs sticking up. Trying to think
> how to make a ply seat top access hatch which sits on it's sealing
> ring and is held down with a flush catch of some kind. Want it to be
> comfortable when sitting on it.

If you are a DCA member and you have the past Bulletins CD then look
at Bulletins 30 page 8 for a completely secure/watertight, cheap
hatch seal that could easily be made flush.

--
Hoping for calm nights

Alastair Law,      
Yeovil, England.
<http://www.little.jim.freeuk.com>          

[Paul H (admin)]

BrianP wrote

Any idea how far away a compass would have to be to be unaffected, or could you swing the compass with all hatches in place and just make sure you only sail a compass course with the hatches in place?

Use good quality stainless fixings - they will be non-magnetic.

Magnets and compasses don't mix.

-Paul

[Jeremy]

Brian,

I've just done a quick test with a group of 40off 20mm diameter neodymium magnets stuck together in a big lump and my hand bearing compass.  The compass starts to deflect at around 350mm from the group of magnets.

My guess is that this is a worst-case, as 40 magnets is more than you'd have in a hatch cover.

I think if you allowed a compass safe distance of 500mm you would probably be absolutely OK.

Jeremy