National 12

General Boards => General National 12 chat => Topic started by: tony on 27 May 2012, 09:46

Title: transom flaps
Post by: tony on 27 May 2012, 09:46
hi guys as a newbee when i purchased my n12 the transom flaps were siliconed on and had cracked ive now removed them, they were also on hinges , can i buy replacments and how do i seal them cheers
Title: Re: transom flaps
Post by: Interested Party on 28 May 2012, 08:07
They are normally held shut using elastic cord from inside the boat.  If the boat is sailed correctly trimmed they should not let water in.  The cord should be able to be released when needed.
They come into play, when trying to get shot of a lot of water inside the boat, post capsize or near capsize - when the self bailers are not enough and you need to rid yourself of a lot of water quickly
I would suggest getting some plastic sheet and cutting out some new ones, using the old ones as templates to re-instate them properly with the hinges.  I, personally, have never seen them for sale.
My classic Starfish (2383) does not have any - but I wished it did after a capsize this weekend.   I also wish I had checked the access hatch on my forward tank - as it floated passed me!  I also wished my forward tank had drain plugs in it.  Doh!
I am considering fitting some.
Hey ho!
Steve H
Title: Re: transom flaps
Post by: tony on 28 May 2012, 08:07
thanks steve for your answers, i have now made them with ply and west epoxy saturation,i have used window sealant as the seal once it rubberises i will cut with a blade which will give a good seal on both surfaces taken your advise to have them in opporation
Title: Re: transom flaps
Post by: Interested Party on 30 May 2012, 08:40
To be honest you should not really need the window sealant.  The flaps should sit flush against the transom on the outside, with the elastic pulling them snug from the inside.
They also should not be in the water at all, when sailing, unless you are sitting too far back - i.e. not trimming the boat properly.
I prefere to have my transom flaps transparent - so I can look through them. This helps with the trimming  This is only useful when you have not got a rear deck or bouyancy bag in the way.
If you look at more modern designs, the holes in the transom have been getting bigger and bigger until they barely have a transom at all.
I am going to be taking a circular hole saw to my transom to make some holes for flaps.  just got to find some hinges.
Cheers
Title: Re: transom flaps
Post by: Not for the boys on 31 May 2012, 04:35
try here for some plastic hinges (bottom of the page)
http://www.dinghybits.co.uk/miscel.html (http://www.dinghybits.co.uk/miscel.html)
 
Title: Re: transom flaps
Post by: Tim Gatti on 08 Jun 2012, 02:32
You shouldn't need hinges - most chandlers sell flexible acrylic sheet for the purpose.
Get a piece big enough to span both openings in the transom and fasten it on the centreline using the lower rudder fitting fastenings.
Drill a hole in each 'window' for shock cord to hold them closed against the transom.
When wishing to use them to empty the boat after a capsize... bear off on a reach, release the shock cord and move weight aft.
If there's enough wind the boat should move forward as the water moves aft out of the flaps. They will spring open due to the weight of the water and close again as the flow subsides.

If there isn't enough wind you have two options:
1. Leave them closed and bail furiously with a bucket (or two) to get the water level down.
2. Sail for the nearest beach, pull the boat up, open flaps and drain out.
Anyone sailing a modern double-bottomed hull will by now have disappeared into the distance!
Tim
Title: Re: transom flaps
Post by: Jerry G (Guest) on 09 Jun 2012, 08:02
You may not even need lackies.  On Crazy Diamond (double bottom Big Issue retro-fitted with foot wells) we originally had the usual double bottomer holes in the transom.  It was far too easy to scoop water over the aft "deck" into the footwells when launching or fiddling with the rudder etc.  Also, in light wind and following sea, each wave would deposit about 1 pint on the aft deck then gently pick the stern up and pour it into the foot well!  We bought thin perspex sheet from P&B, cut out the necessary shapes to give about 1 inch overlap all round the holes, then taped the upper edge to the transom as a hinge.  Initially we used sail repair tape but this tended to become unstuck after a while.  We then used a special Selotape which being clear was not so unsightly.  This is not the ordinary type which degrades rapidly in uv light.  It is 75mm wide heavy gauge tape used for repairing polythene tunnels (we have a large tunnel used as a lambing shed for our sheep flock).  We found that surface tension provided an adequate seal to the flaps without elastic.  They just acted like a non-return valve.  The tape may not work so well on a wood transom, ours was plastic.  You just need to know a nurseryman or sheep farmer with polythene tunnels!