GIS Flotation and drainage?

Watermaat · #1 25th Oct 2009, 03:27 AM

Quote:

Originally Posted by Watermaat

Hi MIK,

as we discussed before, I am very keen to get my GIS optimized in case of capsizing. I will probably sail 99% single handed and sometimes on bigger stretches of water with more severe conditions.

First thing: I will make a "boxed" central seat; one extra bulkhead that closes the front of the existing seat, placed left and right of the centerboard case. I will make this seat 40cm wide in stead of 30cm. Overall this will add significant flotation volume in the wide center of the boat, especially effective if capsized.

Second thing: I would like to use one or two draintubes through the aft compartment above normal waterlevel. These drains should be able get rid of a big amount of water after capsizing and leave much less water to bail out. These tubes will be in 2-3 inch range to have sufficient flow of water.

I found a picture where draintubes are seen in a Finn dingy Attachment 120036 , be aware that the Finn's floor is double, but still below water level ( they keep it low to optimize your hiking position ) . These drains take care of a mayor part of water, the rest is drained by a selfbailer in a well. It seems that Wayfarers have similar drains, but could not find pictures.

I would like your opinion ( and ofcourse from anyone else ) about where to position these two drain tubes.
Vertically : I am considering to have them placed just above the bottum wood in the transom ( bottum of tube about 5 cm above bottum of the hull ) and get them parallel to the seat top through BH4. This should make them almost parallel to normal waterlevel ? The bottum of the tube will enter through BH4 at about 10cm above the bottum of the hull.
I do not dare to place them much lower to avoid inlet of water in normal conditions, I will make a valve kind of closure at the transom end that keeps splash or waves out ( flap-type or perhaps cork-balls on shock-cord )
I do expect they will drain out lots of water, if you put your bodyweight in the back of the boat? Don't forget that this boxed middle seat will leave significant less water after capsizing.

Horizontally: Since GIS is floating deep on the side I probably need to have those tubes pretty close to the center-line centered at about 40cm from each other ? An option is to have one bigger tube in the center, but I need to sort out how that works together with fixing the rudder. One big tube slightly offset would be another option?

Any comment? idea's ? Tips ? Do's and don't's!

Thanks in advance
Ralph

I have posted this in my building thread, but decided to start another thread regarding this. I am very interested in any-ones experience with GIS.

Boatmik · #2 27th Oct 2009, 06:29 AM

Ralph sent me a shorter question direct ... I have not seen the above. It might be a good point about keeping the Drain tubes away from the extreme outside position, but also I think around centre migh not be a good idea too.

Quote:

Ralph Gerssen wrote:

Hi MIK,

We have discussed these "drain-tubes" in GIS aft-compartment a while ago and put this question again in the forum.
I am at the stage to make a final decision where to put them.

I guess that GIS aft-deck is pretty close to parallel on the waterline in normal sailing conditions. Is that right ?
I am thinking to run one or two tubes parallel to this deck. They will end about 2.5 cm above the transom bottom corner at their lowest point. This means they will have to start about 7.5 - 9 cm ( lowest point ) above bottom level in BH4 to be self draining in normal sailing conditions ?
Does this make sense ? I think this could drain the bigger amount of water, if you keep your body-weight well behind. Perhaps you could even sail with the remaining water to a sheltered place to bail the rest out ? ( this in combination with the enclosed middle seat )
I do not expect this height to give much inlet of water in normal sailing conditions ?

Any recommendations?

Thanks in advance

Best Regards
Ralph

Hi Ralph,
I am waiting for my train in New York to go to Mystic so see the biggest small boat museum in the world.

The train has been delayed an hour or more, but there is a stray internet connection I have been able to pick up.

The decks go uphill slightly towards the bow so your plan is perfect. You can use mylar flaps on the outside to prevent the water coming up. Main thing is to cut the speed of water going up the tube the wrong way and the flaps will do that . There are stronger methods too using neoprene and some pieces of plywood stuck to to make a flap with the neoprene acting like a hinge.

But I am really interested to see how it works. The holes probably need to be reasonably close to the sides of the boat so they will still bail with heel. Also keeps the middle part of the area free for a little bit of storage of light stuff. Don't make the diameter too small - I would be expecting a diameter of around 37 to 50mm.

Best wishes
Michael

callsign222 · #3 27th Oct 2009, 02:14 PM

How about a tube running through the boxed center seat as well? It would keep you from running from the now empty stern to the full-of-water bow and keep things more balanced. Same concept as the limber holes but for more volume.

Watermaat · #4 27th Oct 2009, 08:18 PM

Quote:

Originally Posted by callsign222

How about a tube running through the boxed center seat as well? It would keep you from running from the now empty stern to the full-of-water bow and keep things more balanced. Same concept as the limber holes but for more volume.

That has been taken care off, see attached pictures. After carefull coating they will be closed with a ply "lid" . Both 2 x 6 cm .

dkirtley · #5 29th Oct 2009, 01:41 AM

Ohhh, pretty. Seems a more elegant solution than the pvc and such I have seen used or that kind of drain.

MiddleAgesMan · #6 29th Oct 2009, 09:50 AM

You might consider a single on-center intake in bulkhead 4 with a pvc-Y in the aft seat compartment running two tubes out the transom. This should reduce ingress of any water while capsized, on her side.

Watermaat · #7 29th Oct 2009, 10:19 AM

Quote:

Originally Posted by MiddleAgesMan

You might consider a single on-center intake in bulkhead 4 with a pvc-Y in the aft seat compartment running two tubes out the transom. This should reduce ingress of any water while capsized, on her side.

This was one of my initial thoughts too, but capsized on her side water will get in anyway by the submerged gunwale? Once upright it's nice to be able to still drain water when she is heeling and in that case it's better to have two inlets in BH4 a bit more to the side ( but not too much, to avoid water draining in under normal conditions, if you heel very much ) .

joern · #8 30th Oct 2009, 08:13 AM

Hi Ralph;

the dunking of the gunwale and the deepfloating capsized GIS is your assurance against fast drift in higher winds. The higherfloating Raid 41 shows the problems with that, see the threads texas 2000 and Raid 41.
The rationale in draintubes is to get get rid of the water after righting the boat faster and easier than bailing and therefore recover the stability of the boat faster. Lots of water in the boat makes for a difficult balance not only in a wake.
So in my eyes the coming in of some drops of water is no problem if you get it fast outboard again.
For placement of the tubes a figure of the floating lines of the boat with the crew-weight shifted on the rear tank would be useful - MIK, would you mind to help with that?

PVC-tubes mentioned - the problem with PVC is - it is difficult to glue securely. So your wooden pipes are the better solution.

Hope that's helpful - Jörn

Watermaat · #9 30th Oct 2009, 10:00 AM

Quote:

Originally Posted by joern

Hi Ralph;

PVC-tubes mentioned - the problem with PVC is - it is difficult to glue securely. So your wooden pipes are the better solution.

Hope that's helpful - Jörn

Hi Joern,

These wooden pipes are now used through the middle compartment; this "boxed" seat.

I still need to sort out how to make drainpipes through the aft compartment.
My initial thought is to use PVC pipes that are widely available in various sizes. I need to try if there is sufficient bondage with epoxy. Perhaps a wide epoxy filet around these PVC pipes could do the job? Perhaps I could reinforce these filets with glas-tape, to get a bigger surface and bondage? Another option is to cover full length with epoxy-glas laminate ( and use PVC as inner mold ) ? There is also an option of using a more flexible "Sikaflex" or any other marine sealant ( PU based, Poly-sulfide or MS polymer ) or even a combination of glas-epoxy flange with sealant...........I really need to sort out and test a few options before I can make any decision.

Wooden box-pipes through the aft compartment are more complicated if you want to run them parallel on the deck. I wouldnot have thought about that, but making them out of 6mm ply-epoxy and perhaps some glas it is an option I will consider.
Really helpfull thought!

Best Regards
Ralph

Boatmik · #10 30th Oct 2009, 01:49 PM

Hi Ralph,

I have not had any experience with this ... but this is what I would do.

I would look at creating a good surface area for the pipes by adding some extra layers of ply on the inside if necessary to make about a 12mm or 18mm landing surface.

Then the holes should be accurate on the visible faces of the bulkhead and the insides can be sanded to give a little bit of clearance.

Sand the outside ends of the pipe so it is matte.

glue it in with sikaflex (not silicon sealant for many reasons). Clean up the visible faces with turpentine. I would suggest that the outside face be epoxy sealed first otherwise the sikaflex will get in the wood grain.

HOWEVER - you could do a destructive test to see if the PVC will glue adequately using epoxy or build some rectangular pipes from plywood.

MIK

Watermaat · #11 1st Nov 2009, 10:18 AM

I did a first test with PVC pipe and epoxy-glue.
I used a 75mm PVC through 6mm ply with epoxy-glue filet on both sides. I sanded the PVC surface with 100 grid before applying the epoxy.

So far it seems to work pretty well; I am not able to move the tube and cannot manualy break it out of the hole without breaking ply.

I have tried to remove some of these epoxy-glue spots that you see on the left side of the PVC pipe. With some force I can remove them, but this surface has not been sanded before.

Overall bondage seems to be more than sufficient to keep these tubes in place. I will try to cut and sand one side flat with the ply to see if there is still sufficient support to keep these tubes in place.

I will wait 24 hours to see what happens if the epoxy is really cured "rock-hard" and try to do some heat testing ( warm it up a bit to see if it still holds in hot-sunny weather )

Picture attached. Any other suggestions?

Boatmik · #12 1st Nov 2009, 10:27 AM

If you grap onto the tube and try to turn it that will check the shear strength. Because of geometry if you bend it in any direction the ply will break so trying to turn the tube around its central axis would be the test.

Also get a knife and see what happens if you chip off some of the epoxy on the sanded areas.

MIK

Watermaat · #13 1st Nov 2009, 11:10 AM

MIK

If I get a knife point under the epoxy, I can chip off little pieces in the sanded area.

There is NO way I can turn around this tube axial. I even tried this by fixing this tube in a workbench and using the long ply strip as a 1mtr lever to turn the ply around the tube. Finally the end of the 4mm PVC tube broke into a spiral cut.

I also did a lateral breaking test. Finally the ply did brake ( as expected ), but a mayor part of the filet is still oke and fixed to the PVC. Even the opposite site of the broken ply is still attached to the PVC. see pictures.

As far as I see; there is no 100% perfect bondage to the PVC.........but overall bondage in a wide filet is strong enough to hold these tubes in place?

Watermaat · #14 1st Nov 2009, 08:20 PM

Regarding the size of the draintubes;
In racing dinghies tubes or transom holes are relatively big, to get rid of the bulk of water asap. For the testing I used a piece of 75mm PVC tube with 4mm walls ( inside diameter 67 mm ). This would certainly do a good job, if you race and capsize regulary.
For GIS I also could use thinner tubes. The closest match widely available is thick wall 50mm PVC tube with 5mm walls giving 40mm inside diameter.
Ideally it should be something in between (?) but I prefer thick-wall PVC tube since that's much stronger. So I am limited in my choices between 75/67mm or 50/40mm tubes.
The bigger ones ( 67mm inside ) certainly work and do a quick job
The smaller ones ( 40mm inside) are much less visable and still match closely with the wooden drainholes through my boxed seat ( 20x60 mm ). BUT it will take much longer to drain the bulk.
Any advice or comment?

Boatmik · #15 2nd Nov 2009, 12:53 AM

I think it might be hard to find the space to do the big ones if you look at the transom space available.

Also will look pretty ugly on that petite transom

So check. It might be possible to fit the reinforcing on the inside of the tanks for both but fit the small ones. If they don't prove useful then you can run a router around to fit the big ones.

MIK