How to repair Formula 18 keelbox?

Hi there,

It seems that we have a tiny hole somewhere in the port side hull of our Nacra F 18 Infusion mark II build in 2012. I think that hole is located somewhere in the keelbox.

What is the best way to find out the location of the hole? And what is the best way to fix holes inside the keelbox?

Thanks in advance for your tips :-)

P.s. Here's two pictures of our Nacra's port side keelbox.

This is not an easy problem to solve. There are two approaches to finding the leaks: one, gently pressurize the hull (with a very light pressure) and apply very lightly soaped water to the area you think there might be a leak in. The other approach, which is what I do, is to assume you have a leak (all trunks leak eventually) and to fix the leak. My approach on the Mk. 2 trunks has been three fold: First, in areas where there might be some structural damage, i.e board trailing edge slicing into the trunk, I add a layer of fiberglass with epoxy. Second, I think right above where the plastic spacers are on the bottom tends to be prone to leaking, and I fill this area with some epoxy (I used West Systems G/Flex). Finally, I apply gelocat to the entire back edge of the trunk and pull a vacuum on the hull at the same time, so this sucks into the trunk. This has worked pretty well for me. Keep in mind that you are just as likely to have a leak at the very top of the trunk as you are at the very bottom.

Also keep in mind that the front beam bolts can leak, or at least I am fairly sure they do, if you don't seal them. My boat is generally dry unless we are taking waves over the front beam.

Hi there,

A friend of mine works for Nacra Sailing and I had pretty good repair plan from him. I hope this plan helps you others as well.

Morning guys.

So here some instructions to find the hole.

You can use a kite pump on the drainplug on the stern to pump air in to the boat
NOTE:! You can also over do this, and damage the hull. So be gentle with this. Check after 1 pump first how much air is coming out. A bit of pressure is enough (how much is a bit…., really not too much 😊

The other one is having a bucket with soapy water and let the water run on the spaces you want to check.

- Hatch.
- Daggerboardcase top+bottom.
- Any weird damages.
- Ruddergudgeons.
- Beam bed (let beams mounted).

When you find a small pin hole (pinhole or up to 1.5 cm) on the spot you shown on the picture do as follow.

- Use an old batten and double-sided tape to paste some grinding paper 120grid on the batten and grind and rinse the spot.
- Buy a small brush and tape it to the batten. Mix gelcoat and cover it with gelcoat.

When you find a bigger hole 1.5 cm and up you rather repair with glass cloth.

- Get some plastic tape, glass band 160 (or glass cloth).
- Use an old batten and double-sided tape to paste some grinding paper 120grid on the batten and grind and rinse the spot.
- Fold the tape so there is no sticky side. U need +/- 75 cm after folding.
- Prepare the gelcoat and the cloth on the tape.
- Tie/ tape a small wrench on the bottom of the tape, and let it go down the DB case.
- Position the cloth together.
- Use the batten to push the cloth on the damage.
- Remove the plastic gently.
- Use a brush with some gelcoat to make sure it is covered.

Success.

Regards,

Nacra Sailing

www.nacrasailing.com
www.performancesails.com
Hellingweg 110-116
2583 DX The Hague
The Netherlands
T +31 (0)70 3382900

Juha,

Great tips from Nacra directly. I am a bit surprised they have issues in the beam beds. I am not surprised the rudder gudgeons develop leaks over time, it seems about 2 years is max on the sealant. Perhaps a better caulk exists than 5200 (Sikaflex or?). I know the 505 guys bed their rudder gudgeons with epoxy, but I am hesitant to do that.

A similar set of instructions was recently relayed to me for fixing the daggerboard trunks. Use a hair drier on the drain plug along with the soapy water to help find the spots that are leaking. Once found, use the acid brush on a batten technique to apply some laminating resin (west systems or equivalent) to the area. Put a shop vac on the drain plug to apply vaccum to the hull and suck the resin into the hole. This works well with gelcoat too. Vaccum is much easier on a hull than pressure btw; don't overdo it but you don't need to be nearly as cautious as pressurizing the hull.

If you do find your portholes/deck hatches are leaking, these are a very nice drop in replacement that I've found to be leak free and easier to use than the screw-off style: http://www.beckson.com/twistdp.html

I have had great success using a shop vac in reverse. Put the hose in the inspection port and do not try to seal it. This creates pressure for the suds test but allows the bulk of it comeback out through the port hole. It also allows one person to do the job if you are working short handed.