Keel stringer problem

[drewpster]

The center stringer for my little tri-hull has a big gap under it. (1"-1 1/2") The proper way to fix this would have been to cut the timber so that it fit into the keel filling the gap. I did not do that.

Originally the factory simply placed the stringer on top of the groove inside the keel. They then wrapped the stringer in fiberglass forming hat shaped stringer. The problem was that instead of using fillets the glass allowed to bridge in the corners. This left gaps at the stringer's lower corners and under it in the keel. To fix this I ground away the bridged glass and filled the keel.

I thought when I initially fitted the center stringer that the filled area would be high enough to support bedding compound and the new stringer. The problem is that I did not cut the stringer wide enough. If I continue cutting the center stringer to make it fit in to the groove it will not be high enough to support the deck.

The string represents the bottom of the new deck. As you can see there is a large gap under the timber. If I keep cutting the stringer to make it fill the gap the top of it will be too low. This ply was expensive. I could buy a new sheet and start over, but $$$. I could fill the keel some more but that will make it very thick (2 1/2"- 3"). I also considered possibly adding a strip of wood to the top of the stringer when the deck goes down. I really hate mistakes that cost me money! Any suggestions?

 

[Bob_VT]

Re: Keel stringer problem

Cut a filler strip or even in pieces, seal it up and fill the gap. It will leave the decking at the same level. Seat the pieces in with PL to hold in place and then use mat.

 

[Yacht Dr.]

Re: Keel stringer problem

Hello m8..

How many layers of 18 oz roving you plan on tabbing your stringer ? Id say 1 or 2 layers of 1.5 oz mat then 3 layers of 18 oz roving. at that point your top floor gap will be about right. IF too much on your string then grind..too little put another "cap" of roving.

looks like its almost done there.

PS. you really dont want your stringers to hard point on your hull.. I suggest floating stringers ( gap between wood and hull ). your 50 + oz of glass becomes your stringer.

YD.

 

[drewpster]

Re: Keel stringer problem

I had planned on using PL premium to bed the stringers, keeping them off the hull. I was just worried about the width of that gap. How far off the hull the stringers need to be? Does it matter as long as there is no hard contact between the stringers and the hull? I like the filler strip idea under the stringer. (thx Bob) to save on a little resin. Unless you think the glass needs to be thicker on the stringers. I was hoping to hold at about 1/4" thick for everything. (1/4 PL under, 1/4 glass covering)

The plan is to use temporary cross braces to set all three stingers at the same time. I will use the braces to hold the stringers in position while the PL cures under them. I was going to use pieces of CSM to tab the stringers holding them in place. After filleting the corners I intend to cover the stringers in a layer of csm, layer of roving, layer of CSM (1.5 ounce). Do you think that is enough? How much glass needs to be on these stringers?

 

[Yacht Dr.]

Re: Keel stringer problem

Sorry for the late reply drewpster..

If I understand you correctly 1/4" of glass is good around your stringer. You dont need to finish with mat..better to use 2 layers of mat first then mat woving mat woving etc and end in woving.

Regards and good job .. YD.