PDA

View Full Version : Stringers are Shot.



AGUESS
09-08-2000, 03:02 PM
My Stringers are shot. Talked to Donzi, they said that they make them out of 3/4 marine plywood laminated together. I can do this, but was wondering if anyone had any other good advice.

As always, I thank you.

Alex Guess

oldLenny
09-08-2000, 05:00 PM
Use resin soaked 3/4" XL plywood, basically a preservative impregnated board, with UF glues for the laminations, with say 1 1/2 oz mat between each lamination. Encapsulate the whole mess with mat starting on the hull bottom, left or right of the stringer by 6", or so, going up onto and over the "new" stringer and down on the hull bottom other side by the same amount. Mat should be placed under the new plywood laminated stringers as well. Maybe say two layers, very wet. The plywood will be placed with end/edge grain facing the sky and I would take a 3/8" round-over router bit to the two top edges and radius as the resin soaked mat does not like hard (90 degree)corners to bend over and will compromise its integrity to make the turn. Grind the hull area to be reglassed prior to beginning anything and paint brush on a lot of resin prior to the first layment of any mat. The resin (if fiberglass) should be un-waxed. I would use little catalyst as it gives you lots of screwing around time. An overnight cure would be dandy. The last coat of anything, resin/mat etc. will need to have air dryers in it or wax. This lets the fiberglass cure to a "dry to touch" feeling and allows for painting. Subsequent layers of glass will not want to stick to it readily without grinding sanding once again. The un-waxed, no air dry resin is what you use in laying up a boat that is going to get additional layers of glass/parts etc in the near future. When you have layed up your finally' layer you add the driers for painting or a finished feel. Un-waxed resins feel sticky when dry and are not what you would want. Remember, if the stringers were properly encapsulated in the first place you would not be doing it this time. It is an easy ordeal when all is said and done.

P.S. I would lay up the stringers first on a bench or something, however many layers/widths required, all resin soaked to death with mat between each lamination. I would leave resin OFF of the two outsides till later. A heavy weight placed on top of the runs of board horizontally overnight would do the trick. Wax paper can be placed down first and on top of the stacked package as it will not stick to the mess when dry. When dry, I would then cut the layed up board to height/curvature/taper and then place into the boat stringer area for the glassing in procedure.

CDMA
09-08-2000, 05:17 PM
I did the same thing this winter. Lenny's description is nealy the same as the way I did it. A couple of things to add. Play with the glass. It bends better some ways than others. Also I HIGHLY the West System products. I would use nothing else. There technical manuals are also a tremendous help. I would be happy to talk to you about it in detail if you wanted.

Chris

oldLenny
09-08-2000, 05:25 PM
Oh, and by the way. Glass mat has an up side and a down. The down side is way "hairier" and less smooth than the up side. It makes no difference in the long run but one way makes your steel serated rollers and goopy paint brush look like a sasquatch. Look into bi-axial and tri-axial knits if you can. Dont use any roven-woven type to start with or finish with... I would think this is a 3-4 layer makeup on the hull bottom.

AGUESS
09-09-2000, 08:09 AM
Great info. Thanks for the detailed reply. I will start working on this next week, and might have other questions.

Thanks again. It is nice to learn from other masters.

Alex.

oldLenny
09-09-2000, 08:01 PM
AGUESS... one more thing I want to add, for and anybody else reading... You should never glass a piece of wood directly to the hull, even if you have done a scribe job that is the envy of all. The glass will contract when drying, minor mind you, (thousandths), but will "telegraph" the vertical line into the gunwhales. Junk boats and backyard stuff will have this present. This is not of concern to you on the hull bottom, especially as thick as it will be down there, and stringers to boot, but if you are ever replacing a bulkhead or something, remember, "insulate" the transition from hull to plywood with 1/2" or so Kleg-cell or urethane foam. The foam will gobble up the resin and turn into a rock when dry but will compress as the plywood/glass mixture dries and contracts and will not telegraph the vertical line into the hull. Again, this shouldn't even be a consideration on the bottom of your hull as it will be a very thick mix already and shouldn't telegraph anything as the forces are not that great.