first post: Looking for ski boat stringer advice

[82skifine]

Hey guys, new to the forum and have been reading around a LOT. This is an awesome community. Im working on a near mint condition 1982 19 ft Ski Centurion. Its PCM351 powered w/ 200 hrs on it, all interior and exterior is in mint condition.

The only only thing wrong with it is that the stringers are totally shot:facepalm:

I have been reading tons on stringer replacements and feel fairly confident in the whole process when starting from a bare hull, tabbing them in, and then glassing the whole thing.

My question is...

After cutting the top out of the stringer and removing the crud inside, Its pretty well cleaned up and we are left with a GOOD fiberglass casing with a hollow top of where the stringers used to be. Is it possible to just bed the stringer inside of this instead of hacking them off and starting at bare hull?


The internal dimensions of the glass casing left are about 5.5" deep, 2" wide the length of it, with a 3" wide sistered section where the engine/trans mounts midship as its direct drive. With these dimensions its possible to prep the inside of the glass.

One of my older, sea-knowledgeable friends stopped by and we were thinking of rough and scuffing the entire inside of the fiberglass casing. Using 2 layers of 3/4" marine ply laminated as the stringer with a 3rd layer at the engine mounts. Bedding this inside the original fiberglass casing with the PL Premium adhesive. Then filling the 1/4" gaps on the side with a thinner peanut butter to avoid air gaps. The cap the stringer and run a layer of 1708 over it all. Would this work? Seems like a lot less work than starting bare. If I need to I will gut it all, but trying to avoid that.

Any suggestions are greatly welcomed! Im a newb so dont be gentle, Im here to learn

 

[saltwaterbluefish]

Re: first post: Looking for ski boat stringer advice

My 2 cents: Sometimes the quick/less work way ends up being more work in the long run. Since you have spent all this time and effort, I would spend the extra day getting everything ground down. Then you will know you made a good connection between the hull, fiberglass, and wood. Not saying the other will not work, I just know what will work and would shoot for that.

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

Yea thats what I was originally thinking. Then my buddy pointed out that the fiberglass is what gives the stability, and by leaving the original shell and adding to it, the result would likely be stronger than my beginner-ish glassing abilities starting from scratch. This got me to thinking.

Thanks for the advice. Hope to see a few others opinions before I decide

 

[Psiclown]

Re: first post: Looking for ski boat stringer advice

A problem with that is that the bond will not be as strong as if new glass was laid against the stringers. The old fiberglass is already wet out and cured so your bond will be glue to wood, rather than glass/resin to wood. Unless you wrap the new stringers in glass first and bed them while the resin is still tacky. Which would be hard to do since you'll have PL on the bottom and wet resin on the sides. (someone let me know if I'm way off base) If you go the way you are wanting to, be sure to use epoxy resin only.

 

[Psiclown]

Re: first post: Looking for ski boat stringer advice

You do have a perfect setup for pouring Seacast however...nudge nudge wink wink.

 

[Tolyn]

Re: first post: Looking for ski boat stringer advice

Greetings!

Be sure to core sample your transom in multiple locations. With your stringers rotting I would think there is a pretty fair chance your transom is shot or well on it's way. If you are going to go through the effort you may as well just do it once or at least have peace of mind that it is solid.

For what it's worth I started to go the route that you are suggesting with leaving the fiberglass there but found some trying to separate from the hull in places (factory didn't do such a great job I guess), the channels are not so easily cleaned out (in my case anyway) and it really didn't take that much effort to grind them down once they were cut short. Best of luck whatever you decide!

Respectfully,
-T

 

[Bob_VT]

Re: first post: Looking for ski boat stringer advice

Welcome to iboats.

Just to clear....... mid engine with prop shaft below boat? Well, it was mentioned above and you might want to pour your stringer's using seacast or nidabond ......probably the fastest stringer fix but not the cheapest. I know I would spent the extra and go that route myself.

 

[Woodonglass]

Re: first post: Looking for ski boat stringer advice

Yep, Core sample the Transom FOR SURE, and if she's good then I would Definetly go with Seacast, Nidabond, or ARJAY for the stringers. WAY easier and you would NEVER NEVER have to worry about a stringer job again.

 

[QC]

Re: first post: Looking for ski boat stringer advice

Yes this is a direct drive (mid-engine). That does make the transom less critical, and less likely to be rotted

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

Thanks for the replies all. Its mid engine/direct drive.

I forgot to mention we were planning to do one wrap on the wood and let it cure. Then prep it and bed it in PL. With the inside of the old fiberglass casing prepped and the wrap on the stringer prepped I figure a thin peanut butter mix of epoxy resin would hold fairly well.

I saw a thread with the Seacast stuff. Is it really strong enough as there are only two stringers, 5.5" tall and 2" wide? The engine and tranny mounts for the 351 sit directly on the two stringers. Seeing as its a mid engine boat, that seams like a lot of weight (600 lbs id guess) at the center of the strings with no wood in them. I have no experience with Seacast so I may be completely unfounded in my fears of having no real stringer.

Thanks a lot

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

As for the transom

Already laid new mat around the stuffing box, with a fresh dripless pack, but thanks for the concern.

Apparently the previous owner shrink wrapped the boat for about 10 years. They neglected to pull the center drain plug (in front of the engine, accessible form the inside) which is the lowest point in the boat. The rear drains are the lowest point only when trailering it and pulling the plugs on the ramp incline.

 

[Woodonglass]

Re: first post: Looking for ski boat stringer advice

I'm not sure I understand your statement about the mat and the stuffing box and a dripless pack. Could you please educate me. Doing a core sampling of the transom IS the ONLY way I know to make sure the transom is good. If you are saying that you are certain that NO WATER has been able to get to the transom during it's long storage and ONLY to the stringers in front of the engine then OK I understand.

As to the strength of the SeaCast It is MORE than capable of sustaining the weight of your motor.

Seacast Facts​

Seacast has almost triple the strength of marine plywood!
Seacast is made with 35% recycled fiberglass reinforcement...Go Green, with Seacast!
Seacast is waterproof. It does not absorb water, so it does not rot!
Seacast floats!
Seacast maintains resiliency at freezing temperatures and does not creep at elevated temperatures!
Seacast has excellent impact resistance!
Seacast is drill and tappable!
Seacast is very affordable, so everyone can repair a rotted transom!

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

Its an inboard, mid engine boat with the driveshaft running through the bottom of the hull about 3 feet from the rear of the boat. The transom is all glass which is in extremely good shape. The owner had the inside coated in some form af water shedding paint, it beads lik on a waxed car so no other hull issues. The stringers leaked because there were screws through the glass.h I figured you were thinking it was an I/O sterndrive where the wood in the transom would be rotted. I laid new mat over around the stuffing box where the driveshaft passes through the hull and added a dripless greasepack to replace the leaking one.

Gotta love how simple these ski boats are with direct drive, Our old 2300 Maxum was a PITA to replace the transom. Heck I couldnt even get the the rear 2 spark plugs out of the 350 mag. Now, i hinge back the motor cover and the engine is above deck with 360 degrees access. We literally had the engine out in 30 minutes at the start of this project.

I think Im going to do the seacast. For piece of mind on the weight distribution, I am thinking of adding a 3"x2" piece of 6061 aluminum L bar on the inside/top of the stringers where the motor mounts sit. It will be about 40" long and Ill round the inside edges so it wont concentrate any stress on the fiberglass. Its only .25" in thick and I have about 2" of inward and 1" of upward adjustability on the engine/trans mounts so no issue there. Ill coat it in shark hide so it wont oxidize. I already have the al. so it wont be an issue.

Im thinking of adding a few cross pieces outside of the stringers to help support the floor. What would be the best way to form a mold to pour the seacast in with? I should have about 3 gallons left over from the stringers so I might as well use it. Can I just mock up ply with some form of releasing agent on it and pour them? then remove the ply and do a layer of glass?

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

And I know I know, you guys prolly want pictures. Ill get some this weekend when Im home. Again, thanks a ton for the advice!

 

[Woodonglass]

Re: first post: Looking for ski boat stringer advice

OK, excuse me for being so DENSE. I DID read that it was a Mid engine, and I DID read that the Drive Shaft went thru the Hull. But I DID NOT stop to think ABOUT IT !!!!!! DUH!!!! Shame ON ME!!! Thanks for being so patient with an OLD TIMER.

As for your cross brace mold, yep your plan would work. Just wax up the wood really good and glass it up. Then pop off the plywood and pour in the seacast.

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

Haha, thanks for your input. I remember seeing your user name on a lot of informational comments in the other threads I was learning from.

Any suggestions on the type of wax, or will anything work? Also, I saw where seacast has to be used with poly resin. I have only ever used epoxy resin, so any suggestions on a brand or source for the polyester stuff? Im assuming the 1708 i already have should work fine with it. Can you still make peanut butter out of the poly stuff or do specific additive for poly? Sorry for the newb glass questions, but it seems like everywhere I read everyone already knows so its not mentioned.

Thanks!

 

[Woodonglass]

Re: first post: Looking for ski boat stringer advice

www.uscomposites.com is a GREAT source for your supplies. Yep, 1708 will be just fine. Their 435 Resin and some cabosil with chopped fibers will make some GREAT PB. Buy some pumps for the resin. Makes mixin a whole lot easier. Get a GOOD mask, Stinks to High Heaven.

 

[QC]

Re: first post: Looking for ski boat stringer advice

Remember we have that kinda stuff here too http://www.iboats.com/Boat-Epoxy-Resin/dm/*******.153698503--**********.343198111--view_id.217327

 

[Hoggar]

Re: first post: Looking for ski boat stringer advice

You do have a perfect setup for pouring Seacast however...nudge nudge wink wink.

Not trying to hijack but will this stuff work with an OMC stringer mount 200hp Buick 300 or would there be too much tork?

 

[82skifine]

Re: first post: Looking for ski boat stringer advice

im planning to bed a hot cammed 320 hp 351 direct drive with the stuff so I hope so. Im also setting the actual mounts on aluminum L bar to disperse the weight a bit better however.