hull integrity question

[vinnie1234]

Hello all. I'm not sure if this is the right place to post, but if anyone has experience in assessing the condition of the hull with a test run, perhaps you can answer my question.
I have a 1978 crestliner crusader bowrider. Fiberglass hull. I know there is a bit of rot in the floor as there is a soft spot in the floor, just past the helm on the way up to the bow.
Last night I had the boat out for the first time in a bit of chop. Wave height was around 2 to 2.5 feet with a very short interval. Some white caps. I was cruising around 35 km/hr. It's about as fast as I could go without really slamming the hull, but still there was the odd big one here and there and we were bouncing around a bit. I have read posts about bad stringers and been told that you can feel the bow flexing around when the stringers are rotting.
I have never owned a boat so I don't know what is normal but I will tell you what I observed and perhaps someone can tell me if this is normal.
When the boat was bouncing off the waves, I would feel the impact in my feet quite solid. I was paying attention to the attitude of the bow and it for sure did not twist in relation to the stern, but there may have been a little bit of up/down flex. Nothing really noticeable, so little that I am unsure that there even was any flex. It's hard to say when you are flopping around.
I was hitting the waves at about a 30 degree angle, doing some pretty hard turns. Actually in one turn when the waves were coming directly from starboard, the boat actually rolled off the top of a wave and fishtailed and went sideways a bit and it seemed solid.

The only view I have had of the stringers is by looking in the engine compartment where the motor mounts attaché to the stringer. It seems intact and solid.
So I guess my real question is: aside from pulling out the floor to have a look, is there a way to tell if the stringers are decent by driving the boat? If they were bad, would that be pretty obvious? I wonder if this is something I should worry about.

I also notice that when I pull the boat out of the water the hull seems pretty rigid. there is no bow flex when pulling it up with the winch, and there are no apparent stress cracks in the hull. This winter I plan to remove the carpet and replace the bad sections of floor. I then want to glass it over, remove the lounge seats and make the boat a little better for fishing. I expect that if there is an issue with the stringers I will be able to tell once I lift the floor and have a peek.

What should I be looking for?

 

[Woodonglass]

The only way I know of that you can know for sure is to take a drill and drill into the stringers and see what the shavings tell you. If they are light in color and dry...then the core wood is good and the stringers are good. If the shavings are dark and wet...then the stringers are bad. Soft spots in the deck don't always indicate bad stringers below. It all depends on how the boat was cared for.

 

[vinnie1234]

Thanks Woodonglass. If I drill into the stringers at the engine mounts, will that tell me if there is rot up front? I would expect it would have to be pretty bad to show at the back, but the boat has been sitting for years before I got it. I suppose that would give it enough time to spread?
Have you ever been on a boat with rotten stringers? If so, how does it handle?

I should also add that in calm water it feels very solid. The bow comes up steady until it is on plane, and it tracks nice and straight in the water with predictable turns.

 

[Woodonglass]

There are a multitude of examples here on the forum of boats that their threads start out with statements similar to yours and once they remove the deck and start exploring, they find that their stringer are total MUSH!!! I'm NOT saying your's will be but boats typically rot from the bottom up so if the deck is soft it's often a symptom of foreboding below!!! Hope for the best but...be prepared for the worst. A lot depends on how the boat was stored. If it was stored properly with the bow up, and the plug out then the bow of the boat should be the best part. If it was stored level, then who knows. If the plug was left in...Watch Out!!! Since you know you will need to replace the soft spot, at the very least, I'd cut it out and see what lies below at that part of the hull and then go from there. I would also drill the motor mounts to verify their condition as well as drill the transom. If it all checks out fill the holes with 3M 5200 sealant and carry on!!!

 

[vinnie1234]

Thanks. I was actually looking to see if I could find pictures of the structure of the boat underneath, as I can't see too well from under the engine due to the fuel tank. It just dawned on me that I have a borescope at my shop, so I will just take it home, and poke it under the rotten section and see what is lurking under there.
I know that the guy I got it from had it stored bow up with plug out. and the floor is solid everywhere else.
When you speak of drilling the transom, where specifically am I looking? I noticed that there was a hole already drilled into the transom - possibly from a former kicker plate? Anyway I filled it up, but before doing so I noticed that the wood inside was bright and dry.

Next chance I get, I am going to run the scope up under the fuel tank and up in the bow. I will post if I find anything.

By the way, I don't have any 5200 sealant. Can I use one of the following: Permatex silicone gasket sealer, JB weld epoxy or "The Right Stuff" to seal up my drill hole?

Thanks!

 

[Woodonglass]

I highly recommend that ALL boat owners ALWAYS have a tube of 3M 5200 Sealant. It's REQUIRED!!! Silicone and others just don't cut it for boats! 5200 or 4200 IS the absolute BEST sealant for BOATS. THE BEST!!!!! I would not use anything else except Thickened Polyester or Epoxy resin.

 

[REdington]

Vinnie, I get 5200 at the big box stores.
WOG is right that anything silicone does not belong anywhere near a boat. "JB weld marine" will work if you fill the holes and add tape over it so it doesn't ooze back out.

Rodney

 

[vinnie1234]

Thanks guys - and I DO believe you, but as a mechanic and an inquisitive soul, I must know WHY. Why is silicone so bad on a boat? What happens. it works quite nicely on cars or motorcycles........

 

[jigngrub]

Thanks guys - and I DO believe you, but as a mechanic and an inquisitive soul, I must know WHY. Why is silicone so bad on a boat? What happens. it works quite nicely on cars or motorcycles........

If you'll read the tube it will say "Not for below the waterline use". You're better off with a sealant designed for marine use.


Just because the aft section of your stringers and motor mounts look ok, it doesn't mean all is well or maybe you just have a little problem. If your boat has been stored bow down with the front of the boat lower than the stern you could (and probably do) have significant rot, especially since your deck is soft. Boats rot from the inside out and the bottom up and when the deck gets soft it means the rot has been working for a while. You'll find this out when you decide to dig into your boat.

 

[vinnie1234]

You guys on this restoration forum are hardcore pessimists eh? lol. I was thinking to myself how much fun I had in not knowing jack all about boats in april when I got this thing, to complete outdrive rebuild and engine repair. I wont get too smug tho' not after reading this.

It's all in good fun. I guess my real concern is not whether the boat has problems or not. It's fairly safe to assume it does, but I wonder if they are sever enough that I should use the boat? I am thinking that I will use it for this season, and then move it to my shop in February when business slows down. At that point I do the floor work.

If I find that I have major issues and have to re-do the stringers up, how long should I expect it to take? Don't know if this would make a difference in a first time instance, butI have a hoist and every power tool under the sun at my disposal. Plus 30,000hrs+ in the trade as an auto mechanic. What should I prepare myself for?

 

[Scott Danforth]

Lowes has 5200 for $8 for the medium tube.

3M 5200 is a sealant/adhesive that sticks to pretty much anything, even below the water line. it is moisture cured.

Silicone sticks to few things, and doesnt cure well in moisture.

regarding stingers, deck, and transom. if you are motivated, stay motivated, have the right location to work, the correct PPE, and the correct tools, you can get it done in about 40 hours.

fiberglass boat repair tools are more like home demolition tools or tools from a horror film than tools an auto mechanic would use. Drills, sawzall with lots of blades, 7" grinder with 24 and 36 grit discs, multi-tool with lots of blades, and my favorite - a 4.5" angle grinder with 4.5" carbide saw blades.

 

[vinnie1234]

Hi Scott. Nice list. All on hand and available. lol. Moisture cured! Exactly the info I was looking for. I will have the month of February and maybe the first week of march to play with it before I will have to get it out of the shop. I think I should start planning a complete re-do now.

I was thinking about using that epoxy chip garage floor stuff as a floor topper in stead of carpet, and building the floor in sections with opening cubbies for fishing gear and a dedicated tool box. Won't be that big of a deal if I have to carve out the stringers and make it right at that point. I guess the next step would be to fair out the few chips in the hull and new gelcoat?

Has anyone used alternate materials to wood for stringer repair?

 

[REdington]

Has anyone used alternate materials to wood for stringer repair?

Why go back with wood if it rots, right. Well after you rebuild a boat, most will take the necessary work to take care of it and keep it dry so it doesn't happen again. Water in the hull is what rots the wood and if you keep it stored dry, it will last you a long, long time.

Rodney

 

[vinnie1234]

I can certainly appreciate that, however I wonder if wood is truly the ideal material for this. Did the boat manufacturer use wood to save money? Just spitballing here, but perhaps replacing the stringer with something more rigid would help to relieve flexure and the potential for stress cracks in 40 year old glass? The first thing that comes to my mind is carbon fibre rod. You can buy various diameters and lengths and stitch them together with cloth and resin? Lighter, more rigid and won't rot. I think you can get is "boxed" too. Stupid idea? Maybe. hmmmm....

 

[kjsAZ]

CF would be stronger and less flex but only if you make it exactly to shape. If you stitch it together that's where it will break.....

 

[vinnie1234]

Well, i guess I have some time to mull it over. My main concern is that the boat is safe to use for now. Being new to boating I have visions of a massive hull fracture and the bow falls off. It all could have been prevented had I only knew what to look for.... I am sure that won't happen. If the boat were that bad I'm sure I would be able to see the bow twisting and flexing with every move. I just wish there was a way to Guage the condition from a drive. I know in a car I can tell if the frame is soft, or worn bushings - just from a drive down the road. Maybe a marine mechanic would know how to assess this from a test run....

 

[jigngrub]

You can buy marine grade plywood that won't rot even if it gets wet:
http://www.pontoonstuff.com/collect...et-flooring/products/3-4-marine-grade-plywood

It comes in 1/2" thickness too, but not from that supplier.

It's light, strong, and easy to work with.


Compare the rotten stringers on your boat to the chassis on your car or truck. The front and rear thirds look brand new, but the middle is so rusted out you can stick a screwdriver through it. Sure the car stops and goes and turns corners real nice and there's no indication that anything is wrong... but one of these days...

Rot is slow but diligent, it never stops to sleep or takes holidays... and by the time rot is discovered in a boat it has been working hard for years... and in a lot of cases decades. Read the different resto threads and educate yourself in the ways of boat restoration. Here's one about a boat the same age as yours and the OP thought he just had a small soft spot to repair in the deck and all would be good:
http://forums.iboats.com/forum/boat...ll-repair/593526-first-attempt-at-boat-repair

 

[vinnie1234]

I get your analogy, but if the middle section of a car was rotted like that you would know it. The difference between the car and the boat for me,is that I don't fully understand the distribution of force as applied to the hull from the water. In a car,you can put it through specific maneuvers to tell what's going on. For example, excessive torque steer is often the result of worn control arm bushings, whereas if light braking causes the thrust line to change, it could be frame rot such as the trailing arm bushing rotting off the underbody. It would be nice to know how to make a boat sweat

 

[jbcurt00]

It would be nice to know how to make a boat sweat

You drag it into the garage, get out your saw-zall, spade shovel, all manner of pry bars, and a few other demo tools & set them on the bow or splashwell of the boat, play forboding music {Jaws theme perhaps **& punch the garage closer button. As the door half way closed, ya flip off the lights. When the door gets down to the last inch or so of daylight seeping under it, ya turn up the volume on the Jaws theme.................

Once it's locked in the garage, tools at the ready, in the dark, any boat that squeals gets cut, simple as that............... :faint2: :lol:

If it were easy to tell there was 3 seasons of safe boating left, we wouldn't err on the side of caution. I'd love to be wrong, Jig would too. Sadly, utter carnage below decks is significantly more common then anyone would like to suspect.

Sellers that hide it from unsuspecting buyers is too. Unfortunate, but read thru the resto forums, there are lots of similar cautionary tales. And more then a couple that start:

Carp, I barely made it back to shore, the dock...........

Thes ARE boats from the resto forum:

And if most of the resto's didn't start out or end up as full guts, what would we do instead of hanging around the dry dock, leaning over a transom, chewing the fat over a frosty adult libation, b!tching about life getting in the way of boat work/use or actually fixing a boat?

 

[vinnie1234]

Yep. Nuff said. These boats are all in better condition cosmetically than mine. Sun faded, seats torn, etc etc. Jeez. So, how would a surveyor figure this out? I can easily drill the stringer and transom at the back of the boat, but what about the bow.....?