Foam stringer replacement with cap in place

[stephenspann27]

I have a 1998 Sunbird Fish and Ski 190. I bought the hull for $900. I put an 1978 Mercury 140hp TOP motor on it that I had from another boat. After trailer work, new upholstery and lots of motor parts I now have like $4,500 into this thing. That is with doing all the work myself, except for the upholstery. I knew I had something going on in the ski locker area when I bought the boat, but I thought the the design was a wood stringer, with foam along side it, and the foam had detached from the hull. I had been putting off investigating the issues because of all the other problems I've had with the setup. Yesterday I pulled the ski locker hatch while underway and saw how much the hull was moving and it shocked me. It was wipping up with every little ripple in the water. I thought I better stop putting it off and fix it. I had had a fiberglass guy look at the bout when I first bough it. I was showing him some stress cracks in the port side chine, and he said the stringer was probably detached in that area. It turns out he was right. What shocked me though, is as i started chipping away the foam I found that the entire stringer was foam. I'm not sure how I am going to fix this. There is no way i am decaping this hull. I was thinking about getting all the foam out I can, grind everything down, and use some form boats to poor in sea cast stringers. I feel like I opened up a can of worms by chipping all this foam out, but the "stringer' was doing nothing in this area, it was no longer tied into the hull. Let me know how you guys think I should approach the repair.

 

[Woodonglass]

Welcome to iBoats!!!

Sorry to hear about your problems. I think additional pics from a bit more distance are in order. It's really hard to tell exactly what you're working on from the two pics you've posted. I'm assuming the first pic is of the "Stringer" intact and the 2nd one after you tore into it. Is that correct?? Additional pics will give us a better perspective of the issue and allow us to give you much better advice as to a possible solution.

 

[gm280]

As sad as it seems, I honestly can't see how you are going to accomplish your project without decapping it. If it is really worth your time, do it the correct way and you will have a boat for a life time that will never ever be any problem again. Do post the picture like WOG suggested. That is the only way we can see what you are seeing...

 

[stephenspann27]

You are correct about the order of the pics. I'll do some digging on my pc and see if I can find pics from a higher view. Decapping isn't really an option for me. My wife has had it with this project and she wants me to just get a new boat. She woudn't tolerate me spending as much time as it would take to depcap it and do it "right." My plan is to chip out all the foam and then put in a two pieces of plywood spaced about 10'' apart, and pour sea cast between those two pieces. I will properly bed those pieces of plywood with peanut better,and tab them to the hull.

 

[stephenspann27]

Bad stringer is to the left. This picture also shows the ski locker pan in place. I have already pulled that out and cut a new piece to install.

 

[DeepBlue2010]

First, take a breath and cool down. What can of worms you are talking about my friend?! Having a boat is having, living with and being responsible for a can of worms. The sooner you will get to make peace with this simple fact the better for your blood pressure and your overall mental health J

Foam stringers are not that uncommon and they are not necessarily bad by design. It all depends on how they are fabricated. Foam stringers don?t rely on the foam to provide structural support. The foam is there only to provide a ?shape? to glass on. All the structural support is from the glass. The glass in this case is much thicker than it is in the wood stringers case.
Some of these stringers are shaped on a mold and glassed to the hull hallow. The point is, you don?t necessarily need a core for your stringers whether wood or seacast or even foam. Different designers do different things to provide longitudinal structural support for their boats.
As WOG pointed out, I can?t really see what are you working with from the pictures you posted. But, I am guessing you are dealing with delamination of the stringer(s). You need to access if this delamination is in the area you spotted only or all over the place. If it is the former, I don?t think the situation is as dramatic as you think. All you need to do is to start glassing the stringer again ?the right way?. We can give you the details of how to do this when you confirm that this is actually the case.
But if it is the latter, we have to talk J

Post a lot of pictures from different distances or better yet, post a video of you can. Make sure to show us the thickness of the glass you cut from the stringer to get to the foam.
On the bright side, if you had a wood stringer and the wood is rotted, there is no way you can do a localized or spot fix. The whole stringer needs to go. But in your case, a local fix is possible.

 

[garbageguy]

My wife... wants me to just get a new boat

What are you waiting for?
(sorry, couldn't resist - I'm sure there are reasons)

 

[stephenspann27]

First, take a breath and cool down. What can of worms you are talking about my friend?! Having a boat is having, living with and being responsible for a can of worms. The sooner you will get to make peace with this simple fact the better for your blood pressure and your overall mental health J

Foam stringers are not that uncommon and they are not necessarily bad by design. It all depends on how they are fabricated. Foam stringers don’t rely on the foam to provide structural support. The foam is there only to provide a “shape” to glass on. All the structural support is from the glass. The glass in this case is much thicker than it is in the wood stringers case.
Some of these stringers are shaped on a mold and glassed to the hull hallow. The point is, you don’t necessarily need a core for your stringers whether wood or seacast or even foam. Different designers do different things to provide longitudinal structural support for their boats.
As WOG pointed out, I can’t really see what are you working with from the pictures you posted. But, I am guessing you are dealing with delamination of the stringer(s). You need to access if this delamination is in the area you spotted only or all over the place. If it is the former, I don’t think the situation is as dramatic as you think. All you need to do is to start glassing the stringer again “the right way”. We can give you the details of how to do this when you confirm that this is actually the case.
But if it is the latter, we have to talk J

Post a lot of pictures from different distances or better yet, post a video of you can. Make sure to show us the thickness of the glass you cut from the stringer to get to the foam.
On the bright side, if you had a wood stringer and the wood is rotted, there is no way you can do a localized or spot fix. The whole stringer needs to go. But in your case, a local fix is possible.

Thank you for the lengthy reply. I will be able to get more pics this weekend. The fiberglass casing around the foam was pretty thin. On the starboard side stringer I could see some movement with the boat under way, but it hasn't cracked/torn away from the hull like the port side did. I think i can probably just re-tab the starboard side. I plan to get the new ski locker pan installed this weekend. That will give me a nice clean area to lay on/in and chip out the rest of the foam. I will also replace the horizontal foam piece that runs across the back of the ski locker and divides the gas tank from the ski locker. It probably provides some strength against twisting. it was torn as well. I'm thinking this boat must have hit some object or massive wave and that's what caused this section to delaminate. Like I said above, I saw it before buying the boat, but I thought it was just superficial flotation foam. The foam itself does appear to be good closed cell foam, I wasn't able to get it to hold any water. I just came across some more pictures. I will be posting them below.

 

[JASinIL2006]

In the pictures above, in post #5, the surface on the left of the locker wall looks different than the surface on the right side; it almost looks like the left side had been patched or something in the past. Is that the case, or is the difference in appearance just due to the cracking?

The stringers and bulkheads on my boat were engineered (foam core with fiberglass on the outside), and the fiberglass walls of the stringers were quite thick. The way my boat was constructed, if there was any weak spot, it would be in the spot where the stringers were tabbed to the hull. I'm just wondering if your stringer was bad or if it's connection to the hull was poor and failed. If it was the latter, the fix would not be too bad, I would think.

 

[stephenspann27]

Port side stringer, before I started demo. You can see there is been a lot of flexing and the tabbing has broken.

Also, port side stringer, close to rear of the boat, in the bottom left part of the picture you can see the tear in the horizontal stringer

This is the starboard stringer, the arrow points to where I saw flexing when running down the river.

This is the horizontal stringer in the ski locker, the gas tank is behind it. Ski locker pan is removed in this photo

You can see a piece of the fiberglass from around the stringer laying in the rubble.

 

[stephenspann27]

What are you waiting for?
(sorry, couldn't resist - I'm sure there are reasons)

Not having a boat payment makes me feel less guilty when I burn through 46 gallon tanks of fuel. I also like not having to obsess over chips and scratches like I would with a new boat. If i were to buy one, it would likely be a Glastron GT205 with an outboard. I do really like the layout of this sunbird, it does a good job of being a fish, and ski boat, plenty of deck space to fish from, plenty of seating for cruising.

 

[stephenspann27]

In the interest of scale, you can see the ski locker in this photo:

 

[Woodonglass]

Probably what has/is occurring is the Freeze/Thaw cycle. The foam is wet and when it freezes it expands and causes the glass to crack. then when it thaws it contracts. You MIGHT be able to grind down the areas that are cracked and delaminated and then apply Peanut Butter and additional 1708 glass layers to beef up whats there. You could even use the Pink or Blue slab foam from the Big Box Stores to replace the foam "Stringer" and or Bulkhead. The Glass is what carries the load and provides the strength, in theory. the Problem IS, that you probably have additional issues in more areas throughout the rest of the under deck structure. The Foam Cored Stringers and Bulkheads are critical to the over strength and safety of the Boats Hull. If you fix this one area that doesn't necessarily mean your boat is "Good to Go" I'd highly recommend you do a LOT more investigating in all areas that you can access to ensure you don't have more serious issues elsewhere.

 

[stephenspann27]

Probably what has/is occurring is the Freeze/Thaw cycle. The foam is wet and when it freezes it expands and causes the glass to crack. then when it thaws it contracts. You MIGHT be able to grind down the areas that are cracked and delaminated and then apply Peanut Butter and additional 1708 glass layers to beef up whats there. You could even use the Pink or Blue slab foam from the Big Box Stores to replace the foam "Stringer" and or Bulkhead. The Glass is what carries the load and provides the strength, in theory. the Problem IS, that you probably have additional issues in more areas throughout the rest of the under deck structure. The Foam Cored Stringers and Bulkheads are critical to the over strength and safety of the Boats Hull. If you fix this one area that doesn't necessarily mean your boat is "Good to Go" I'd highly recommend you do a LOT more investigating in all areas that you can access to ensure you don't have more serious issues elsewhere.

I'll look more closely at all sub floor areas of the boat for more problems. I don't agree with you on the freeze/thaw theory for two reasons, one is this is a good quality closed cell foam, I put a piece of it in water, and forced it to the bottom, after sitting underwater over night I pulled the foam out and it was still dry. The second reason, is the boat is in,and I believe always has been in Houston, which almost never gets below 32 degrees.

 

[stephenspann27]

In the pictures above, in post #5, the surface on the left of the locker wall looks different than the surface on the right side; it almost looks like the left side had been patched or something in the past. Is that the case, or is the difference in appearance just due to the cracking?

The stringers and bulkheads on my boat were engineered (foam core with fiberglass on the outside), and the fiberglass walls of the stringers were quite thick. The way my boat was constructed, if there was any weak spot, it would be in the spot where the stringers were tabbed to the hull. I'm just wondering if your stringer was bad or if it's connection to the hull was poor and failed. If it was the latter, the fix would not be too bad, I would think.

I believe you are right about the port and starboard sides being different. There is a step in the port side, like a second foam board was added there. I think it had to of been at the time of construction though. Everything appears to be aged the same amount.

 

[tpenfield]

Interesting that the port stringer does not appear to go up to meet the cockpit deck, whereas the starboard stringer does. Not sure if the starboard stringer touches the under side of the deck, but it appears to go higher.

Sunbird is not the best built boat you will find, but you can certainly make it better than new. It appears that your boat is of the modern design era where the cap and cockpit are one large single piece? If so, then you certainly have a challenge.

In order the fix the stringers, you should assume that you will have to replace the entire length of them and not just what you can see. Any cracking of the hull in those areas?

Your best approach right now is to see what you can get access to beyond what can be reached from the ski locker. Given that it is an outboard motor setup, that may be tough. Stick the smart phone in places that are hard to see and reach and get lots of pictures to post.

In order to do a proper and thorough fix, the cap/cockpit may need to come off. If the boat is of the older style design where the main cockpit deck is not part of the cap assembly, then you would be in a better situation.

We'll be with you all the way.

 

[stephenspann27]

Interesting that the port stringer does not appear to go up to meet the cockpit deck, whereas the starboard stringer does. Not sure if the starboard stringer touches the under side of the deck, but it appears to go higher.

Sunbird is not the best built boat you will find, but you can certainly make it better than new. It appears that your boat is of the modern design era where the cap and cockpit are one large single piece? If so, then you certainly have a challenge.

In order the fix the stringers, you should assume that you will have to replace the entire length of them and not just what you can see. Any cracking of the hull in those areas?

Your best approach right now is to see what you can get access to beyond what can be reached from the ski locker. Given that it is an outboard motor setup, that may be tough. Stick the smart phone in places that are hard to see and reach and get lots of pictures to post.

In order to do a proper and thorough fix, the cap/cockpit may need to come off. If the boat is of the older style design where the main cockpit deck is not part of the cap assembly, then you would be in a better situation.

We'll be with you all the way.

This is one of those modern designs, the floor, which is part of the cap does not touch the stringers. There is actually a layer of plywood over the stringers, but the floor is about 1'' above that. The floor is really thick, you can jump on it and it won't flex at all. The plywood under the floor could rot away, and it wouldn't make a difference. There are stress cracks in the gel coat on the underside of the boat, the worst area is near the chine which lines up with this bad stringer. I don't think the actual fiberglass is cracked, just the gel coat. If this was a rotted wood stringer, I would agree that the entire stringer must be replaced, however it is just a delamination problem, which hopefully is localized to the ski locker. I will certainly look at the rest of the boat harder. On another note, the transom is water logged, but, the wood core is thin compared to the overall thckness of the transom. The wood could probably rot away, and it would still be strong.

 

[tpenfield]

Keep in mind that based on the pictures, the stringer was not well bonded to the hull originally, so the separation may not be localized either. or could develop in another area along it length.

 

[stephenspann27]

Keep in mind that based on the pictures, the stringer was not well bonded to the hull originally, so the separation may not be localized either. or could develop in another area along it length.

I went out to my storage to look the boat over. It looks like the foam stringers were formed outside of the boat, laid in, then tabbed in. The chine, from the inside of the boat is a valley, the foam stringer sits level across the valley, instead of dipping into it. I can see almost all of the other parts of the stringers throw other boat compartments, and I don't see any other problems.

 

[stephenspann27]

I got a new ski locker floor installed. The more I look at the stringer... i wonder if it's even structural, or if it's just there for the flotation foam? Is it possible that the hull is thick enough not to need stringers? The boat floor is built into the cap, and it doesn't rest on the stringers.