Hull Structure

[mtsinner7868]

While gutting my Reinell, along the entire bottom between the stringers and all along the reverse "V"s running bow to stern as the hull steps up to the sides..... there are 2 x 2 wood blocks 1/2" thick on a mesh (like designer ceramic tile) laid down and glassed over. The grain of the wood is going the 1/2" way.

What exact purpose(s) does this serve ? I can't imagine it being structural too much as there is no strength with the way the grain is in the blocks.

 

[jbcurt00]

Re: Hull Structure

Dampen hull vibration, dampen the sound of water lapping at the hull and glassed over

They make a fiberglass lamination that's lighter then the same thickness made entirely out of fiberglass layers &/or lamination that's stronger then similar weight of fiberglass only layers.

I'd put them (or 1/2" CSM wrapped plywood squares) back when you start rebuilding her. Reinell wouldn't have put them in unless there was a reason for them. Particularly a production boat builder.

 

[tpenfield]

Re: Hull Structure

Got some pics to share ? . . . when you say "reverse Vs", do you mean the strakes? Might be a core layer, but not sure if Reinell 'cored' their hulls . . . :noidea:

 

[Bondo]

Re: Hull Structure

Got some pics to share ? . . . when you say "reverse Vs", do you mean the strakes? Might be a core layer, but not sure if Reinell 'cored' their hulls . . . :noidea:

Ayuh,.... It sounds like end grain balsa corin' material to me too,...

 

[mtsinner7868]

Re: Hull Structure

Pics.....





Hull vibration and sound deadening is a moot point in my eyes when the whole hull was originally filled with foam ! I figure I will replace it with strips of plywood instead of individual blocks and glue them to the hull then glass over them with one layer. The blocks I took out were NOT attached to the hull..... only laid in place and glassed over. Only places they were glued to the hull is where the resin dripped through when the top was glassed. They came out easy after cutting the glass.

I'm even considering a 1x stringer sitting on top of the plywood I put in its place to give it more structure connecting it to the floor above. Am I going in the right direction here or will this create a problem ? I'm NOT putting foam back in.

 

[Woodonglass]

Re: Hull Structure

Yup purdy sure that's a cored hull. There's also a good chance that the foam served as a structural component to that hull. You might want to contact the MFG to consult with them on that aspect.

 

[mtsinner7868]

Re: Hull Structure

Yup purdy sure that's a cored hull. There's also a good chance that the foam served as a structural component to that hull. You might want to contact the MFG to consult with them on that aspect.

Not a good chance the foam was structural..... I believe it to be fact that it was structural since the stringers were basically suspended in the foam. They were partially glassed to the hull on one side half way but the foam was the overall structure to it. But the foam was also the downfall to the whole system. Once waterlogged and cycling through the freeze/thaw of MT it destroyed itself not to mention promoted rot it ALL the wood. I have a great disdain for foam in boats. I've never seen it do anything but act as a sponge andcreate problems. One of my other boats, after only 4 years from brand new, had saturated foam in it...... I won't put it back in. I will add more structural framing/stringers before using foam. That is my plan moving forward at the moment.

 

[Woodonglass]

Re: Hull Structure

OK, but... hulls that were designed to be supported by the foam can be problematic to be re-engineered to be supported by stringers and bulkheads. Not saying it can't or shouldn't be done. Just saying it can be problematic especially if you're not a marine engineer or have a background in that arena. I'm NOT and don't have one but I have researched it enough to know that it's detailed and involved and something I DON'T want to delve into. Foamed boats Can be an issue but most of the time it's due to neglect and improper care and maintenance. If you care for and maintain them properly I see no reason not to reinstall the foam. Especially now with the new improved more water resistant foam. It's your boat and you're free to do with it as you see fit. I'm just making observations based on my experiences and acquired knowledge.

 

[tpenfield]

Re: Hull Structure

The discussion of the pro's and con's of foam comes up on a regular basis, and I'm with WOG on this issue.

Foam gets blamed for things that the foam had nothing to do with. . . it just ends up holding the 'bag', or the water in the case of boat structure. If there were no foam in a boat's structure, there would still be water, if the boat was exposed to the same conditions and care that cause the foam to be wet. The only difference is that the water would be sitting there all by itself.

The water that finds its way into the chambers of a boats structure, foam or no foam, will still want to work its way through the fiberglass and into the wood. The water would much rather go to the wood than it would to the foam.

So, foam gets blamed for stuff that it really had nothing to do with. I'm sure we all experience that in our life times

To WOG's point, if you are to take a boat that had foam as part of its structural design and go without, you are really putting back about 1/2 of the structural strength. Foam does 2 things . . . it provides flotation and it provides strength . . . and in many cases lots of strength. So, those are the factors regarding foam that you should take into consideration in planning your restoration.

If you had a boat and its foam got wet after 4 years, then the structure would have gotten wet in those same 4 years without the foam. There probably was another issue at play there that the foam got blamed for . . .

 

[mtsinner7868]

Re: Hull Structure

The discussion of the pro's and con's of foam comes up on a regular basis, and I'm with WOG on this issue.

Foam gets blamed for things that the foam had nothing to do with. . . it just ends up holding the 'bag', or the water in the case of boat structure. If there were no foam in a boat's structure, there would still be water, if the boat was exposed to the same conditions and care that cause the foam to be wet. The only difference is that the water would be sitting there all by itself.

The water that finds its way into the chambers of a boats structure, foam or no foam, will still want to work its way through the fiberglass and into the wood. The water would much rather go to the wood than it would to the foam.

So, foam gets blamed for stuff that it really had nothing to do with. I'm sure we all experience that in our life times

To WOG's point, if you are to take a boat that had foam as part of its structural design and go without, you are really putting back about 1/2 of the structural strength. Foam does 2 things . . . it provides flotation and it provides strength . . . and in many cases lots of strength. So, those are the factors regarding foam that you should take into consideration in planning your restoration.

If you had a boat and its foam got wet after 4 years, then the structure would have gotten wet in those same 4 years without the foam. There probably was another issue at play there that the foam got blamed for . . .

Sure...... foam gets blamed for a lot that it probably shouldn't, I agree wholeheartedly. But the fact remains that all boats are going to get wet inside eventually, history is on my side there ! But with an open hull system the water can easily be removed in a sense before causing permanent long term damage if designed to do so. Just the ability to vent the bilge is a 100% improvement over forever trapping moisture within foam.

And yes there is the strength a foam "cored" hull has over a framed one.... no doubt. And that is the issue I am dealing with at this very moment. But I do believe I can restore the structural integrity of this vessel without foam...... As a former professional builder with a little engineering background, I think I can do so. Just looking for what others have done in my position as I can't be the only one in this position....... just too many project boats out there ya know

 

[Bondo]

Re: Hull Structure

Sure...... foam gets blamed for a lot that it probably shouldn't, I agree wholeheartedly. But the fact remains that all boats are going to get wet inside eventually, history is on my side there ! But with an open hull system the water can easily be removed in a sense before causing permanent long term damage if designed to do so. Just the ability to vent the bilge is a 100% improvement over forever trapping moisture within foam.

And yes there is the strength a foam "cored" hull has over a framed one.... no doubt. And that is the issue I am dealing with at this very moment. But I do believe I can restore the structural integrity of this vessel without foam...... As a former professional builder with a little engineering background, I think I can do so. Just looking for what others have done in my position as I can't be the only one in this position....... just too many project boats out there ya know

Ayuh,... Welcome Aboard,.... I've been an Anti-foamer forever,....

But, so long as proper Drainage, 'n as you note Ventin' is accomplished, the foam won't Hurt nothin', by itself anyways,...
Every nook, 'n cranny needs to be self-drainin' to the pumpable bilge,...

 

[ondarvr]

Re: Hull Structure

While gutting my Reinell, along the entire bottom between the stringers and all along the reverse "V"s running bow to stern as the hull steps up to the sides..... there are 2 x 2 wood blocks 1/2" thick on a mesh (like designer ceramic tile) laid down and glassed over. The grain of the wood is going the 1/2" way.

What exact purpose(s) does this serve ? I can't imagine it being structural too much as there is no strength with the way the grain is in the blocks.

Balsa is a very common core in fiberglass construction, but if not done correctly it ends up looking just like what you found, it can be very strong and durable though. There was very little professional engineering done on older runabouts, they just built them and if it broke they made it thicker, but not necessarily in the correct way. Also the way it was intended to be done.....and how it was actually done by the crew building it can be very different, resulting in some odd construction and corresponding failures.

The Balsa is there to stiffen the hull, was it needed….hard to say without inspecting it in person to see how stiff it is without it. But to leave out the Balsa and the foam would be a double whammy that would most likely create some issues. You may need to add more glass to the entire surface, or more stringers to make up for removing both of them.

 

[jigngrub]

Re: Hull Structure

But the foam was also the downfall to the whole system. Once waterlogged and cycling through the freeze/thaw of MT it destroyed itself not to mention promoted rot it ALL the wood. I have a great disdain for foam in boats. I've never seen it do anything but act as a sponge andcreate problems. One of my other boats, after only 4 years from brand new, had saturated foam in it...... I won't put it back in. I will add more structural framing/stringers before using foam.

... and the haters keep on hating!

Foam is your friend, and can be worth it's weight in diamonds when you really need it in case of an emergency.

A boat that's shown the proper care will never have water intrusion problems and saturated foam or rotten below deck wood structure. Boats that are abused/neglected and left out in the elements to suffer rain, snow, and ice will age very quickly and of course have water intrusion problems.

A boat that's kept trailered and garaged when not in use will last forever, one that kept trailered and covered outside will last for decades, one that's left uncovered on the trailer with the bilge plug left in or tied to the dock will last about 4 yrs.

There are different methods, designs, and materials you can use when rebuilding your boat that'll let you use foam and still have a very water resistant below deck design. I will expand on these if you're interested, but if you're still hell bent on rebuilding without foam I won't waste my breath.

 

[Woodonglass]

Re: Hull Structure

mtsinner, just so you'll know, ondarvr (post #12) is one of our resident experts on fiberglass hull construction. He's been in the industry for over 40 yrs working with all the major Boat mfg's and he really know's his stuff. I've learned a LOT from him over the past several years so you'd do well to listen and learn from him when it comes to putting your boat back together. IMHO I'd really think long an hard about putting foam back in that hull. It's designed for it and once again, if you do it properly and then care for her and maintain her properly you will never have to worry about it getting waterlogged again. It just won't happen.

 

[metriccrescentwrench]

Re: Hull Structure

... there are 2 x 2 wood blocks 1/2" thick on a mesh (like designer ceramic tile) laid down and glassed over. The grain of the wood is going the 1/2" way.

What exact purpose(s) does this serve ? I can't imagine it being structural too much as there is no strength with the way the grain is in the blocks.

You're describing end-grain balsa, and it is VERY much a structural component of the hull. Manufacturers have used it for a long time because it allows a stiff enough hull to be built with less fiberglass (and weight). If you spend some time studying up on composite structures you'll learn that it's the compressive strength of the core material that makes the structure strong (much like an I beam) - and balsa is VERY strong in compression. You absolutely MUST replace that material with at least it's equal, don't cheap out by using plywood. West Systems has a good write up on their website (sorry, I don't have a link) explaining how to replace balsa core. It's a LOT of work to do it right (I just finished replacing the core in a bass boat I'm rebuilding for my son).

If I ever do another boat project and find rotted core I'll more than likely take the boat to the dump right then and there.

 

[mtsinner7868]

Re: Hull Structure

I really appreciate everyone's input. I learn more from these forums than anywhere else.

Balsa is a very common core in fiberglass construction, but if not done correctly it ends up looking just like what you found, it can be very strong and durable though. There was very little professional engineering done on older runabouts, they just built them and if it broke they made it thicker, but not necessarily in the correct way. Also the way it was intended to be done.....and how it was actually done by the crew building it can be very different, resulting in some odd construction and corresponding failures.

The Balsa is there to stiffen the hull, was it needed….hard to say without inspecting it in person to see how stiff it is without it. But to leave out the Balsa and the foam would be a double whammy that would most likely create some issues. You may need to add more glass to the entire surface, or more stringers to make up for removing both of them.

Funny...... while doing some reading yesterday that is exactly what I learned. In a nutshell..... the manufacturers used in-market testing as the market really didn't know (or care obviously) what they were purchasing, now that's funny !!! And when things broke they did just that, added more glass. The balsa core was a savior within two industries when discovered. When introduced to the boat industry it forced engineering and was a cost cutting measure when the glass got too expensive and in grabbing hold there saving the failing balsa industry at the same time. Nice ! And through the cycles of to from and back to the balsa core over the last 60 years or so, the manufacturers still can't keep the cores from rotting. Hydraulic erosion being the main cause from what I read.

The cores of my boat may be a victim of workmanship IMO as you mention. Correct me if I am wrong here.... but for the proper "truss" like strength of a core design I believe the core needs to be fastened to both top and bottom layers of the fiberglass . What I removed was only fastened on the top. The bottom was only glued to the hull where the resin being laid on the top leaked its way down to the bottom. I pulled 95% of fiber mat out in one piece that the balsa was originally glued to. Maybe its supposed to be that way, I don't know, you tell me. But it just doesn't seem right to me from a common sense strength perspective. And if the hull is dependent on being foam filled for strength, why the core then ? Sounds like a little over engineering maybe.....

Jigngrub.... I'm not hell bent on rebuilding without foam. Its just that I've just never seen any foam that didn't have water in it. I guess that makes me a "proud" hater. Emergency ! That's why I have life vests in the boat. And the boat ain't worth a fortune so if she goes down I'll grab my fishin gear before she goes too far under and all is good...... I got more boats

On a more serious note..... Please expand on these different methods, designs, and material you mention ! I am interested as are probably others. And you won't be wasting your breath.... I promise.

 

[metriccrescentwrench]

Re: Hull Structure

Correct me if I am wrong here.... but for the proper "truss" like strength of a core design I believe the core needs to be fastened to both top and bottom layers of the fiberglass .

That's absolutely correct. But just 'gluing' it down with resin won't work worth a darn. I had mentioned that I replaced the core in a bass boat I'm rebuilding. Basically you have to paint every single surface of the core with epoxy to waterproof it, then 'bed' it in filler on the surface of the hull, and glass over it. On a complete hull that's quite time consuming if you're working alone without the benefit of a manufacturing facility.