Re-coring a hatch with foamboard

[Lazy Daze]

I know some of you have done work like this before and some may want to try your hand at it sometime. By no means is this the only way to go about doing this type of work, but I thought some of you might enjoy the procedure.

I'm recoring the floor of an older Grady (24' Walkaround) that my brother and I bought to leave up in Maine. I thought I would try something different for the floor hatch. Given that it's easy enough to rectify, either now or even when it's in the water, I thought it might be fun to try something that hasn't (to my knowledge) been used before. There are obviously foam coring materials available (Divinycell, for example) so the idea of using foam is not at all new. What I'm going to experiment with is the inexpensive pink/purple foam-board insulation that you can get at Home Depot. I've got some leftover pieces of 3/4" board that I'm experimenting with right now. The picture below is of an unaltered piece of foam and one that I (very) quickly put a layer of glass on the top and bottom with epoxy resin.

The amount that it stiffened up is amazing. I'm going to do some weight tests to help quantify this. The only thing that concerns me a little bit is that, while the epoxy seems to bond extremely well with the foam board, it does not soak in very far. Meaning, if I pull on the edge of the fiberglass, I can rip the layer of fiberglass off the foam (and a light layer of foam comes with it). Ultimately, I don't know if this will pose a problem or not since everything will be completely encapsulated with fiberglass and there "shouldn't" be any ripping-type motions going on! As another quick test, I also quickly epoxied a piece of bare foam to a scrap of fiberglass and it's stuck on there good - can't even start to pull it off. A third test was to epoxy two pieces of foam together and same thing - they're now like one piece and I can't pull them apart.



This is a bit messy looking, but this was taken in the midst of removing the fiberglass cockpit floor (the heater kept it nice and cozy in there) and the wet wood underneath. I had built an extra large frame for the shrink wrap and installed a couple shop lights so I could work at night. Besides, during the day, the blue shrink wrap gave everything a blue tint inside - the shoplights negated that. Once the weather turns a little nicer, so the overnight temps aren't so cold, I'll put new marine plywood down (not taking a chance on an experiment with the floor) and reattach the floor skin. I've also got build a brand new hatch (for another area) from scratch (not even an old piece to make a mold from)

 

[spfortjohn]

I looked at new Gray White boats after the sale of my Searay and it surprised me that Grady still uses wood in the production of it's new boats. Most if not all of the builders now do not use wood. I looked at Edgewater, Key West, Scout, and none of them use wood.

 

[dpmulvey]

That's ingenious! If it works, the weight savings are going to be substantial and should equate to better fuel economy. Please keep us posted and include pix.

 

[Chris Nowell]

Thanx for sharing the project. My only question is; how the heck do you find the enrgy to work on boats, at night, in the freezing cold, after working on boats in the freezing cold all day?!!!!? Do you know of some sort of secret supplement or something?

 

[Lazy Daze]

Glutton for punishment?

Working at the marina, while I do enjoy it, is a job. Working on my own boats is fun - even relaxing. It allows me to do some special things and try new things that I couldn't do at the job. Primarily because of the extra time it would take and 90% of the customers just want things fixed "normally" - not "specially". That's not to say I fault them for that - but that's why I enjoy working on my own boats as I get to stretch my skills a bit more. Case in point is this little project - obviously there's no way I would jeopardize a paying customers boat for an experiment. But on my own boat - especially when I know I can always fix it if it doesn't work - no problem. Truth be told - I don't know if this is going to work. But it'll be fun figuring it out - for me, the process is what makes it fun.

 

[mwph]

I hope I never have to do it. But thanks for letting us watch you do it.
I'm sure I will learn something, and for me, that's why I'm here. Thanks again.

 

[390x]

I know acetone will eat that foam immediately. I don't know if catalyzed resin will or not. I guess you'll find out!

 

[Lazy Daze]

I know acetone will eat that foam immediately. I don't know if catalyzed resin will or not. I guess you'll find out!

Already tried it up in the first post and it bonds well.


Crazy couple of weeks. Finally got around to seeing how much weight these little scraps of styrofoam can hold.

This one is how I balanced the weights on each piece of foam:



This is 15lbs on bare foam:



This is 25lbs on bare foam. The weights are now contacting the foam, keeping the foam from sagging any further.



This is 25lbs of reinforced foam. The reinforcement is only a thin layer of fiberglass cloth on each side:



This is 75lbs on reinforced foam, very slight bend:



At 85lbs, it failed and the weight contacted the foam. I believe it actually could of held more, but I think I failed to evenly the support the weight on the piece of small wood and the edge of the wood "point loaded" the foam, creating a crease and cracking the fiberglass.








However, I was happy to see that the fiberglass never sheared away from the foam, even when bending it numerous times. I'm pretty satisfied that it's at least worth the effort to use this cheap stuff and see how it holds up. To stay with the "experimental" theme of this project, I'm not going to poke any holes (was actually thinking of 1/4" holes all the way through) in the foam or cut it up. I am 100% confident that either one of those ways would be superior, but that defeats the purpose of what I want to try. BUT, I want to point out, that I am doing this STRICTLY as an experiment and for the "fun" factor. I DO NOT recommend anyone using styrofoam for anything more permanent/structural than an easily accessible hatch. Even then, as they say, proceed at your own risk! :smt001 There is NO WAY that I will be using this foam for the main parts of my floor. If this styrofoam fails, it's only a couple hour job to redo it with plywood or something like Divinycell.

 

[mwph]

Cool testing. With just a few square inches supporting the load, and just one sheet if cloth, it looks pretty stable to me.

 

[Oar Play]

I'm following this thread. Very interesting...,


Sent from my crappy iPhone using Tapatalk

 

[trit21]

fyi, my fuel access panel is foam filled with fiberglass and gelcoat that I redid recently due to a crack on the hinge. No problems supporting people walking on it etc. My gunnels where my rod holders are are also cored with balsa and now a portion is cored with 1/2"PVC and no problems with walking on them. The wood got wet and I had to redo the coring and fiberglass covering along with gelcoat. Coring material is just a filler. THere should be a top and bottom structure of fiberglass with the coring material wetted to the glass mat/strand. THis will provide a very solid surface.

 

[Lazy Daze]

Coring material is just a filler. THere should be a top and bottom structure of fiberglass with the coring material wetted to the glass mat/strand. THis will provide a very solid surface.

Yes, 100% agree. My concern lies with the type of foam - it's styrofoam and the epoxy does not penetrate the foam anywhere near what it would if it was wood or vinyl foam like Divinycell. The epoxy adheres extremely well to the styrofoam, it just doesn't penetrate. I was a little worried about flexing and shearing, but after that un-scientific experiment above, I'm less worried.

 

[Bob & Sue]

Dennis,
I have 3 engine hatches on all 3 the I think it's fireproofing or soundproofing material is starting to coming loose around the edges they will need to replaced soon or end up in the bilge. I had thought of using 1" foam board with aluminum on one side to replace them for better soundproofing, do you know of a spray on fire proofing material I could use on each panel? My only worry would be the foam burning if I had a fire.
Interesting post hope it all works well sure looks like it will. Enjoy following your you tube videos have picked up some good ideas, it's great when you can work in a field you love and enjoy.

 

[Lazy Daze]

I don't have any personal experience with spray-on soundproofing. I've read up on Lizard Skin and have contemplated using it, but have not actually done so. It gets used alot in the automotive industry and I don't see any reason it wouldn't work in a boat, but that's as much as I know about it. MLV (mass loaded vinyl) is great upgrade. It comes in thin sheets that can be applied. But, it also comes suspended in the middle of foam (like what you're contemplating). It works much better suspended in foam since the foam allows it to vibrate/move somewhat. I honestly can't see how any spray-on material would work better since vibration is still going to be transmitted through.

As far as a fire goes... I think there might be other things to worry about than whether or not the foam is going to melt! :smt001

Definitely a nice gig to have! Especially the way I'm set-up here.

 

[Lazy Daze]

Cool testing. With just a few square inches supporting the load, and just one sheet if cloth, it looks pretty stable to me.

And I'm sure it would of held more, much more. I really think that when I set that last 10lb plate (on top of the 75lbs that were already there), I set it down unevenly. It collapsed quickly before I even completely set the 10lb plate on - which makes me think I was setting the weight down unevenly -- and with the narrow piece of wood supporting it, it wouldn't take much to get the weight off-center.

 

[dpmulvey]

Just talked to a structural engineer friend after showing him the thread. He is in industrial roofing and uses foam for insulation and weight purposes. What density foam are you using?

 

[Lazy Daze]

I honestly have no idea. It's just the plain-Jane, Owens Corning R4 3/4" extruded polystyrene that you can buy at Home Depot.

 

[Lazy Daze]

So, time has been my enemy here. Between two work schedules, the kid's after school stuff and normal "honey do" stuff, I haven't had a whole lot of extra time. I've also been working out in the boat on various things, too. Structurally, though, the hatch is done and I'm very happy with the results. Could not detect any deflection when I stood on it with one foot. For good measure, I even jumped on it. I'm confident reinstalling it in the boat. We'll see how long it lasts!

I had to rebuild the one edge of the hatch since it had been cutoff by the previous owner. I used fiberglass "L" channel for this. I notched it to fit in and then epoxied and glassed it in place. I'll come back later and trim it flush with the other edges. For extra support, I added a single layer of fiberglass mat between the hatch and the foam. I also reinforced the edges/lips. It's rough looking right now, but it will be nice in the end. Although this is going to be a "work boat" and doesn't really need to be super pretty - just functional and reliable.



Since this hatch will be on hinges, there was no need to reuse the deck plate. So I filled in the hole.









With a layer of 1708 bi-axial...


Last step was to fill the topside level with epoxy. I'll be painting the floor when I'm done, so it allows me some leeway on this step to not have to worry too much about "prettiness". I'm also going to use this hatch as a mold to make another hatch for the boat - which will cover the area that the stern drive used to be.

 

[sbw1]

I wonder what Grady would say if you asked them about this idea? It could be there are boating codes and standards that allow only certain types of fillers based upon engineering and safety concerns. I believe there was a lawsuit against a manufacturer that concerned fillers that lead to a death. Might have been against Grady.

 

[Lazy Daze]

I wonder what Grady would say if you asked them about this idea? It could be there are boating codes and standards that allow only certain types of fillers based upon engineering and safety concerns. I believe there was a lawsuit against a manufacturer that concerned fillers that lead to a death. Might have been against Grady.

I'm sure any manufacturer will say this isn't "approved". As I mentioned above, this is more about experimentation than anything else. I'm absolutely confident that this poses no safety risk, regardless of what is "typically" acceptable. I wouldn't do it if there was any doubt. This isn't about cutting corners - I've got plenty of marine ply available if I had wanted to do it that way.