CRAZY IDEA - Great Stuff Expanding Foam for Hull Fillers

[Signet]

If nothing else, I'm sure this thread will supply some laughs. But still, it's an idea.

I am building the Ragusian Carrack by MarisStella, watching Olha's videos, etc., and she show, and everyone suggests, gluing a lot of support blocks between bulkheads to help support and glue planking (single planking in particular), and especially around large changes in curvature like the bow and stern. Modelers have used all kinds of wood for this, usually soft wood, and I've read about people using balsa as well. I think I remember someone saying sheet foam could be used, although that might be more wishful thinking.

Anyhow, I wonder about the possibility of using Great Stuff expanding foam (considered a low expansion foam) to fill the areas between the bulkheads. Yeah, I'm serious. I know, I know, quit laughing and pay attention. Great stuff sticks to things very well (like members of a built-up hull), can be easily cut and sanded, even painted and filled. Using on a hull such as this:


it would fill many nooks and crannies (probably too much, so I may have to block off some areas to prevent it from going there), attach itself really well. Hopefully, careful filling would result in it standing proud of the bulkheads, and then that material could be easily cut off. My son has an electric wire foam cutter which would work quickly and more smoothly than sanding or using a Dremel and with less mess. Of course, final shaping would have to be by sanding.

Foam core wings and such are used for RC airplanes, and when covered with a thin wood or plywood are extremely strong. This method, I think, would actually help stiffen the hull and make it very strong, especially once covered with 1.5mm walnut strip planking.

Yeah, I know I've come up with this idea because I'm lazy. The idea of measuring and cutting numerous wood blocks to fit into the hull, then shape them all, does not sound like fun. And I know there isn't always an easy way out, but was wondering if anyone thinks this has a chance in Hades of working out?

 

[Corsair]

I don't know if the wire for styrofoam would work the same on the expanding foam. Even if it did, you should be careful of fumes (even the fumes from cutting styrofoam are toxic) .I would also be concerned about warping the structure if you do all of one side then all of the other side, so I would suggest doing one cell on a side at a time alternate sides. I would also think you would want some sort of false deck on the bulkheads or mabe some cardboard pieces below the level of the lowest deck just to keep the foam in the area you want. You would also want to protect the area where the mast is set down into the hull or any other area that needs to be protected because something will need to be inserted later on and fastened.. Also, you should use a great deal of caution when you are sanding to make sure you are not inhaling any of the material

The expanding foam is quite sturdy so I would think it would support the planking well. I think it would be easy to shape and sand. You could cut off the large pieces of excess foam using a hacksaw or a jewelers saw or something similar.

I think it would be interesting to see how it works.

 

[dnalley]

I like the idea, but you had better be careful because that stuff goes crazy. I could see an advantage on certain models but less on others. We are here to experiment, isn't that what we do in everyday life? Go for it on a few test parts first.

Happy modeling

 

[Uwek]

I would be very very careful with expanding foams, especially these which are used in building construction works.
These foams are producing over a certain period real pressure forces and there is the possibility, that the bulkheads get to much forces.
The next problem could be, that you have maybe a surface, but with which kind of glue you want to fix the planking on top of the foam.
Not that the glue is reacting with the foam? ......
.... Just an opinion by myself without any real knowledge - I would be very very careful

 

[lakedaisy]

Agree with Uwek. And this stuff is VERY sticky. Gets everywhere. Why don't you ask Olha since you have referenced her and she is an engineer (if I recall correctly).

 

[Corsair]

I would be very very careful with expanding foams, especially these which are used in building construction works.
These foams are producing over a certain period real pressure forces and there is the possibility, that the bulkheads get to much forces.
The next problem could be, that you have maybe a surface, but with which kind of glue you want to fix the planking on top of the foam.
Not that the glue is reacting with the foam? ......
.... Just an opinion by myself without any real knowledge - I would be very very careful

yes, the glue is a very good point. THe foam will have lots of bubbles of air in it, so most likely a CA will not work with it and may have a reaction with the foam (like gasoline and styrofoam) so you should probably use a white glue for it. Test it before you use it on a kit !

 

[Signet]

I don't know if the wire for styrofoam would work the same on the expanding foam. Even if it did, you should be careful of fumes (even the fumes from cutting styrofoam are toxic) .I would also be concerned about warping the structure if you do all of one side then all of the other side, so I would suggest doing one cell on a side at a time alternate sides. I would also think you would want some sort of false deck on the bulkheads or mabe some cardboard pieces below the level of the lowest deck just to keep the foam in the area you want. You would also want to protect the area where the mast is set down into the hull or any other area that needs to be protected because something will need to be inserted later on and fastened.. Also, you should use a great deal of caution when you are sanding to make sure you are not inhaling any of the material

The expanding foam is quite sturdy so I would think it would support the planking well. I think it would be easy to shape and sand. You could cut off the large pieces of excess foam using a hacksaw or a jewelers saw or something similar.

I think it would be interesting to see how it works.

Pretty much exactly my thoughts.

 

[Signet]

I like the idea, but you had better be careful because that stuff goes crazy. I could see an advantage on certain models but less on others. We are here to experiment, isn't that what we do in everyday life? Go for it on a few test parts first.

Good idea to try it on test parts. I don't have any extra, but just a few pieces of scrap together would give me an idea.

 

[Signet]

I would be very very careful with expanding foams, especially these which are used in building construction works.
These foams are producing over a certain period real pressure forces and there is the possibility, that the bulkheads get to much forces.
The next problem could be, that you have maybe a surface, but with which kind of glue you want to fix the planking on top of the foam.
Not that the glue is reacting with the foam? ......
.... Just an opinion by myself without any real knowledge - I would be very very careful

Forces produced as it cures/expands is my main concern, of course. I want to think that since it's not restrained in any way, it would just expand, but if other foam kept it from expanding, it could buckle bulkheads.

Glue should be a problem; any white glue works well with foam, including Great Stuff.

 

[Signet]

yes, the glue is a very good point. THe foam will have lots of bubbles of air in it, so most likely a CA will not work with it and may have a reaction with the foam (like gasoline and styrofoam) so you should probably use a white glue for it. Test it before you use it on a kit !

Some foams expand more than others (up to 10 times more), and those that do have more bubbles (of course). Great Stuff is considered low expansion, so should have less bubbles. White glue works fine on it, but yeah CA and even some paints would not.

 

[Signet]

Agree with Uwek. And this stuff is VERY sticky. Gets everywhere. Why don't you ask Olha since you have referenced her and she is an engineer (if I recall correctly).

While I'm an engineer too, she's an engineer with incredible experience in ship model building, so I agree and have asked her to chime in if she finds the time.

And I agree about it getting everywhere. In my nightmares I picture a roughly ship-shaped blob of foam covering almost all the wood, with no idea where to begin to make it look like a ship, or even find my "finely crafted wood" again.

 

[Dave @W]

Be really careful!!!
I tried it on a piece of a Dumas boat and while it filled the space kinda OK, it did expand beyond my control almost destroying that part before I could dig it out. Yes, I did use their low expansion version but since it expands at an uncontrolled manner, you will end up with areas that expand faster then others even if your item is open ended. What happens is the outside will dry pretty fast ceasing any further expanding but the inside part will keep expanding as it dries minutes or even hours later. Overall, it cost my time for removal and a repair as well as that can of foam.
Good idea for many things but not for delicate model boat building.

 

[Signet]

Be really careful!!!
I tried it on a piece of a Dumas boat and while it filled the space kinda OK, it did expand beyond my control almost destroying that part before I could dig it out. Yes, I did use their low expansion version but since it expands at an uncontrolled manner, you will end up with areas that expand faster then others even if your item is open ended. What happens is the outside will dry pretty fast ceasing any further expanding but the inside part will keep expanding as it dries minutes or even hours later. Overall, it cost my time for removal and a repair as well as that can of foam.
Good idea for many things but not for delicate model boat building.

Yup, that sounds like my worst nightmare. Exactly as you say, whereas outer portions might harden, preventing further movement there, and allowing expansion at the bulkheads. I was hoping small layers might help avoid this, but maybe not.

 

[Philski]

Forces produced as it cures/expands is my main concern, of course. I want to think that since it's not restrained in any way, it would just expand, but if other foam kept it from expanding, it could buckle bulkheads.

Glue should be a problem; any white glue works well with foam, including Great Stuff.

It seems to me that the expanding foam would naturally take the path of least resistance and not put that much, if any, pressure on the bulkheads. Make a test fixture of sorts, resembling a kit or build, measure the distance between bulkheads, insert the foam, measure again after curing. Or - you could brace each bulkhead with temporary supports prior to filling to insure rigidity. Since I don't know how the foam will react with different adhesives, I'd just use balsa.

 

[Dave @W]

It seems to me that the expanding foam would naturally take the path of least resistance and not put that much, if any, pressure on the bulkheads. Make a test fixture of sorts, resembling a kit or build, measure the distance between bulkheads, insert the foam, measure again after curing. Or - you could brace each bulkhead with temporary supports prior to filling to insure rigidity. Since I don't know how the foam will react with different adhesives, I'd just use balsa.

Phil - it sounds like it should work but at what cost to your many hours plus dollars spent. Repairing/redoing is not as much fun as the initial building. Balsa or very soft pine is the only way I'll go now after my "experiment".
One other thing to note is that while this stuff sticks to almost everything, it will leave gaps and air spaces as it really isn't low enough viscosity to flow as well as you would think. I've stopped using it around windows after distorting the frames even open without the trim molding installed

 

[Philski]

Phil - it sounds like it should work but at what cost to your many hours plus dollars spent. Repairing/redoing is not as much fun as the initial building. Balsa or very soft pine is the only way I'll go now after my "experiment".
One other thing to note is that while this stuff sticks to almost everything, it will leave gaps and air spaces as it really isn't low enough viscosity to flow as well as you would think. I've stopped using it around windows after distorting the frames even open without the trim molding installed

Where needed, I chose balsa....

 

[Bryian]

Been using expanding foam in my plank on bulkhead models for 20 years. You need to leave off a few planks for ooze out.

 

[Signet]

Been using expanding foam in my plank on bulkhead models for 20 years. You need to leave off a few planks for ooze out.

Ahah! Someone HAS tried this! I'd be doing this before planking is on, so that after shaping and sanding, it would help support the single layer of hull planking. Do you have any pictures or forum descriptions that show what you've done? Any thoughts, for or against, things to do, things to not do?

 

[DomCee]

I had never filled my hulls before and I thought about using expanding foam for my current build because the hull has large spaces but it is horrible stuff to use, sticks to everything and is very difficult to control. I had some spare blocks of low density modelling PU foam and found it to be really easy to cut and shape. I am in the process of planking and a bonus is that long push pins hold very nicely into it so you can hold the planks in place without nails, wait for the glue to cure and then just pull the pins out. I have attached the tech. data pdf for the stuff I used.

Dom

 

[Hoss6262]

Just found your thread. Seems you've got quite a bit of advice, all of it really good. I've tried this on a model once. The comment on controlling the expansion is one that is key, especially in small tight spaces. A fraction of a second too long on that nozzle and you've got a big foamy mushroom/wart growing out of your hull. Also, as stated, you're going to test it. Make the test as close to your application as you can. Two other points to offer. Foam can be found in different densities. Go as light as you can. The less dense it is you will find the easier it is to cut/sand. Use release agents where you don't want the foam to adhere to.

I had a summer job, between college semesters my freshman year where I sprayed this stuff commercially. After spraying a few million gallon crude oil tanks in Jersey City, New Jersey, that was enough for me.

Personally, I wouldn't try it again on a model. And interestingly enough I just had a conversation with a materials specialist at a local distributor of special materials, Reynolds Advanced Materials. I shared my needs and she recommended a light weight epoxy putty. I specifically asked her about expanding foam, which they did have and she steer me away from the foam, citing expansion challenges. She recommended epoxy putties.

Here is their putty page.

Epoxies – Putties Materials from Reynolds

Putties used for a variety of fabrication or sculpting applications, are available as rigid or semi-rigid.

www.reynoldsam.com

I went with the Free Foam Air putty, which is the lightest density. I tested it and it is very workable for a couple of hours and fully cures in 24 hours. It sands well and can be sculpted with a variety of tools. I will be using it to fill voids in my ship's bulkheads. I will be using it to fill bulkheads inside the hull of my ship to support a false deck. Supporting a false deck or supporting outer hull planks, the principle is the same. I went with the trial size, which the representative conservatively estimated would fill 95 cubic inches. Trial size was like $36.