Floor Support & Frame - Page 2 - Fiberglass RV


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Old 09-30-2010, 03:49 PM   #15
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Name: Rachel
Trailer: 1974 Boler 13 ft (Neonex/Winnipeg)
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Okay, so, cored floor repair.

I have to start out by saying that I would still really like to see photos of the inside of the floor, and where it meets the walls/shell. Since I can't see that, I'm going to be a bit more general.

Also, I'm coming from a boat perspective, so some of the materials I'm suggesting are a bit of a step up from original egg construction.

So, for starters (again, I'm making some assumptions here since I can't see your details), you want to sand off any "gunk" from the top of the lower shell. Also, if it's weak (and it probably is), you may need to shore it up from below while you work (say, thin sheets of junk ply held up by something; you just want to make sure to establish and keep the flatness while you work, and you will need to be able to put pressure on the floor).

Once you have the shell clean and smooth (I would probably use something like a Porter Cable 7335 with 40 - 80g paper; of course be careful and test gingerly before you go whole hog), then vacuum and wipe it with denatured alcohol or acetone. This should all be taking place on the "raw" (not gelcoated) glass. I would also sand about 4" up the sidewalls. If there are any damaged or too-thin areas, you can reinforce them with fiberglass now.

Next you would mix up some thickened epoxy (cabosil) and spread it on the inside of the lower skin with a notched spreader. Then you place your core on the epoxy (no need to use one huge piece - actually balsa core is made in about 3" squares - the skins and epoxy will bond it all together - one huge piece would be pretty unwieldy).

I checked with someone about the MDO, and apparently it is just plywood with a paper facing bonded to it and could probably be used, although not ideal. Personally, I would not use it or plywood, because that is just extra weight. I would use either balsa or foam core. I'm not sure exactly what thickness you need; but a boat deck of about 4' or more in width would probably use 5/8" or so core. The further apart you space the skins (with the core), the stronger they are, but it's not actually the core that is making it stiff; it's the space between the skins and the bond. Did you say what thickness was there originally?

Once you are sure the core is in and properly down, you can fill any gaps with more thickened epoxy. Then you can either let it cure and clean/sand, or you can keep on going as long as it is still "green" (dentable with a thumbnail) and get a chemical bond without sanding. But, you have to watch for heat buildup if you are getting really thick/large areas of epoxy curing. Also, you may need to stop and cure/sand at this point if things are too lumpy. This is a bit of a judgement call. Being new at it, I might stop here and let things cure, then sand/wipe, continue. Less potential for a big whoopsie that way.

Next, you coat with neat epoxy, and then lay on the top skin, working epoxy thoroughly into the weaves (white cloth should turn totally clear). I would use something like 1708 biaxmat, a couple of layers, although that is probably slightly overkill. You can use a layer of something like 6-10 oz cloth on top if you want a smoother finish, and/or fair with thickened epoxy (microballoons and a bit of cabosil). Roll/squeegee out all of the air (they make little spiky metal rollers for this). Then I would probably let things tack up to the green stage, and then go back with some ~5" strips to tab up onto the sidewalls. After this gets "green," you can go back with thickened epoxy to fair the surface if you need it smoother.


There is some good information on the web at either WEST System's site (they have a great usage manual online), or System Three's site (another great free manual).

Some places to buy supplies:

www.raka.com

Boat Building and Woodworking Supplies (Jamestown Distributors)

Fiberglass Coatings Inc. Your Single Source for All Your Fiberglass Needs

This was really not as detailed as it could be, but.... there is a lot to say, and numerous little details that depend on the exact situation and how things look, how they go, etc. which I don't know right now. I wanted to give you an idea what to do, but I don't want to feel too responsible either, since there are numerous ways to do it, experience counts, etc.

If you do plan to go ahead with it, feel free to PM me if you like and we could talk/call, etc.

Oh, and for sealing core penetrations. If you have an area you know will be a largish penetration, you can lay it up now with solid glass. But for fastener and other smallish holes, I would just go back after you are done, "overdrill" them with something like a 1" bit, and then fill in with thickened epoxy (cabosil). After that cures you re-drill the (smaller) hole through the center for the fastener (or, if you want to be extra smart and not have to have someone on the bottom holding a nut, you can tap the holes, then go back and put the nut on at your leisure).

This should keep leaks from getting to the core. Then you can use caulk or whatever to bed your stuff, and if there is ever a leak it is "just" a leak, not something seeping into the core and insidiously ruining it.

There are "waterproof" cable pass-throughs too, like these; it kind of depends on what you are actually running.

CableClams - Blue Sea Systems

Raya

PS: I'm sure I forgot or misstated *something*; I would recommend reading the free guides from WEST and System Three, and comparing notes. They are the pros.
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Old 10-01-2010, 06:00 PM   #16
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Trailer: Bigfoot 13.5 ft
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Quote:
Originally Posted by Raya L. View Post
Okay, so, cored floor repair.

I have to start out by saying that I would still really like to see photos of the inside of the floor, and where it meets the walls/shell. Since I can't see that, I'm going to be a bit more general.

Also, I'm coming from a boat perspective, so some of the materials I'm suggesting are a bit of a step up from original egg construction.

So, for starters (again, I'm making some assumptions here since I can't see your details), you want to sand off any "gunk" from the top of the lower shell. Also, if it's weak (and it probably is), you may need to shore it up from below while you work (say, thin sheets of junk ply held up by something; you just want to make sure to establish and keep the flatness while you work, and you will need to be able to put pressure on the floor).

Once you have the shell clean and smooth (I would probably use something like a Porter Cable 7335 with 40 - 80g paper; of course be careful and test gingerly before you go whole hog), then vacuum and wipe it with denatured alcohol or acetone. This should all be taking place on the "raw" (not gelcoated) glass. I would also sand about 4" up the sidewalls. If there are any damaged or too-thin areas, you can reinforce them with fiberglass now.

Next you would mix up some thickened epoxy (cabosil) and spread it on the inside of the lower skin with a notched spreader. Then you place your core on the epoxy (no need to use one huge piece - actually balsa core is made in about 3" squares - the skins and epoxy will bond it all together - one huge piece would be pretty unwieldy).

I checked with someone about the MDO, and apparently it is just plywood with a paper facing bonded to it and could probably be used, although not ideal. Personally, I would not use it or plywood, because that is just extra weight. I would use either balsa or foam core. I'm not sure exactly what thickness you need; but a boat deck of about 4' or more in width would probably use 5/8" or so core. The further apart you space the skins (with the core), the stronger they are, but it's not actually the core that is making it stiff; it's the space between the skins and the bond. Did you say what thickness was there originally?

Once you are sure the core is in and properly down, you can fill any gaps with more thickened epoxy. Then you can either let it cure and clean/sand, or you can keep on going as long as it is still "green" (dentable with a thumbnail) and get a chemical bond without sanding. But, you have to watch for heat buildup if you are getting really thick/large areas of epoxy curing. Also, you may need to stop and cure/sand at this point if things are too lumpy. This is a bit of a judgement call. Being new at it, I might stop here and let things cure, then sand/wipe, continue. Less potential for a big whoopsie that way.

Next, you coat with neat epoxy, and then lay on the top skin, working epoxy thoroughly into the weaves (white cloth should turn totally clear). I would use something like 1708 biaxmat, a couple of layers, although that is probably slightly overkill. You can use a layer of something like 6-10 oz cloth on top if you want a smoother finish, and/or fair with thickened epoxy (microballoons and a bit of cabosil). Roll/squeegee out all of the air (they make little spiky metal rollers for this). Then I would probably let things tack up to the green stage, and then go back with some ~5" strips to tab up onto the sidewalls. After this gets "green," you can go back with thickened epoxy to fair the surface if you need it smoother.


There is some good information on the web at either WEST System's site (they have a great usage manual online), or System Three's site (another great free manual).

Some places to buy supplies:

www.raka.com

Boat Building and Woodworking Supplies (Jamestown Distributors)

Fiberglass Coatings Inc. Your Single Source for All Your Fiberglass Needs

This was really not as detailed as it could be, but.... there is a lot to say, and numerous little details that depend on the exact situation and how things look, how they go, etc. which I don't know right now. I wanted to give you an idea what to do, but I don't want to feel too responsible either, since there are numerous ways to do it, experience counts, etc.

If you do plan to go ahead with it, feel free to PM me if you like and we could talk/call, etc.

Oh, and for sealing core penetrations. If you have an area you know will be a largish penetration, you can lay it up now with solid glass. But for fastener and other smallish holes, I would just go back after you are done, "overdrill" them with something like a 1" bit, and then fill in with thickened epoxy (cabosil). After that cures you re-drill the (smaller) hole through the center for the fastener (or, if you want to be extra smart and not have to have someone on the bottom holding a nut, you can tap the holes, then go back and put the nut on at your leisure).

This should keep leaks from getting to the core. Then you can use caulk or whatever to bed your stuff, and if there is ever a leak it is "just" a leak, not something seeping into the core and insidiously ruining it.

There are "waterproof" cable pass-throughs too, like these; it kind of depends on what you are actually running.

CableClams - Blue Sea Systems

Raya

PS: I'm sure I forgot or misstated *something*; I would recommend reading the free guides from WEST and System Three, and comparing notes. They are the pros.
Raya,

Thank you for the great information! Here are a few additional pictures so that you can get a better idea of the project (The pink stuff is the original adhesive that Bigfoot used to bond the lower shell to the 3/4" plywood subfloor). I did a little research on MDO. Although heavier than needed, it is different that normal plywood from everything that I read. The layers "overlays" and outer covering are resin impregnated, resulting in increased stiffness as well as durability in exterior environments. Although I would prefer something lighter, I own three 4' x 8' sheets of MDO, and so it will have to work as the core.

I do have a few addtional questions. Do you suggest making the thickened epoxy by adding the Cabosil to the same West 105 that I'll be using for normal glassing? Just follow the mixing instructions? Also, what about the penetrations for the bolts that hold the shell to the frame. I'm a little unsure about overdrilling these, adding epoxy, and then redrilling for bolts. Is this what you recommend?

I'm excited about getting started. I've struggled for some time to find a good, long-term solution to the floor. It is such a relief to know that it will be both durable and strong. Thanks again!

Carl
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Old 10-01-2010, 06:30 PM   #17
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Name: Rachel
Trailer: 1974 Boler 13 ft (Neonex/Winnipeg)
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Okay, I guess I have to write something outside the quoted area, or my message is "too short."

Quote:
Originally Posted by Carl G View Post
I do have a few addtional questions. Do you suggest making the thickened epoxy by adding the Cabosil to the same West 105 that I'll be using for normal glassing? Just follow the mixing instructions?

Hi Carl,

Although you can now buy pre-made thickened epoxy, I like to mix my own. You can do it as you go along, use various thickeners (strong but hard to sand, for structural stuff; less strong but easier to sand for fairing, etc.). Also you can easily vary the texture according to what you are doing (i.e. mayonnaise consistency; peanut butter consistency; "oops, that's too much" consistency , etc.).

Seriously, the exact texture/amount of thickener is not critical. I mix my resin and hardener thoroughly first, then start adding thickener and stirring a bit at a time until I have it how I want it.

You'll see that in the WEST System guide, they also describe the consistencies in terms of well-known food products, to make it easier.


If you don't want to buy every thickener in the book, I would probably go with colloidial silica (cabosil), for strength, and microballoons, for fairing (if you need to fair). Note that colloidial silica can be very "fly away" and you don't want to be inhaling it.

When you are wetting out the cloth, you can just pour some resin on and then start spreading it around. Or, for smaller pieces (like when you tab edges), I wet them out ahead of time on a sheet of plastic laid over cardboard, then roll them up and move them into position.

Also, what about the penetrations for the bolts that hold the shell to the frame. I'm a little unsure about overdrilling these, adding epoxy, and then redrilling for bolts. Is this what you recommend?

Yes, that is what I would do. Not only does it seal off the core, but it provides a rigid epoxy annulus so that when you tighten down on the fastener, you aren't going to crush the wood. If you want to go whole hog you can tap the annulus, but just re-drilling the normal type fastener hole is fine too. You just want to end up with a decent sized ring around the fastener hole. I usually use something like a 3/4" or 1" bit, depending on the fastener size. Coat the inside of the large hole with neat epoxy, then thicken it and fill the rest of the hole. Tape off around it. A syringe or straw works great so you can fill from the bottom and avoid trapped air, but not entirely necessary. You can trim off overage at the green stage.

I'm excited about getting started. I've struggled for some time to find a good, long-term solution to the floor. It is such a relief to know that it will be both durable and strong. Thanks again!

On the campers I have looked at closely (Boler, Scamp, Trillium, Compact), you won't have any trouble exceeding original factory strength or methods. Just plan it out like a stir-fry, so that once you get going you have everything ready. And like painting, don't rush to the last step.

Raya

Carl
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Old 10-01-2010, 09:35 PM   #18
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Trailer: Bigfoot 13.5 ft
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One last question. All of the cabinets were screwed to the floor. If I replicate this method, I will be placing numerous penetrations into the core. What are your thoughts on this one.

Thanks,
Carl
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Old 10-01-2010, 10:46 PM   #19
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Name: Rachel
Trailer: 1974 Boler 13 ft (Neonex/Winnipeg)
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Well, realistically, unless you get a bunch of water in the interior, things would probably be fine with the screws going directly into the core (presuming MDO has good holding power), especially with some bedding (a slightly chamfered hole helps with this, but of course exposes more core).

On the other hand, if you want to be SURE, you could overdrill-fill-redrill where the screws will go.

If you want to help some, you could coat the insides of the plain holes with neat epoxy (say, with a pipe cleaner or something), but it's debatable how much better that would be than plain holes. Some, I suppose.

It's one of those things where you have to balance your expected use/abuse of the trailer, how much extra effort it would be, whether you would lose sleep over it if you didn't do it, etc.

Raya
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Old 10-02-2010, 12:03 AM   #20
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Sounds good. I'm most concerned first with the holes that penetrate to the outside of the trailer; cabinetry screws less so. I'm planning on completely re-working the windows and will monitor them in the future for any potential leaks. That should do the trick. Thank you again for the help. I'll be sure to post pictures at various stages.

Carl
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Old 10-02-2010, 12:09 AM   #21
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Carl,

Actually, your damage probably came from inside in years past. I don't think road spray would ever cause that. OTOH, the epoxy annuli are a good thing where you will be tightening down, and why not improve upon things since you'll be into "the goop" anyway.

I'm sure I glossed over or left out a few things, or was not able to take your specific project details into account, so if I can help further I would be happy to.

Raya
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Old 10-02-2010, 04:05 PM   #22
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Trailer: Bigfoot 13.5 ft
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Quote:
Originally Posted by Raya L. View Post
Carl,

Actually, your damage probably came from inside in years past. I don't think road spray would ever cause that. OTOH, the epoxy annuli are a good thing where you will be tightening down, and why not improve upon things since you'll be into "the goop" anyway.

I'm sure I glossed over or left out a few things, or was not able to take your specific project details into account, so if I can help further I would be happy to.

Raya
If I go with the epoxy annuli, I would prefer to have fewer fasteners into the floor, if anything to save a little on the install time. Bigfoot had quite a large number of screws fastening 1x lumber framing into the floor (Almost looked like someone was screw-gun happy). What do you think about reducing the overall number of screws and then supplementing the cabinet frame mounting by using epoxy as an adhesive where the 1x framing meets the glassed floor. I would think that this combination of screws and epoxy as an adhesive for the 1x lumber would be as effective if not more so than just using numerous screws. What do you think? This would certainly save on the install time if using the expoxy annuli method for all of the mechanical fasteners.

Also, I've been thinking about the bolts, which go through the floor from within the trailer and then through factory holes in the c-channel frame below. Producing the annuli for these might be a little tricky. After I have installed the MDO core, adhered the lower glass to the bottom side with thickened epoxy, and then glassed the top, I'll have to drill from the inside of the trailer through the floor, meeting the factory drilled hole in the frame. Because of space limitations due to the c-channel, there will be no way to drill from the underside of the trailer. Therefore, I'll have to have some way of precisely marking where to drill from the inside. I guess I could place the MDO in the trailer, mark it from beneath, drill a small hole, and then install a temporary screw that will protrude on the inside of the trailer. I could then adhere the bottom, do all of the glassing with this screw produding. That would give me a precise center to drill the large hole for the annulus. The only problem is that I will eventually hit the steel frame when drilling this large hole. Will I encounter any problems in completing the hole and removing the material?

Carl
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