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Old 08-24-2018, 06:23 AM   #1
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Marine Grade Plywood or Coosa Board That is the Question

I need some help. I'm struggling with what type of sub-floor material to use. At this point I'm trying to decide between Marine Grade Plywood and Coosa Composite Board. If I do go with the Coosa, do I want the Blue Water 20 or 26? Also, if anyone is privy to good deals I'd love to save some money.
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Old 08-24-2018, 09:43 AM   #2
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Marine grade should do a fine job.



I recommend focusing on eliminating leaks along with having a way to find them. I also limit the time of exposure by having a roof over the trailer. I also installed a secondary roof coating to seal up the roof. Kinda sounds like a lot but no reason your trailer couldn't last another 26 or more years.


How is the frame?
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Old 08-26-2018, 09:41 PM   #3
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Quote:
Originally Posted by sgschwend View Post
Marine grade should do a fine job.


I recommend focusing on eliminating leaks along with having a way to find them. I also limit the time of exposure by having a roof over the trailer. I also installed a secondary roof coating to seal up the roof. Kinda sounds like a lot but no reason your trailer couldn't last another 26 or more years.


How is the frame?

Thanks for the info. Two reasons I'm considering Coosa. It's waterproof essentially and it's much lighter than plywood.

My frame had some significant rust issues, but the bad outriggers have been replaced and the rear part of the SS tube has been replaced. I have a friend who welds.
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Old 08-27-2018, 03:25 PM   #4
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I'm not familiar with this Coosa product but if it's a synthetic product like the white boards we can get at HD and Lowes for home use I'd be suspect about it being structurally as good as traditional plywood. If others have used it and found it comparable please forget my comments here. I'm just wondering if the spread of the frame members might be too wide and this being used for a subfloor might flex more than plywood. However if it's manufactured to be more dense it just might be a great alternative.
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Old 08-27-2018, 04:09 PM   #5
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As airforums No 1 fan of Coosa board I can personally atest to its incredible properties.

Do you want it? I guess it depends on how long you plan on keeping your trailer? The longer you want to keep it, the more you'll want to spend the extra on Coosa.

Coosa has a water absorbtion of less than 1%, 40-45% lighter than plywood; will not promote mold, mildew, fungus, or rot. Marine grade plywood is still organic and thusly will be exposed to these issues. If you epoxy the marine grade plywood you have just negated the extra cost of the Coosa by the expense of the epoxy.

As far as going with Coosa 20 or 26 I was told that Coosa 20 will span up to 16" with little to no deflection. I went with 3/4" Coosa 20 (it was all my supplier could get) and just machined the end to fit the channel.

The other thing to remember is this.......If you were to choose from two trailers for sale, both the same model and model year in the same condition; one has a marine plywood subfloor and one a Coosa board subfloor, which one would you choose and how much would you pay more for that subfloor; especially if you show them the benefits of Coosa board. Just keep a piece to dunk in a bucket to show them.

The piece of mind knowing that water will never be a problem again, is just priceless.

Cheers
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Old 08-27-2018, 04:14 PM   #6
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Quote:
Originally Posted by polarlyse View Post
I'm not familiar with this Coosa product but if it's a synthetic product like the white boards we can get at HD and Lowes for home use I'd be suspect about it being structurally as good as traditional plywood. If others have used it and found it comparable please forget my comments here. I'm just wondering if the spread of the frame members might be too wide and this being used for a subfloor might flex more than plywood. However if it's manufactured to be more dense it just might be a great alternative.
Please see my post above for an explaination on the benefits of Coosa, but I wanted to answer one of your comparisons to whiteboard or plastic based boards.

Plastic based boards expand and contract, thusly screws would have to be slotted and gaps would have to be allowed for to accommodate this; Coosa on the other hand doesn't expand or contract by any appreciable rate at all, so no allowances need to be taken into measure.

Also the weight of these plastic boards at 5/8" thick would be significantly higher than Coosa board.

Cheers
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Old 08-27-2018, 05:43 PM   #7
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ThanX Tony for clearing that up. It sure seems to be a much more sound product than I had given it credit for. I've never seen it so only going from my experience of those white boards. For what I've used them for they worked great but certainly for only cosmetic looks and durability. I'd like to see it just to understand it's possible uses.
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Old 08-27-2018, 06:48 PM   #8
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I have seen 4'x8' -1/2" marine plywood at Menard's for $49 a sheet. Cost effective upgrade from the factory floor that lasted how many years?
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Old 08-27-2018, 09:28 PM   #9
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I have seen 4'x8' -1/2" marine plywood at Menard's for $49 a sheet. Cost effective upgrade from the factory floor that lasted how many years?
I don't think 1/2" is thick enough. 3/4" is more like it.
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Old 08-28-2018, 07:39 AM   #10
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I used ACX 5/8 plywood & treated it with penetrating epoxy.
I took an epoxyed scrap & seed it out side under the eave of my shed. In the shade. No rot at all. This was 3 maybe 4 years ago. It's still out there proving itself.
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Old 08-28-2018, 08:39 AM   #11
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The answer to your question depends mainly on how you are using your trailer and how long you wish to own it.

Coosa Board is unquestionably the best sub floor material possible. It is lighter weight than plywood, essentially waterproof, so it will never rot or go soft, impervious to mold, bugs, varmints, etc. -- all while being just as strong and easy to work with as plywood. Once you put it in, it should last for the life of the trailer, which means the significant pain and trouble of replacing the floor will never have to be done ever again.

MGP, while better than untreated plywood, is heavier, and still susceptible to water and bugs.

If you use your trailer lightly, and only plan on keeping it for a decade or so, then MGP is cheaper, and you may get away with replacing the entire floor only once in the time you own it.

The key problem is water. I don't care how well you seal the trailer, water is still going to get to your floor. It may come from leaks, from intrusion around the wheel wells, from plumbing leaks, from spills, from condensation, from your fridge, around the toilet and shower stalls, from around windows and doors, from a vent, from the refrigerator chimney and/or vent doors, from around the rear bumper. You may have to replace sections of sub floor around your door, under the sink, in the bathroom, and so on. This is a major pain and also costly. So costly, that it would have been cheaper to simply have put in Coosa to begin with.

Since I use my trailer 5-days a week in summer, and have owned it now for 12 years and plan on owning it for a good deal longer, Coosa board makes tons of sense for me.
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Old 08-28-2018, 08:52 AM   #12
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Like many of us. I also spent a lot of time researching alternatives to plywood when I did my restoration. The weight saving of coosa is great and I would have purchased it or one of the many alternatives for that reason. Unfortunately the difficulty of actually obtaining these materials turned me a bit sour. Either suppliers wouldn't return my calls and emails, or the expense was outrageous.

My worries for rot were also a tad silly. So it came down to the extra price for the savings in weight. My trailer was built in 1971 and had sat in a field in Missouri for 20 years prior to purchasing it. The only rot in the floor was under the fridge due to the vent leaking and in the usual rot in the bathroom.

If that is the only rot in 40 years then my maintenance will now prevent that from happening again.

When the question comes down to marine plywood or not. From my research, the extra price you're paying for with marine is to have void free ply. The glue is the same as exterior grade plywood. If somebody knows different to this, then I'm all ears.

I would also not use anything smaller than 3/4. An airstream chassis is built very lightweight with the flooring making up part of the structural integrity. Using a material that is too thin leaves the chassis suspectable to cracking welds. Especially in the outer areas where the body joins. Even with 3/4 from the factory, when a shell off is performed most people are going to find a few pieces of their frame that have cracked welds

If my budget was unlimited and someone wanted to actually sell my the Coosa, I would have brought it. However, with my restorarion I think I'm glad it never happened because by the end, my budget was all but stripped and those lithium batteries probably would have been substituted for lead ones due to my extremely depleted bank account.
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Old 08-28-2018, 04:56 PM   #13
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Quote:
Originally Posted by Isuzusweet View Post
As airforums No 1 fan of Coosa board I can personally atest to its incredible properties...
Coosa has a water absorbtion of less than 1%, 40-45% lighter than plywood; will not promote mold, mildew, fungus, or rot...
The other thing to remember is this.......If you were to choose from two trailers for sale, both the same model and model year in the same condition; one has a marine plywood subfloor and one a Coosa board subfloor, which one would you choose and how much would you pay more for that subfloor; especially if you show them the benefits of Coosa board. Just keep a piece to dunk in a bucket to show them.

The piece of mind knowing that water will never be a problem again, is just priceless.

Cheers
Sidekick Tony

All very good points Sidekick Tony. While I believe that Marine Grade plywood would be just fine and a big upgrade from the OSB used in my AS from the factory, I'm like you, if there is something even better why not use it.

Along with the fact that water won't hurt it, I particularly like the reduced weight factor. We do intend to use our AS for many years to come. As a matter of fact we'll be full time once our rebuild is complete.

I called Coosa yesterday and spoke with a technical rep. For our application, my spans are 24" OC, with a 35" span in the very front (actually this space is supported by the spare tire), he recommends the 3/4" Bluewater 26 which he said was specifically designed to replace Marine Grade Plywood. I'm fortunate because it's available from a local distributor, so shipping costs are not a factor which is a nice plus. I'll need about 7, 4' x 8' sheets. I believe I was quoted $275 per sheet. So yeah, expensive, but I didn't tear this thing down to the ground to skimp.
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Old 08-28-2018, 05:32 PM   #14
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If you have gone as far as what you have shown......Coosa is a no brainer; and like I stated, you'll get your money back and more if you sell her and state you have Coosa as a subfloor; it just tells people you didn't scrimp on your renovation, and you're not hiding anything.

Cheers
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