after a long pause, it's time to start building

[Bob Hammond]

Hello, I finally quit that bad habit that used up my time (the job), and now it's time to wander after I wonder.

When I last posted, i was shopping for ideas, and i had refurbished the chassis of my bodged-up trailer. It was a Kmart kit trailer from about 1985, that I'd modified to carry a sunfish sailboat. Previous estimates are that it will bear about 900 lbs, and so a foamie is planned. i see that the 'state of the art' of foamies has advanced, and so I'll go that route. I have a full arsenal of woodworking tools, with the exception of a chainsaw which would only be necessary if the Frustration/Insanity Index gets above 8.0 on the Richter scale.

I do have a few considerations and questions that I would like to present:

1. Having read various threads that extoll the virtues of a panel made of ply/foam/canvas that results in a composite stressed skin/torsion panel. I think I'll do that. Early experience suggested using 2" EPS, and a recent discussion recommended 1" material. Other than the R-values, is there as significant structural difference?

2. With respect to framing the deck and edges of the walls, many people are concerned with rot, to the extent that a few people have attempted to use no framing at all. When i consider the materials, there's plain old spruce (excellent strength/weight ratio), cedar (much weaker but it has reasonable rot resistance), and pressure-treated (PT). With respect to PT, most people are very concerned with exposure to the chemicals, but i think that the cumulative time of exposure is so low that the risk is negligible. My principal objections to PT are that the wood is green, heavy, and of low quality that is very prone to warpage. So i think I'll use cedar, and make timberframe joints, i.e. bridle tenon joints on the corners, and pegged lap or dado/dovetail for the crossmembers.

3. Everybody seems to like get the deck and sidewalls up as soon as possible, which is understandable. For me, I'll need to build the deck directly on the chassis or build a strongback, and then use the deck as an assembly table for the sides. But before all, I think it would be best to build the doors with frames as a complete assembly, such as would be done in a house. i think perhaps the same should be done for the back hatch, as soon as i decide on the body style.

4. Returning to the subject of preventing mildew and rot, has anybody ever thought of heating the cabin when the trailer is not in use? With a foamie, i would expect that an incandescent lightbulb of 60-75 watts could raise the inside cabin temperature enough to reduce the relative humidity (RH) to prevent mildew. if the trailer were covered with a tarp, a couple of bulbs might just reduce the RH enough to retard rot also.

(I've advised the Lady Wife that installation of a cast iron tub is 'iffy', for now.)

[GPW]

Sounds like a good plan !!!

[KennethW]

I do have a few considerations and questions that I would like to present:

1. Having read various threads that extoll the virtues of a panel made of ply/foam/canvas that results in a composite stressed skin/torsion panel. I think I'll do that. Early experience suggested using 2" EPS, and a recent discussion recommended 1" material. Other than the R-values, is there as significant structural difference?

2" in the floor and 1" on the remainder worked for me. It is not as solid as 2" but works. With 2" in the floor that would be all you need unless you are extending past the trailer more the a foot. If you made the shell off the trailer it will made it easier to wrap the canvas up the sides and under the floor when canvasing under the floor and canvasing the walls (working flat would make it easier) by wrapping both way you will have a strong joint. By not having on the trailer canvasing the ceiling with it upside down may be easier too.

. With respect to framing the deck and edges of the walls, many people are concerned with rot, to the extent that a few people have attempted to use no framing at all. When i consider the materials, there's plain old spruce (excellent strength/weight ratio), cedar (much weaker but it has reasonable rot resistance), and pressure-treated (PT). With respect to PT, most people are very concerned with exposure to the chemicals, but i think that the cumulative time of exposure is so low that the risk is negligible. My principal objections to PT are that the wood is green, heavy, and of low quality that is very prone to warpage. So i think I'll use cedar, and make timberframe joints, i.e. bridle tenon joints on the corners, and pegged lap or dado/dovetail for the crossmembers.

Get the shell done the see if you need any support under it. It would save weight if you didn't Have to have the wood. I would try to stay away from wood when possible.

3. Everybody seems to like get the deck and sidewalls up as soon as possible, which is understandable. For me, I'll need to build the deck directly on the chassis or build a strongback, and then use the deck as an assembly table for the sides. But before all, I think it would be best to build the doors with frames as a complete assembly, such as would be done in a house. i think perhaps the same should be done for the back hatch, as soon as i decide on the body style.

I build the whole shell as one piece and cut the hatch off and then added the water channels.

This is just my thoughts.

[Bob Hammond]

Now i've got the chassis prepped for welding two angle-iron reinforcements from the front corners of the frame to the tongue, and the total weight of the roadready chassis will be just slightly under 200lbs.

Now it's time to gather the materials for the cabin. i think i'll use 2x cedar framing all the way through, with 1" foam. The deck will be skinned with 1/4" birch-cored underlayment. i'm considering cork for the interior floor and maybe also the walls if it is not too costly. i have 1/4" lexan on had for Wiley-style windows and maybe a skylight. The galley will have vertical cupboard style doors that will be inset in the opening.

[Bob Hammond]

Ken, i'm considering your thoughts about eliminating the wood frame, but it seems to me that a frame would make it easier to square up and assemble the shell. Maybe a temporary assembly form or support framework would work.

I've done a little more testing and discovered that Watco Teak Oil finish does not degrade the Owens Corning foam. I poured it on full strength as I would do for finishing wood, and it dried in about 8-12 hours. After a week of full exposure to sunlight @ 85+F, there is no visible damage to the foam. The oil does dry with the characteristic yellowish cast.

Next, I've been researching cork as an interior surface material. Aside from being waterproof, cork is naturally quite fire, mold, and rot resistant. You might remember that cork was used for the interior surfaces of submarines, which had very high humidity levels. I believe that it could be glued on to foam or FRP with contact adhesives that do not have organic solvents, such as 3M Fastbond. Here's a link to a supplier that has various thicknesses of cork in useful widths & lengths:

http://www.mantoncork.com/

[Bob Hammond]

After considering a few styles and making a cardboard model, I came up with something that I like, and then discovered that it is very much like atahoekid (Mel's) 'Road Foamie'. His build-log is, and will be, very helpful (thanks so much for taking the trouble to document your build!). Likewise, KCstudy's log is very helpful because he discusses in detail not only the methods of construction but also the mistakes and how to correct them.

All that said, I am decided on a 2x2 cedar frame because it will help me (the one man crew) get things put together square and plumb. I don't think I will encapsulate the cedar because water will get in anyway, and if it is trapped in there it will definitely promote rot. Here is a pic of a cedar deck and rail that I built 24 years ago (in Michigan) with no preservatives on it (it is sitting on PT sleepers). The railing was built with mortise and tenon construction (with a half-lap joint in the lower rail that is concealed inside a mortise in the post). There is only one place where it has rotted, inside the corner post. The top rail was mitered directly over the post, and water drained through the crack and into the endgrain of the post.

As for the ongoing materials/technique testing, I found that sharp No.4 bench plane can be used to trim off the Gorilla Glue squeezeout from a foam joint with ease and speed. Incidentally, I expect the No. 4 and a blockplane (Stanley 9-1/2 or 60-1/2) will be extremely useful during the building process.

Also, when estimating weight, it is helpful that Menards (menards.com) lists the shipping weight of many materials, e.g. a cedar 2x4x8' weighs 9.3 pounds.

(I'm sorry if you get a crick in your neck from turning your head sideways to view the photo!)

[GPW]

“ because water will get in anyway, “ ... Likely NOT if you do it right ...

[KCStudly]

Thanks for the plug. The reason I used 1-1/2 inch thk foam was primarily because it matches the 2x nominal sticks (more or less... plan on sanding your foam flush to your frame as the foam is seldom every true in thickness).

Not sure why you would use an oil finish on the foam; I would be concerned about adhesion on following operations. On the other hand, once I had my foam sanded into shape, I wish I had started by coating it with epoxy (or TB2 if doing PMF/canvas). The hard shell would have made it easier to work on without so many of the little miscellaneous dents, dings, scrapes and damages.

[Bob Hammond]

KCstudy,

The reason for testing the oil finish was that I may treat the interior trim and door woodwork with it, and I was wondering if it would degrade the foam if the oil somehow got onto the foam.

There is something that nags me about the use of TB2 in layers: How does a second layer of glue adhere to the first cured layer? I assume that it Is usually only a poor mechanical bond that will separate and fail. Is it necessary to fuse them, probably with heat from a clothes iron?

Also, someone suggested using fiberglass insect screening as a patching/reinforcement material or as a covering instead of canvas. I'm doubtful of using it as a covering material, but it might be ok for reinforcing joints since it would be thin and probably not show through a canvas cover. Are there any opinions about that? (I see that a 72" x 25 ft roll of heavy duty fiberglass screening is about $30 at the orange box store.)

[GPW]

" There is something that nags me about the use of TB2 in layers: How does a second layer of glue adhere to the first cured layer? “

What Layers , usually just the one eh ? ... Actually if we glue twice,we roughen any smooth surface with a little sanding ( the tooth) , and in reality T2 softens a little bit on the surface when wet... We’ve never had problems , but usually don’t do “layers" , just as a matter of course ...

If you’re referring to a second “sizing” coat over an already glued on canvas , yes , but that’s with highly diluted T2 , meant only to encapsulate /saturate every fiber... Has nothing to do with attaching the canvas ...

Is that what you’re worried about ... ?

[Bob Hammond]

Yes, it was the sizing coat over the previously glued canvas that concerned me. What about repairs, if/when necessary?

Does anyone have experience with this fiberglass-faced foam roof decking panel? It looks resistant to dents, but it may be hard to find in 1-3 sheet amounts.

http://www.menards.com/main/building-ma ... 9128969316

[GPW]

Tha sizing coat is a "given” and ensures that all the canvas fibers are protected ... Then Primer over that , then paint ... That’s what’s usually done , or the sizing coat left off and the first coat of primer thinned ... otherwise Thick primer will “ride" on the top of a thick canvas and not sink in thoroughly ... Ask me how I found that out ....

[greygoos]

Yes, it was the sizing coat over the previously glued canvas that concerned me. What about repairs, if/when necessary?

Does anyone have experience with this fiberglass-faced foam roof decking panel? It looks resistant to dents, but it may be hard to find in 1-3 sheet amounts.

http://www.menards.com/main/building-ma ... 9128969316

I just bought some. They type I have doesnt dent easily, I dropped a hammer on it a few times and didnt see any dents. It did puncture the fabric and foam when I gave it a good whack. It is or was my intention to use it for a build. Unfortunately physical limitations at this time prevent the project from going through. My advice to you would to go with what you believe will work for you. You get a lot of good advice on here but you also get negative comments when trying something new which can be discouraging. Good luck with your build.

[Bob Hammond]

Greygoos, Thanks for the info. Maybe I can find a source of the panels, or I'll just move along with the original plan, so that I can get this done in a useful amount time -- say a month or two.

I'm not too concerned about the negative comments. I don't think that anyone here is deliberately nasty. I think that they're more of a constructive criticism of the building methods than a criticism of me. While it's not necessary to always accept criticism or advice, it's generally a good idea to listen to it.

[GPW]

QUOTE: “ I don't think that anyone here is deliberately nasty. “ We don’t think so either , but sometimes people believe they are Right from a certain perspective, and can be quite insistent , but it’s all for the Greater Good ( the Greater Good ) ... Besides we all must BEHAVE since our Moderator abandoned us years ago ...
I believe most folks here just want to be HELPFUL !!! Preventing others from making their mistakes ... Something that would play well in the Real World ....