What wood size for extending bed off trailer for "foamie"

[JDHIV]

Thanks ALL !!!
I have decided to go the route like a couple of others on this forum did (i.e. OHBUGGER & PJO129) by using a large full-sized truck cap/canopy and building a sort of wooden analogous truck-bed underneath it and mounting that in top of the floor I glue/screw/bolt to the trailer. So, I think MUCH of what you all posted is still useful !?

But, I'm still going to build a good flooring that is cantilevered out beyond the current width of the trailer...

...My current plan (as per help from my father) is to attache a flooring of 7 2x4's as cross-members on my trailer...and topping that with 1/2" B/C-grade plywood and filling the "voids" under that with 1.5" sheets of foam. This will get a protection layer of either RV roof paint and/or spray on truck liner. Then, I'm likely to make a roughly 2' wall in the standard construction of a typical American Wall...a baseboard layer of 2x4 running around the base of 3 walls (2 sides + 1 front) and running 2x4 vertical 'studs' spaced ~20" or so on-center and then a top-board on that (all glued/screwed & L-bracket screwed together...........this top-rail of 2x4 (or 2x3?) will be what the truck cap rests on and is bolted to....Foam will fill the spaces between 'studs' and eventually skinned in either the foamie fashion of T2 glue and canvas +paint or plywood and the inner skin will be thin 1/8" Luan or something to cover up the foam.

I will likely paint all wood with the "magic mix" rather than using pressure treated.

I will make this campable to start and then work on refinements.

Thanks to OBUGGER & PJO129 for their pioneering (?) work on this design....My overall budget and time frame didn't let me make a true TD shape or foamie construction THIS time around....but SOMEday I will take what I have learned and will continue to learn here to do so!!!

[KCStudly]

2x4's are overkill, IMNSHO.

[JDHIV]

Thanks for chiming in KC !

I haven't seen any activity on ANY of my posts lately for about 2 days...wondering if people got bored with me or annoyed that I changed to a different design?

And I will continue to be thankful for any/all advice/help I get !!!

I was told by someone that the bed subfloor lumber that I'll run across the trailer side-to-side (that the ply will be bolted down through and attached to)......that it doesn't matter in the bed if you use 2x2, 2x4, or 2x6 IF YOU ARE NOT going to orient them with their longer dimension facing UP...so putting a 2x4 up is better than on its side and on its side is just as good as a 2x6 on its side....I don't want to make my bed too tall...so putting them any way but flat is not going to happen....so I could use a 2x3 on their sides...but for marginal weight gain...I"ll likely just use 2x4's in the subfloor....but when I build a half-wall on top of that I may use 2x4's or 2x3's in the baseplate-stud-toprail (i.e., basic american 2x4 wall construction) as I don't want to lose too much width when I will properly orient the studs they way you'd expect.

I also have to put my base plate over my half-hexagonal shaped fenders that I saved from the Popup I gutted....so a little mitering and judicious use of angle brackets bent to the angles I make a kind of arch out of 3 short pieces of wood...I won't put any studs over that though...any maybe "header" the top rail above that into the flanking studs?

I'll copy/paste some of this into my new thread on my build.

Thanks!

[kudzu]

Can't answer your questions because I don't know the answers. Yet I am interested in your topic as it applies to my own build. Was thinking of using only 1x2 & 2x2 for my floor even though I'm extending 12-18" off the back.

I think along the way my brain mashed up info from torsion boxes with SIP construction. What I was planning is more like SIP construction. Don't think you really need that for yours.

[JDHIV]

Thanks Kudzu!

I just ran some quick calculation assuming I'm using kiln dried 2x3's or 2x4s from subfloor all the way up to my 22" high walls to support the truck cap.

2x4's would be 180lbs of lumber....while 2x3's would be 140lbs...so there is 40lbs of weight to save by using all 2x3's!! .............UNLESS someone can talk me out of 2x3's for good reasons...I think that is how I'm going to go.?

With all other things being equal....I would have either a 790lb or 750lb trailer (not including any foam, inner wall skinning or the framed out rectangular boxes I plan to build INside the trailer for couches/beds like OHBUGGER did in his build. AND that also doesn't factor in the GEAR (i.e., cushions/bed, battery, wiring, power converter camp stove and etc...)

What do y'all think?????????

_John

[pchast]

John,

If you use the same principal as a torsion box for the sides, just skin the inside you can use 1x3's for the uprights, 1/8 ply outside 3/8 inside, and a 2x for the top load bearing part.

It should save about a 1/3 of the wall weight?

[KCStudly]

You are not building a house. Think airplane not tank, especially if your TV has limitations.

Look at Aggie Tom's Silver Beatle build. His floor is 1x2 on the flat and there is a great pic of his cabin self supporting itself over the entire length here.

I would not worry about your slight overhang at all.

My floor is 5 mm marine ply top and bottom; 2x2 cedar perimeter frame where the screws are to hold the cabin walls to the floor; 2x2 cedar main xmbrs where the bolts go thru the field of the floor to hold the floor to the intermediate xmbrs; and 1x2's on edge where there are no bolts. There are a few small chunks of 2x stud placed strategically in the sandwich across the front and back where to reinforce the areas where bolts will be and where my galley counter frame will screw into. The voids are filled with 1-1/2 thk blue foam board and the whole sandwich is put together with quality water based contact adhesive and wood glue.

Currently my floor, bulkhead and walls are assembled and attached to a relatively narrow build cradle. I have climbed in and out a couple of times w/o much notice of the floor flexing, and I haven't even added any of the cabinet frames (which are my integrated roof spars).

The strength is in the sum of the parts and how you combine them (both in geometry and joint strength... integrate joints into structural lines, make your joints fit tight, glue and screw, etc.).

Think airplane, not tank.

Please don't take offense, but sometimes newbies can be very exuberant, ask the same questions that have been asked many times (I'm sure I did, too), and get impatient when an exact answer is not provided. There are no exact answers. You are responsible for your own build. People are more than happy to help by providing personal experience or by steering you to information that we feel may be of use to you, but only you can decide how you will use that info and what will work for your skills, available tools, financial commitment, and build resources (shop space, etc.).

My guess is that people may be reluctant to offer their advice until you show that you are capable of making some of these responsible decisions, or at least that you have done some more research into the basic building techniques and materials. Show that you can work thru a few simple problems by yourself, then people will not feel as if your whole project hinges solely on their advice and they will give it more freely.

Perhaps I'm way off base, but these are my honest thoughts to your questions.

[JDHIV]

John,

If you use the same principal as a torsion box for the sides, just skin the inside you can use 1x3's for the uprights, 1/8 ply outside 3/8 inside, and a 2x for the top load bearing part.

It should save about a 1/3 of the wall weight?

Thanks Pchast! I think what you are saying is make the 3 walls that I have to make to basically mimic a pickup truck's bed (shorter front and two longer sides) and make 3 torsion boxes perpendicular to my floor? So, I can use 1x3 "studs" (the uprights) within the skin (skin the with the ply as you said), and then top it with a 2x3 or 2x4 that the truck cap will sit directly on?

This sounds good and I just may do it!!

BUT ONE Q: How would you attach each wall/side to the floor? Maybe there is something about turning torsion boxes on their sides that I don't get...or maybe it is torsion boxes.

Thanks again Pchast!!

_John

[Wobbly Wheels]

Glue them on (PL Premium, etc) and use long enough deck screws from underneath to clamp it till the adhesive cures. At least, that's how I'd do it. The important part is to make sure that those screws pass only through wood (not foam).

[JDHIV]

You are not building a house. Think airplane not tank, especially if your TV has limitations.

Look at Aggie Tom's Silver Beatle build. His floor is 1x2 on the flat and there is a great pic of his cabin self supporting itself over the entire length here.

I would not worry about your slight overhang at all.

My floor is 5 mm marine ply top and bottom; 2x2 cedar perimeter frame where the screws are to hold the cabin walls to the floor; 2x2 cedar main xmbrs where the bolts go thru the field of the floor to hold the floor to the intermediate xmbrs; and 1x2's on edge where there are no bolts. There are a few small chunks of 2x stud placed strategically in the sandwich across the front and back where to reinforce the areas where bolts will be and where my galley counter frame will screw into. The voids are filled with 1-1/2 thk blue foam board and the whole sandwich is put together with quality water based contact adhesive and wood glue.

Currently my floor, bulkhead and walls are assembled and attached to a relatively narrow build cradle. I have climbed in and out a couple of times w/o much notice of the floor flexing, and I haven't even added any of the cabinet frames (which are my integrated roof spars).

The strength is in the sum of the parts and how you combine them (both in geometry and joint strength... integrate joints into structural lines, make your joints fit tight, glue and screw, etc.).

Think airplane, not tank.

Please don't take offense, but sometimes newbies can be very exuberant, ask the same questions that have been asked many times (I'm sure I did, too), and get impatient when an exact answer is not provided. There are no exact answers. You are responsible for your own build. People are more than happy to help by providing personal experience or by steering you to information that we feel may be of use to you, but only you can decide how you will use that info and what will work for your skills, available tools, financial commitment, and build resources (shop space, etc.).

My guess is that people may be reluctant to offer their advice until you show that you are capable of making some of these responsible decisions, or at least that you have done some more research into the basic building techniques and materials. Show that you can work thru a few simple problems by yourself, then people will not feel as if your whole project hinges solely on their advice and they will give it more freely.

Perhaps I'm way off base, but these are my honest thoughts to your questions.

NO WORRIES KCS!!! I take no offense and your time and thoughtful response are appreciated. I ask a lot of q's because I'm not especially handy which I can blame my dad for really not teaching me much...thinking he was saving me from hurting myself...... and I think my visualization skills are a bit lacking, not that my intelligence is. SO, I end up not really being able to "see" (even with pics sometimes) what people are suggesting....if/when I do..I begin to assimilate and process all the knowledge and try to come up with own concept(s).

Also, my tools, financial commitment, skills, and shop resources are all lacking...making this all that much harder...but still I persevere! LOL

After I finish this reply..I'm going to look at Aggie Tom's Beetle and see what I can glean from it!!

As I read how you described your floor and structure...I just don't quite visualize it...like what are the Main vs Intermediate members...what does "on edge" mean? as in the 1x3's are on edge...meaning they are vertically 3" and horizontally 1" ? A few other terms and or descriptions elude me...but I'm going to see if I can find pics of your build and as "they" say, "a pic = 1000 words" :-D

I guess my understanding on just how to design my 'geometry and joint strength... integrate joints into structural lines...' I think some carpentry knowledge would be beneficial in this venture....I'll likely not fully understand such things and allow the too-many different opinions to swallow me up in a void of 2nd-guessing and productive inertia!

As you said, I will figure out what is right for me...even if my understanding isn't optimal and maybe the worst that will happen is that I'll err on the side of "tank" .vs. airplane....but I'm trying!!!

As far as working through the problems myself....I think I am (see my immediate next post on what I have done so far and what I think I'm planning to do) !!

Yep, I'm definitely in the categorie of exhuberant and impatient newbies!! LOL But I have been reading this forum for HOURS (and hours and hours) and have picked up a lot despite getting lost in all of it more often than not). I will come up my own (hopefully correct-enough) 'answers' and hopefully not overbuild too much.

Thank you for your time!!
_John

[KCStudly]

"Small moves, Ellie" - Contact the movie.

Dimensional lumber is sized nominally based on the supposed rough cut size before milling and sanding, so 1x2 nominal lumber is only 3/4 x 1-1/2 inch actual size. When people say (or write) 1x or 2x they really mean 3/4 or 1-1/2 inch true measurement.

Yes, on edge means 1-1/2 tall (floor core thickness) x 3/4 wide.

Hrs. and hrs of reading is nothing. I spent a full year here reading build threads, construction techniques, the foamie section, and on and on before I made my first post.

There is a lot of information available here and plenty of experience to learn from. The most successful builds, IMO, take time.

The fast first time builders usually have issues that either stop them in their tracks, cause them to have many "do-overs" or result in a lot of, "I'm not happy with (fill in the blank) and will do it differently on my next build".

Just one perspective.

Build what makes you happy.

[JDHIV]

Thanks!

I teach...so I get way too distracted by work (even on the weekends) to be able to keep a project like this going and I get so distracted by other things I don't think I could spend a year reading this website...but we'll see!

I want something kind of quick and dirty...but functional and lightweight....so, we'll see what I end up with....I'll be happy to have a camper that I don't have to pop up or set up in any way.

Also, if I end up with anything wobbly in my structure...I could always install a pair of brackets inside the cabin and put reinforcing aluminum bars in them only while towing...easily removed when camping .

But, YEP...I'll happily (or UNhappily) report how my relatively quick and sloppy (?) build goes in the other thread (my build thread) and I will make it campable quickly...and work on refinements over the fall/winter....though I wanna try winter camping and being self sufficient (i.e., no campsite water/electr. hookup) and not freeze...we'll see...but document it all for better or worse!

Thanks!!!!
_John

[GPW]

J’, the natural tendency of us all is to Overbuild ! Turns out a simple skinned foam box , well fitted and assembled like KC said , is Very Strong !!! There does seem to be a point of diminishing returns as the size of the trailer is increased...which might require some internal bracing , or the use of Thicker foam ... all very easy to implement , in many and various ways as discussed here.
There has always been some skepticism and doubt from the new readers, but all that has been proven unfounded by the many successful Foamie' trailers that have already been built , and well travelled ...

"Dimensional lumber"... What a Rip Off !!! ... I’m old enough to remember when a 2X4 was actually 2X4 , and quite more substantial than todays offerings ... almost the size of the “modern” 2X6 ... Since the consumers have so willingly accepted the new smaller sizes (for some reason still unknown to me ) now it’s a standard ... as with so many other situations now , where we are promised more , but actually get much Less ...
Whichever lumber you use , always stand the long dimension up ...that’s the strongest way ...as is commonly done with studs,joists, rafters , etc...You could even use 3/4 X 1 1/2” for supporting a floor ,stand them up and use More of them ... simple “backyard” engineering ...
“Twice as thick is EIGHT times as Strong.” That’s the rule , so you can take that and run with it !!!
Again , like KC said ... “Think airplane , not tank “ ... True Dat’ !!!

[GPW]

More :

When using wood , you have to also consider the wood itself ... not all wood is the same ... some is denser , stronger, thus heavier... and can be used in smaller sizes to produce the same strength factors as a larger lighter wood . Some wood is more resistant to breaking and seems logically a better choice for trailer building ... For example , a small dimension Hickory framework , would do the same job as a much thicker Pine frame, and be less likely to fail in most possible situations... bending rather than breaking , a property of that wood .. Naturally all framing wood should be knot free (clear) and straight grain .
I always wondered why most people use the lesser woods for their trailer frames when other Better woods are commonly available ... likely too much reliance on the HD to supply all their needs ... more a “convenience “ than actually searching for the Good stuff ... Check out a real lumberyard for better woods , and Not that expensive ... many times the lumber yards have beaten the HD prices with a better product ...

Some woods I’d consider for framing , where strength is important without too much bulk ... Hickory, Pecan, Oak, Maple .... Hickory possibly the favorite as it was used on wagons in the past , where strength was important ... In a lumberyard , it may seem expensive, but you must remember, you don’t need as much of it ...

If you want to get scientific about it , there’s a book ... “Understanding Wood” ... that explains it all ... http://www.amazon.com/Understanding-Woo ... inw_strp_1

[JDHIV]

Thanks for the advice and words of support!! While a "foamie" is not in this build's future.....wood is and always will be...so a lumber yard is a good idea and for the walls I have to build to support the truck cap...I'll check on out and see.

Also, that book on wood is definitely at least going on my "want" list on Amazon!

Thanks!!!!
_John