Okoume wood vs Baltic Birch

[grr8]

I keep reading about overbuilding your first teardrop... I am definitely going to be guilty of this!
I am just about to start the sandwich method of wooden construction with 3/4" foam inside. So I am trying to decide the materials and place an order this week.

I have access to 5X10ft Okoume from a nearby boat shop. It is marine ply with waterproof glue. But overall, it is considerably more expensive than baltic birch (5X5ft). (thickness 3/4")
The 3/4" Baltic Birch does not use waterproof glue and would need to be scarfed together to form the 5X10ft panel.

I am not familiar with fibreglassing over the wood - so is the fibreglass sufficient to alleviate any concerns about the necessity of choosing Okoume over Baltic Birch? Is it also a combined method of urethane first to keep out water moisture?

In order to lessen the high cost I could construct the sandwich using 3/4" BB core and okoume for the two outside panels?
I am not sure how durable the Okoume would be. Would 1/8 be sufficient for inside and outer panels?
I do like the idea of a full 5X10 board for the outer panels. Actually I wonder why not even use a stud framing method instead of a 3/4" skeleton core?

I overbuilt the trailer frame - it is 5X9ft - 2X3X1/8 steel tube - laid out with roughly 16-20" centres. So I regard this as a good enough foundation to lay 3/4" BB directly on top - maybe with a barrier between the wood and steel?? And if I can figure out what to sandwich to the underside of the steel frame, I am considering insulating between the steel members (underneath the floor). Ideas?? Is it even a normal thought to consider spraying insulation into the 2X3 members?

So many questions. Thanks in advance - this is an awesome community!! And I apologize if this has been covered elsewhere. I'm sure it has, but I did search first.

Thanks very much,
Glen

[linuxmanxxx]

Do some research on torsion box building for strength and weight reduction. The framing with an eighth inner and outer skin is plenty and if completely glued on surfaces, much stronger than skeletonized or plain plywood builds. I built in box rectangles with rounded radius up top in front for aero and looks. The internal space this way is much greater than the traditional teardrop style and a much faster build. Curves on the roof add much more complexity and build time.
Steve

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[noseoil]

Overthinking it!

3/4" AC plywood for the wall panels is fine. A butt joint is fine for the scabbed-on part of the wall to get 10' long sheets, no need for a scarf joint to make the longer sheet. I used 3/8" dowel pins for the plywood joint & Titebond(cringe), since it will be covered & bonded with the 1/8" skins both inside & outside. Okume is great stuff, but it's spendy & not necessary for a trailer.

If you look closely at the the rear galley section (look at the wood grain), it has the joint for the 3/4" side wall. There are only 3 dowels & glue holding it together in these images. "Handle with care" on the wall when moving it at this point, but once the 1/8" BB is glued in place on the inside, it's plenty strong enough & won't break from handling. The outer sheet (after the wires are run) makes the complete sandwich & there's no way this simple, weak, wonky joint can break, without destroying the surrounding wood entirely.

[Capebuild]

This is my first trailer build so interpret what I can say about your question with that in mind. I'm responding to your question in that I did wind up using okoume for the inner and outer sheathing sections, the flooring panels, and will use if for the headliner, outer ceiling and hatch paneling. I also used MDO board for the middle panel of the wall sections. I used the MDO which came in 5x10 with exterior glue which the supplier did stock. Where I purchased my ply panels the supplier did not have Baltic Birch with exterior glue in 5x5 1/4 inch panels or 1/8 inch panels. Yes, the okoume was more expensive. It's also about 1/2 the weight of BB ply (which is one reason I went with it). Just as an example, a 5x10 foot sheet of 5/32 okoume (they didn't have 1/8 inch so about .030" difference in thickness) cost $109 and weighed 12#s. I would have had to buy 2/ 5x5 sheets of the same BB to get the 10 feet, and it didn't have exterior glue. Each sheet would have been $35, so 2 sheets would have been $70 (almost a $40 difference when compared to okoume) and the weight per 5x5 panel is 13#s so 2 panels @ 26#s.

If I had to do it again, if I could "easily" find the 1/4 or 1/8 inch panels of BB held together with exterior glue, I might consider that. But the okoume is nice wood, light and pretty tough stuff, comes in 5x10' panels..... and also a bit pricey. Doing it again I'd also follow Noseoil's suggestion on how he made his inner frame..... removing more wood from the inner section, more like he shows. My middle sections have a bit more meat and came out a bit heavier and I think if I had removed a bit more material I could have probably shaved about (maybe) 10 #s off each wall section.

John

[tony.latham]

I am not sure how durable the Okoume would be. Would 1/8 be sufficient for inside and outer panels?
I do like the idea of a full 5X10 board for the outer panels. Actually I wonder why not even use a stud framing method instead of a 3/4" skeleton core?

I prefer 1/8" on the inside and 1/4" on the outside since I drive screws from the outside and need more meat.

And... I use 3/4" CDX plywood for the skeleton portion of the wall. It's fine.



On my first 'drop, I used 1 x 4's and it was a LOT more work --as in two more days. Too much joinery.

I'm a big fan of Baltic. From time to time I've thrown scraps in a water bucket for a few days, pulled them out, and let them dry. I've never had glue separation.



Tony

[grr8]

Thanks guys! I appreciate Noseoil's comment that the okoume is not necessary. Although is that because the exterior is sealed well by using paint or stain finishes? (and fibreglass)
I created an issue by making the trailer 5' 2" in width.
Now I have to solve the 5ft plywood material with the 5' 2"roof width. I am considering a bullnose which will extend to the material. Or, perhaps even better, is there trim which will cover?
I'm attaching my recent photos of the templates which are ready, and the design. Please feel free to post suggestions of potential issues which I may encounter.
I am using Tony's book to help me, and I am a big fan of John's build! My favourite teardrop (if I were to buy one) is the Vistabule. I can't wait to see yours.
You are all such invaluable resources to me, as a newbie, as I struggle through. (Veteran teardrop crafters) I appreciate you all.
Best,
Glen

[noseoil]

The frame I found measured in at an actual 5' 1/2" wide, due to the front bend being 1/2" wider than the back of the frame (where I measured it when I first saw it & put a tape on it). I didn't realize it was bigger until I got it home & started measuring things for the layout & looking at what I had.



Our "solution" was fitting the top panel (the 5' Baltic birch top sheet) with a 1/4" gap on top at both edges. I fixed the 1/4" wood gaps with small pieces of 1/8" glued in place, but the top 5' aluminum skin was too small & was solved by using the aluminum flanges on the moldings to cover the gaps. They were set in butyl rubber & screwed down so the small gaps were covered with moldings & have not leaked. I figure the seams being open aren't a big deal since the roof metal "floats" under the moldings. It's held in place on the ends with stainless steel screws, at the top by the solar panel & roof vent's flange. The wood body was given 2 full coats of urethane prior to skinning, so it's sealed up well enough & so far there have been no problems with leaks. Unless you measure it, the "5' wide trailer" still looks like it's 5', but it's actually bigger. All's well that ends well.



One thing I would look at with your design would be the lower edge of the cabin entry doors. It might be better to have a flat bottom on the door. It would be easier to get in and out if it's level with the frame. Otherwise, it looks like it's pretty narrow in the lower corner & might grab a foot on the way in or out. I like the basic shape of the side panel & profile. All of these little design things to look into...

[KCStudly]

What noseoil said about the shape of your door bottoms x2.

Picture yourself sitting down fanny first into the doorway, taking your shoes off, then leaning back, pulling your knees up and rolling you feet back in past the aft door jamb.

Now picture yourself reversing that process. Now sitting in the doorway, a little groggy after waking up. You're going to want to sit there a minute or two (or longer, taking in the scenery) before you put your shoes on. You don't want the sill to be digging into the backs of your legs, and you don't want to whack your feet everytime you swing in or out.

[grr8]

Howdy fellas,

It was a big week up north at my Mom's garage - she is happy to be spending time with her son after all these years away from the coop. (I flew the coop many, many years ago ;-)
I was able to figure out the router bits issues finally! I had a 3/4"+ sheet of heavy 5X10 particle board hanging around. So I used it to make a template. Then I routered along edge with a combination of guide bushings and ball bearings. My ball bearing bit needed to be the final pass. I had to start with guide bushings so I could make a few shallow cuts instead of a deep haul. (I tried the deep haul - not an easy thing to do)
After all the back and forth to the northern lumber and hardware shops (limited selection) I made a sample of the doors. I started with a template and cut out a one inch wide rabbet and then flush cut with the 1/4" spiral upcut - So essentially I end up with a 3/4" rabbeted edge for the door seals.
It is gratifying to have the walls shaped and positioned on the floor to get a "real world" sense of what it will be like - no roof yet - but it's still cool.
The door has been cut out of my template. I had it standing on the floor and it was much larger than I expected - 49" tall X 34" at the widest point.
The door is unique - thats for sure. The bottom of the door is going to be considerably lower than the mattress. And that's because the mattress is elevated - imagine having one foot of "crawl space" (for lack of a proper term) under the bed for storage of photo gear - large heavy lighting stands mostly. Two 1 ft X 1ft wide stand drawers run the length of the interior from front to kitchen bulkhead. (over 6ft in length) They are positioned at the sides - and they will pull out through the rear kitchen area.
So this stand case will be the lowest entry point - even though the door dips lower - it will have a flat comfy entry (about 30 inches in width). And there will still be 3ft width of open area for foot room when the mattress is converted into a couple of facing couches between the stand cases. When the bed is in couch mode you would need to sit on the stand case and stick you feet out. So it should still be an easy in/out. Enter on your knees and exit on yer butt.
I hope it is as easy as I want it to be - it will be approx 30 inches from ground to top of mattress.

I'll keep you posted - but I have a week away to visit my daughter in BC.
Can't wait to get going again.

Glen

[Shadow Catcher]

Inch and a half EPS aluminum frame Filon exterior. I have 0 confidence in RV caulks and we had leaks.

[grr8]

Is it necessary to use aluminum trim around the perimeter of the home built wooden door if it is sealed with fibreglass? I am using rubber doorstop bumper seals and I would love to find a lap seal for the outside gap between door and wall. Now that I am rabbeting the door and wall, I need to consider if aluminum needs to be accounted for.

Thanks
Glen


Sent from my iPhone using Tapatalk

[KCStudly]

TPCE is epoxy/fiberglass over foam with inset cedar framework around doors and door openings. There will be no aluminum trim (although I will add an aluminum rain visor/"mini awning" over the doors). I will be using Trim-Loc bulb seals that use integrated channel rubber that locks onto the inner door stop flange. (Tony Latham uses this same method.) The inner door stop flange is offset from the inside wall panel the correct amount to set the seal compression when the outer wall and door skins are flush. A bevel cut into the door sill should help prevent water standing under the door. Door edges and jambs are fully glassed. The only thing I haven't glassed is the perimeter of the face of the inner door skin where the seal actually contacts. This surface has been stained and poly'd. I will probably paint a band around here with black enamel, too, as an added layer; but at least the vulnerable edges of the skins are fully "potted" in epoxy.

[working on it]

Is it necessary to use aluminum trim around the perimeter of the home built wooden door if it is sealed with fibreglass? I am using rubber doorstop bumper seals and I would love to find a lap seal for the outside gap between door and wall....

* I used the raised curve of the aluminum threshold to create a slight friction-fit with the door, and use a stiff vinyl door sweep to create on overhang to seal off the threshold/door from water being blown in, or thru surface tension. My 3/4' thick floor sits on the trailer frame, and the sweep overhangs it by 5/8", leaving an 1/8" gap above the steel frame (the 48" wide floor/deck is centered on the 50" wide trailer frame, so 1" of frame is exposed, preventing further overhang depth).

w/o a rubber seal at bottom; a "friction fit" atop alum. threshold and a door sweep to shed water

door sweep and threshold.PNG (111.45 KiB) Viewed 638 times

* For the upper part of the door, I made a 1/4" stop/jamb (of 3" wide oak lumber) surrounding/bracing it, and used '67-'72 Chevy truck doorseals attached to it. Because I didn't use offset hinges, and the seals were very thick, I trimmed about 1/2" of rubber from the inside curve of each in order to achieve a flush (but very tight) compression seal.

doorseals and water protection (2).jpg (249.23 KiB) Viewed 638 times