Re: Wandering First Build - Finally Going Again

[Prototear]

About a week and half ago I made some curved ribs out of plywood for the roof. Not all the roof structure will go lengthwise like these ribs, but I'll need a few to frame in the Fantastic Fan and the sunroof - some will go across the trailer and those should be easier to cut since they won't need to be curved. I traced the 1" side frame tube then cut them with a bandsaw.


These ribs are about a 1/4" long intentionally since I was just mass producing them and I'll trim them when I install them. I made them of leftover 5/8" plywood I had in the shed and doubled them by gluing them together before cutting and adding some screws after cutting them.


I was deciding how long to keep working on Saturday night since I had to pack for a trip to Chicago and just when I thought I could do a another pair of ribs my bandsaw blade broke so I had to call it a night. On my trip to Chicago with a side-trip to Michigan to visit friends and family, I stopped by Vintage Technologies to see the aluminum extrusions like hatch hinges and trim to decide what I needed, and I had a great discussion with Frank Bear. He was a great help!

Now that I'm back home I hope to make more progress this weekend.

[Prototear]

I've had some interruptions but have made some progress on and off in the last month. On a trip last month I stopped by Vintage Technologies and met Frank Bear and got some small trim samples to use as I plan the details. http://teardroptrailerparts.com/Hinges___Aluminum_Trim.html


I've been delayed finalizing my order as I've been trying to work on a way to seal the door. Many DIY doors use T-molding around the outside edge but I don't think it will work with my design, mostly because of my small upper corner radius. If I could plan it over with a larger corner radius I probably would, but since I've already committed all but one last piece of this great aluminum honeycomb panel I want to stay with doors I've started.

I tried the T-molding sample to see how much it might be shaped and I don't think it will work for this smaller radius. In looking for alternatives I realized that I have a T-molding already there that just needs to be exposed from the honeycomb panels. I tried cutting my scrap partially through and the honeycomb inside can break free fairly cleanly, leaving an overhanging layer of aluminum with only some epoxy residue. I'll try to carefully cut off about 3/8" or 1/2" around the edges to create the overlap I need to attach a Trim-Lok seal on it.



This pictures shows just a simple straight weatherstripping I had in my garage to stick on there then I found a Trim Lok shape that should work. I ordered this http://www.zoro.com/g/Trim%20Seal%20Sid ... egory=9053 from Zoro Tools and it fits but is a little loose. I can add some material on the inside edge of the overhang to thicken it for a better hold by the Trim-Lok.

[Prototear]

Meanwhile, I have also been working on ribs for the roof and wasn't satisfied by those I had cut so far. It was hard to make them cuts precisely and especially hard to be consistent for ribs that would be parallel to each other and should match. My friend Marty (who also wants to build a trailer sometime) was deservedly more blunt and suggested another way to make better ribs. With his advice (and wooden boat building experience), we made a plan for making curved plywood ribs to fit. I made new cardboard templates of the curves and we cut some forms out of some 6x6s on his big bandsaw.



I then got some 1/8" luan and cut it into 6" wide strips to layup in the new forms with Dap Weldwood plastic resin glue for 5/8" thick ribs.


I have formed many ribs and the put the last one in the form tonight. I hope to trim and install them this weekend. The preliminary check on the curves seems to match and lay consistently on the frame!

[Prototear]

I've been slowly making steady progress but haven't made an entry in a few weeks so I have some catching up to do.....

The shaped roof ribs turned out as expected! I trimmed them and also finished welding some tabs on the roof cross-members to hold them. Here are the aft ribs (in front of where the hatch hinge will go) with the Fantastic Fan placed to check the fit:


Here are the front ribs. The front ribs and the outer pair of the aft ribs are spaced 1/3 of the way in, about 24" on center to accommodate the roof skin layout I'm planning (more on that later).


These ribs are attached with 1" x 1/4" flathead screws into the angle tabs. The main purpose of the screws is to stabilize the ribs and the ribs will be held in the long run by compression of the ribs into the cross-members. I may need to grind the ends of the screws to stay within the volume of my 1" thick roof.


I've got more pictures from the last couple weeks uploaded and will add them here soon.

[Prototear]

The center section of the roof's ribs are the most challenging because I had this "brilliant" idea to install a sunroof sunroof there. I'm sure it will be worthwhile in the end but the detailed shape of it is proving to be a challenge. The primary holding mechanism is for the top frame and interior trim ring underneath to clamp on the sheet metal roof of a car or truck (or a teardrop in this case). The cross-section of the clamping frame is shown.


It can be clamped with either the frame and trim ring, or with a peeled back trim ring with a L-shaped ring that would get clamped instead. For now, I'm going to use the full trim ring to clamp it, leaving the option later to peel back the trim ring and use the L-ring inside because once I peel the trim ring I'll not be able to switch back to the other method.

To do this, I'll have the wooden frame on the roof set back from the perimeter of the sunroof about an inch to allow full access to the skin on top. The frame on top has to roughly match the contour of the sunroof which is flat fore-aft, but has a crown of about 3/16" side-to-side. Unfortunately, this is just the opposite contour of my teardrop roof (flat side-to-side, and curved fore-aft). It is upside-down in this picture before installation.


I made the frames for this section of the roof 5-1/2" wide and cut out the side contour of the sunroof, while the fore and aft edges are contoured poplar 1x3s. This is assembled with pocket joints and gorilla glue. After the initial installation, I checked the fit using scraps of doorskins cut to mimic the eventual sheetmetal skin then attacked it with a belt sander to shape the poplar.




After getting as close as I could to matching the contour with the sander, there was a gap on the front edge (as expected) because the front is curving away from the top so I started to build it up with more thin plywood. Once I build up a few layers I'll sand it to fit the contour and try to keep the contour manageable for the eventual aluminum roof skin. The leading edge of the front plywood skin is attached to the steel cross-bar with VHB tape (getting familiar with it on my first use of it before using it on the skin eventually) and the rest with gorilla glue to fill any tiny gaps that may be lurking. The next layer(s) will probably be glued with Weldwood plastic resin as I did with the curved plywood ribs I made.


My plan for the roof skin is to have 4 relief joints where it comes into the sunroof frame so I'll be able to manipulate the skin slightly and avoid causing weird bulges elsewhere. The trailer frame is 72" wide, and I'll have one 24" band down each side (matching the roof rails in other areas) and a middle band overlapping between them (about 26" wide). This will also allow me to cover all or most of my trailer with the 4 4'x10' sheets of 0.050" 6061 that I got on craigslist from a metal shop that was closing.

I wanted to get all this work with the clamping and shaping the roof out of the way before I start to install the 1/8" birch plywood skin for the ceiling, inserting the pink extruded polystyrene and wiring.

[Prototear]

I have gradually built up the front ribs to shape it to fit the sunroof frame. This picture collage shows the sequence of buildup with clamps, trimming, sanding, and repeating. There is quite a bulge built up already along the front but it is hard to see it in these flat pictures. I might need one more narrow strip added to the front but I can decide that when I fit the aluminum skin on top eventually. I wanted to get enough of this built up before adding the ceiling skin and foam insulation.

[Prototear]

I've been working on a few other things along the way, some to be sure they will work when it comes time to install something, and also to finish welding any small pieces before I try adding my ceiling skin and foam insulation. (Welding with finished wood and foam in place is bound to be messy.)

I got my Trim-Lok for the door and I tested the fit of it on my favorite scrap of aluminum honeycomb panel. I routed off the outer 7/16" inches or so, leaving on side of the panel sticking out farther to act in place of the T-molding. The 3/8" wide trim fits well over the edge of the panel and with a little residual honeycomb left stuck in the epoxy that held it together.

With the amount I need to cut off the edges of the doors, I'll need to remake the little cooler slide-out doors because it will leave the ones I made too small, particularly since I already cut out a hole for the door latch and don't have room for cutting the edge back any further. I'll really need maximize the size of these doors within the constraints of the frame opening for my slide out cooler. Fortunately I have enough leftover to make 2 new little doors so I can recover!



To finish some odd welding tasks, I've also cut and shaped a steel grid for the tongue out of expanded steel sheet. Here is is trimmed and primed but not yet painted or welded. There are also 4 tabs for mounting a tongue box someday if I choose (I probably will add one eventually but it not a high priority until after I get this completed enough to weigh it and pass the state patrol inspection).

[Prototear]

I've been planning my wire routing and it seems like the most practical thing is to have a couple main wire runs under the floor, one for AC and one for DC. I have come into a problem just like the one KC had (http://www.tnttt.com/viewtopic.php?f=55&t=48630&start=2025#p1081749) where the conduit connectors we want to use don't quite accommodate the 1/2" thick floor. KC's progress ahead of mine helped me see how I can make it work. Thanks KC!

I am leaning toward not using the waterproof flexible conduit but just a cable holder with a compression fitting and fasten the cable bundle to the frame securely with some drip loops at the floor penetrations. Which ever I use, the portion of the conduit connector that goes through the floor is the same. Using my favorite honeycomb panel scrap again as a prototype, I drilled a hole in it that is 7/8" on the bottom side and 1-1/8" on top to recess the locknut down into it and tighten it against the bottom layer. I used the HF conical step bit that got the holes the right diameter in one stroke leaving a little scrappage of the honeycomb to hold the locknut from rotating while tightening the cable holder from underneath. I may add some epoxy around the locknut to solidify it in the actual installation. Here is the test piece from above showing the locknut down inside the panel and from below with a scrap of extension cord through it (the cord I'll eventually use will be heavier 12 gauge for the AC).




I was able to carefully drill this scrap on a drill press so 'll need to be careful when drilling with the floor panels already in place.

[KCStudly]

Curious, how do you plan to seal the cut edges of the honeycomb around the trim seal and other places like it?

[Prototear]

Curious, how do you plan to seal the cut edges of the honeycomb around the trim seal and other places like it?

Great question KC! I have 2 different cases for covering the open edges. One option I didn't choose that was one of the recommended approaches was to fill the entire edge with epoxy, but that seems like lots of work to do manually. Fortunately, the fine honeycomb cells are watertight from one another so that if water gets into one cell it won't propagate into adjacent cells.

The first case is for the floorboards - these are riveted with a thin doubler but first I wrapped the edges with cold weather aluminum HVAC tape, Nashua 324A. Before committing to this, I wrapped a scrap and subjected it to many thermal cycles alternating between a day in the the freezer and hours in front of a 1500W heater. After several days of this there was no sign at all of tape damage or peeling. In the case of the floorboards, all the edges are within the trailer either along a steel frame member or at the base but inside the wall. Here is a picture of the front edge of the trailer that is still visible (with a 3/4" x 0.063 aluminum angle as the doubler with the upward edge for attaching the interior wall):



The mess behind the aluminum angle is lots of sawdust from the recent roof frame work on the aluminum honeycomb floor panels It actually looks good when I clean up after myself, but i just haven't lately.

The second case is for the doors, probably the case that prompted your question. I will build the door from honeycomb panel on the outside, 1/2" foam in the middle and 5mm birch plywood for the interior. I'll have a plywood strip in place of the foam along the outermost 1" of the middle layer for a fastening medium, and wrap the whole edge with a 7/8"" wide aluminum trim strip HT09 http://teardroptrailerparts.com/Hinges___Aluminum_Trim.html. This will still leave just over 1/8" gap deep in the corner behind the Trim-Loc that I'll probably fill with a sealant that I'll put all the way around the whole honeycomb edge before wrapping the trim around it (and waiting for it to dry before installing the Trim-Loc. I'll likely use the same sealant I used under most of the floor panels, Loctite PL S30 http://www.homedepot.com/p/Loctite-PL-S30-10-fl-oz-Black-Polyurethane-Roof-and-Flashing-Sealant-1675273/203163733. Anyway, that is my plan for now....

[Prototear]

This weekend I did my final welding on the frame, or I sure hope so anyway as this is the second or third time I thought I finished welding

To fit my cooler slideout doors, I needed to have another vertical frame member for the latch and galley cabinet attachment so I cut a piece for each side from scrap of frame I cut out months ago. I also needed 2 extra wide frame tabs for mounting my hinges here since my doors will be so close to these frame pieces that the screws of my hinges would go only into the foam insulation without them.

I also needed some additional diagonal braces in the wheel wells to attach the fender eventually. The frame currently allows for fenders with 45 degree beveled corners, known as 45/45 double break Jeep fenders, but I couldn't find fenders to fit but was able to come close with 70/20 double break Jeep fenders. I was able to get one made to my dimensions from http://www.fendersnmore.com/products/all.php. Since my wheels are half in and half outside the main frame, I only needed a narrow fender to cover the rest of the wheels, about 5 or 6 inches wide, kinda like a big fender flare. I was unable to get such a skinny pair of fenders but I got one 12" wide fender that I'll cut down the center and use half on each side. The curved finished edge will be outboard and I'll rivet the cut edge to the exterior skin/frame with aluminum angles. To attach it this way I needed the 70 degree braces to attach the sidewall skin and the fenders. Although it fits the contour around the wheel well perfectly, I'll probably cut a couple inches off the ends since it is the shortest I could get made and it still hangs a bit below the frame.

I bought this back in April and my wife was on a road trip to LA so she picked it up at their will-call desk and hauled it to Seattle. She was visiting relatives only about 4 miles away and it saved shipping it.

Here I was checking the fit and marking the points where I needed to weld the braces. Notice how the fender looks weird being too wide but it will be cut in half.


I welded the wheel braces in place but had to remove the wheels to do it comfortably. My welds are getting better - this one didn't look like my usual rabbit turd welds (that's what my neighbor calls it).
http://www.tnttt.com/gallery/image.php?album_id=3076&image_id=122881

Here are the pieces all welded, cleaned and primed. The tabs for the door hinge are on the vertical piece just aft of the wheel well.
http://www.tnttt.com/gallery/image_page.php?album_id=3076&image_id=122881

I also tried to weld the steel mesh to the tongue but in trying to apply enough power to penetrate the 2x2 box frames it incinerates the mesh leaving almost nothing to attach. This didn't work on the first few places I tried so I gave up before damaging the expanded steel mesh any further. I'll attach it with some steel bar stock and fasteners underneath instead. Even though this welding here didn't work, I think I still concluded all my welding on the trailer, finally. I used bunge cords and a big scrap of wood to hold it in tension for welding, but I'll leave these cords in place until I get the bar and fasteners ready.
http://www.tnttt.com/gallery/image_page.php?album_id=3076&image_id=122881

[noseoil]

In aircraft work we used a lot of honeycomb for structural & cosmetic panels. There are a couple of ways to deal with edges. One is to use a "kerfing bit" in your router to run a slot into the center of the edge of the core. This will allow for epoxy & an aluminum "T" molding to be bedded in place to seal the edge. Hopefully, you can find the right size molding. Easier to do if you can lay the panel with the edge facing up for your epoxy fill. Another way is to use the router to remove the core about 3/8" to 1/2" deep. Again, epoxy and a hardwood (rock hard maple) edge will fill the core and give a good attachment point for glue and fasteners. This is a nice solid edge.

A third method is a bit more crude, but will work OK. Use a hammer & block of wood and bash the honeycomb in to a depth of 1/4". Leave it ugly and then fill with bondo. Once the bondo sets up, the edge can be sanded and painted. This is OK for what you're doing, but bondo can wick moisture out of the air, because it is just polyester resin & talc. You must seal the bondo edge with a good paint to keep water out and prevent corrosion.

Enjoying your build, waiting for weight report on this one. Looks to be plenty strong ("strong like buffalo") for your loads and rolling. Best, tim

[Prototear]

Thanks for the suggestions on the honeycomb edges, Tim!

This gives me more (and better) options to consider. I've been working about 3 areas at once on the trailer (plus more projects at home and work) so I'll be a while before I get back to the door edge. Stay tuned for some attempts on my scrap pieces to see what successes or lessons I find before I commit by trying it on the actual doors.

[Prototear]

Its been about 8 months with no progress due to other projects at home and work but I'm eager to get this finished so I can use it this summer!

I have been building a big wall unit in my basement with a Murphy bed in it so the teardrop has suffered. The wall unit is large and I used used teak from several cabinets I got for free or cheap on Craigslist. I have several pieces of teak laminate left over so perhaps I could use it in the teardrop cabinets but I'm not sure if I have enough and I'd have to check the weight of the teak laminate (some over particle board, some over plywood) compared to birch plywood. I plan to unbury my trailer from all the other debris in the garage this weekend and make at least some small progress on it.

About a year ago I described an idea to make my trailer convertible for either camping or for hauling cargo with the galley cabinets removed http://www.tnttt.com/viewtopic.php?f=21&t=55403&start=15. I still hope to do this since the steel frame allows the option of not having to install the cabinets or a support wall for strength. I would have 2 cabinet sections - a lower cabinet with the countertop and an upper cabinet to sit on the forward edge of it. A rough layout of the lower cabinet might be shaped like this, with openings on the ends to accommodate the slide-out for the cooler through small side doors.



Because of the sloped contour of the aft trailer frame wall I would need to move this cabinet forward away from the hatch opening, making for either a longer reach to the countertop or the need for a small folding countertop extension to fill that space (then possibly risk interfering with a top drawer in the cabinet). To get around this dilemma I am thinking of modifying the trailer wall contour to get closer to a Benroy shape with a flatter back end. I could either weld on a 1" square tube bent to the new shape, or build up on top of the existing frame to fill this gap. I would want to avoid any weird lines so it doesn't look like the afterthought it really is. The green line in the photo below shows how I'd shape it.

Fortunately I took a 1-evening welding class recently http://www.allmetalarts.org/classes/and improved my technique.



Before I pursue these ambitious changes, I still have some normal work to do like run wires. I'm also thinking about whether to start the walls from the inside or from the outside as there seems to be pros and cons of inside vs. outside first. If I do the outside first I can check it for water leaks before committing the inside and hiding leaks, particularly with the tricky sunroof installation. Of course, I would have to finish whatever changes I do to the rear contour so I have to install the side skins only once with no extra seams.

[Prototear]

I had thought through many schemes to change the aft contour to reduce the slope over the galley but finally gave up since I want to get this trailer done and start using it. I figured I could devise some way for a small improvement and spend some more money and lots of time as the summer approaches and passes me by with no trailer to show for it. I figured it was time to make some real progress on the build!

I considered what order to install the foam insulation, outer skin, inner skin and wiring. I thought of installing wiring first to see all the routing paths, and even considered routing wiring through the top side frame tube as a conduit but finally decided against it in case I were to nick the wires when drilling for rivets or screws later.

I then decided to install the wall foam insulation then the outer skin. The inner skin can be installed later and I also intend to make it removable anyway for maintenance. Here is the initial foam insulation in the side walls with some tape for a tight seal within the wall. This is 1" closed cell foam. I had mostly pink foam from HD, but my contractor friend gave me some blue foam from Lowes. I used a hot knife from HF to cut it and got a mix to make the most of the materials. I found that the blue foam cut noticeably cleaner than the pink foam, with less smoke and charring and generally better looking.



In preparing to install the skin next, I realized 2 issues that I had to solve first. The first one was that the frame needs one more piece over each of the small aft utility doors I'm planning to attach the skin firmly, but to weld something on means that I have to be careful to not melt the newly installed insulation. These doors need to fit under the countertop in the galley (for the slide-out cooler). I'll probably put the cooler only on the right side but want provisions to do it on the left side too. I had to make some pieces to go over the door but made it wider so it can also serve as a bracket for the countertop to be installed eventually. I also had to keep this extra width from interfering with the eventual galley hatch frame. Here are the brackets I made and installed today.



The other issue to solve is how to use the 3M VHB tape for the skin installation now that I have the sealing tape on the exterior frame around the foam insulation. This could prevent the VHB tape from directly adhering to the metal (painted steel) frame. I had planned on using at least some sealed rivets to install it however. The skin is 0.050" so I think it will be stiff enough to not bulge in thermal changes though.

I think I will cut back some of the sealing tape holding the foam so that I can get about 1/2" of the 3/4" wide VHB tape to adhere to the steel frame and still supplement it with some rivets, but maybe a few more than I was planning.