Lightweight TD build based on Mike's Ultralight design

...ask your questions in the appropriate forums BUT document your build here...preferably in a single thread...dates for updates, are appreciated....

Lightweight TD build based on Mike's Ultralight design

Postby jonw » Thu Nov 10, 2011 4:22 pm

Hi everyone -

I stumbled upon the world of teardrops about a year ago when I saw a picture of one in a miata.net forum and then found my way to this forum. Owning several Miatas, nearing retirement and looking for a cheap way to travel around the country, and being handy with woodworking I decided to build one.

I spent the winter lurking in the forum, and decided to build one based on Mike Schneider’s ultralight plans in the Member Designs forum:

My design and build critera were:
  • Keep it light so I could tow it behind a Miata (I also own a CRV that I use to tow things with)
  • Keep it simple – optimize for build ease
  • Keep it cheap – try to build it for less than $2000
  • Take my time and do it right – I didn’t want to have to build a second one to get it right
  • Make it so my wife will like it and come on trips in it with me
  • Complete it over the summer so I could use it for a mid-October music festival

As it turned out, I lost my job in early June, so all systems were go to work on this project. I spent that month gathering parts and materials and started building the second week in July. Much of what I needed I got from Harbor Freight, Northern Tool, etrailer.com, and a local RV parts store. I kept a spreadsheet with the cost and weight of everything I ordered or bought to also keep track of what had or had not arrived yet. If people want I’ll add a post with links to what I got from where…

I finished by the end of September with some days off for other commitments, hurricanes, etc. I’ll do a day-by-day journal below with pictures.

I made a few changes to Mike’s design:
  • I made it 5 feet wide instead of 4. This was a big concession to the wife but I’m glad I did it. The inside is quite roomy and fits a queen size memory foam mattress pad. The wider kitchen area now is much more useful and the additional storage space is good too.
  • I used 5/8in. marine plywood for the walls instead of building a frame and covering it with 1/4in ply. I calculated this only cost me an additional 25 pounds but saved me hours of woodwork and about $125 in materials. It especially saved me a lot of work building a curved frame around the profile edge that I did not want to get into. I did keep the bottom trim piece which was a nice design element and was useful for running and hiding the running light wiring.
  • I changed the radiuses of the front and rear bottoms slightly to give me an extra 2-3 inches room on both ends. This allowed my tall wife to sleep with her legs straight and made the rear storage area much more usable.
  • I changed the shape of the door to make it wider to more easily swing your legs getting in and out, and to make it easier to install all the door edge mouldings (less corners)
  • I changed the cabinetry a little so that the bedroom has a place for a flat panel TV if wanted and two small compartments, while the kitchen has a single large opening into which we could put a microwave or toaster-oven if needed. At the moment that is where the camp stove gets transported
  • I decided to install a ceiling and insulate the roof since what I came up with didn’t add hardly any weight
Here are some interesting design and material elements I used that you’ll see in the build photos below:
  • I used marine plywood for the floor (3/4in) and walls (5/8in). – solid (no voids) and waterproof. Because there is no frame, it was especially important that the floor be stiff and strong as it essentially is the frame
  • I did not use any tar or goop on the underside of the floor. Just multiple coats of spar urethane
  • I bought a torsion axle de-tuned to 1400 lbs instead of the usual springs and axle. Very clean and easy to mount, and rides well
  • All the non-ply wood is poplar, which is a strong light hardwood that is as easy to work as pine. It is cheaper and lighter than oak or maple. All joists, frame pieces, and hatch ribs are 1x2 poplar
  • Titebond III was used for all bare wood to wood gluing, and GE Silicone II caulk used for all other glueing (with screws) and caulking
  • I didn’t stain any of the wood. I just urethaned the poplar and marine mahogany plywood and it came out looking great. One of the advantages of the marine plywood is that even the bad side is covered with the same wood as the good side (as are all the inside plys), so it looks pretty good as well. At the recommendation of another builder I used Minwax Spar Urethane for all exterior surfaces (multiple coats) and just used fast drying water based Polycrylic urethane for all interior finished surfaces
  • I used a roll-up bamboo shade for the ceiling – lightweight and attractive, although it was not cheap (~$50 at Lowes or HD, I don’t remember which)
  • For insulation I used two pieces of 1/2in foam sheets to achieve 1 inch of insulation. This made it easier to address the curvature, and I could run wiring between the sheets of foam
  • I found some lightweight corrugated plastic panels and Home Depot that I used between the front-most ceilling “joists” as a headboard we can lean against without fear of breaking the bamboo. I also intend to use it for the underside of the hatch
  • Because the exterior walls are not skinned I used Kreg screws to attach the roof joists and cabinet frames to them
  • I chose to put self-stick vinyl floor tiles on my countertop instead of dealing with laminates, since I had hatch doors to work around. If I ever need to I can replace any single tile, or replace them all if I want a new look
  • All the interior ply surfaces for the cabinets, countertop, and hatch skin are 1/4in luan plywood (non-marine)
  • I splurged for a small yellow-top deep cycle Optima battery placed in the storage compartment behind the axle. It’s a D75/25, gives 48 amp hours with 100 reserve minutes, and weighs only 37.8 pounds
  • To save time and insure it would look professional when I was done I ordered crank-out windows, hurricane hinge, and all my aluminum mouldings from Grant Whipp at Li’l Bear Tagalongs. Grant was great to work with and answered a lot of questions for me
  • I predrilled all screw and screwnail holes in the edges of the wall plywood to insure that the fasteners went in straight and that they wouldn’t split or push out the plywood. With marine plywood I may not have needed to do this, but I wanted to play it safe

So how did it come out?

The finished trailer weighs in at 720 pounds with the memory foam, battery, and camp stove. Tongue weight is only 65 pounds which which means I can easily lift it up and move it around by hand, and the Miata should have no trouble towing it. I’m happy with the tradeoffs I made

The final cost of all parts and materials is a bit shy of $4000. Much of the additional weight and some of the additional cost is due to going with a 5 foot wide trailer. The floor alone cost almost twice as much as a 4x8 sheet to get a piece 5 foot wide (which was also 10 feet long instead of 8).

At the end of the day it took me twice as long and cost twice as much as I had originally thought it would. If I were doing it again I figure I could trim 20-40% off of both now that I know what I’m doing. But it was a learning experience, I took my time, and I didn’t make any critical mistakes that I couldn’t recover from.

I did learn some big lessons that I’ll share with everyone here so maybe it will help you avoid some of the issues I had, and would have saved me time and cost (of re-doing things) had I known. I’ll put what I think are the most important ones first:
  • In general, whenever a curve is involved your calculations and measurements will be wrong. Always cut or order material larger than you think you need and trim it to fit after dry fitting
  • Dry fit every piece or assembly before gluing it in place
  • VERY IMPORTANT: store your aluminum dry and indoors if you will not be using it shortly after receiving it. If water and condensation gets between packed aluminum sheets that are touching they will discolor, become etched, and get white deposits all over them that cannot be removed
  • Cut the hatch frame (not the skin) 1/4in shorter at the top (at the hinge) and bottom (that rests on the counter) to allow for spacing at the hinge and other things that seem to affect how it fits. You can always put weather-stripping and/or rubber/plastic bumpers on the bottom of the hatch frame to take up any extra space. Likewise leave 1/4in space on the sides of the hatch frame (not the skin) outer ribs and the wall
  • For a perfect hatch fit, cut hatch plywood skin a little wider than needed, and after mounting on hatch frame and fit in the teardrop, mark the trailer edge and trim the excess off
  • When applying edge moulding along a curve do not work too far ahead of where you are. Just drill, glue, and screw 2-3 holes at a time. Otherwise things won’t line up as the molding tightly follows the curve after being attached
  • Measure your floor dimensions up front – don’t assume it’s the exact dimension you ordered. My 60in. wide marine ply turned out to be 59 7/8 inches. I had to trim down a number of pieces I had already cut
  • When you make a trip to the hardware or big-box store buy twice as many screws, glue, etc. as you think you’ll need and return any you don’t use when you’re done
  • Check any hidden wiring for continuity and shorts early on when they can be replaced if needed without having to remove too much and re-do a lot of work
  • Apply finish to the exterior walls & trim after it is mounted on the floor, not before. This will allow you to use Titebond to more strongly glue wood-to-wood pieces
  • When gluing to vertical surfaces (such as cabinet faces) glue the piece being attached and then apply it to the wall. If glue is first applied to the wall it will drip all over before you can attach the other piece (don’t ask me how I know this…)
  • Do not wipe up spilled drops of glue. Let them dry and then use a chisel to dislodge them, otherwise they will prevent stain and sealer from penetrating as the surrounding wood and it will look awful. This is a standard woodworker “trick”
  • Mark all pieces as D (for driver) or P (for passenger) sides, instead of R and L so there’s no confusion relative to which way you are standing
  • For exterior walls (for woody designs), if using spar urethane varnish thin it first with mineral spirits and apply multiple lighter coats. Otherwise the finish will be blotchy where brushed sections overlap. The effect may be exaggerated if applying the finish in the sun (where it dries more quickly and tends to thicken up). You’ll see this on the underside of my floor in the pictures below, and on the sides if you look closely
  • The 4x8 rolling work platform that I could roll in and out of my garage and provided a flat surface for drawing and measuring on worked great
  • Measure twice, cut once. Or measure three times…
  • For larger aluminum cuts, .040 aluminum is easier cut with a sabre saw with a metal blade than tin snips or aviation shears
  • To draw up walls, etc. to the piece being attached, drill holes large enough so the screw threads don’t bind
  • If you are building a trailer wider than 4ft, consider getting a trailer to haul materials if you don’t have a big pickup or flat bed truck at your disposal
  • Get a power or compressed air caulk gun – I got this idea from someone else on this forum
  • Practice being proficient cutting curves with a sabre saw if you need to
  • You can never have too many clamps

And now, the journal and pictures…
Last edited by jonw on Tue May 22, 2012 10:26 am, edited 3 times in total.
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Day 0 - Prep...

Postby jonw » Thu Nov 10, 2011 4:31 pm

Built a 4x8 movable platform from 2x4s and a sheet of ¾in ply sheathing, mounted on medium size lockable casters so I can wheel it in and out of the porta-garage. Cut up a 2x4 into pieces for drying supports and to keep edge of leaning ply off the ground. Cut up some 3/8 ply for clamping helpers and to use for leveling large pieces in the chop saw, etc.

On hot sunny or rainy days I put up an EZ-Up in front of the Harbor Freight porta garage, and stored everything in the porta garage at night.

Here's a picture showing my work area and the platform being used to draw the wall profile on my masonite template
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Days 1 & 2

Postby jonw » Thu Nov 10, 2011 4:35 pm

Drew out the profile on a sheet of 1/8in Masonite, and then cut it out with a sabre saw. You can see in this picture the additional space I got from changing the bottom radius. Mike's original shape is the pencil line.

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Day 2 was spent driving into and out of Sommerville, MA to buy the marine plywood, and fitting a 5x10 sheet in the back of a pickup truck bed without damaging it. Got home and got the first side cut out of a sheet of 5/8in marine Meranti mahogany ply

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Note that cutting was done on saw horses, not the movable platform...
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Days 3 - 5

Postby jonw » Thu Nov 10, 2011 4:47 pm

Cut floor down to 5x8 from 5x10 and cut front and rear edges to match the angle of the profile curve at the floor. Put first coat of Spar Varnish urethane on floor bottom and edges. Cut out second side and exterior (bottom) trim 1x4 poplar pieces

Next day lightly sanded and put second coat on floor bottom and edges, cut all 3/4x1 in. pieces of popular (roof trusses, fender trim, cabinet frames, etc. Put up 10x10 portable awning in front of porta-garage to provide some shade and allow working if raining.

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Changed door from square to a double radius curve for the top and open edge to give it a little more height, and so I can use a continuous strip of edge molding and T molding

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Day 5 put 3rd coat of spar urethane on floor bottom and edges
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Days 7-11

Postby jonw » Thu Nov 10, 2011 4:59 pm

Finished routing trailer running light wiring channel in back side of floor trim piece. Cut out door from template Masonite, and trimmed 1/4 in off door piece to allow for 1/4 in gap on all sides. Traced onto walls and cut doors out of walls and trimmed doors to correctly allow for the 1/4 in. gap.

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Cut holes in Masonite door template for windows & flush pull latches. Took axle to welder, picked up battery box from RV parts store, got more supplies from Home Depot. Cut out window and latch holes in doors.

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Used Kreg Jig to assemble fender trim that I later had to throw away because the wheels stuck out too far and the fenders could not be directly attached to the side wall.

Sanded and put 2 coats of Spar Urethane on all walls, doors, and exterior trim. put on third coat of Spar Urethane. Not happy with finish as areas where there is overlap is much thicker and some spots look dull/dry. Thinned Spar Urethane and rolled two coats on door, walls, etc.

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Days 12-15 (no pix)

Postby jonw » Thu Nov 10, 2011 5:04 pm

Cut angled edge of front and rear floor cleats. Ripped 4 1/8in strips for inside ceiling backing and cut notches for these in the inside of all roof spars (so they will sit flush).

Cut hole in floor trim for front amber running light and routed channel larger to accommodate more wires. Glued up double roof spars for the fan joists, assembled bottom frame that separates sleeping compartment from below-counter storage area. Ripped 1 in. boards for counter doors. Caught my finger on table saw blade spinning down - ouch!

Cut and glued up countertop hatch door frames (you'll see these later...)

Had tongue channel steel re-welded to coupler (welder I was using wasn't beefy enough). Rained the rest of the day...
Last edited by jonw on Sun Feb 12, 2012 4:34 pm, edited 1 time in total.
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Day 16

Postby jonw » Thu Nov 10, 2011 5:12 pm

Measured and drilled holes in tongue channel for bolts to attach to floor. Black square plate with hole in it is washer for bolt on inside of floor. You can see the front edge poplar 1x2 cleat attached to the top of the floor (which is upside down in this picture).

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Used a wire wheel brush on drill to clean off surface rust, primed with spray etching primer

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and then with flat black topcoat. If I had known about it at the time I would have used POR15 instead.

Mounted stabilizer jacks to underside of floor

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Here's the bottom of the floor, ready to flip over to start working on attaching the walls...

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Day 17

Postby jonw » Thu Nov 10, 2011 5:20 pm

Ran trailer wiring inside trim routed channel and covered with wax tape and masking tape so glue wont get in channel and wires could be pulled through if they later need to be replaced. Attached external bottom trim with trailer wiring embedded in it

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Trimmed roof trusses 1/8 after discovering floor was 59 7/8 instead of 60 inches wide. Also trimmed 1/8 off cabinet frames already built.

Set torsion axle angle to 22 1/2 degrees, and then power brushed, primed and painted axle to protect from rusting. Would have used POR15 instead had I known about it at the time.

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Day 18

Postby jonw » Thu Nov 10, 2011 5:26 pm

Made jigs to hold walls at right angle to floor, including screwing a piece of 2x4 to floor to attach them to (at other end of floor near drill and caulk gun).
Drilled holes in bulkhead frame and glued and attached to floor (so it can be used to hold walls perpendicular when they go on.
Positioned 4 bar clamps ready to use for walls

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Note the front and rear 1x2 cleats attached to the floor in this picture. Kreg screws on their ends will also be used to hold the walls when attached to the floor.
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Day 19

Postby jonw » Thu Nov 10, 2011 5:38 pm

Dry fitting the walls

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We need to re-glue and screw the external floor trim to the bottom of the wall after one piece fell off when moving it. So much for Silicone II adhesion strength (by itself).

The BIG mistake here was in finishing the walls before putting them on the floor. Otherwise I could have used Titebond glue for the bottom trim and they would not have separated from the sides.

Then attached both walls to floor with Silicone II caulk and clamps, and screws from the front and rear cleats and the bulkhead frame. We left the bar clamps in place for several days until there were enough frames and cleats attached to the walls with screws to insure they were secure.

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Attached most roof "joists"

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Close-up of doubled-up vent roof joists - note that it is not critical that they be absolutely straight

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Days 20 - 23

Postby jonw » Thu Nov 10, 2011 6:10 pm

Attached countertop frame to bulkhead frame and side walls

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Applied first coat of Polyacrylic urethane to insides of doors. Routed edges and attached front wall/floor cleat towards the front of the doors, and removed bar clamps no longer needed.

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Attached inside ceiling curve strips with glue and brads. These were used to enable the non-stiff bamboo ceiling to maintain the curve of the profile without sagging. It also keeps the insulation in place.

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Loosened countertop frame and re-glued with some clamps and Kreg pockets for better strength.

Realized windows I bought were 18 inches wide, not 15. Cut out wider window openings in doors and re-urethaned edges.

Cut 1/4in luan panels for countertop and 2 of the 3 lower bulkhead covers

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Glued and screwed luan countertop to frame. Glued small pieces around countertop hatch openings to act as hatch stops.

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Built out and dry fitted above countertop cabinet frames

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Added brace below rear countertop frame piece to remove flex in that area. Finished countertop frame pieces and glued and screwed into place before closing up shop in advance of hurricane Irene.
Last edited by jonw on Thu Nov 10, 2011 9:10 pm, edited 3 times in total.
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Days 24 & 25

Postby jonw » Thu Nov 10, 2011 6:15 pm

Cut out and dry fit all cabinet faces, including cutouts for bedroom and kitchen facing 120v electrical boxes

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Finished cabinet faces plus bedroom/kitchen cabinet dividers.

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Routed out channel in countertop and hatches for living hinges, so hinges and screws sit flush with plywood so they will get covered with countertop tile when applied

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Days 26 - 28

Postby jonw » Thu Nov 10, 2011 6:25 pm

Attached interior electrical boxes to cabinet frame (needed to rout/chisel out some for the boxes tab so the luan ply that covers it will sit flush).
Glued, clamped, and screwed or tacked rear shelf, cabinet divider walls, and front and rear cabinet face pieces.

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With Bob Brewers help re-attached the tongue and front tongue jack. Added weighty items (battery, doors with windows, etc.) and used a bar clamp as a fulcrum to measure the tongue weight at various points. Ended up using the plan-recommended 40in point from the rear for a tongue weight of 55 lbs. Used two car floor jacks to hold up the trailer while attaching the torsion axle. Drilled and glued a rear floor cleat on each side for the axle bolts, and to help hold the walls to the floor in that area.

Reattached the axle with longer bolts, #8 this time. Reattached the rear stabilizer jacks we had to take off the day before because they interfered with the tongue weight exercise. Put the 14in. wheels on the axle and decided indeed they looked too big. Plus…

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Primed and painted the fenders (again should have used POR15) at which time I discovered the fenders are not big enough for the 14in wheels (damn!), plus with the torsion axle the wheels stick out farther than the edge of the fenders. Thinking about what to do about these things. :thinking:

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Traced and cut and fine tuned a hatch ribs to use as a pattern and then cut 2 of the 3 remaining ones before it started getting dark

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Last edited by jonw on Thu Nov 10, 2011 6:35 pm, edited 1 time in total.
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Days 29 & 30

Postby jonw » Thu Nov 10, 2011 6:32 pm

Hooked up wiring for 2 of the 4 outlets for 120v power and ran out of wire :x

Had to rewire the first outlet due to open ground condition. Discovered black was hot wire.

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Then discovered GFCI connector resets itself after power is removed so I decided to move the GFCI switch to wall above countertop. Ripped up portion of the countertop and replaced with new piece with cutouts for wiring coming up for CTek charger, GFCI unit, and kitchen light switch box (which you'll see in upcoming pictures...).

Completed 120v wiring and outlets, fed primary 12v wiring to location for fuse box, and attached battery box without vent (yet).

Cut last hatch rib and cut hatch header and footer pieces.

Bob made cuts for flush-mount ring pull countertop hatch handles, and worked on enclosures for electrical outlets and fuse box connection sections on both sides of the kitchen top shelf.

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Days 31 - 34

Postby jonw » Thu Nov 10, 2011 6:41 pm

Cut out galley hatch ribs and reinforcing cross pieces from 1x6 poplar, and glued and screwed together. Struggled with what to do about a hatch latch...

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Sanded and applied 2 coats of Polycrylic urethane to all cabinet surfaces and interior walls and floor. Attached fusebox and 12v connection panel, wired two together, and attached battery leads. Attached GFCI switch and battery charger to kitchen wall, decided to move galley hatch light switch closer to electrical connections and go with a single gang switch box. Closed up passenger-side electrical area on top shelf with screws and finish washers

Cut and drilled aluminum for galley hatch latch support and rotating wire pull

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Cut and glued up sister rib pieces for door latches to be drilled through

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Last edited by jonw on Sun Feb 12, 2012 4:37 pm, edited 1 time in total.
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