Introduction: Teardrop Trailer

It seems that somehow the links to most of my build log pictures aren't working anymore on instructables, but you can see them all on my website or, if that doesn't work, here is the link to the original album:

I contacted instructables and I'm working with them to fix this problem.

Each step is one day.

First of all, my day job is software programmer. This is my first build. I have basic knowledge of wood working and I have some tools. The build is going to take a while (a month? two?). I only have time to work on it from 8PM until I go to sleep (about 3 hours) and in weekends when we have nothing else planed.

My plan is to keep the price under $1500 $2000. You can buy already made teardrops for $4000-$11000.

My Hyundai Sonata can pull a trailer of 1000lb max. My plan is to make the teardrop be under 700lb with all the equipment inside.

The only size of plywood that I can bring home is 4'x8', so everything that's made of plywood should fit in that size.

Here is how the side wall of the trailer should look like.

A list of parts with links from where I got them:

  • Trailer. I'm going to use the 4x8 Super Duty Utility Trailer from Harbor Freight Tools to built the teardrop on. On the time of creation of the website, the trailer was on sale for $350. I got in mail a %20 off coupon and that made the price $280. Note: If 4' wide is not wide enough for you, you can use this trailer . It's a little more expensive, but 1 foot wider.
  • Doors. You can build your own door. I won't. I'm afraid that I'm not going to be able to make it water tight, so I'm going to use already-built doors. I was lucky enough to find two brand new doors for $230 both, from someone who builds teardrop as a business. Here is his business website, he sells anything you need for a teardrop, including kits and custom made teardrops ( ). Note: You can use only one door on one side, and a window on the other side. I got two doors because they were cheap and I won't have to step over my wife if I have to pee at night. You also can get them from eBay .
  • Vent. I need a vent to put on the top of the trailer. I need one that's able to move lots of air (the door windows won't open on my doors). From my research the best vent is " Fan-Tastic Fan ". I already ordered one from eBay for $120.
  • Hatch hindge. For the big door that lifts open at the back of the trailer. This should be water proof. I'm using a " Hurricane Hinge ". Already ordered from eBay for $71. You also can get it from here .
  • Porch Lights. I need two porch lights to install above the doors. Ordered 3 from eBay for $63. 12V LED.
  • Dome Light. I also need some dome light for the inside the teardrop. Already ordered from eBay for $17.99. 12V LED.
  • Water pump. The best pump I found is the 12V Whale GP1352 submersible water pump. You can buy it from eBay for as low as $25.
  • Hatch handles. Got those from eBay .
  • Aluminum. I called around all the sheet metal places that I found in my area until I got the best price. I got mine from , they are from Portland Oregon.
  • Aluminum Molding. Go here and click "Online parts catalog" then go to "Moldings"
  • Sink/Stove combo. Got it from here .

Tools I use:

  • Box cutter
  • Pencil
  • Framing square
  • Wrenches. Big ones. You'll need for the trailer 16mm, 17mm, 18mm wrenches (I suppose this depends on what brand of trailer you are using)
  • Wireless drill
  • Jigsaw
  • Chop saw
  • Table saw
  • Sander
  • Belt sander

Cost so far:

Vent (Fan-tastic Fan)$120
Hatch hinge (5' hurricane hinge)$71
12V LED Porch lights (3 pcs)$63
12V LED Dome light (1 pcs)$18
Black spray paint (2 bottles)$12
1/2"x4'x8' Birch plywood x 3pcs (one for the floor and 2 for the side walls)$120
5mm Utility plywood 4'x8' x 2pcs (for side walls interior)$23
2x4x96 x 8pcs (for the frame, not sure if I'll use all 8 of them)$22
Exterior screws (1box)$8
Henry Asphalt Emulsion (1 gallon)$12
Bolts & washers & lock washers & nuts to bolt the floor frame to the trailer (3/8" x 3" 20pcs)$26
Bolts & washers & nuts for spare wheel (1/2" x 6" 2 pcs)$6
Hard foam insulation 1/2" 4'/8' (one sheet)$10
Hard foam insulation 3/4" 4'x8' (3 sheets)$30
Sink-Stove combo$187
12V Cigarette lighter socket (2 pieces)$16
Automotive Fuse Holder Box Holds 6 Blade Fuses$14
Electric Facet & Pump System$50
1/8" birch plywood (3 pieces)$70
Wood stain$12
Aluminum sheets 4x8 (1 pcs) 4x12 (2 pcs)$170
Aluminum molding, plastic insert for molding, External Drip Cap$160
1 Gallon Contact Cement$10

Step 1: Day 1 - February 8th 2012

Feel free to click on the pictures to see them in full size for more details.

The trailer box opened.  Looks small. 

Lots of screws and parts. 

Here are the doors I bought. Is two of them in that box, shiny and new.

Hmm.  All the trailer parts look the same.

The trailer starting to get shape . 

I had to go buy some more wranches, mine are too small. Enough for tonight. 

I woke up in the morning with muscle pain everywhere. I discovered some muscle that I didn't know I had. Crawling on the floor trying to put a trailer together is not easy :-)

I'll have to paint the trailer frame black. Red with aluminum gray won't go nice.

Step 2: Day 2 - February 9th 2012

Today I painted the trailer black. I only painted the sides that are going to be visible after the teardrop structure is on top.
Here is the paint I used:

And here is the trailer painted. Tomorrow I hope I'll finish putting together the trailer and I will start working on the frame for the teardrop's floor.

Step 3: Day 3 - February 10th 2012

The trailer is done. I installed the wheels and the trailer jack. I didn't attach the fenders yet, I'll do that when the teardrop is on top of the trailer.

To make sure the trailer is square, check all the corners to be 90º, and also measure from the tip of the tongue to the center of the wheels (the green lines in the image bellow). The measure should be exactly the same.

Here it is:

And the trailer jack:

And a detail of the wheels install:

Step 4: Day 4 - February 11th 2012

I'm hopping for good weather today. I have in plan to go and buy 3 sheets of 1/2'' 4'x8' plywood and 6 2''x4''x8'.

One sheet of plywood is for the teardrop's floor and two for the side walls.

If the weather stays dry and I can get them home, tonight I'll start working on the frame for the teardrop's floor.

Wish me luck.


The weather was good. I got the plywood and the 2x4s.

I used the table saw to split the 2x4 in 2x2s:

And then the miter saw to cut them to length:

The floor frame (the plywood under the frame is there just to have a flat surface, is not connected to the frame):

Held together by metal angles. I got some good advice that I should use exterior screws (last longer when in contact with humidity), so I replaced all the drywall screws with exterior screws.

The picture shows the drywall screws.

... and a long screw:

This is how the frame turned out:

The 1/2" plywood that would be the flood of the teardrop on top of the frame, just to check the size and looks.

I had to cut a little piece on the side. The floor looks good!

Step 5: Day 5 - February 12th 2012

First the bad news. The Fan-Tastic Vent I bought from ebay came with the dome cracked. I contacted the ebay seller and Monday we are going to find a solution.
The rest of it looks and works good:
The fan has 3 speeds and the flow of air can be set in or out:
I made some modifications to my Fan-tastic Vent to have more control over the fan's speed (and noise). I used a voltage regulator - LM317, one resistor and one potentiometer. Here is the schematic:
Now from the potentiometer the speed can be set from very very slow and quiet to full speed.
Initially I tried to control the speed using PWM but that actually makes it noisier. This solution with LM317 works perfect.

The following video shows the new speed control:

Here is the LED dome light I got:

The 5' long hurricane hinge:
Water, you shall not pass!

The bolts with washers, lockwashers and nuts that I'll use to bolt the wood frame to the trailer:

I'll use those 6" bolts to place the spare wheel under the front of the trailer:
Asphalt emulsion to paint the wood frame and plywood on the side that is going to be connected to the trailer. This is supposed to protect the wood from the water. 

Step 6: Day 6 - February 13th 2012

Waterproofing and insulating the underneath of the floor. 
NOTE: Do not paint the sides of the floor.  You are going to need the sides clean to glue the walls to.
After painting each section with the tar like emulsion, I place the hard foam insulation (I used a box cutter to cut the insulation) and secure it in place with few screws with big washers. 
Make sure you don't drill the screws to reach the other side.
In the picture, there is another piece of plywood in the front section of the floor. That's where the spare wheel will hang under the trailer. The plywood is glued and screwed to the floor board.
The consistency of the emulsion, looks and feels like melted tar.
The insulation pads secured in place. The emulsion is going to act as an adhesive to keep the pads in place. If that's not true, then the screws are going to do the job.
All done. I went crazy with the tar and made sure that I have some even on the screws. No idea if that's good or necessary, but it seemed like a good idea at the time.
After testing thoroughly everything....
.... I have some advice... use gloves when you deal with the tar.

On the can, on the label, it said that it could take 2 to 7 days to dry in cold weather. I'm hoping that is going to take less.

Step 7: Day 7 - February 15th 2012

First the good news: The replacement dome for the Fan-Tastic Vent just came and doesn't have any cracks! Hooray!
Get the floor ready for bolting to the trailer frame:
  1. Put the wood frame on top of the trailer, clamped to stay in place
  2. Tap it with a hammer where the frame rests on top of bolt heads that keep the trailer together (this will mark where the trailer's bolts are and you'll need to carve some spaces so that the frame will lay flat on the trailer)
  3. Use a 1" spade bit to make space in the wood frame for the bolt heads.
The floor is bolted to the trailer. 
I'll make the side walls from 1/2" 4'x8' plywood.
Drawing the curve that gives the teardrop trailer the nice shape (the pencil line is barely visible):
I used 2 home made compasses (just a piece of wood with a nail on one side and a hole for the pencil on the other).
First one is 19" long from the nail tip to the pencil tip and one is 48". 
The curve at the left of the paper (the back of the teardrop) is made from 2 arc circles, the first one has a radius of 19" (the 19" compass) and the second one 48" (the 48" compass). This will give the curve at the back of the trailer an arc ellipse shape.
Note: Ignore the 18 5/32 dimension on the drawing, I didn't use it, the correct dimension for the 19" radius arc is 19" from side and 19" from bottom.

Warning: do not try to cut both walls in the same time, stacked together. Doest't work. One by one, slowly, works the best ;-)

I used one of the doors to trace the shape on the plywood. Here is one side walls with all the cutoffs. I used a jigsaw to make the cuts.
The door fits perfect in the space.
I used the side wall that's already done to mark the next wall.
Both walls are cut. I'll need to use the sander a little on the edges.

Step 8: Day 8 - February 16th 2012

I made two more side walls from 5mm plywood. Those are going to be used to "skin" the interior of the trailer. The side walls are going to have 3 layers:
  1. The exterior walls are going to be the 1/2 plywood
  2. Hard foam insulation
  3. The 5mm plywood on the interior.
I painted the bottom edge of the 1/2 plywood walls with the Henry's Emulsion (the tar like thing, remember?) to protect it from humidity. Again, just paint the bottom edge (the walls are upside down in the picture).
Both walls are protected now at the bottom edge.
I made a right-angle jig from one of the corners I cut off when I made the 1/2" side walls. We'll use this when we attach the walls to the floor to make sure the walls are perpendicular on the floor.

Step 9: Day 9 - February 18th 2012

Getting the first wall up.
The wall is glued and secured with exterior screws to the floor's frame.
The wall from another angle. The wall is hold in place with the help of the right angle jig I previously made and one of the corners I cut off when I made the walls.
The second wall is up, glued and secured with screws to the floor's frame. Two temporary beams keep the top side of the walls.
Just another angle of the two walls.
Framing of the walls. The walls need to be framed for the hard foam insulation. The frame is hold in place by glue and screws.
The framing is slow and boring.
Framing the door.
Done for today. The edge of one wall and the door are framed.

Step 10: Day 10 - February 20th 2012

Working on the framing for the second side wall.
Both walls are now framed. This wasn't fun. I have a limited number of clamps and I had to wait for the glue to set before I could move to the next segment.
I run out of scrape wood with the framing, for the last piece I had to hunt under the shed.
Tomorrow I plan to work on the frame for the cabinets for the back of the teardrop.

Step 11: Day 11 - February 21st 2012

After looking at all design options, we decided to make just an insulated divide between the kitchen area and the sleeping area. We won't build any cabinets into the sleeping area (at least not big ones above the feet), we will build a bunk bed there, for our 3 years old girl.
The divider installed. I stopped here with the build today, because I'm waiting for FedEx to bring a sink-gas-stove combo I ordered for the kitchen area and I need the dimensions before I go any further.
The insulation installed in the divider. I'll cover the insulation on this side with plywood when I decide how to build the bunk bed.

Step 12: Day 12 - February 22nd 2012

I started the wiring for the lights and the vent. I'll have 2 porch lights, one on each side walls, a dome light for the interior, 2 reading lights and the vent's fan. I will also setup some extra wires for a radio and speakers.
Here is the basic schematic on how I'm going to install the wiring.
The frame that is installed on the walls, next to the back panel, is the in-wall support for the bunk bed I'm making for our 3 years old daughter.
The porch lights wires.
This is the sink-stove combo we got for the little kitchen. Looks blue because is covered with a protective film for the shipping, but the sink and stove are stainless steel.
Here is the size of the sink-stove combo compared to the size of the back of the teardrop. You can see the wires on the right side, it's where I'm going to install the fuse box.
I'll have to label those wires, I need to know which is what.

Step 13: Day 13 - February 23rd 2012

Gluing some scrap wood blocks in the walls to support the light switches. 
You can see a pair at the bottom left corner and top right corner of the picture. 
The lower one is for the reading lights. I got two two LED bendable reading light from Ikea that I'll set in the wall.
I also got this mirror from Ikea that I'll put it in the cabin for my wife.
Detail of the light switch support in the wall.
I used too much glue. Oh well, this will be covered anyway.
Insulating the walls of the "kitchen area". The horizontal beams in the wall are to support the frame for the countertop.

The skin installed on one side (is "skin" the right word?)
Both sides insulated and "skinned".

Step 14: Day 14 - February 25th 2012

A mirror we got from Ikea for the inside of the teardrop. It was $5.
We got two LED lamps to use them as a reading light inside. They work at 4V DC. They costed $10 each at Ikea.
I'm going to replace the wiring with this. 
Working with the insulation.

One wall done.
Both walls done!

Step 15: Day 15 - February 27th 2012

The inside skin of one side wall installed. The light switch for the porch light, the reading light and the switch for it also installed. 
The plywood I used is 5mm tick. The plywood is glued and screwed to the framing on the wall.
I got the faucet and the water pump in the mail yesterday. The faucet looks fine, but I think it's a bit too small (short), so I'm not sure if I going to use it.
Here is a pump that interests me (Whale GP1352).

The fusebox that I'm going to use
Cigarette lighter socket, panel mount outlet 12V

Step 16: Day 16 - February 28th 2012

The interior skin installed on the second side wall too. This is also 5mm plywood. The "nice" side faces the interior.
I replaced all the drywall screws I used so far with exterior screws. 
Exterior screws.
Done with the side walls so far. Both porch light switches are installed. The reading lights and switches installed also.

Step 17: Day 17 - February 29th 2012

The frame for the bunk bed made from 2x4s.
The bunk bed. Now I have to make something so my daughter won't fall of the bed.

Step 18: Day 18 - March 1st 2012

Today I started working on the front wall and the roof. The front wall is going to have a window that opens (remember, the door window doesn't open for my doors).
Here is the frame of the front wall with the space for the window.

Step 19: Day 19 - March 3rd 2012

All spars installed. The vent fits nicely. I installed spars at every 7-8".
Another angle.
... and another
... looks good.

Step 20: Day 20 - March 4th 2012

Interior skin for the front wall and roof installed. The skin is 1/8" birch plywood.
The skin secured in place with screws.
Glue on the spars where the skin is going to touch.
I cut some insulation, just to see how it looks like.

Step 21: Day 21 - March 5th 2012

The window, door and vent in place to check see if they look good together.
Nice, isn't it?
The foam insulation cut, but not yet in place. I'll have to untangle the electrical wires and find out what to do with them first.
On each side of the trailer I have:
  • wires for the porch light 
  • wires for reading light 
  • wires for the speakers
Then on one side I have wires for the dome light and on the other side wires for the vent's fan.

The wires for the vent and dome light.
Here is how I'm running the electrical wires on the spars.

Step 22: Day 22 - March 8th 2012

Today I received the new pump and faucet. the pump is submersible, and fits through the opening of any container (even milk jugs). You just drop it in the container and you have water at the faucet.
The pump is Whale GP1352.
This is the stain I'm going to use for the interior of the trailer.

The interior stained, one coat. Tomorrow I'm going to do a second coat.

I connected a 270 Ohm resistor for the reading lights on the positive wire (same wire that the light switch is on). The voltage coming from the battery is going to be 12V, the reading lights work on 4V. 
Hmm. Just saw in the picture that the heat shrink insulation on the ground wire is broken. I'll have to make sure I fix that.

Step 23: Day 23 - March 13th 2012

I used this stain for the floor and it took about 3 days to dry (oil based) first coat. Yesterday I did the second (and last) coat... I'll have to wait another 3 days to continue.
I installed the frame for the vent. This was necessary because the vent is ticker than the roof.
I also installed the frame for the window. The frame is cut from 5mm plywood.
You can see the floor color is darker than the walls, I used a different stain. 
The frame glued and clamped in place.

Step 24: Day 24 - March 22nd 2012

The outside roof skin installed. The skin is 1/8" birch plywood.
The skin is glued to the frame. Screws keep the skin in place, but I'm going to remove them when I do the aluminum siding.
I have to cut the opening for the window and roof vent.
The trailer is ready for the aluminum siding, I'll have to wait for a sunny weekend for that.
Starting the hatch for the back of the trailer.
I made the sides of the hatch from 2 pieces of 1/2" plywood glued together.
Waiting for the glue to dry.

Step 25: Day 25 - March 24th 2012

Today is sunny and clear, so I'm planing to do the aluminum siding. My wife's father Ross and my son Vlad are going to help.
First of all make sure the walls are perfectly flat and all the screws heads are countersunk.
You will need a gallon of contact cement
We applied the contact cement with a painting roller on the side of the trailer and on the "ugly side" of the aluminum sheet.
Wait for the contact cement to set (read the instructions on the can). Usually, after 20-30 minutes, when the surface is tacky (not sticky), you are ready to put the aluminum on.
I don't have pictures of the process, we were too busy and I forgot about the camera, but I'll try to describe how we did it.
We attaced some pieces of 2x4 to the trailer frame at level with the level teardrop to hold the aluminum we can easily place it correctly.
We cut some same size sticks/dowels (at least 36" long) to keep the glued aluminum away from the plywood before "Contact". We placed the sticks on the plywood vertically, at about 12 inches (or so) from each other so the aluminum doesn't touch the wall surface before is correctly aligned with the wall (I'll make a drawing on the above picture to show):
We placed the aluminum on the 2x4s and then when the aluminum was aligned with the front of the teardrop, we removed the center stick first and smoothed down with our hands as we removed the succeeding sticks.
We finished up by rolling it out with a rolling pin.

Now to cut the aluminum siding to shape (after it was glued to the plywood wall), we used a 2HP router with a 1/2" straight flush trim, bottom bearing bit.
One mistake we made, we didn't put some masking tape on the aluminum where the router slides and there are few small scratches... so my advice is to put some masking tape over the aluminum along the path that you are going to cut.
Cutting the back side. Make sure you have protection glasses on.
Ross is holding the piece that we are cutting out.



The door opening: first I made a 1/2" hole for the router bit from the inside. Ross was counter pressing a piece of plywood on the other side the aluminum so we don't make a bulge in it when I press with the drill.
Cutting the door opening.

Ross getting ready to apply the contact cement on top and front of the teardrop

The aluminum in place over the roof. You'll need to weigh it down and I suggest straping it down from forward to aft with tow straps over sticks on the area of your spars.

DONE! I'll leave it like this for a day and then I'll have to cut out the opening for the vent and for the window.

Step 26: Day 26 - March 29th 2012

This is the molding I got. It came in two 16' long pieces. I also got 2 rolls of 25' black vinyl insert.

To install the molding and be able to bend it around the curves of the teardrop, I'll need to soften the aluminum first (annealing). This is done by heating the aluminum to very high temperature and then letting it cool down slow. Aluminum doesn't turn orange when hot like steel, so you'll have to decide when is hot enough without melting it. 
Use a propane torch...

... and slowly move the flame on the aluminum molding on the portion that you want to soften.
Move the flame slowly back and forth on the length of the molding. When you think is hot enough, let it cool down by itself. Do not put it in water, that is going to make it harder. 
DO NOT TOUCH IT WITH YOUR HAND WHILE HOT! - except if you want a permanent tatoo on your hand to remind you of the time when you built the teardrop.

Use something like clear OSI sealant (what I use) from Home Depot to fill the space between the aluminum skin under the molding. Don't be stingy with the stuff but don't get messy either.
(Thanks Danny for the tip)
Put the sealant on the corner and then install the corner molding over. Bend it nicely around the curves and secure it with screws.
Install the window with the same sealant under the frame.

Same sealant to install the doors.
I installed a window drip cap. I also have two for the doors.

Done for today!

Step 27: Day 27 - April 7th 2012

Time to build the hatch. I hate this part because I don't know exactly what I'm doing, so I'm just doing guess work. Have patience with me if I make a mistake.

First, to make the ribs (sorry I don't have pictures for that step... I forgot about the camera when I did this), I got a 4'x4' piece of 3/4" birch plywood and got it next to the wall, at back, where the wall is curved and I traced the curvature of the walls with a pencil. Then I cut along the curve with the jigsaw. When one cut was done, I traced another line about 2" from the cut, parallel with the cut, to make the shape of the rib. I used the jigsaw again to cut the rib. When the ribs were cut, I clamped them to the wall and with a belt sander I sanded the edges to make sure the side walls and the ribs are the same.

I made 2 ribs from 3/4" birch plywood.
I clamped some 1/4" dowels between the side walls and the ribs to measure the distance between the two ribs. I'll need this measurement to cut the horizontal beams that make the top and bottom of the hatch.

The bottom horizontal beam in place. I have the 1/4" dowels under it.

Two older, uglier ribs that I made before will be part of the hatch too.

Looks good!

Few beams connected to the ribs to make the hatch stronger.

I'm glad I'm done with this part.

Step 28: Day 28 - April 10th 2012

1/8" birch plywood covers the hatch. The plywood is glued and screwed to the ribs and beams.

Contact cement painted over the "ugly side" of the aluminum.
Contact cement painted over the hatch.
When the contact cement dried a little (about 20-30 minutes), put the aluminum over, using the same method as in the Step 25.

Step 29: Day 29 - April 18th 2012

Hurricane hinge installed. 
I'm installing the molding on the sides of the hatch using aluminum rivets.
You'll need a rivet tool for this. Harbor Freight has some cheap, good ones. 
Nice rivet.
Molding installed and the black plastic insert ... inserted.
Detail of the hurricane hinge. The hinge extends out about 1" on each side, this will work as a rain gutter.

The hatch insulated with 3/4 hard foam insulation from Lowes.

Step 30: Day 30 - April 27th 2012

1/8" birch plywood makes a good skin for the interior of the hatch. Also, I installed the locks.
The handles look pretty good. I like it.
I used peg board for the back of the "kitchen". It will be useful for hanging stuff on it.
The frame for the countertop.

Countertop installed. 
I covered the countertop, the kitchen floor and backsplash with linoleum tiles from Lowes.

The faucet installed in the countertop. 

Step 31: Day 31 - April 29th 2012

Big news! I had the first towing test and my Hyundai Sonata didn't even feel the trailer behind.
Here are the pictures of the trailer behind the car:

And some pictures from the interior. I still have to do some things inside the trailer, I have to make a rail for the bunk bed, to install speakers, to install a small screen for entertainment... (probably our Kindle Fire).
The size of the bed inside the trailer is 6'6" long and 4' wide.

Step 32: The Kitchen

The hatch support bar installed. I used a closet hanger rod and flanges (I think that's what they are called).
I made a hole through the flange and rod for a safety pin, I don't want the support bar to fall off if wind lifts the hatch a little.
I used safety pins on both sides.
The seal for the hatch. Water you shall not pass! (again)
The faucet is locked open. The red button starts the water flow. I used a 5 second timer I build for the water.

The stove is connected to a propane cylinder.
The submersible water pump.
From the pump, the water goes directly to the faucet.

From the sink, the greywater drains....
... under the trailer in the greywater container.
The electrical panel under the sink. Everything is 12V.
On the left side is the ground bank and the little box with the transparent cover is the fuse box.

The timer I made for the water pump. It's a classic monostable 555 timer tuned for 5 seconds. For each press of the button, the pump is going to pump for 5 seconds.
Here is the schematic (download the Eagle file bellow):
The hatch light is mounted above the sink.
The light can be flipped up like this if you need light farther back. 

All the electric needs for the teardrop are provided by a deep cycle battery that I bought from Walmart for $70. 
The battery is 110  Amp hour and I suspect it's going to last up to two weeks on one charge. I left everything ON, including the vent's fan, for a whole night and in the morning the battery was over 90% full.
Detail on how I mounted the battery box on the trailer's tongue. I got the battery box also from Walmart for $9.
The power cord coming out from the battery box, it's for the charger.
Post scriptum:

I saw some comments proposing solutions on how to charge the battery. Here are two ways you can charge the battery with the towing vehicle while driving.
First one, the simple one, you just connect a wire to the positive terminal of the car battery, put a 30A fuse on the wire and connect it to the positive terminal of the trailer battery.
The negative from the trailer battery goes to the car ground. 
This way both battery are charged while driving the car to your destination. 
When you turn off the car, disconnect the trailer battery from the car battery to avoid discharging the car battery when you use the electricity in the trailer.
(click on the images to see them in full size)
The second method, a little more complicated, is to use a continuous duty solenoid. Make the connections like in the schematic bellow.
This way, you don't have to manually disconnect the battery when the towing car is not running. The solenoid will disconnect the battery automatically when you turn off your car.

That's about it for now.  
I will post more pictures after our first trip which it's going to be on June 7-11, 2012 in Grants Pass, Oregon.
Lots of teardrop builders/owners are going to meet there and party: "TearJerkers Birthday Bash 2012, celebrating 15 years of TearJerkers"

Who knew that there are 
Teardrop Gatherings and Teardrop-Friendly Events... here is a list I found:

My wife said that now I proved myself so I should start remodeling the kitchen. :-)
"Let no good deed go unpunished."

Thank you for reading my build log and ... go make some sawdust!

Post scriptum 2:
I added another page with pictures from our first trip to "TearJerkers Birthday Bash 2012, celebrating 15 years of TearJerkers" in Grants Pass, Oregon. It was lots of fun. Check it out.

Step 33: First Trip

Our first trip was to Grants Pass Oregon, for the "Jefferson State Chapter of TearJerkers Birthday Bash 2012, celebrating 15 years of TearJerkers".
Teardrops are starting to come and back up in their spaces...
... while we are unpacking...
... and getting ready...
... to eat dinner.
Story and beddy-bye time.

One of the mornings my wife getting the breakfast ready...
(she's very pretty)

... while Madeline is watching "Blues Clues" on the Kindle Fire. 

Breakfast is ready!

Thanks for the good food mommy!


Another teardrop
and another
and... you guessed, another

This one is a 1947 original...
it was reconditioned, but most of it is the original.

My preferred teardrop/towing vehicle combination.
The guy made this. He said he started it last year in August. Chevy engine, automatic transmission... amazing.

Getting ready for potluck.
I'll better get in there too if I want to eat
Talking, eating and having a beer.

Fun people. 

That's about it. Everyone is leaving.

Make It Real Challenge

Runner Up in the
Make It Real Challenge

Woodworking Challenge

First Prize in the
Woodworking Challenge

Wheels Challenge

Runner Up in the
Wheels Challenge