My cargo teardrop build

[znelson]

First off, I want to say that this forum is a fantastic resource for trailer build ideas and techniques. I've spent the last few weeks reading dozens of build threads; learning from others' mistakes and ideas has been invaluable.

So, without further ado, here's my story and build journal...

I have a family of four and we travel everywhere in a Saab 9-5 wagon (4-cyl). We love that car because it is a) paid for, b) reasonably fuel efficient (23-30 mpg), and c) fits our family. Last month we got a Great Dane / English Mastiff puppy who is growing rapidly (surprise!) and we're quickly realizing that he's going to take the entire cargo area of the station wagon. I started looking at options for procuring cargo trailer and really fell in love with teardrop trailers.

I searched far and wide for small cargo teardrop trailers and found a couple on this forum. This is closest to what I want to build: http://www.tnttt.com/viewtopic.php?f=2&t=23737. "Eggbert" is another similar one.

I started with the Grumman 2 shape by following the YouTube videos for modeling it in SketchUp. I then scaled it down to 6 ft long and 3 ft high, and modeled it on top of a Northern Tool 48x40 trailer frame. The stock trailer tongue isn't long enough on the 48x40 trailers, so I plan to swap the tongue out with a 9-foot section of 2" receiver tube purchased from a local metal supply shop. The new tube will extend the tongue and pass under the entire trailer to the rear, providing a rear 2" receiver on the trailer. This will allow me to attach my bike carrier to the back of the trailer. Here are some photos of the 3D model:





Unlike campers, this won't have any vents or windows. The only door will be the rear hatch. The floor frame will be 1x3s with a 3/8 plywood floor. The walls will be sandwich construction of 1/4 plywood and 1x2 frame. I plan to wire the walls for side clearance lights and tail lights, and the ceiling for a dome light. The width including the walls will be 40 3/8" to fit within the edges of the trailer frame so the walls can rest upon the sides of the trailer. I will use a Li'l Bear "Better-than-hurricane" hinge for the hatch, and gas springs inside to lift the hatch. I plan to skin in 1/8" baltic birch, epoxy with Raka, and then my wife will give it a cute paint job.

I'm entirely a novice. My most extensive construction projects to date are some rough 2x4 shelving units in our storage closets at home, so this is going to be quite a learning experience.

[znelson]

The first step was to get the trailer. I was going to use a Harbor Freight trailer frame, which was about $50 less, but the two local Harbor Freight stores each only had 1 of the 2 boxes in stock and they have no way to order something to be picked up in store. Their advice to me was to check back each Monday to see if the latest truck delivery brought in one of the trailers that I wanted, or order online for delivery with a $100 shipping fee. Ugh.

Northern Tool had the trailer in stock, matched their online price, and accepted an online coupon code in-store. I got the model with 12" wheels for better highway performance.

Here I am putting the trailer together with some "help" from my daughter. The instructions with the trailer are OK, but the diagrams explaining how to lay out the steel frame members are pitiful. In this case, I managed to get everything bolted together before I realized it was entirely wrong:



Then I disassembled and re-assembled, correctly this time:



Repacked the bearings as I was putting the axle and wheels together:



And, skipping the rest of the trailer build details, the trailer:

[znelson]

The floor frame is built out of 1x3 select pine, glued with PL adhesive, and screwed together with green DeckMate screws.



The floor itself is 3/8" plywood, again glued with PL and screwed down.



The puppy likes to "help" by sitting on things and occasionally chewing on (usually important) things:



Whew! It fits exactly like it was supposed to. I shouldn't be so surprised.



Before I attach the floor to the trailer with bolts, I'm going to seal the bottom with roofing tar.

[znelson]

I got eager to see the profile, so I skipped straight to that and saved the floor tarring for later.

I started transferring the outline onto the wall plywood. I considered using the foci and string method for drawing the ellipses, but instead I chose to draw measurements every few inches. The measurements were transferred from the SketchUp model to the plywood using a carpenter's square. This was slow and tedious, but I'm hoping I only have to do it once and I can trace the other 3 wall pieces from the first.






Then I cut it out with a jigsaw:





I'm quite pleased with how it came out:



The notch in the back is where the hatch will overlap the walls.

[StockCube]

Looking good. You should be done in no time without all the fancy bits to slow you down.
I plotted my profile that way too - it was pretty easy to be honest - I think a lot easier than trying to plot elipses and so on.

[bobhenry]

It kinda looks like Eggbert !

[znelson]

It kinda looks like Eggbert !

Yeah, Eggbert was one of the first little cargo teardrops I found on here. Thanks for the inspiration!

[znelson]

I waterproofed the floor with the black gooey stuff yesterday. I applied it twice to get it nice and thick and into all of the cracks and corners. It was just as everyone described: incredibly messy. I wore rubber gloves (do this!) and junky old clothes and it was really no big deal.

Before the goop:



After 1 coat of the goop:



After 2 coats of the goop:

[znelson]

Yesterday was also trailer modification day. I got some family help welding the replacement tongue onto the frame, and welding the top corners of the trailer so I could remove the top bolts. I had been contemplating how to notch out the bottoms of my walls to deal with the top bolts, but this solves it completely.

The new tongue is a 9' section of 2" receiver tube from a metal supply shop. The tube hangs off the back end of the trailer to provide a rear receiver for a bike carrier or an additional cargo carrier in a pinch. 9' may be longer than I actually want the tongue to be, but it's always easier to shorten it than to extend it down the road.

Some welding:





Then some grinding to smooth out the welds:



Then some primer on the welds and bare receiver tube tongue:



Then black gloss enamel to finish it up:



Finished top corner without the bolt head sticking up:



The trailer wiring did not hold up very well to the welding, so I expect I'll get to rewire the lights soon. The old wires don't reach the car anyway because of the extended tongue...

While I was at it, I replaced the coupler on the tongue with one for a 2" ball. So much easier to standardize everything you tow to one ball size so you aren't changing hitches all the time.

[bobhenry]

Fantastic !

That's the way they should be built.

If you leave the tongue long it will make a great motorcycle trailer.

That was why I lengthened mine. There is less side load force when you drop one wheel in a chuck hole.

It will tow like a dream and if you want you can add a tongue box or even extend the body forward a bit you have the option now. You will love he rear receiver also. If you sleve the inside down a bit it will accept a category two (1 1/4) draw bar sized accessory or bike rack.

[znelson]

If you leave the tongue long it will make a great motorcycle trailer.

That was why I lengthened mine. There is less side load force when you drop one wheel in a chuck hole.

Interesting, thanks for pointing that out!

...if you want you can add a tongue box...

Definitely something I've been considering...

You will love he rear receiver also. If you sleve the inside down a bit it will accept a category two (1 1/4) draw bar sized accessory or bike rack.

Actually, I have a bike rack and a HF aluminum rear carrier each with 2" tubes. I've been using them on my class II receivers with step down adapters, but now I can ditch the adapters with the trailer.

[znelson]

Learning a lot and making mistakes as I go here...

Cut out slots on the inside wall layers for the spars to pass through (they will pass through the inner wall layer but not the outer wall layer):



Then I built up some structure inside of the walls:



Next I added pieces around the perimeter of the walls:





What??! That's not part of the trailer :



Let the PL adhesive set for 24 hours and then routered it flush:




This worked GREAT at first! Then, things went a little bit downhill... What happened was: The bearing on the router bit is just above the cutting surface. Above the bearing is a black collar (visible in the picture above). The black collar had a set screw in it to keep the bearing down close to the cutting surface. After getting part way around the wall, the set screw apparently vibrated out. The bearing began to walk up the shaft of the bit, and occasionally it would slip off of the plywood guide. It took me a while with the excessive noise and piles of wood shavings to even realize things had gone awry.



I also managed to chip off two small pieces (look above the upper and lower spar slots). I'll cut small custom pieces to fit in here and glue them into place:



Finally, I jigsawed the sharp interior corners that were rounded to the radius of the router bit:



And this is where the two walls ended up so far:




Just bought a pile of LED trailer lights at Northern Tool and 100' of trailer wire, so the next step is to prepare the wiring before closing up the walls.

[StockCube]

You seem to have dripped some oil onto your dog

As for the router bit - yeah I had that problem too. I think it helps to go a certain way round the project ie clockwise or anticlockwise but I can never remember which so I have to keep stopping to tighten the wee nut with an allen key.

[KCStudly]

I had the same problem with 2 of those Freud bits. I was able to continue by stacking 2 bearings on the shank and pushing them up against the collet so they couldn't walk around on the shank.

Replacement collars are available, but you will likely have to buy the tiny hex key, too, and the shipping costs more than the parts.

A little drop of small fastener locking compound might help.

[Cliffmeister2000]

Looks great!

As far as no windows or vents, how is your dog to breathe? Here in Arizona, you could cook a turkey in an hour in an unvented trailer.