The Annex - 5 1/2 wide X 10 long X 5 high

[JohnSw]

The Annex was designed to be an extra bedroom at my son's house as well as a camper. He had a very narrow driveway on a busy street with a utility pole 2 feet from the street end of the driveway. Based on these limitations, I chose to limit the width to 5 1/2 feet. This also allows for good visability to the rear with standard miorrors.

I wanted to have more than just a bed inside so I made the length 10 feet.

The 5 foot height allows for under the bed storage and more head room elsewhere.

The profile I came up with is below:

[JohnSw]

I chose the Northern Tool 5 X 8 bolt together trailer for a number of reasons. First, it's a 5X8 not a 4X8. I wanted the extra wheel width for stability. I also like that the Northern Tool C channel was beefier than the Harbor Freight frame. In the for what it's worth category, the tires on the NT are 5.30-12 versus 4.80-12 for the HF. Same physical size but with a higher rating.

In order to make a 10 foot trailer out of an 8 foot trailer, I took one of the cross members and cut it in half. That gave me enough material to overlap at the joint and extend the trailer 2 feet.

At this time I was driving out of the neighborhood and saw a trundle bed frame at the end of a driveway. Just the thing I need to finish my trailer thought I. Well I finished the trailer but, as I read somewhere, those bed rails are harder than a woodpeckers lips! I ended up buying a Drill Doctor to resharpen the drill bits. I would recommend them for fence posts and not much else.

Here is an overall photo of the trailer frame, less tongue and axle. It's taken from what will be the tongue end of the trailer.





This is a better picture of the 2 bed rails making up the rear member of the trailer. Also shown are 2 angle pieces which define the location of a recessed well in the floor ( trying to get more headroom).





This is even closer showing how the rails are tied together to stiffen them.

[JohnSw]

Because I extended the frame 2 feet, I moved the axle rearward 17 inches. I did some back of the envelope calculations to come up with the 17". Unfortunately that envelope doesn't exist anymore...
I used the information found here:

http://www.angib.pwp.blueyonder.co.uk/teardrop/tear81.htm

This can also be found in the "Design Resouce" section at the top of the forum under "design library" and "trailer balance".

Using a cross member for the side frame extension works really well since it's sized to fit inside the side C channels. If you look close in the photo below you can see the overlap of the rails.

[JohnSw]

I elected to attach the 1/2 inch plywood floor directly to the trailer frame. I used a forstner bit to counterbore clearances for the trailer bolt heads. The last thing I did before attaching the plywood was make sure that the trailer bolts were tight. I did buy new locking nuts that use a mechanical interference to lock themselves in place rather than use the nylok style lock nuts. (I like metal better than plastics)

In order to make up the height differences between the cross members and the side rails (the cross rails fit inside the side rails), I used 1/2 galvanized washers, as required, to level the floor attachment points.

I just let the plywood overhang the trailer frame on each side by about 3 1/2 inches. Once the walls and the interior compnents are attached, it will be strong enough that no additional support is necessary.

This photo shows the assembled trailer with the floor, wheels and the tongue and a side wall frame which has been built using the trailer as a work table. It's a very full single car garage.

[KCStudly]

Good job so far! I look forward to following along.

[JohnSw]

Thanks KC. I'm way behind on the build journal. A few more posts & I'll be caught up..
John

[JohnSw]

At this point in the narrative it's Fall of 2011, the trailer with the floor attached, is in the garage. If it was a 1940's movie, the camera would be focused on the calander and months would be rapidly falling away. There are other projects taking time away from the trailer and my son announces the impending arrival of a third grandson. Now he needs a bigger house. He finds one which doesn't need "The Annex" but I realize that now I do. We don't have room for three grandsons to sleep. After helping my son fix-up his old house to help it sell, work begins again on "The Annex". The profile remains the same but a side door is eliminated and the window purchased for the door is incorporated into the side wall.

My walls are 1 X 2 poplar frames with the joints glued with Titebond II and screwed with pocket screws.

At some point I lost some photos of my side walls. This is the only one I have of just the frame. The sides are identical except for the window sizes.





Here is a closeup of the frame joints....

[JohnSw]

In order to make the front radius I used a compass that I got years ago..don't remember where or why I got it but it worked great. Simply attach the pivot point and the peice with the drafting lead pencil point to a yardstick and you are ready to go.





The roof also has a subtle curve. In sketchup, it measured 2026 inches. Didn't seem like using a string tied to a tree would work so I came up with this solution...

[JohnSw]

The walls are skinned with SurePly plywood underlayment. According to the phone call I made to Patriot Lumber, SurePly has a waterproof adhesive. I attached the ply to the frame with Titebond II and 5/8" long by 1/4" narrow crown staples. It's easy to use more staples than necessary and I'm sure I did. I spaced them about every 3" or less. I'm using a cheap harbor freight stapler which has worked flawlessly so far. It's not that I don't trust the glue (well maybe it is because I don't trust the glue) but the staples provide mechanical attachment and good clamping force for the glue.

I bought 3/4 inch Dow styrofoam to insulate the walls. Interestingly, the Dow 3/4 inch insulation measures 1/32 of an inch over 3/4 inch. Of course the 1 X 2's are exactly 3/4 by 1 1/2. I removed the plastic sheeting from the insulation and rolled every blasted inch with a 1 inch wide wheel to compress it to fit. This must be the only lumberyard item that is BIGGER than the nominal dimension. I think my blue box store changed insulation brands and now it measures under 3/4 (after I had bought mine, of course).

Here's a photo of a side wall with the insulation.





In addition to the Titebond II I used to attach the ply to the frame, I used PL premium to attach the foam to the ply.

[JohnSw]

I sharpened one edge of my 3" drywall taping knife and used that to cut the foam. I works fantastic.
Here is a video from Fine Homebuilding demoing how well it works. BTW Fine Homebuilding has a bunch of useful tips in the video series "There's a better way"

http://bcove.me/p2utgnav

(Although this link doesn't say Fine Homebuilding, it is the correct link to the video..)

[JohnSw]

In the upper right of the rear wall I plan to put 3 computer fans for ventilation. In the lower right will be a slide out room AC unit. I also framed a place for the tail lights.





I built 2 wiring chases into the lower front wall as well as 2 paths for ventilation. I plan to have some ventilation through the floor under the bed into the storage area. These paths will have slots just above the level of the bed. I don't know if that's clear but when I ge the walls up I'll take additional pictures.

[JohnSw]

I've chosen to use epoxy to coat the exterior. I purchased Raka 127 low viscosity resin and 606 slow hardener. For the fiberglass I got the 3.25 oz style 120 cloth. I epoxied the sides and use fiberglass tape on the joints between plywood sheets.

I used the glass fabric on the short front wall and on the rear wall. I wish I had used the fabric on the sides as well. The fiberglass tape is heavier (6oz I think) and hard to eliminate the bump from the tape with just epoxy. I decided not to worry about it. On the rear and front where I used the glass it looks perfect with no added work. I don't think it took any more epoxy either.

Here is a shot of the side wall...




In the above photo you can see the gallon jugs for the resin and hardener with their pumps. I use the pumps a couple times to meter out the resin & hardener and decided it would be better to use the technique of using disposable plastic cups one inside the other with the outer cup marked.

The inner cup holds the resin and another pair of cups takes care of the hardener. You pull the inner cups out, save the marked outer cups and mix the epoxy between the 2 inner cups. You can then put 2 new cups into the marked cups for the next batch of epoxy. Works really sweet.

[JohnSw]

I dumped the mixed epoxy into a disposable roller tray and used a foam roller to apply it to the plywood. I spread the fiberglass & worked out any bubbles with a plastic scrapper. I made sure the fiberglass was completely wetted. Where the fiberglass extended over the edge of the plywood it was very easy to trim with a utility knife after it had hardened.

I did have one batch where I carelessly spilled some epoxy after I had combined the resin and the hardener but before I had mixed it. I decided that the now unknown ratio of resin to hardener was better off being unused. I set the disposable cup in one of the paint trays and mixed another batch.

Check out the result in this photo... can you say exothermic reaction.. Look closely at the cup next to the epoxy, it has a hole melted in it from the heat! One of the advantantages of putting the mixed epoxy in a paint tray is that it spreads it out so it stays cooler and reacts slower.

[JohnSw]

t's been awhile since I posted any updates so to continue the build...

Once the exterior of the sides, rear wall and lower part of the front wall were epoxied, the wall assembly started. Here is the rear wall braced in position. If you lok close you can see that the exterior skin extends beyound the wall framing. This allows the end of the wall to be covered. Any extra will be routed off later.

[JohnSw]

This photo shows the rear wall, the side walls and lower part of the front wall joined.