The Grand Design Momentum 397TH with the Happijac Option comes with two benches that face each other that fold into a lower queen sized bed and a moveable deck that holds a standard queen sized mattress that creates an upper bed. The system works well if two queen bunkbeds are needed; however, for us we only need one queen bed. What we needed was to convert the HappiJac lift in our Grand Design Momentum 397TH to an Office Desk.
The lower bed that is made from the chairs that face each other are too lumpy to comfortably sleep on and the default height for the top bunk that can hold a nice mattress requires a ladder to get into it. We decided we would be better off removing the chairs completely since we will never actually be sitting back there and remove the stops from the top bunk so it can be lowered to a normal height (no ladder required to get in).
The side benches are connected to brackets that has 5 self-tapping wood screws that hold them in place. Removing the 10 bolts per side removes the bench completely. We pulled them out and put them in storage. After the benches are removed there are brackets that are connected to the Happijac lifting system. We removed the 2 brackets from the door side by taking out a couple of screws on each bracket and they come off like a standard shelf. We left the brackets on the other side of the garage that will be used to hold a custom desk.
How to Fabricate the HappiJac Office Desk
The first part of our The HappiJac Office Desk build was to get some lumber from Home Depot. What will eventually be the top of the desk was cross-cut and rip-cut to size at Home Depot for free. They have a panel saw that cuts plywood perfectly straight. It is much easier for them to make these cuts than to try to cut a large piece of plywood with a circular saw. We don't keep a table saw in the camper 😉
After getting the panels rip cut I laid them on top of the brackets to make sure the length looked good. I made the desk as long as I possibly could without hitting anything when it was lifted.
The next step in the The HappiJac Office Desk fabrication process was to take the long 6″ boards seen in the pic above and to glue and screw them down along the edges of the main desk board. This process adds strength and height to the desk. The plywood is 3/4″ thick and the wood boards are 1/2″. Combined the desk will appear to be 1.25″ thick.
The picture above shows the 1×6″ boards in their final location. I initially cut them to be about 1″ longer than the backing board. I also mounted the boards all around the desk to overhang the edge by about 1/8″. To get a perfectly and level edge I will use a router to square them up with the top desk surface. Everything was glued and screwed together to create a strong bond. In the picture you can also see a couple of cross boards. Those will be used to connect to the mounting brackets in the coach. The desk parts were left to dry for about 2 days. It was winter and I wanted to make sure they had ample time to dry.
Creating the 3″ Corner Radius
I then radius the front corners. I did not want to walk by the desk and constantly bump my leg on a hard squared off edged corner. I've found a good radius for a corner is 3″. To me the nice gradual curve looks good and it isn't too tight to bend laminate around. To get a radius of 3″ I needed to create a 6″ circle. I will use a router to follow 1/2 of the circle making a 3″ radius. I used a cheap 6″ hole saw I found on Amazon to cut a perfect circle out of a scrap piece of 3/4″ plywood. This is the hole saw I used.
6″ Hole saw
The next step in the The HappiJac Office Desk build was to use a router to square the sides and to follow my radius template. Using a router with a patterning bit makes an exact duplicate of whatever the router is following.
Router Patterning Bits
To start I rounded off the corners following the circle I cut above. To do this all I had to do was to screw in the the 6″ circle as close to the edge as I could get them then used the router to follow that edge around making a perfect 3″ radius on the 3/4″ plywood. Then I removed the 6″ circles and used the router with the tempting bits to follow around the entire desk. This cut the boards I set to overhang by 1/8″ when I glued them down to be an exact match to the top.
Laminating the Plywood for HappiJac Office Desk
This is a winter project so I took the newly fabricated plywood desktop home to my heated garage. I had to find some laminate that had about the same color and texture of the wood in our Grand Design Momentum 397TH garage. After a long search on Amazon I ended up going with Formica. They make awesome laminates that hold up well and they have a big color selection. I ended up picking the color they call Prestige Walnut. This is the link to what I ordered.
Formica Laminate: Prestige Walnut 4ft x 8ft Sheet
The first thing one needs to do when laminating a countertop is to glue down the edges first. You may notice that the edge steps I have above are cut nice and straight. It is possible to cut the laminate with a utility knife and a straight-edge, but it is not easy. The cuts need to be the full 8″ length of the sheet. When snapping the edge where it is scored the laminate sheet can crack destroying it. Although a purpose-built tool can be expensive, it is always better in my opinion to get the right tool for the job. The next time I do a project like this I have the tool I need. I used this awesome laminate strip cutting tool.
Virutex C015L Portable Handheld Plastic Laminate Slitter
The pic above shows the first laminate edge glued onto the back edge. I always like starting with the back to get the feel for what I am doing. To glue it down I just bought some cheap rollers and laminate glue from Home Depot. It is easier to buy the laminate glue locally than it is to ship since it is considered flammable hazardous goods. However, this is the link to what I used on Amazon's site. You can order it. They just have to ship it ground.
DAP 7079825312 Gel Original Contact Cement Qt Raw Building Material
Building the laminate edge strips
The next step was to router the edge strips down to the exact match to the top and bottom of the desk. This part is fairly easy, but you do need to take your time. If the router gets out of control it can damage the laminate and hose the project. Now that the laminate is glued down it is NOT easy to remove and start over. This is the laminate router bit I used.
CMT 807.190.11 3-in-I Flush Trim Bit
It was a bit tricky to go around the edge, but I was happy with how it came out.
Gluing the top laminate down.
This is what it looked like after routing down the top edges.
One of the things to note in this project is that the desk can be moved all the way up to the ceiling in the garage. That will expose the bottom of the desk. I did not want to laminate the bottom of the desk, so I painted it with flat black stain. I used stain because it will seep deeply into the wood and will never chip or fade. This is what the bottom of the desk looked like after I painted it.
Mounting the Desktop to the HappiJac Brackets
The final step of the project was to mount the desk to the Happijac brackets. That part is fairly easy. I just used some 1″ long 1/4″ wood screws and attached the desk to the brackets. This is what the final project looks like.
The The HappiJac Office Desk project took about two weeks to complete. I had to fight with the weather and wait on shipping from Amazon, but overall it was well worth it. The desk looks OEM and it gives my wife and I ample room to work with great views out of the windows.