Can I just ad a layer of bubinga to MDF desktop?

[Larry Rasmussen]

Hello all,

I'm an ok rough carpenter and cautious beginning furniture maker. What is discussed here is an irregular shaped desk, built into a corner amost works out to a triangular shape. Size is 7' long X 40" at the widest point. The 7' side and one end are supported continuously along the walls that form the corner. Where it bulges out in the middle to 40" will be supported by a floor to table drawer unit about 12" X 12" at that edge. Darned if I can get this new computer to decrease the resolution enough to post the picture. My old editing program just offerred it as an option. Besides the above description I'll add that the ends come out 20", one un supported and one supported by the wall. From there it just goes out at 45 degrees and meets in the middle with that widest point being 40" from the wall.

In case you're wondering my wife and I are always wanting to get on the computer at the same time so I knocked out this temporary MDF desk top and we picked up a second computer. After a trial period of 3 mos we decided it is a go for permanent installation.

I've got a decent size piece of 4/4 bubinga from a cancelled speaker project. I would simply pick up more of these boards, edge glue them for the table top and call it good. There has been no sagging on the 3/4" MDF but I think a single veritical support on the unsupported end would make it bombproof.

OK my questions. I've never built a table top. I can edge glue easily enough, undecided about using an edge bit, spline or dowels.

1. Any opinions on the spline vs edge bit vs dowels?

2. Should I use an MDF backer for extra stability? The edges will be double bubinga regardless- going back in a few inches on the underside. I am not sure whether the lamination of bubinga to MFD on the remaining single thickness portion would reduce the tendancy to crack or warp with the seasons or exaggerate it because the two laminated materials will react differently to changes in moisture level.

Any advice appreciated,
Larry Rasmussen,
Seattle

[Josiah Bartlett]

Don't laminate anything that thick to MDF- the bubinga will need to expand and contract with the seasons, but the MDF doesn't. This will crack the desktop.

4/4 is plenty thick and strong for the desktop, I would just support it properly and leave it all bubinga, don't bother with the MDF at all. Edge gluing will be plenty strong, with or without biscuits.

[David DeCristoforo]

"Don't laminate anything that thick to MDF... don't bother with the MDF at all. Edge gluing will be plenty strong..."

Seconded

[Larry Rasmussen]

Thanks guys. There is always a disconnect between me thinking about a project and overbuilding for no reason or in this case to my disadvantage and the reality of the situation. I wasn't sure about laminating the different materials but when started I looking critically at the mock up I am using now in 3/4" MDF I realized I could probably park car on it. Last few weeks I thought for sure I'd have to reinforce it somehow.

Regards,
Larry

[Paul Simmel]

>>> The edges will be double bubinga regardless- going back in a few inches on the underside.

You should somehow get a diagram or pic up, because it sounds like you will have some sections of end-grain you intend to band. If so, that's going to be a problem unless you float it (with splines at least). Like a bread-boarded table top edge which runs perpendicular to the wide grain.

[Dick Bringhurst]

Larry == Use "PIXresizer" its freeware. Its easy to use. Dicl B.

[Larry Rasmussen]

Paul thanks for that input and it looked like from a reply above someone thought I would be edging. I'm simply going to glue enough boards together to make the top, using shorter pieces where it tapers and start over but this time just going back same several inches from where cut edge will be and leaving the middle blank. Boards will be oriented the same way as far as grain goes and final shape will be cut after they are laminated. I'll let the end grain show, there will actually just be about 20" of true end grain one end, the rest will be half end grain cut at about 45 degees from grain line.

Ok I'm going out to the garage to glue up two short boards as described then cut and finish, make my final decision from there.

Thanks for the freeware tip Dick. I'm sure the capacity is somewhere in front of my nose but I'm not finding Vista that intuitive so far so will check out the freeware.

Larry

[Peter Quinn]

Larry, I've made a few tops out of bubinga and aside from the seasonal movement issues of gluing engineered material to solid wood bubinga is so darn strong I'd find it hard to believe the MDF would act as much more than additional weight. MDF will not contribute any strength as it has little to give, and bubinga doesn't need the help anyway. That's going to be a nice place to park your computer.

As to the question of dowels/splines/glue joint bits, take your pick. They may all help with alignment during glue up but none will contribute much strength and a good long grain to long grain glue up wont need any additional strength anyway.