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Tips, Techniques & Info

The Down Draft Sanding Box
by
Ironsides
with contributions from Gord Schindler, Skip Pothier and Fred McClennan

Introduction

Like many modellers, you probably have a small workshop in your basement.  This is usually a cramped area that you have somehow managed to declare your space.  Most likely, it is right next to the furnace, probably because nobody else in your family wants to be next to the furnace.  In winter, that makes it nice and warm and the noise from the fan motor and blower gives you some "white noise" that gives you some "tranquility".

But, did you ever notice how fine dust is drawn magically to the furnace and how it manages to go all the way upstairs?  Did you ever notice that the layer builds up after you sand your latest project?  And how about that fine white powder that floats around when you sand the spackling?

Does your wife have a problem with your sanding dust?  Here is the solution.  A down draft sanding box.

Concept

If you sand over a box that has a down draft, the dust will fall and be trapped in the box.  If that down draft is supplied by your home's built-in vacuum, then good portions of that dust, especially the finer particles, will be sucked away forever.

If you don't have a built-in vacuum, then you can derive the suction from a Shop Vac®.  However, unless you can find one of the new "silent varieties", you will have to wear ear plugs to deaden the noise.


digifoto by Gord Schindler

Construction

Assuming that you have a built-in home vacuum, install an extension into your shop.  Dead easy, just make sure you mock up all the pipes, elbows and wall plug-in before you use that glue - it sure sets up fast.

You could be a hero and make this all out of nice, expensive wood.  But, the simplest way to do it is to go to Home Depot® and buy a plastic box for less than $10 that is designed to store rolls of gift wrap.  The box is approximately 33 inches long, 15 inches wide and 6 inches deep..  You might want to buy two as it is just right for Monokote® or Ultracote® or any of the other covering material.  But I digress.

At the store, buy yourself an extra four feet of the 2 inch built-in vacuum pipe and an end cap for one end.   If you don't already have some, buy yourself enough 1/4 inch hole pegboard to cover the top of the box.

Cut the pegboard so that it drops down into the box and sits about one inch below the top.


digifoto by Gord Schindler

Take a 2 inch saw tooth drill bit and cut two perfect holes at each end of the plastic storage box, with the centre about one and a half inches from the bottom of the box.

Insert the pipe so that it runs the whole length of the box.  Cap the end away from the vacuum outlet.

Run the  flexible hose from the pickup tube to the built-in vacuum wall receptacle.

Measure the length of the pipe that will be inside the plastic box.  Drill holes about 3/8 inch diameter every four inches on opposite sides of the pipe, but staggered so that there is a hole every two inches on one side of the pipe or the other when viewed from the top.


digifoto by Gord Schindler

Make standoffs  that you can glue every 6 inches to the bottom of the pegboard to stand on the pickup tube.  In the view above, the pick up pipe has been rotated from the horizontal to show the holes.  In addition, one plastic standoff in shown in the centre.

Equally, you could to run 3 or 4 wooden dowells from side to side to support the peg board.  Simply  drill holes in the sides to hold them and then silicone them in place

Thread a plastic tie down through holes at both ends of the pegboard so that you can lift up the pegboard to vacuum out any residual dust.

Fine Tuning     by Fred McClennan

The vacuum pipe needs to be sealed to the box with silicone sealant.

The sanding box isn't a 'vacuum attachment'.   You want a high volume draft moving through the vacuum pipe, not a high vacuum.  The vacuum pipe should be drilled sparsely at first.  After assembly, fire up the vacuum and hold
the hose close to the vacuum pipe.  If the hose tries to 'grab' the pipe, you don't have enough holes or the holes aren't large enough.  Drill extra holes until the hose no longer tries to 'suck onto' the vacuum pipe.  Listen
to the vacuum itself when you do this . . . it'll tell you when it's moving enough air and not trying to collapse the pipe from vacuum.

The box needs to be partitioned into three compartments to equalize the draft across the length of the box and prevent the area nearest the hose connection from trying to do all the work.

The 'test' for correct draft is done with a sheet of paper.   Dropped flat from above the box, it should settle directly and not float off to one side.  It should flatten out immediately, not 'eventually'.

Lastly, the sanding box won't get "all" the dust.  Balsa dust, particularly the very finest sort created by finish sanding with 200 grit or finer paper, can float in the air for days.  The box will nab the vast majority of balsa
dust, but don't expect it to turn the place into a 'clean room'.

Operation

Plug in the vacuum and sand over the box.  The plastic box edges are soft and will not damage soft wing parts etc.  If you want extra protection, slip half inch pipe foam insulation along the top edges.


digifoto by Gord Schindler

Once you have accumulated quite a bit of dust, bring your wife down into your shop.  Point out with glee the obvious collection of the dust.

Reward

Carefree winter building and no dust problems.  Sure, and every day is a perfect flying day.

 

version 5 dated 21 Feb 2002