Magnetic Building Board
An attractive project for a Sunday afternoon.
Like many of you, I have a backlog of kits to build. At least three of them are ‘built up’ wings and one or two are even built up fuselages too. My workbench is pretty solid and mostly flat with a monolithic (and sacrificial) slab of 18mm (3/4") MDF (medium-density fibreboard) on top. It’s fine for day to day model work and other DIY tasks, but its not really smooth enough or flat enough for building a +1500mm (60") wing panel for a scale glider where a few millimetres of difference between each end could mean five degrees of wash out or in. Add to that: MDF is a hard material, so pushing modelling pins into it is near impossible. The end result is that the workbench isn’t ideal to build traditional wings on.
Thus, I have been putting off and actively avoiding a few builds that I really should JFDI (AKA just do it already).
Requirements Gathering
In the build queue, there’s the 3.6m (142") Pat Teakle Salto (~1/4 scale):
- Requirement #1: A board that will take an 1800mm (70") span wing panel.
There’s also a little 2m VTPR glider from Silence Model with very small and fine tips needing accuracy to maintain the correct span-wise section:
- Requirement #2: A board that’s flat.
My current build bench is in the garage / shed that’s watertight but unheated and the existing workbench is dual-use between modelling and other DIY activities:
- Requirements #3 and #4: A moveable / portable board and a board that’s dimensionally stable in varying conditions.
The final consideration is practicality; this is a hobby, not a business:
- Requirement #5: Quick and easy to source and build using ‘off the shelf’ components wherever possible.
Imitation is the Greatest Form Of Flattery
The idea of magnetic build boards has been around for years. A quick Google returns dozens of forum threads and posts as well as a few retail offerings.
The concept is pretty straightforward: a sheet of steel on a flat base and some magnets.
Where there is some variation is the type of base and thickness of the steel.
My Version
Following Requirement #5, I wanted to build mine ‘in a day’ with parts from the local hardware stores. A limiting factor was the steel sheet: I could only find sheets in 1000mm x 600mm (39" x 26"), so there was always going to be a join. I picked 0.75mm (20 AWG / 1/32").
Meeting multiple Requirements (#3, #4 and #5) using MDF sheet as the base board was an obvious choice. At 18mm x 1800mm x 600mm (3/4" x 71" x 26") it’s a pre-cut size that’s well stocked in the UK and is pretty stable in most conditions — especially with a coat of paint to seal it.
I wasn’t keen on using glue to attach the sheet to the base board as a didn’t want to introduce any thickness variation caused by high or low points in the adhesive (Requirement #2). However, because the steel sheet was in two parts (to meet Requirement #1 and #5) the solution was to use some aluminium angle along the edge to clamp the sheet in place, sandwiching the sheet between the angle and the MDF. The angle section would serve and additional purpose in helping to keep the edges neat when stored elsewhere. (Requirement #3)
The top edge received a similar treatment, though in that case, it was a full-width wood strip as I’d run out of the angle section!
As the sheets were a pair of 1000mm (39") wide panels whereas the base board was 1800mm (71") wide, there was an excess to trim off one end.
Finally, the selection of magnets proved a little tricky: most of the forum posts and other ‘how to’ articles suggest using square ‘ceramic’ (also known as ‘ferrite’) magnets with links to US suppliers. In the UK however, it's quite hard to find square or smaller rectangular ferrite magnets. There are lots of circular, but very few others. The next choice was ‘rare earth’ (also known as neodymium) magnets which are readily available from Amazon and other retailers online or otherwise.
A drawback of these small but very powerful magnets can be they crush the delicate balsa we often use (and skin!) as the ‘snap’ into place or together, so care needs to be taken! Having explored options and read many posts, I settled on two shapes:
- Rectangles — a pack of 10 sized: 20mm x 10mm x 5mm (0.78" x 0.39" x 0.2")
- Cubes — a pack of 25 sized: 10mm x 10mm x 10mm (0.39" x 0.39" x 0.39")
In Use
The first project to land on the board is the starboard wing of my 2m VTPR project from Silence Models of France, the Akhénaton V². The range of magnets on hand were ideally suited to keeping the ribs both upright and secure on the board during gluing and initial layup. I also used a few ballast weights to ensure things were snug to the board across the span.
One thing that was clear however, was separating the magnets from the base board could be tricky at times. Add some ‘tails’ to them with the label printer. It was an easy fix and doesn’t seem to impact their attraction or alignment. I may do some more experiments as time progresses.
Time and Costs
Remembering Requirement #5, the only ‘custom’ part of the project was trimming the steel sheet down from 2000mm — both sheets combined — to 1800mm. Other than that, all the other materials such as screws, angle section, tools and the like were off the shelf or on-hand anyway.
The whole build took less than two hours (excluding travel) and all in, ~£100 ($120 USD, €113) including the magnets. The costs could probably be reduced with more efficient materials sourcing, but I bought the MDF and steel off the shelf from retail hardware stores as a Sunday afternoon project.
So was the magnetic building board project worth it? I’d say “yes!”
The Proof
Here’s the first pair of wings off the table. Lining up their leading edges, trailing edges and 1st, and last ribs, there’s barely any perceptible variation; further, both are still flat after building and skinning the top surfaces.
Next Steps
As mentioned, I may revise the magnet tails once I have used them a bit more and see how they last. I will also probably expand the number of magnets I have. The current stock was sufficient for this wing, but a larger wing would likely need more.
My current focus for the board is wings, but many of the source articles also show fuselages being built. There are several plans for 45 and 90 degree templates, with magnets attached, to aid such builds. With time, I may build a few of those too.
And finally, the steel is ‘raw’, so that will need some paint or other maintenance to prevent it rusting. On the whole, the other tools in the workshop fair pretty well as it’s not inherently damp, but prevention is preferable to fix! Another option would have been galvanised sheet steel, but none was available off the shelf locally.
If you have any questions feel free to add them in the Responses section — you get there by clicking the little 💬 below. Thanks for reading and good luck!
©2023 Marc Panton
Resources
- The Panton Anthology — The complete works of Marc Panton as they have appeared on the pages of the New RC Soaring Digest.
- H–101 Salto Short Kit from Pat Teakle. — “The return of the H101 Salto is a welcome return with a new fuselage mould and new wing section (HQW 2.5/12) now with scale trailing edge air brakes…”
- Akhénaton V² 1975 MM par Silence Model. — “Nouvelle version du célèbre planeur de voltige acrobatique dessiné par Ludovic Clavier. Un kit plus poussé pour des vols extrêmes…”
- Magnetic Building Board-a-palooza — A pre-configured Google search for all things magnetic building boards. Go wild.
- Realth Bar Magnets Magnets: 20mm x 10mm x 5mm from Amazon. — “Helpful to shower door” or for magnetic building boards.
- Wukong Magnets: 10 x 10 x10mm from Amazon. — “Powerful enough to meet your daily needs” or for magnetic building boards.
- Conversion Chart for Millimeters, Decimals and Fractions from Electriduct.
All images by the author. Read the next article in this issue, return to the previous article in this issue or go to the table of contents. A PDF version of this article, or the entire issue, is available upon request.
