You may have noticed that we almost always use 30 lbs. high density urethane (HDU). We are sometimes asked why we use such a heavy board (30 lbs. per cubic foot) — after all, a 15 or 20 lbs. board is very easy to work by hand (and a little cheaper). In fact, when we are building a scale model we sometimes use 4 lbs. HDU — we can sculpt it using our bare hands!
In general, HDU (whatever the brand) is a versatile material. It cuts easily, there is no (wood)grain to contend with, it hold’s paint well, and it is very stable. But there is a downside too — it has no structural strength and the lighter weights are downright fragile!
When we first looked at HDU, 15 and 20 lbs. board was the industry standard. Then by chance, at a Letterhead meet in Minnesota, my father met Kellie Miller from Coastal Enterprises (the makers of Precision Board brand HDU). Dad expressed his concern at the fragility of HDU. Kellie just smiled at him, dug under the display table, and pulled out a sample of 30 lbs. Precision Board — “nobody uses this,” she said. At the time, Coastal Enterprises was the only company to offer such a heavy board (although it is more common now). In fact, we sometimes use 40 lbs. HDU if the project needs to be especially durable.
30 and 40 lbs. HDU routes at the same speeds as the lighter weights. Glueing pieces together is no different. Mind you, carving 30 lbs. HDU by hand is a challenge, we prefer to use an air powered die grinder — it is much easier than doing things with manual tools!
We keep a few small samples of the various weights of Coastal Enterprises’ HDU on hand. (HDU is rated by the weight per cubic foot and ranges from an impossibly light 4 lbs. up to an ridiculously heavy 90 lbs.) When we are discussing materials with a customer we sometimes pull out our sample of 18 lbs. board. We run a fingernail into it leaving a very visible mark every time. We explain that this is the material many sign shops use for a dimensional sign. Then we hand our sample of 30 lbs. board to the customer — they can't leave a mark on it... It speaks to the quality of our work.
Quality materials (and tools) are critical for quality work. And, in the end, our labor and expertise are worth far more than any other portion of a project. Skimping on materials risks damaging our long term reputation (and the value of our expertise), that’s why we use 30 lbs. HDU.
The 18 pound board in the picture above bears witness to the abuse it has taken, over the years, for the sake of a sale.