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In 1930, articles and advertisements appeared in several Finnish magazines for a slide rule developed specifically for the lumber industry. The slide rule was made by Nestler and was patented in Finland (Figure 1)
The slide rule could be used for volume calculations, pricing calculations and saw pattern calculations, factoring in losses due to drying and the width of the saw cut.[2]
This slide rule is more complex than the well-known Nestler 31 Timber Trade Slide Rule[3] and also does not correspond to the Nestler 11H or 0116. Earlier, in 1929, Th. Wulff advertised the Nestler 31. In the same advertisement he announced a novelty: a "Swedish forest pole" for the price later asked for the Finnish Nestler (Figure 2). It is not clear whether the "Swedish forest stick" refers to a slide rule.
Figure 1: Finnish timber trade slide rule by Nestler. Advertisement by Th. Wulff in [1].
So the Finnish Nestler was almost twice as expensive as the Nestler 31. The Finnish Nestler is 25 cm long.
Notable are the half lower scale and the markings for the St. Petersburg Standard.
The St. Petersburg Standard is a volume measure based on 120 boards of 12 English feet long, 1½ inches thick and 11 inches wide.[5] A St. Petersburg Standard thus amounts to 120*(12 feet)*(11 inches)*(1½ inches) = 23760 feet*inch².
It is up to the reader to calculate how many slide rules can be extracted from 1 St. Petersburg Standard.
In a series of articles[6] the sawmaster Erkki Kalari discussed the use of slide rules in the timber industry. He also described the Finnish Nestler, but concluded that an ordinary Rietz is just as useful. The article in which Kalari discussed the Nestler shows a photo of the slide rule. Kalari suggested that in addition to the "gauge marks" for cubic meters in St. Petersburg standard (4,672) and English foot 1×1" in St. Petersburg standard (23760) more marks could be added:
21726 = French feet 1×1" in St. Petersburg standard
23074 = Danish foot 1×1" in St. Petersburg standard
7242 = meter 1×1" in St. Petersburg standard.
Figure 2: Nestler 31 and an announcement of a "Swedish forest stick." Advertisement by Th. Wulff in [4].
In retracing the value for the French foot, it turned out that what was meant here was not the normal "pied du roi" of 9000/27706 meters, but a French foot that was used specifically for the Baltic lumber trade and is 1/3 meter long. So the French have at least two feet, and the king's foot is smaller than that of a lumberjack.
Based on his comments, we may rule out that Erkki Kalari is the inventor of the Finnish lumber slide rule.
Searches in Esp@cenet, DepatisNet and PatentScope yielded no corresponding Finnish patents. Fellow slide rule collectors could not help in this either.
The Finnish slide rule appears in advertisements and catalogs until at least 1938.[7] The only evidence that this slide rule really existed is the photo in the fourth article by Erkki Kalari.
If you own a Nestler with a prominent half lower scale and markings at 23760 and 4672, please let me know!
Figure 3: Comparing the feet of a king and a lumberjack. (DALL-E)
References
References
“Metsämies: Suomen metsänhoito ammattimies yhdistyksen aikakauskirja” [The journal of the Finnish Forestry Association] nr.12 (1 December 1930) n.p.
“Suomen puu: suomen puutavara-ja paperimiesten äänenkannattaja” [The voice of the Finnish timber and paper industry] nr.22 (26 November 1930) page 374. In addition to the article, this magazine contains an advertisement by Uittokalusto O.Y. [A.B. Flottningsmaterial] for this slide rule without mentioning the name "Nestler" or the patent.
Nestler Katalog (1938) p.13
“Tapio: Suomen metsänhoidon ystävien seuran aikakauskirja” [The magazine of the Society of Friends of Finnish Forestry] nr.5 (1929) n.p.
Ir. J.C.A. Oortgijsen, “De houthandel in Nederland” in “Nederlands Bosbouwtijdschrift” nr.88 (August 1935) page 307
Erkki Kalari, “Puutavaramies ja laskuviivotin” [Lumberjacks and slide rules] in “Suomen puu: suomen puutavara-ja paperimiesten äänenkannattaja” [The voice of the Finnish timber and paper industry]
nr.7 (14 April 1934) page 136-140 (general, Rietz)
nr.9 (12 May1934) page 186-189
nr.13-14 (14 July 1934) page 260-263
nr.19 (11 October 1934) page 334-338 (about the Finnish Nestler, with photo)
nr.20 (26 October 1934) page 348-352
nr.9 (12 May 1936) page 200-208.
Note: before 1927, Erkki Kalari was called Erkki Gammal. Many Finns changed their Swedish-sounding surname to a Finnish name around that time.Uittokalusto O.Y. [A. B. Flottningsmaterial] Katalog 3, Helsinki (1938) page 22
A Dutch version of this article was published in MIR 91, December 2023 . Thanks to Jürgen Nestler, Timo Leipala and Andreas Fassbender for helping to find more information.
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