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Heartwood formation and eucalyptus

Dean Satchell's blog
Monday, November 26, 2012

Denis Hocking emailed the EAG committee with this on 26 November 2012:

Hi folks, Just a note on E. longifolia. Knocked over an 18 yr old specimen yesterday hoping to get some posts out of it. Only got firewood, hardly a hint of heartwood. It was a somewhat suppressed tree up on a dune, so not a top specimen, but disappointing. So cut down an adjacent E. globoidea of similar size and also suppressed, only about 3 growth rings of sapwood so plenty of heart. Don’t know how general this might be for E. longifolia.

This appears to be general for symphyomyrtus group species. Although my experience is limited I have found this applies to E. saligna, E. longifolia, E. quadrangulata and even E. bosistoana (although I’ve only cut down two 10 year old trees). There seems to be a certain age where symphyomyrtus species suddenly put on heartwood. I’d guess 25 years. I thought I had heartwood (appeared that way) in a 8 year old quadrangulata but 5 years later the whole thing was rotten. Not so with 12 year old E. macroryncha (stringybark, monocalyptus group), 5 years on the ground and the heart is still sound while the sap has completely rotted away. 10 year old E. sphaerocarpa (monocalyptus) only has 1 cm of sapwood and shows why the EAG needs to continue our focus on monocalypts and stringybarks. Of course there is also E. cladocalyx, a truly remarkeable species for heartwood, the symphyomyrt exception but not really related to what we know as symphyomyrts.

One of Jim Coxes 25 year old E. longifolia had fallen down recently and we cut it open, the heartwood content was reasonable. Ten year old thinnings had no heart. Ben McNeil just dropped a few 10 yr old quadrangulata and sent me some pics because he couldn’t see any heartwood in these, which aligns with my experience. Monocalypts have a narrow sap band. Even at 25 years saligna has a big sap band, frustrating for the saw miller, who wants red heartwood!

Wooden windows – a missed opportunity?

Wink Sutton's Blog
Thursday, August 30, 2012

Our house in Rotorua was built in 1969. It has single pane glass windows in wooden frames. Although winter condensation is only a minor problem, when it does occur it is confined to the glass. Our holiday home was built in 2009. It has aluminium frame windows with, by regulation, double glazing. There is still the occasional winter condensation but, in contrast to our Rotorua home, it now occurs on the window frames and not the glass.

Compared with wood, aluminium easily transfers heat and cold but eliminates the need to repaint or re-stain. Aluminium is also less likely to distort in later life. If wood could be permanently finished, and this eliminated the need to repaint or re-stain, the market for wood, especially for clears from our pruned radiata, could be enhanced.

In the mid 1990s I visited a factory in Sweden making impressive wooden framed triple glazed windows. The market for these windows was high-rise buildings. The windows were expensive but were well designed and were of a very high quality. They were very flexible as they could be opened both vertically and horizontally, obviously not at the same time.

Most impressive of all was that the windows were guaranteed for at least 50 years. All the wooden components were painted with what looked like an epoxy finish. Understandably I was not told what was used but I was informed that it contained a hardener and that the finish must be applied within one hour of mixing. A condition of the 50 year warranty was that the seal on the wooden window frames must remain unbroken. The window was supplied with a clamping structure so that the window could be permanently fixed in place without the need for any nails or screws.

I have long thought that New Zealand has missed a wonderful opportunity. We should concentrate on wood’s advantages, such as its low thermal conductivity, and develop ways to overcome any disadvantage, such as a permanent finish which eliminates the need to repaint or re-stain.

Such a development requires innovative thinking, a focussed and intensive research effort, excellent design, a great deal of capital and a major global marketing campaign. However, the financial rewards could be impressive. Is such thinking now beyond us? What other opportunities have we missed?

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Disclaimer: Personal views expressed in this blog are those of the writers and do not necessarily represent those of the NZ Farm Forestry Association.

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