Alright I'll address all of this. Keep in mind, sure you could ski park on a 50/50 or a tour and they probably would a pretty fun park ski given how light they are, but the "tour core" is not going to be as durable as the "stock" core. Bamboo is just a stronger material. Losing grams is not free, but paulownia is a pretty good trade off. Paulownia is quite a bit lighter (less dense) compared to bamboo and is not as strong as bamboo.
kid-kapowpaulownia is wood that is used in lots and lots of skis (from ON3P, Icelantic, Moment, Line, and so on) and snowboards (throughout Mervin's range - aka Lib and Gnu) usually mixed with other types of wood such as bamboo, ash, maple or aspen. Its use is not limited to touring skis.
Most of what ON3P builds uses a 100% bamboo core. The only time paulownia is used is when weight savings is an objective. I can't speak to other brands but at ON3P paulownia is only used when the ski is intended to do well going both uphill and downhill.
kid-kapowIn this case I would assume that the extra thick bases took up the slack compared to other wood cores used in skis from other manufacturers or bamboo. There is also not a huge difference in density between bamboo and paulownia. Some claim it is the tree with the heighest strenght to weight ratio of all trees and others have found that has similar properties to poplar, the he most commonly used species of wood for ski cores according to 4FRNT. 4FRNT also specify that they add paulownia to poplar cores to decrease weight while also increasing the torsional strength.
The advantage of a 50/50 layup (thicker base/edge) vs the tour layup (thinner base/edge) is really to give better impact resistance to rocks, stumps, etc... The thicker UHMW and steel does slightly stiffen the ski, but it mainly adds weight and increases impact resistance. We were hesitant for a long time to build a ski with thinner base and edge since ON3P is predicated on durability, but we wanted to build a competitive touring ski and realized how much weight could be saved by going to a thinner base and edge. When we started testing the tour cores, torsional rigidity was a factor at the top of our mind, and torsionally the tour cores hold up to the stock cores. This has to do with the spacing of the bamboo stringers in the core, the mount plate, and the triaxial fiberglass.
I'm not sure about the weights and densities listed in that thread. If you go to wood-database.com, paulownia
is listed density at 280 kg/m3. Bamboo
density is listed with a range of 500-850 kg/m3. At ON3P we have found our paulownia to be slightly lighter than these figures and the bamboo in the lighter side of the 500-850 range. If you look at the elastic modulus, paulownia is listed at 635,000 lbf/in2 and bamboo at 2,610,000 lbf/in2. A real world example of this is how easy it is to break a piece of paulownia vs how difficult it is to break a piece of bamboo... bamboo just bends and paulownia snaps. In comparison to paulownia, bamboo is a little more than twice as dense, yet based on the elastic modulus about 4 times as strong.
kid-kapowSo based on my understanding paulownia seem like a realtively suitable core material for the use. So why do you strongly recommend against it? Have you had issues after use with your skis?
The reason I ask is not to call you, but but to understand where you are coming from. Especially as I would not hesitate to do anything with 50/50 ON3Ps that I do on standard layup ON3Ps. :)
I think paulownia is a great material and very suitable core material. I was pretty pretty blown away with how well it skied. I would just hesitate at using it in the park.. or any time the ski will be taking heavy impacts, I just know that bamboo reacts better to a folding impact. I have never had any issues with my skis nor have my friends... Its just what I layed out before that makes me want to steer people away from it. I'm sure you could get away with riding the 50/50 or tour in the park but I also think that 100% bamboo meets the conditions of park riding much better than paulownia.