Ian

I try to minimise my carbon emissions. However flight doesn't have a good alternative to carbon fuels. I'd love a plane which could fly on biodiesel which is a reasonably feasible projects. Did you know that there's a special page on wikipedia dedicated to climate change conspiracies. https://en.wikipedia.org/wiki/Global_warming_conspiracy_theory However as I've stated I like to use profligate amounts of energy by travelling for pleasure, buying manufactured goods, swimming in winter and flying for fun. However as a someone with a vaguely scientific bent I don't see this as mutually exclusive to a zero carbon emissions philosophy. However to continue down this path I think that nuclear is the only real answer. I believe that scientists are generally smarter and more believable than either football players, politicians and hairdressers. They put their theories up for public scrutiny and accept the criticism. They generally get promoted and remunerated for being right, not being popular or charismatic. I also accept that at some point in the future we're going to be asked to demonstrate that we're carbon neutral and will get taxed when we're not. On the other hand because you think that this science stuff is all junk you'll probably just get old and bitter.

Bill Gates likes private jets and thinks that dumping CO2 is bad. So he offsets his carbon footprint. https://www.ladbible.com/news/technology-bill-gates-spends-7000000-each-year-to-offset-his-carbon-footprint-20210215 So does Jeff Bezos. https://www.cnbc.com/2021/11/05/why-bill-gates-and-jeff-bezos-buy-carbon-offsets-how-they-work.html So it might be reasonable to enforce a carbon neutral policy on emission for all travel, but you can start with the rich.

I suspect that you're making it a bit hard for yourself, you don't need to work in volumes, just pressure will work. There's a column of air above every square meter of land the weight of that air creates a force of 101.3 kPa. Divide this by gravity and you have about a ton of air above you. The % by weight of air that is CO2 is 0.063 and we want to reduce CO2 by about 0.25 This works out at about 16.2kg per m2 of CO2 or 4.4 kg m2. So for above your farm of 1500/2.2 hectares 110454 tons of CO2 or 30123 tons of carbon. There's a fair margin of error but you get the gist. This is similar to the pissing in the pool argument. Yes I understand that people do it however most people don't, and while it isn't grand, it's better than the alternatives. Also it's not the "global warming true believers" its what science says. You know that thing that allows engines to run, planes to fly and medicines to work. It really is that good. Your views are in the same camp as the "world is flat", "that vaccines cause autism", "The UN and Bill Gates vaccines programs are sterilizing women" and "fluoridation is a communist plot". Take a look at https://en.wikipedia.org/wiki/List_of_conspiracy_theories#Science_and_technology It has some corkers that you might want to believe in. I'm not out to hurt your feelings, but if you say dumb stuff I'll let you know, and I'm letting you know. 😉

I'm not really sure of your point here. Are you saying that burning either Coal or Uranium makes the world hotter as a heat input. Appreciate the allcaps but nuclear is the safest form of power generation, this includes deaths from Chernobyl and Fukushima . https://www.altenergymag.com/article/2020/03/what-is-the-safest-energy-for-the-future/32904 I agree that what we're seeing in the Ukraine is cause for concern however the deaths are being cause by guns, bombs and bad people. About 14400 people have died so far in the war. None of them from nuclear power. This is a good example of perceived risk vs actual risk. It's a bit like the fear of flying. If you include greenhouse gas polution, coal is not cheap, none of the CO2 capture processes have come close to removing the carbon from the exhaust and they drive up the cost enormously. China is going nuclear, solar and wind in a big way. "Coal's Dead" get over it and move on. It's not smart its dumb. But we have gone a long way from the original topic of lead in fuel. Lead in fuel like coal and all the majority fossil is a dead technology. Find good alternatives and move on. Don't try to persist the status quo as this just causes more harm.

Fuel cost is a negligible input in nuclear. So efficiency isn't particularly important in that space either. However higher temperature plants can operate much more efficiently. Solar salt has been more expensive than expected when implemented. You're better off installing solar PV panels and heating the salt electrically for storage. Not to say that someone won't find a better way but no-one has become rich doing it yet. In terms of land usage. https://www.nei.org/news/2015/land-needs-for-wind-solar-dwarf-nuclear-plants

I was thinking something like this. It removes the residual humidity and lowers the risk of corrosion. https://www.aviationconsumer.com/maintenance/engine-dehydrators-engine-saver-prevails/

Peak efficiency is just that and tends to fall off pretty quickly especially with turbines. Solar cells are only about 20% efficient but the input is cheaper ;-). One of my recent surprises was the combined heat and power systems are less efficient at electrical production than their standard brethren. It's more cost effective and flexible to generate electricity more efficiently and buy heat pumps. Otherwise you need to force people to build close to power plants on tiny blocks. Coal, oil and gas are fossil fuels bringing carbon back into the atmosphere from millions of years ago. It cheap (excluding pollution costs), energy dense and readily available often near to where the power is required. Solar and wind are also cheap, however they are diffuse and intermittent. Wind as a resource is good for SA and Tasmania however not so much in other areas so you have Another way of looking at the problem is to look at the following https://en.wikipedia.org/wiki/Tûranor_PlanetSolar Nice boat but with all those solar panels it generates 93kW under the best rated conditions. I used to have a subaru which could output 200kW all day and night. Even with the streamlined hulls it can only cruise at 5 knots. Michael Phelps swam at 3.8 knots setting the world record. I love solar and wind and the new storage technologies. I just think that it's a bit of a fantasy thinking that they're going to sustain modern society in anything more than a bit part. I want zero carbon and I like to use lots of energy doing stuff like flying planes and travelling. Unfortunately I think that this can only happen if something like nuclear takes the majority of the load. Fusion's still a generation away unless someone cracks something like muon catalyzed fuision At the very least look what someone smart thinks about this subject. (They also point to the fact that old nuclear plants can only load follow slowly) https://www.withouthotair.com/c26/page_186.shtml He covers off on what is required for pumped storage to work in a country like the UK.

Is anyone using active extraction of water from the engine case? Ie an air pump going from the engine case to water absorbing beads to stop corrision?

One other thing, the way that markets work is that when things are plentiful they're cheap, when they're scarce they're expensive. We want people to invest in solar, however they'll make little or no return once there's an excess of power so investment in plant stops. The people storing power want to buy this power as cheaply as possible to store it however the solar farm operators need a return to recoup their investment costs. Do you install solar as a loss leader and vertically integrate or buy it on the market from the suckers who have already deployed the capacity. Essentially in the market the daytime cost of power will tend towards zero as more plant is deployed. If you have a business that is energy intensive which can run in this window go for it, however if you need constant power you're out of luck. This is the real cost of intermittency and its far larger than people think.

The term you want is dispatch-able power and nuclear can do this. The French have been running their reactors in a dispatchable manner for years and have demonstrated . Some newer reactors designs are inherently load following, by removing heat for power generation it increases the reaction rate. Actually have a look at that study and consider the impact of developing these sites. It would have a massive environmental impact. Most people don't remember the protests relate to damming some rivers in Tasmania however this proposes something with an impact 10 or 100 times the size. Like planes everything's a compromise and all of these proposal come with huge environmental impacts. Wind farms and solar in German can't be rolled out because of the environmental impact of the high voltage power lines and local protests. Australia is seeing similar protests as landowners are being asked to accept infrastructure that the cities want but they get no gain from. They don't want to run the powerlines underground because it's too expensive. The people in cities don't want to pay for this excess. Politician will exploit this divide. Yes they are however they're not free and they wear out, for example I just bought over a thousand Li Ion cells for a project from China. They're like car tyres in a few years they'll be shot and they'll need replacing. The tesla battery pack in SA is not economic in a daily cycling role however it makes money by: Getting paid for a power reserve function Delivering peak power when the prices is very high. That way they maximize the return on the infrastructure without wearing the pack out. I'm not saying that these technologies won't play a part however the scale of the problem is against them shouldering the bulk of the load. To do so would come at a considerable expense and consumers are used to things becoming cheaper not more expensive. Rooftop solar is good, however it generates power when after you've driven to work (in your electric car) so you either need to store it for charging in the evening, or transfer it across the grid to the powered car park.

Considering how dry and flat Australia I'm don't think that pumped hydro is a great idea. You need your holes in the right place and 99% of mines aren't. Look at the real capacity of Snowy Hydro2 in terms of Annual output and look at its cost it really struggles to stack up. To get your head around the scale of the problem have a look at https://www.withouthotair.com/ there's a downloadable book on the site. It is a simple read and gets away from stupid terms like "2000 households". It was written by David Mackay and amongst other things was chief scientific advisor to the UK government. Bill Gates has also written a good book on the subject, simple enough for most people to get their heads around the subject. Australia's electric energy consumption was 265TWh per annum. The problem with these systems is that they don't operate 24x7 they only operate efficiently between 10-2 so you have plant sitting idle for most of the day. Not great from a capital perspective. From a capacity factor point of view not very efficient even though the power source is free. Whereas with a permanent industrial heat source it can operates 24x7. It all depends on the cost of the plant v the inputs. You also need a carbon source as a feed.

There are a number of things which aren't mentioned in this article. Renew Economy is anti-nuclear so any article like this should be taken with a grain of salt. France is an energy exporter, it generally exports power to Germany and the UK and the rest of Europe. Normally it exports power at a profit. The argument is a bit like reserving Gas for domestic consumption in Australia. However we decided to sell our gas at prices lower than we can buy it. Water based nuclear power plants operate at lower thermal efficiencies than either Gas or Coal. This is simply the law of thermodynamics. Times of drought impact these types of nuclear reactors more due to available water an differential temperatures. Newer generation high temperature reactors don't suffer in this way and can be designed to be water free. France has some of the lowest Greenhouse emissions in Europe and Germany is the biggest emitter. France has demonstrated the ability to manage their nuclear fleet in a load following manner working hand in glove with renewables. The French stance on nuclear appears to have been a winner for them. Germany has undergone an abrupt turnaround in their public sentiment towards nuclear recently This is not to say that their aging nuclear fleet doesn't have problems, they need to standardize on a new design and roll them out in a manner similar to their first plant rollout where they achieve significant economies of scale and lowered production costs. But they are better positioned than Australia and their emissions reflect this. If we go down the path of electric vehicles we're going to need an enormous increase in capacity of the electrical system. Intermittent renewables are a great supplement but aren't suitable for industrial capacity or sporadic consumer demand. For instance the whole article relates to how painful the lack of availability can be, solar and wind are this to the core so going down that path will be painful. Hydro storage works well when it's wet however Europe is dry at the moment. Australia is always dry so hydro isn't an option. Australia is missing a huge opportunity to develop new nuclear plants and it's a pity because none of the other technologies quite stack up. Hydrogen's a bit of a joke, Ammonia was dangerous in the 1930, biofuels are good but don't have the capacity, batteries are expensive and wear out and fossil fuels don't work without emitting CO2. Fossil fuels are going to become a much smaller part of the economy going forward and maintaining a fuel with a known neurotoxin in this mix just isn't going to fly. So fasten you seatbelts and choose one which you think will last through the change. My bet is jetfuel because it's going to be difficult to find any alternatives any politicians love their travel, however an automotive fuel would also be a good bet.

Just thinking, given the cooling and anti-knock effect. Its sounds like a lean efficient climb be achievable? Using fuel for cooling has always seemed a bit extravagant. Also have you looked at the internals of the engine through a borescope, the water is meant to keep everything very clean.

Good to see it's being done. How are you finding head/exhaust temperatures, engine sound etc?

Does anyone have a figure on how many planes received a dunking in the floods? Are they written off or are they likely to appear on the market at some point?

Injection into the inlet plenum works. There are some pretty simple systems out there that just use windscreen wiper pumps and a light to let you know that water levels are low. You could also go for the STC version which is about $15000 or an off the shelf automotive system. I've been playing with an arduino to provide better gear up landing warnings. However it occurred to me that a very similar system could automate the whole shebang as well however YMMV. Simple rules like > 80% power turn on injection are reasonable. Water's pretty cheap octane improver. This paper suggests the following formula where w = water and f=fuel flow. So if you wanted to standard 91 octane rated fuel in an engine which expects 98 you could inject a water to fuel ratio of .42 and have the added bonus of the heads running significantly cooler. There's also the benefit of the cost savings. 91 is about $1.57, 98 is about $1.73 and avgas is current about $3.08 in Canberra at the moment. The main reason to include methanol/ethanol in the mix is as an antifreeze so if you're flying in conditions where icing is a concern it's a good idea. The key point to remember is that you only need to do this at low altitudes and higher throttle settings, so the water tank can be reasonably small depending upon your flying. In an ideal world it would be good if there was a combination of engine management system and a higher pressure pump connected to an injector to keep the water fuel ration in the right zone. Some car fuel injectors are stainless and can work for this purpose. The main risk is additional water making it's way into the sump. But normal combustion products include water and it should only really be used in takeoff and climb. Cruise and landing temperatures should clear any excess moisture. But in comparison to the damage and costs that high temperatures and detonation create it's a very manageable risk.

It is best to look at the Modulus of elasticity and the Ultimate Tensile Strength (UTS) or Modulus of Rupture (MoR). You may not get the desired outcome if one material loads to failure before the other approaches 20%. (Also below I know the ratios are a thousand or so out but you get the gist) MoE of Ironbark is 23GP, MoR 185 ( Ratio ~8) MoE of Hoop Pine is 13GP, MoR 90 (Ratio ~6.9) MoE of Balsa is 3.7, MoR 19.6 (Ratio ~5.2) From http://www.performance-composites.com/carbonfibre/mechanicalproperties_2.asp MoE Std CF 70 GPa and UTS 600 (Ratio ~8.6) MoE Eglass 30 GPa and UTS 440 (Ratio ~14.7) This might imply that a match up of Carbon fibre and Ironbark or Hoop pine would, from a structural point of view be better than E-Glass in a propeller. However you could also argue from a protective point of view the E-Glass would allow a safer failure mode by being having the ability to absorb failures of the internal material to an extent allowing a visible inspection to easily identify failures. It would also be under less load when surface damage occurs managing the associated stresses around the point of damage.

Bamboo is different again from wood, plus its a composite. I'd contact the manufacturer but you might scare them if you mention propeller. This paper might give you insight into the challenges. https://www.sciencedirect.com/science/article/pii/S1359836822001603 All woods (including bamboo even though its a hardened grass) use fundamentally the same building blocks and strength is somewhat proportional to density. However some timbers of similar density differ in strength as they use the underlying building blocks more or less efficiently. I'll leave you with the pictures to mull over from one of the earlier articles I posted. All the adhesives bar one produce wet wood failure. They also noted that they had issues with the RF application leading to lower strength of some test samples. This demonstrates Markdun's right relating to the fact RF can be more difficult to apply compared to epoxy and that it can introduce technical risk. A later test using acelylated timber shows the difference in treated timbers. I have searched for any studies demonstrating newer epoxy formulations resistant to the standard de-lamination tests however I've only seen published successes when surface preparation treatments are used. The manufacturers of the new improved epoxies might be able to point to successes in this area.

All, good robust debate and getting the facts on the table is always interesting. The key points which I was trying to make are as follows. Fixed pitch propeller design can be optimised to your cruise speed using freely available software. This should enable anyone with access to a large format CNC to develop wooden propellers optimised for their aircraft. Of course it is possible to do this by hand but your mileage may vary. When choosing timber for the props, there are a wide variety of timbers easily available in Australia which weren't available to manufacturers in Europe and the US. The thickness of the propeller can be reduced by leveraging stronger materials, increasing efficiency. However there may be a weight penalty. Similarly carbon fibre composite density is even greater. Also note that the bending moment increases as thickness decreases. Some Australian species have some interesting properties which while historically haven't been used in propeller construction might facilitate some design efficiencies. Generally resorcinol will produce a better, environmentally more resistant bond than epoxy. However joint quality, clamping pressure and minimum temperature are very important. It is far easier to produce a good bond with epoxy, hence why resorcinol has fallen from favour. As an aside I grew up (a long time ago) helping to build and occasionally sail moths out of Australian Red cedar. While soft and light it didn't rot and bonded well. Supply was always interesting though.

A couple of the articles that I posted relate to acetalysed timber which greatly reduces the likelyhood of rot as it reduces the water absorption of timber. https://www.accoya.com/au/acetylation-what-is-it-and-what-is-acetylated-wood/ Its available on the market but I'm not sure at what price. But I think most of us won't live long enough to care. Some of the eucalypts also have exceptional in ground durability as well. Red and grey ironbark, spotted gum, tallowwood and turpentine all have greater than 25 year in ground durability, above ground > 40 years. However they are heavy which except for niche applications such as propellers might preclude their use. There's been some work in Europe combining hardwood and softwood in laminated beams using the stronger woods on the top and bottom and the lighter weaker wood in the core with really promising results enabling lighter and stronger "composite" beams. The ratio that they found most beneficial was about 15% on the top and bottom of the beam or spar. A similar approach has been used with Carbon fibre or Fibreglass replacing the stronger timbers.

Apologies for joke in relation to forestry, I was trying to be funny but it may have missed the mark. I'm sure that structural analysis, material design analysis & testing etc is all part of the curriculum. However your formal training should make you appreciate the relevance of the research relating to epoxy-wood bonds. In a related query I was recently pointed to Robert McGavin who works for DAF in Queensland recently wrote "Barriers to the Effective Adhesion of High-Density HardwoodTimbers for Glue-Laminated Beams in Australia" which is an interesting read if a bit sad from an adhesive point of view. If anyone ever has an adhesive related question he's probably the right person to chat with. Resorcinol is a technically more difficult glue to use correctly which I alluded to, however there are also some PU and Isocyanate glue which also don't tend to exhibit the moisture related delamination issues which epoxy is prone to which are gap filling. From a propeller construction perspective it where the "joint" is simple from a topology perspective it makes sense to use the best adhesive. For a more complex joint where clamping pressure can't be applied epoxy might be the most suitable. However if the joint is simple, clamping pressure can be applied, and maximum durability and strength is required then in most cases resorcinol is a better choice. It also washes up in water which makes cleanup simple. Pretending that epoxy has obsoleted all other glues is somewhat misguided, not a golden hammer. What it comes down to is whether you'd feel safer buying a used wooden aircraft or boat built with epoxy or resorcinol especially if weather exposed. Resorcinol correctly applied has an outstanding record of maintaining a bond in difficult environment, epoxy not so much, but it is certainly easier for non-craftmen to apply and create something. If you clicked on the links associated with the strength of the timbers involved you may have seen that Ironbark in this instance was grey ironbark or "Eucalyptus paniculata". Rather than write the full botanical name I thought that most people would find the term Ironbark simpler. In relation to making propellers out of ironbark I haven't heard of it being done either however there may be some aerodynamic advantages due to it's superior strength allowing the use of lower profiles. In relation to your query about seasoned or unseasoned timber I suspect that this is a bit of a red herring. If you read the papers they all deal with seasoned timbers with specific moisture contents. The issue relates to moisture exposure post seasoning which impacts the adhesive performance across a variety of tests. While internal framing can be fully shielded this protection can't be provided to propellers. Stone chips, rain etc and the exposed nature of propellers makes it likely that the timber will be exposed to moisture ingress as you can't control the weather when flying.

This file didn't appear to attach however it shows a mechanism to reduce the degree of delamination which epoxy often suffers. Hydroxymethylated_resorcinol_coupling_agent_for_en.pdfHydroxymethylated_resorcinol_coupling_agent_for_en.pdf

Sorry for the long post but while you may have studied forestry you didn't study engineering. 😉 The key here is repeatable research rather than belief and proclamations from on high. Epoxy glues are fantastic however they shouldn't be used blindly and their limitations should be well understood, especially when using them in things which can cause you harm. I'm not saying that resorcinol is an easy glue to use, it's harder than epoxy to use however used correctly creates a better bond. I know that there are a lot of opinions in this area however the rigorous studies all point to poor bonding qualities with timber when exposed to moisture. While there are lots of different epoxy formulations chemically they're very similar and the bonding results are the same. Happy for you to demonstrate the error of my ways however I haven't come across any testing programs where epoxy bonds in wood exposed to testing have survived standard de-lamination testing methodologies except where a primer such as resorcinol is used on the wood surface. Epoxy is gap filling, easy to use and readily available. You just need to be very careful when using it as a bonding agent for timber, especially in harsh environmental conditions. Attached is the appendix of Classic Boat which provides a professional boat builders opinion, also attached another study which tested both wet and dry wood failure on four different glue types including epoxy. In the conclusion epoxy actually bond more effectively to acetylated wood, but not unmodified wood. The paper Hydroxymethylated_resorcinol_coupling_agent_for_en.pdfHydroxymethylated_resorcinol_coupling_agent_for_en.pdfHydroxymethylated_resorcinol_coupling_agent_for_en.pdfHydroxymethylated_resorcinol_coupling_agent_for_en.pdf Starts with the following quote which is relevant for anyone considering using epoxy for externally exposed structural purposes. Resorcinol Formaldehyde can be set at room temperature or can be heat set. Phenol Formaldehyde PF is a very similar adhesive to RF and is often mixed with RF to create RPF adhesives which can also set at room temperature. Australian Standards specifies Type A adhesives for marine ply, both RF and PF are classed as Type A. RF is more reactive than PF and in some cases will bond with timbers more successfully than PF. The main reason to use PF rather than RF is price. RF is more expensive hence its limited use in this role. Actually RF is classed as a phenolic compound, it just has more reactive groups enabling lower temperature reactions. The main reason for changing glues is price and ease of use. This page give a good overview https://www.matildaveneer.com.au/stuck-on-you-plywood-glue-bonds/ Type A (A-Bond) This is the strongest bond and is also waterproof. It’s produced from a phenol formaldehyde resin that is set under heat and pressure. The result is a permanent bond that can be exposed to heat, cold or wet conditions for a long time without deteriorating. This glue bond is used for structural, exterior and marine plywoods. Type B (B-Bond) Less durable than Type A, a Type B glue bond is waterproof but will deteriorate after several years being exposed continuously to weather. It is usually produced from a Melamine-urea-formaldehyde (MUF) resin. Plywood with a B-Bond is best used in situations of limited weather exposure, e.g. exterior doorskins and concrete formwork. Type C (C-Bond) This glue bond can only withstand occasional exposure to dampness and as such is most suitable for general internal uses. It should not be used for structural applications or wet/damp areas. This glue bond is usually produced from urea formaldehyde (UF) resin. Type D (D-Bond) Similar to Type C, Type D is also made from urea formaldehyde (UF) resin. D-Bond Plywood is best suited to internal uses where it is completely protected from wetness or dampness. It should never be used for structural applications. Australian structural hardwood timbers are significantly stronger on average than softwoods and hardwood species used in the northern hemisphere, using standards methods of testing strength which is measure in force per unit area. I'll list a few of the accepted timber strengths. Grey Ironbark Modulus of Rupture 185MPa Spotted Gum Modulus of Rupture 142MPa Rose Gum Modulus of Rupture 119MPa Hoop Pine MoR 90MPa Norway Spruce MoR 63.0MPa Sitka Spruce MoR 70.0MPa Radiata Pine MoR 81.MPa I could go on but you get the drift. Happy for you to add your own figure with published Module of Rupture figures. You can also get an idea of the timber strengths from the following link which shows European glulam beam strength vs Australia standard strengths https://ash.com.au/blog/gl-au-nz-vs-europe/ . The main reason for the difference is the fundamental difference in strength of the base material, Australian hardwoods being stronger lead to significantly higher engineered wood ratings. In fact there is growing interest internationally in using Eucalypts originally grown for pulp, for engineered wood due to its high strength. The main species grown in this manner is Eucalyptus Globulus which is also known as southern blue gum. An articles on this are below. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7078706/ I suspect that you've become confused by the concept of strength to weight ratio which is a related concept, which is relevant to airplanes but is a derived measurement based upon strength in MPa. Aluminium is not as strong as steel as it has and ultimate tensile strength of 90MPa in the unalloyed form and up to 690 MPa with special heat treated alloys whereas special steels have a UTS of up to 2690. However on a strength for weight basis they're pretty equivalent. But the point which is missed is that you can make a propeller from ironbark which is thinner and more efficient than one made from spruce while still retaining the strength properties in tension which is where most failures occur. Due to the increased Modulus of elasticity the propeller can also maintain greater stiffness with a thinner section. In fact based on the figures above you can have a stiffer propeller with half the thickness. ClassicBoatAppendix.pdf glue-comparison-strength2021.pdf

Resorcinol penetrates and chemically bonds with the wood, this is one of the things which makes it's bond so durable. Very early Mosquito's were built with casein and later versions with urea formaldehyde. https://en.wikipedia.org/wiki/De_Havilland_Mosquito#Fuselage . Problems were found (often due to loss of aircraft) when these aircraft were deployed in tropical environments. Urea Formaldehyde while strong is not as weatherproof as resorcinol. My understanding is that later Mosquitos and some of the Australian Mosquitos were built with resorcinol which mitigated many of these issues. Not saying that the build quality was high on the Australian planes but the glue was better.

I noticed a few people recommending epoxy as a lamination glue, there are better glues, epoxy has a poor record compared to other glues in relation to resisting de-lamination and glue-line failure. About all it has going for it is that its easy to use. Epoxy is good with fibreglass and carbon fibre but not wood. I'd be wary of a plane build with epoxy. The gold standard for wood glue is resorcinol, it is the glue recommended in most plane building standards and is also in the Australian Standards for commercial exterior glumlam glues. Basically moisture penetration weakens the epoxy-wood bond permanently even after drying. Is your prop likely to ever get a stone chip and then get rained on or fly through a shower? Resorcinol is the glue used in marine ply and was also used in WW2 to fix the Mosquito delamination issues in tropical environments. One thing to note is that resorcinol doesn't have gap filling properties and requires a relatively high clamping pressure which shouldn't be a problem when making propeller glulam blanks. Some isocynanate and PU glue also have good results however results vary across manufacturers and formulations. A lot of research has been done in this area I've attached one paper and the text from it is below. The research was looking at gluing acetylated wood, however the control was un-treated wood and the text relating to epoxy is pretty damming. An example of a primer is a resorcinol primer applied to the wood surface which chemically bonds with the wood surface and achieves a strong bond with the epoxy. Australian woods are significantly stronger than their northern hemisphere counterparts, for example ironbark has a tensile strength about 2x that of english oak (famous for it's strength) however they are difficult to glue, however this strength provides the ability to create a thin strong prop which is appealing. Again resorcinol glue appears to be about the best adhesive in this regard according to research done by the Queensland Government which is about the only Government agency actively doing research in this area which is a pity as from an engineering perspective these timber have great structural potential. Also if you're going to the trouble of building a propeller you can use the wonders of computer software to get an optimal design for a particular speed and generate a cad file and have a machine carve your blank. I think that I generated this using https://web.mit.edu/drela/Public/web/qprop/ but it was a while ago. Unless you have thousands of HP big paddle shaped things are far from optimal, thinner designs with an airfoil that goes towards a point will provide a significantly better outcome. Below is an airfoil generated to provide optimal thrust at about 160 knots with about 180 hp. glue-comparison-strength.pdf