Markdun

I definitely don’t agree with the view that resorcinol is a better glue than epoxy; but a lot depends on the epoxy- there are hundreds of different sorts of epoxy, of widely difference strength and hardness as there is widely different additives/fillers. So it all depends. Timber boats are almost universally glued together with epoxy, including laminated veneers, double diagonal plywood, strip-plank, laminated beams. Similarly nearly all timber aircraft built now are out together with epoxy glues, including laminated wing spars, wing ribs etc etc. In most cases the glue join failure when subject to sheer or tension is of the wood fibres either side of the epoxy, not the epoxy itself. An epoxy glue used for a wood propeller should have a similar hardness as the timber used and use an appropriate filler, like cotton fibres. I’d suggest a System Three or T88, ir even Bote Coat ‘Poxy Glue’ with a 1:1 mix ratio (harder to get wrong). These glues can be used in high humidity, unlike some others, eg WEST’s. The one draw back off epoxy is that it not UV resistant. It’s incorrect that resorcinol is used in the manufacture of plywood, marine or otherwise. Almost exclusively used are thermosetting glues such as phenol formaldehyde. The veneers and glue are layered in a press and then subject to microwaves to set the glue. It’s not worth ply manufacturers to stuff around changing glues.... they are nearly all the same. The difference between marine ply and others are that in marine ply the veneers are the same thickness and the sheet will bend the same when stressed lengthways or sideways. ‘Structural grades’ may have lower quality veneers and/or achieve the same bending length vs widthways by having inner veneers thicker. Any comment about Australian timber being stronger is just coddswallop. We have over 500 species of eucalypts and other hardwoods and around 100 or so species of softwoods/conifers. The variability between species and even within species is enormous. Like epoxy, when it comes to timber its horses for courses. If one wants to generalise one could say that the softwoods/conifers (gymnosperms) have stronger wood because in general the wood cells are longer and have overlapping tapered ends (toilet paper), compared to the hardwoods (angiosperms) where the wood cells/fibres are more like cylinders (the Australian newspaper). But it ‘all depends’. I try to use E.delegatensis (Alpine ash) for props, but this comes with densities from 300kg/m3 to 900 kg/m3. Or one of our gymnosperms, like Aurucaria cunninghamii (hoop pine) which is a bit soft for a prop (not so with 3 coats of epoxy), but also highly variable in grain characteristics .... some samples I’ve seen you would not build a box with it. Some ‘Ironbark’ species might be exceptionally strong, but they are also exceptionally heavy, frequently with densities greater than 1000kg/m3, ie they sink in water. Sitka is not strong, but it is light and stiff, which makes it suitable for aircraft building. If you milled up a piece of ironbark to be of equivalent strength as spruce it would be lots smaller, probably a bit heavier, but it would be really bendy.... totally unsuitable. My experience has been in successfully building the Jim Maupin designed Carbon Dragon which was almost exclusively Sitka Spruce, with carbon fibre tows laminated into grooves milled in the Spruce (including the 6mm square wing rib stock which had a 2.5mm channel routed which was subsequently filled with carbon fibre and epoxy). I have also built the timber Minimax made from Hoop pine, Pinus radiata, Douglas fir and various types of plywood. I also have Cygnet I built in the 1990s with epoxy laminated Douglas fir wing spars and hoop pine geodesic lattice top and bottom of the wings. Now over 20 years and 1000 hours without an epoxy glue join failure. I have also refurbished a Corby Starlet with resorcinol glue joints. Several wing ribs and some plywood resorcinol joints had to be repaired (with epoxy). I also have built several boats; the latest an 11m ocean sailing catamaran: all critical glue joints are epoxy except the strip planks which are powalina, of similar density and strength as balsa. This is glued with the moisture cured polyurethane expanding foam glue. Some of my deck beams are from our rot resistant cypress pine glued with epoxy, but as this wood is extremely oily you must wash it with acetone before gluing. Mark. BSc(Forestry)

I’m new to this idea of a low fuel warning as there is such a device on the J200 I’m restoring, and I am inclined to heave it overboard. My current and past aeroplanes didn’t/don’t have one. You know how much fuel you put into the tanks; you then checked this by dipping the tanks; you have an indicator of fuel level from either a window or a fuel level sensor; you have calculated fuel remaining from fuel consumption multiplied by time (either estimated or via a fuel flow sensor). It seems to me the only scenario is that fuel has leaked out... which would have been picked up in your walk around or from your EMS fuel flow high alarm setting. Don’t get me wrong. I’m a total Nervous Nellie when it comes to fuel starvation. In an unfamiliar aircraft I flew from Kal to Forres, I calculated estimated fuel remaining every 20 minutes and compared that to my flight plan and adjusting fit the headwind. This was from fuel burn estimates using 3 sources of data: from estimated fuel burn; from the unknown calibration fuel flow computer; from the wing tank fuel level gauges (one of which I had to do a ‘Taranaki’ repair on because the LAME found it too difficult...& of-course that doofer repair remains 5 years on). Yeh, yeh, more work, a bit autistic, but it gave me something to do, other than tick off each railway airstrip we flew over while the owner held the stick. We landed with 35l actually remaining compared to my estimate of 28l, from 100l at Kal.

Can’t see the rationale of holding an RAA-Aus fly in at a security controlled airfield.

Don has heaps of experience in the Thruster and I would defer to his experience. For my part I was never able to comfortably and predictably land a Thruster to how I would have liked. The issue I think is that it has exceptionally high drag and there is just not much energy to convert from kinetic to generate lift without stalling at the lower airspeed (42kts say); you really do have to push the stick fwd quickly to avoid stalling of the engine quits, and any flare on landing is very short because it stops flying very quickly indeed. Brendan, it was a requirement when I first learned to fly that any student would need to read and be knowledgeable of the PoH before they hopped into the aircraft. At a BFR a few years back I had to put the instructor off a little while to give me time to: (1) read the PoH; & (2) familiarise myself with the aircraft and its controls (with the PoH in my hand); & then (3) do a quick daily inspection for myself. There was no problem with this, and in fact I think she was impressed that I did so. The plane was unfamiliar to me, and after the BFR she said she was more than happy to hire the aircraft out to me. Always read the PoH. Mark

I always thought a ‘good landing’ is one where the pilot and passenger(s) can walk away after landing; and a ‘very good landing’ is one where the aeroplane can take-off again after the landing.

Yeh, OK. Perhaps its more how I like my plane trimmed and rigged.

No.... increased air speed, lift force on wing moves fwd etc. But in an aircraft with a 30hp motor, throttle position or power setting has v. little to do with speed, except on the ground.

Maybe the pitch forward needed to offset the pitch up from full thrust is built in for the Airbus so in case of EFATO, there’s no rush to push the stick fwd to avoid a stall like you have to do in a Thruster? Having built several engine out the front aircraft, I know that thrust line adjustments of the engine are usually needed in most aircraft builds to minimise throttle pitch effects, and this is true for low, mid and high wing aircraft. It all depends on the displacement of thrust from drag vertically. And you can make small adjustments with washers under the engine mounts (or failing that modify the engine mounting). It also depends on what the pilot finds acceptable. On my mid-wing Minimax I adjusted ad-nausea to the point where power changed pretty much affected rate of climb/decent but not AoA or speed. The Corby (low wing) tends to pitch up with the throttle over 100kts with its zero downthrust, as does the Cygnet (shoulder wing) despite its (from memory) 3 degree s of downthrust.

Airbus obviously need more washers on their upper engine mounts for more down thrust..... shouldn’t be big pitch change with power change.

OK, I’ll bite; why not fly on trim? On my Cygnet it’s a servo tab on the elevator with a Bowden cable control. And as Nev said, it’s also there for redundancy say for a broken elevator control wire (but I can’t see that happening) or the elevator control horn falling off from too much rust (it is down there in the tail which gets dragged through the creek and mud occasionally and more frequently the wet grass). As I said I’ve tried to fly a circuit on trim, but It’s bloody hard giving the pitch oscillations.

I’ve always thought flapping the controls (quick inputs) just adds drag (which can be a thing you want sometimes). Flapping the rudder definitely does add drag on a sail boat. The secondary effects of the rudder are pretty much immediate in my experience. I’ve flown many a model with just rudder (including aerobatics) or rudder and elevator; and I’ve practiced circuits with just rudder and elevator trim tab in the Cygnet (ie. hands off the stick). The issue there, for landing particularly is that when you move the elevator trim you get a cyclic pitch response... about 3 ups and downs before it settles down again.... so you would need a very long approach.

And pick the wing up with rudder. Do Jabirus have washout so the wing stalls near the wing root first? That could be why you are mushing down at 500fpm... maybe half your wing is stalled.

In the Cygnet, Wombalong is a fiddle either uphill or downhill. The Corby is much more demanding landing downhill..... its short coupled so is very twitchy, and tends (with my unskilled hand) to gain too much speed when you slip down through the trees landing downhill. Have to admit I’ve had to do several go-arounds and once actually used the brakes... and this is a 700m long strip! Despite the low 30kt stall, 50kt approaches seem awfully slow, particularly in the very thermic conditions we’ve been having recently.

Forgot to mention..... aide memoir for outlanding: DLOSSS. Direction into wind first, then length, then obstructions (fences powerlines gullies), then slope, stock and sun. But remember if you have that catastrophic money to noise converter stop at altitude you will cover more ground to get to that good paddock going downwind.

Don, in NZ (Paraparaumu) gliding a guy bunged off at about 100’ because he took off with his brakes out (he misinterpreted the tugs rudder waggle as a wave off). We lost sight of him behind the tower... he was over some market gardens (not good landing). He did do the 180 degree turn, but wholly shit, despite being low, and landing on the first bit of airport, he was fast with the downwind component. He rocketed through all of us ; caravan & gaggle of gliders) at the downwind end of the grass, crossed the GA bitumen runway and only just pulled up before some hangers. You have to be pretty desperate to land downwind off field.

Don, it all depends on what you mean by ‘best’. If you are punching into a headwind and ‘best’ is travelling the most distance into the wind across the ground for a given loss in altitude you need to go faster than best L/D, & going with the wind you’d want to go at minimum sink rate which is usually a bit slower than best L/D. With climb there’s a few other factors. For example you know my Cygnet with the 1835VW would climb best (fpm up) at a bit under 65kts, but it’s best L/D was 57kts. My guess is this is because the engine developed a bit more power and the prop a bit more efficient at the faster speed. With all the extra horses off the Jab2200 i haven’t really looked as climb is always more than necessary and why cook the engine going slow?& And what about the beauty of side slips and air brakes; you stop it or put them away and presto, the plane is in takeoff configuration.... unlike full 40 degree flaps. Not sure what went wrong when I inserted the video clip of the Cygnet landing. Mark

IMG_0879.mov IMG_0879.mov IMG_0879.mov Here is a similar technique. On my strip the trees are a lot closer, and in any breeze you need to punch through the tree turbulence (I use 1.5 x stall speed + 0.5 wind speed for my approach), and then you get wind sheer with little breeze below the trees. In light winds like in this clip where I took the son’s GF for a circuit, I had a bit too much speed despite the slide slip dropping down over the power lines and trees and landing down hill. No fancy smanchy airbrakes. 10m wing span in a plane with about 420kg TOW. IMG_0879.mov IMG_0879.mov

Yep, but it’s not just ‘error’; its also chance... that willy willy or an engine hick-up, could deliver the same damaging result. I know I was thinking in the Blanik those many years ago... i hope there’s no gust because if there is we are going to land heavy. And it was my instructor who got the full wroth of the CFI. On the opposite of the equation the discussion in the article also clarified why if your approach and flair is too fast why you float, float, float and have to go around, particularly if your wings are long.

I saw on YouTube a clip about practising flying slow at altitude to build skills for short landings where you land with significant power with high angle of attack... hanging off the prop so to speak. It reminded me of a training flight I did in a Blanik as recent solo pilot where the instructor had me land without using the ‘brakes’ but adjusting glider path descent by slowing down below best L/D and minimum sink speed, with a sort of reverse flair a bit above the ground to avoid a hard landing. Our landing was OK, and it was a good learning experience except for the bit involving the CFI yelling at me afterwards. I think the article below explains the situation pretty well and why one should be very cautious, no, scared, of flying on the bad side of the lift-drag polar. https://www.aviationsafetymagazine.com/features/behind-the-curve-2/

I use Leukosilk tape 50mm wide which you can buy from a chemist. Its simple and it lasts about 10-15 years, is white and can be spray painted with acrylic or Stits Polytone which not only makes it conform to your livery but also protects it from UV. I use it to seal the wing root/wing fairing gaps on the Corby and the rudder and elevator gaps in the Cygnet. On some hinge joints you need quite a complicated tape arrangement and this would be the case for the Frieze ailerons on the Cygnet and all the Corby control hinges. The glider people are full bottle on those.

Nev, in anything less than 5 Celsius I pull carb heat for start too....yeh, yeh the exhaust is not hot right at a cold start, but it heats up bloody quick. Mark

Interesting. A couple of comments. First, what you describe is not a choke, but the starting enrichening system of the Bing CV carb (semantics I know, but it can have a consequence if you think it is a choke) . Second, the large hole in the enrichening metering disc does not need to be exactly lined up with the hole in carb body; it only needs to be open to that port which is pretty wide...as it needs to be so as the metering disc is rotated and the largest hole is covered up the next size hole (less rich) is uncovered. Third, at 2000rpm the enrichening system would be mostly bypassed as it needs the throttle butterfly to be closed to work. That is why one needs the throttle fully closed for the Bing enrichening system to work... it provides both fuel and air for a rich fast idle. A mistake people can make is to think that cracking the throttle open a bit (like a traditional choke) will help start a cold Jab...it won’t. Unlike a choke it will make little difference if any at all once the throttle is opened. It needs a big difference in MP vs inlet air pressure (vacuum if you like). Try pulling the enrichener at cruise throttle settings and watch your EGTs.... you may be surprised that they increase or stay the same... mine increase a tad. So don’t expect it to provide more fuel at higher than fast idle rpm. I have heard of ppl drilling the largest hole in the metering disc a bit larger... maybe your mod is easier, but I’ve never had a problem starting my two Jab2200s when cold: turn fuel on, turn mags on, close throttle fully, pull enrichening knob while pressing starter... engine starts once fuel fills the carb bowl in maybe around 12 compressions (if fuel in bowl, then usually in 3-6 compressions). Lithium battery, so no problem cranking. Once engine fires up I let the enrichening knob go (it returns to off from the spring on the Bing) and adjust the throttle for fast idle.

SE2 broadcasts position, altitude, speed and course (ie. velocity), plus your call sign (for Ra-aus it Romeo XXXX, the Xes being the last four numerals of your rego). Its low output (20W i think) & is not picked up by Musk’s satellites. The 200W ADSB devices are picked up by satellite and they now cover the globe. So Airservices ground stations are becoming irrelevant technically (maybe not economically) at least for the full power versions. That said, my airstrip is around 30nm from YCBR and they cant see me with the ADSB. They can see me from about 3500’ with SSR transponder. The app ‘flightradar’ seems to picks up my SE2 up a bit higher ~ 4500’asl, but of-course that all depends on some guy with a receiver on the ground plugging the data into the internet. The main reason I got the SE2 was to help avoid frequent low (500-100’’agl )military rotor wing aircraft overlying my airstrip and a situation one day where I had to dodge one on downwind when landing & they dont listen to the area frequency. According to the guy I talked to in the airforce they use ,see & avoid’, & they declined my offer to land at my place for a coffee so we could discuss how to better avoid each other. I found out they generally do have ADSB turned on, but frequently with data missing, like call sign. However the SE2 has been quite useful,,eg. finding a friend flying his plane and also being able to avoid a rescue helicopter coming directly my way...i could see them and they could see me (changing direction and altitude to avoid them) but as my aircraft didn’t have an SSR transponder, ATC was none the wiser. Actually ADSB should reduce the need for ATC and controlled airspace because it puts the info directly to the pilots. It really is amazing how many other aircraft within 10-15nm you see with ADSB, that you wouldn’t know or see without it. People are probably aware that many drones have SSR transponders in ModeS, but increasingly they will be full ADSB. Im told the ADSB devices for drones are already down to the size of s small matchbox, only s few grams and can emit 200W ... much more expensive than SE2 though.

My wife tells me that once my head hits the pillow I take 5 breaths and I’m fast asleep until sunup. She takes ages to go to sleep worrying about the state of the world, children starving and abused, people mistreating animals and all the other women (the sisterhood) around the globe awake & concerned, or tending their awake hungry babies. I think all the crap I think about is so unimportant it’s not worth worrying about and lose sleep over.

Do you mean the potato jammed up the exhaust pipe prank? Don’t think it works all that easy at 8000rpm. I’ve only ever had an aero 2 stroke Diesel engine running backwards..... can’t recall whether I stopped it with a rag in the prop or my fingers in the prop....in the days of youth and control line model planes.