kasper

And the query on undercarriage position is relatively variable for you - you can make up a second set of undercarriage tripods to move the wheel positions later if you find them too far back.  Moving 100mm would be relatively easy with a set up you have drawn.  

All else fails consider a tank in the centre section front wing behind the spar.  Yes the weight for the fuel is behind the pivot so when standing still you have to lift the weight on the control stick in addition to the wing weight but as soon as the wing lift starts it disappears. 
 

you could have 10-15l up in the wing and a 5l tank further back from the current position to get your cofg movemenet reduced full to empty fuel

1 hour ago, Marty_d said:

I would have thought the Pipistrel Alpha Electro would have met their requirements.

Possibly.  But it’s still very limited range and the battery is very expensive and change is a hassle plus you’ll need 4-5 battery packs per airframe to keep it flying constantly as a trainer and it will never cover the military training syllabus - it’s not in any way aerobatic. 
 

think outside the box.  An aluminium air battery has far lower cost than lithium and much greater energetic density - but it has to be recycled and not recharged.  So a battery weight the alpha has could be replaced with an aluminium air battery giving near 3!times the power.  
 

If I was the military a system of plugging in for 1.5hra of aerobatic on a  Good airframe that is then battery out and replace with new and have all the old ones recycled would be better than large banks of recharging highly expensive and chemically able to burn batteries.  
 

and recycling an aluminium air battery is possible - you add electricity to covert the oxidised aluminium into new aluminium and you go again.  In effect the end point of the aluminium in a battery of this cycle is the baulxite you started with as ore from the ground … but already refined and sepretate from spoil.  

34 minutes ago, facthunter said:

Something I've been thinking of for a  while. Your  rear wheels look too far aft of the CofG This could make landing  difficult  so ask about. Better to do it now than later. Nev. 

Not sure I agree on this one ... the CofG of the aircraft is not on the CP of the front wing ... it is between the CP of the front and rear wings based on their shared load of the lift provided at touchdown/takeoff.  as a rule of thumb most fleas are considered safe if their CofG is at around the 25% of combined chord of the two wings plus any gaps. 

That would put the CofG only just in front of the main wheel of this design.

To correctly work out the furthest rear point for the CofG you need to calc the lift splits front/rear accounting for all interwing impacts on the lift achievable from the rear wing from the front wing

Fortunately is generally is the case that the front wing lift becomes critical first and you work off the max lift the front wing will produce at max AofA and that sets the lift split between front/rear and you have a safe point.

Never forget - the flea/tandem wing is really a canard and front wing dictates the minimum speed and the lift split and CP posiutions of the two lifting wings sets the effective angle of attack for the fuselage and from that you can work the overall CofG and the approx landing/takeoff angles that will then dictate which wheels touchdown/takeoff first.

eg for the HN290 and 293 tailwheel as designed they naturally three point in the landing config because on full back stick in the hold off the fueslage adjusts with reduced rear wing lift to touch the tailwheel just before the mains - equally on takeoff the mains lift before the tailwheel as the front wing lifts them off before the rear wing can lift the tailwheel.  NEVER try to 'wheel' land or 'wheel' takeoff a tailwheel flea - you will find you need to be over 70knts to get the damn tail up and you do not want to be anywhere near the ground at that speed with a short coupled undercarriage.

Lots of fun with pous but I would strongly disagree that the main wheel positions for this one are at all too far aft.

Or thermal solar direct to liquid hydrocarbon fuels to use in existing IC engines.  An example fo the technology spin off from research out of Zurich:

https://synhelion.com/technology

May be years away but if more countries around the world price carbon into hydrocarbon from crude oil this cycle becomes not only possible but price competitive.

And I wager that is will always be easier to fill an airliner with liquid fuel to burn in existing engines than it will be to get all the infrastructure and equipment change required to move over to battery/other stored electric forms of running an airliner on electric alone - the energy density of hydrocarbon liquid fuels is just SO high it is not funny.

6 hours ago, duncan_rtfm said:

I'm confused.  The heat distortion temperature of West system is 50 deg C..  Bote Cote is 55 deg C???

I can only say what I've experienced. T88 out performs bote cote when I have used it.  

9 hours ago, walrus said:

Kasper, regarding flap asymmetry, in the absence of an asymmetry cutout circuit, I was taught always to extend flaps while straight and level. That way you will sense a failure as an uncommanded roll. If you extend flaps while turning you may not sense the failure until too late. 

Nothing new there.  I extend flaps on downwind and then on base and final. I cannot recall ever extending them during a turn. 

My concerns with asymetric flap are not on extension - I expect to see/feel any asymmetry as I extend the flap. 

My plans have always been - as were taught to me in AUF training last century - was to talk myself through the flap extension and positively confirm to myself both extension and pitch change as expected with being prepared to stop extension and retract if not happy - then go around and do flapless.  As flap extension always starts at circuit height I know if things are starting to go wrong with flaps I have height and time to deal.

My concerns are for either flap retraction in part or asymmetric once on final. 

My experience with an LSA55 Jab flap handle popping out in the early days scared the bejeezus out of me as it was uncommanded, unexpected and unpleasant.  That was WAY back in the Jab airframes history when the flap detents were just fibreglass and not even an ali plate ... the holes wore and out popped the flap handle with a spectacular drop from the air.

All I can say is if I was unexpectedly on final with asymetric flap retraction I am kicking in any and all rudder and dealing with either an untidy arrival (if very late final) or removing flap and powering up to go around.

The website is a pretty horrid mess that RAAus know they need to fix. 

I'll start sounding like a broken record.  Call RAAus and ask for membership and they can do it over the phone.  No doctor cert required and you can get on with building. 

Sorry all but you are out of date with inspections and out of touch with 95.10 which is different. 
 

both 55 and 10 have 4 inspections since the last tech manual. 
 

10 does not have the same permits and test flying.  It’s just registered and away you go. 
 

and whilst an inspection is standard L4 any L2 can be specifically authorised to do an inspection- that can be for. A specific single airframe or all of a type of aircraft depending on what the tech manager is feeling like allowing and what is asked for. 
 

basic rule - talk to tech office and all the mish mash of out of date and cross type discussions disappear 

But let’s be a little more reflective. 

spar varnish has been used for decades before epoxy came along and when not exposed to uv it’s stable for 10-15 years.  Polyurethane is similar.  Inside a uv reflective fabric wing it’s fine. 

people are not used to recovering fabric wings every 10years or so and maybe should - you still want to go in and take a look.  I’m. Up to my third look inside the sapphires wing to keep track of the structure. 

an experimental single seat airframe is just that experimental. I’m happy if my airframes get 10 years use before I review/recover/scrap or retire them 

and can we speak about the elephant in the room - old age.  Most builders are not spring chickens. My flea airframes and the single seat trike will be owned and flown by me only. I designed them. I fly them and they have no value as aircraft just as residual parts.  If I started a new airframe today it will take me five years to finish it and I will have 15 years of flying it before my flying life becomes spectator only. 
 

if Duncan is building a personal one off flea type and is near 70 yo it’s unlikely he will be doing a first life refurb on the airframe and saving $2k on epoxy looks a reasonable choice

people can’t understand how my airframes cost so little … second hand expensive bits and low cost new bits with risk all on me.  Simples.  

1 hour ago, jackc said:

The only way to know that is, IF RAAus made a statement concerning the legal liabilities it’s members could be subject to?

I guess the constitution may have the answer?

Simple and clear. 
 

memebr liability is limited under the corporate structure to our investments in the company plus $1 is liquidation. 
 

so any law suit is basically limited to the value of the building we own in Canberra as it costs more than $1 for a liquidator to send you a letter of demand for the $1 you are liable for. 
 

director liability is their problem.  It’s a company they that is how it’s been run for the past few years so leave it to them to have cover.  

1 hour ago, jackc said:

Well,   maybe there needs to be audit checks on aircraft self certification, IF there is no audit regime in place by any organisation responsible for the relevant aviation sector, then it’s negligence on their part.

Ask the FAA how the MAX fiasco went for Boeing?

The car industry seems to do it better 🙂

 

https://www.infrastructure.gov.au/vehicles/legislation/certification/vehicle_certification.aspx

Jack you are talking apples and pears.  Either you want a certified by the government regime as a necessary step to have public safety OR you have recreational flying with lower standards as the risk to the public is limited and the risks from a societal perspective is acceptable. 
 

if you want an audit of LSA self certification with an “out” for the manufacturer because the govt said it’s ok the you are scrapping any and everything the raaus and it’s predecessor orgs have fought for for the past 40yrs.  
 

sorry but if you want fully  certified aircraft go to GA. Accept the costs and accept the restrictions.  
 

LSA was never intended to be the same as certified GA and if you thought it was you were very misled in that belief. 
 

LSA is trust your manufacturer not trust your government- if your manufacturer disappears you become an orphan airframe.  If your manufacturer told fibs you live with the consequences of those fibs and go back to the importer/manufacturer.  

1 hour ago, jackc said:

I might suggest there could be RV-9 and Piper aircraft in the same boat, only meeting MTOW with an underweight pilot and enough fuel for 2 circuits, yet have 2 seats and are RAAus registered?

It would appear the Bristell fiasco is a result of ‘self certification’ ?  A system proven to never be reliable in many cases outside the aircraft industry, and maybe in it?

But you are missing the whole point of LSA manufacturing - its self certification by manufacturers of not just compliance with the design standard for the type but also self certification of the individual airframes they manufacture and maintain.

So-

IF a manufacturer tells fibs about the performance characteristics of the aircraft in the design certifications and is caught out ALL airframes get grounded.

IF a manufacturer tells fibs about an individual airframe meeting the design standard then THAT airframe gets grounded.

My understanding was that the initial concerns (from wherever raised) were that the spin characteristics may not meet the performance characteristics of the design standard do it was potentially a ALL airframes get grounded.

However, when they did a check of the spin characteristics they also did a check on the airframe they were looking at and found additional certifications concerns being POH errors AND an unmodified from factory airframe that was SIGNIFICANTLY over the empty weight it was certified by the manufacturer to be and that weight made the use of the POH to determine CofG made the actual safety margin minuscule thin AND operators were likely to exceed legal MTOW based on the invalid empty weight

Overall if faced by that - even if you were dobbed in my RAAus  or provided with a strong steer to look in that direction by them the onus and liability for the errors (and the losses to the manufacturer or importer resulting from the errors) sits squarely with the manufacturer.

Very simple really - the errors were made by the manufacturer and have to rectified by them to get the fleet flying.

Bristells may be able to fly again  ... but if I were an owner with an empty weight plane that is higher than I was told at purchase I would be getting my lawyers to sue the importer/manufacturer ... 

25 minutes ago, duncan_rtfm said:

As you say - the 23xxx is very thin.  Not a lot of meat there.  Perhaps my initial choice of the 747 might be a better choice, and my larger than average wing (6.9m, 5.7m span) will compensate for its relatively low ClMax?

 

My router bits arrive this afternoon, and I'm itching to begin cutting ribs...

 

Duncan

Well for your purposes based on those wings I would say CL max will not be critical.

If you are looking at a 300kg MTOW with something in excess of 12m^2 of total wing.  Even discounting the rear winglift loss due to downwash and lower AoA when the front stalls you are looking at a landing speed in the 30's is my guess regardless of what section you use.

Plug in the router, find a nice fat section that has low 1/4 chord pitch moment with minimal movement in moment with AofA that will allow you a good spar depth up at around 22-24% chord and plug it to the cnc and go.

Mr Benz ... Planey is showing his age and interests.

For example The WWII Benz engines in the bf109/me109 were fuel injected and that was a functional advantage compared to the merlin carburetted engines in the spitfire and hurricane ... until the orifice was added to the carburetor on the Merlins  ... google merlin and orifice if you dare 😉

 Fuel injected engines are generally not impacted by neg G  .... a carbi with a fuel float bowl will be  ... the fuel pick up comes from the bottom of the bowl and in neg g that bottom is full of air so not good for engine running

Nobody has ever flown the Fraser section sucessfully in a flea.  Plus that undercamber in the front is not constructionally easy to achieve in a farbric wing.

I'll not attack the person but the single flea built with that section was wing sized to his 'claims' and hell it failed to deliver - big time failure to deliver.  Very few people I know want to be in a very short coupled aircraft on small undercarriage going as fast as you had to to get that little monster off the ground ...  I would not have been worried about the pitch moments but rather how little lift it achieved compared to the claims.

The NACA section 23112 was on one of the HM293s I flew and it was no better or worse than the HM293 section on the original 1946 drawings from Mignet that I have flown the same day at the same airfield in France.

NACA 23012 is quite a thin section ... the flea bike will not in honesty be a fast plane so a thicker section allows lighter structures for a given strength of greater strength of a give weight

If you want to think about it the front wing is really a flying wing - the sectional choice open to you are any/all sections that have been used successfully in any flying wing that is not reliant on pendulum stability ... I'll point to to Martin Hepperle and his sections - google it.

The sections he has designed are primarily for models but have been successfully used in a few man carrying flying wings - hang gliders and two different sailplanes to my knowledge.

In terms of flying wing sections strange as it sounds the Horten IX jet from WWII has three rather nice sections - the mid span section has nice physical characteristics for fabric wing construction and was tested in the wind tunnel back in the late 40's ... technical papers on the section and the tests are available and can be used to compare to other modern sections (NACA sections are not modern .. they are just well published and available)

John Ronsz has done a couple of sections used on flying wings and helicopters that you could consider but helicopter sections tend to be too thin to be constructionally viable in a flea.

Lots of options.  My HM293 under construction is using a section not previously used on a flea - I'm using a flying wing section - and that was chosen not just for low 1/4 chord pitch movement but the ability to put a light/strong spar within the wing at the chord position where I needed to.

Medicals are not the end of the world.  Both ppl and RAAus are pretty ok on medicals. 

But you really need to decide which way your going now.  You are up to the first closure on your fuselage and you really should be working with an inspector now and agreeing what they need to see and when.  Plus what pics they want taken when they are not there but will be available when they do inspect. 

Call RAAus and ask to talk to tech office.  They are operating remote so it will be a call back but they can and wil tell you what they will require even if you're not a member

And forum rules require not attacking a person but the topic.  
 

spacey had a run in with auf more than 25 years ago and has not acted on many offers of assistance to rectifying the issue he has. 
 

Raaus tech are Approachable helpful and well meaning.  Unless you want to do something that is on the edge of what is permitted they are great to talk to and deal with.  
 

and to be open - I’m saying that from a position of having multiple run ins with tech office over the years and not particularly agreeing with the directions raaus tech seem to be going.  I may disagree with them but they are good at supporting and helping get outcomes for the vast majority of items that they deal with. 

If you intend to register it raaus then the costs during construction are similar for inspections if you find a friendly raaus person.  More expensive if you go with a business running l2 who gets approved to do your inspections. 
 

Once it’s registered the annual costs are higher intbh longer term with raaus because you have membership plus registration annually.  Once registered with casa your costs to operate year on year are lower IF you have your saaa maintenance course ticket.  
 

id ask the first question - what pilots certificate/licence do you have?

that is a good clue which way to go.  You can then decide to accept the costs or not.  
 

either way you should decide NOW because you need to get your inspections planned and the person sorted now.  
 

you should have an inspection before permanently closing any structures or any inspector is going to be less comfortable with what your are presenting.  
 

8 hours ago, APenNameAndThatA said:

So, the throttle is the throttle and the mixture is the choke. Obvious to me NOW... Thank you so much for posting. 

Ish

the throttle butterfly is the throttle because it is downstream of the Venturi and is restricting the amount of mixture admitted to the cylinders but not changing the mixture itself. 
 

A choke is a form of mixture control because it it upstream of the Venturi and regardless of throttle position it changes the air/fuel mix. 

in an aircraft engine the mixture control is actually adjusting the opening in the Venturi that is admitting the fuel. 
 

to put it against a common two stroke carbi - the Bing 54 from your rotax 503 and 582

1. The throttle is not a butterfly valve but the sliding barrel.  And the throttle barrel has a tapered needle moving within the main jet off the bottom of the slide.  Has the advantage of giving a more even mix change and volume change with throttle movement …. Two strokes are more sensitive to mix changes and have the ability to eat pistons with ease.

2. there is no choke butterfly and instead there is a secondary fuel transfer route that has a simple on/off stopper lifted by the choke cable.

nice video and great photography 

just like all the trike out there - variable hang points.

Just be grateful I did not suggest an electrically operated hang point movement for the front wing - very nice on the trikes I've flown with that but it is a bit overkill for a single seat flea.

For me in a trike its a little more constrained ...

I have laminated paper map in the knee bag with the plan in black chinagraph on it and use a red chinagraph on the clear plastic for actual - I can then see variance in actual from planned.

I have the airfield plates or mud mad drawings with frequencies in the clear pockets on the bar mits and have a chinagaph on a lanyard attached to the mits to update or note running details on them - generally new frequencies/squark codes on left and QNH changes and fuel use on the right.

On top of that I have a Avmap Geopilot II moving map colour GPS on the dashboard - its nice because its got nice easy to use with gloves on joystick and buttons - no touchscreen because I have yet to find conductive gloves that work on tablets and in open cockpit flying as gloves.

 I have been playing with a tablet and planning software but as I say in a trike I just can't get it to be as safe (not departing through the prop) and easy to use as chingraph and sleeved plastics.

Over to the other trike pilots - what do you do for planning and flight progression management?

29 minutes ago, skippydiesel said:

True! - Nothing personal but if you inhabit one of the "great powers" of the day you will be criticised (hopefully with some objectivity) by those that do not - thus it has always been.

OK - I'll admit it, I am engaging in thread drift ...

But as I have lived, worked and flown ultralights/microlights in Australia, the UK, the EU, the USA and Colombia I have had the joy of seeing local views and perceptions from a variety of perspective and in several languages.  Many similarities on nationalism and national pride exist in all countries about their own systems/aircraft but it is a very clear difference have perceived in terms of the degree of nationalist view from within the USA to the rest of the world when it comes to ultralights/microlights/LSAs.

Well if you are reconsidering the wing  ...

All semi modern pous I have flown (14,290,293,360,1000,1100 plus non-Mignet pou layout) have an issue with the trim on the front wing.

They nearly all have nicely put very low cp movement sections on the wing so up to stall the stick load is linear to angle of attack/load with a significant increase in load at the stall as the cp moves.

BUT nearly all have put the pivot point in front of the cp and have a constant pull load on the stick.

I have flown with bungee trim to restrict the stick load in the mid range of the flight envelope and also with a fixed trim tab on the front wing to achieve the same unloading of the stick

BUT if you are looking at redesign and redo on the front wing consider exactly where you put that pivot point to minimise the trim load.

Look at the graphs for your chosen section (or change your section choice) to put your pivot at a  point that will be minimally in front of the most forward point the cp is likely to be at in normal operations - usually occuring when at minimum AofA. 

You will then find the pull force in flight much less of an annoyance than it otherwise would be.

eg the HNM290FB has a pull force that is distracting for longer than 1 hours flight

I think you will find the pull force likely to be less than ideal at 22% of chord pivot.

To work out the expected pull force you will need to work through the entire airframe calcs as its one of the last numbers that pops out after you have worked through lift splits fore/aft and the sectional AofA for the selected airspeed.

And as a reminder - the pou layout is a cannard and the rear wing is at a significant apparent AofA reduction due to downwash from the front wing so the actual load on the rear wing is amazingly low so you generally have to estimate a massive differential between fore/aft wing loadings/area.

Have fun