The Fleabike

[duncan_rtfm]

A quick question:
Yes, I know this has been asked and answered many times, but I'm still confused.

 

I joined SAAA half-way through their financial year because I wasn't aware that RAAus had people to help and mentor builders (their main thrust is in pilot training).  Since then I have learned that they do in fact have a building support program (although this is hard to find on their website).

 

SAAA have just billed me for the 2021/2022 financial year, and I'm not sure this is the way I want to go.  I'm building a Flea, and a watchful eye on my construction, as well as a guide to the necessary paperwork to get the plane into the air is what I'm after.  I have heard some less than complimentary stories about RAAus being inflexible and expensive.  Is this true?  And if I join RAAus, will I be able to call on the assistance of qualified people to get me into the air?

 

Sorry to be asking this again, but I need some help with all the political crap which seems to be the norm in and SAAA vs RAAus discussion.

 

Regards,

Duncan

[spacesailor]

Well, here,s a negative for RAA, no Information what so ever ,. Not even a letter to inform me that the plane l was building has been deemed unregistrable.

After it was given interim registration. 

spacesailor

[kasper]

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.  
 

 

[spacesailor]

Photo,s & more photo,s

How you can do photography whist building ?, beats me.

spacesailor

 

[kasper]

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. 

[spacesailor]

A little clarification. 

AUF registered said 95-10-1103 Hummel bird no problem.

RAA Deregistered it, with out ANY correspondence at ANY time.

I was informed by L2 on final inspection.

RAAus has my particulars, but to this day have never , other than ' membership renewal ', sent one item of information to me.

spacesailor

[duncan_rtfm]

OK, I have a PPL, gained in New Zealand about 15 years ago.  I understand I would need refresher courses in Nav, Law, Radio and probably a few others.  That's fine, and I accept that.  And I'd need some serious refresher stick time also.  I'm now 69, so medicals are going to be a problem I assume.

 

Duncan

[kasper]

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

 

[kgwilson]

I have a PPL but decided to go RAA as the costs were less when considering class 2 medicals & I am not getting any younger, now 71. If there is any small issue that CASA finds they don't like it can cost thousands and even when the doctors clear you CASA can still turn it down. The difference now is the RPL, and a DAME not being required as your doctor can issue a RAMPC which is basically the Truck medical. With an RAA Pilot Cert you self certify up to age 75 that you are medically fit to drive a car and BFRs are much cheaper. Other than that you can't go into CTR. Well you are not supposed to but I do anyway & have never had an issue even though my PPL is not current. Carrying passengers is not an issue with the Fleabike.

 

Maintenance and materials are much cheaper under RAA. Nothing has to be certified if you build it yourself. Keep a detailed build log with cross referenced photos & then there is the final inspection which you do yourself observed by a L4. I think the rules now include a pre cover inspection of the fuselage and possibly wings but I am unsure. When I built my aircraft (finished 2015) this was not a requirement. This can be any Lame so long as the RAA fee has been paid to register him/her as L4. From that point on no-one but you has to inspect or maintain your aircraft & you can modify it as required. Annual membership has just gone up to $275.00 from today with annual aircraft single seat rego now $93.50. Membership provides 3rd party insurance of $20 million and Sportpilot magazine plus other regular updates & support if needed. I have always had good support on the few occasions I have rung RAA.

[duncan_rtfm]

Thanks for the info guys.  I'll give RAA a call today.  I got Peter Leonard round a month or two back.  He looked the fuselage over, and was very happy.  He said he'd put me in touch with someone to walk me through the process, but that turned into some documentation sent via email only.  Since then I have built a second fuselage incorporating all the lessons I learned in the first one.  Very easy to see inside, however, even though it is now all but finished, because a number of panels are screwed on, rather than bonded.

 

Thanks again,

Duncan

[duncan_rtfm]

With regard to airfoil choice, it seems there are a number of contenders. 

1. The tried and true NACA23012
2. the supposedly superior NACA 23112
3. the 43015 (spoken highly of, but for which I can find no coordinates)
4. the F5Fras15 (lower Cm that the 23012 or 23112 above)
5. and out of left field somewhat the NACA747A315 (it has a very low pitching moment, good stall characteristics, and extremely low drag)

I had been planning to use the 747A315, but the F5Fras15 is very attractive.  I particularly like the rock-steady CP position, and the low Cm (0.05 in the cruise condition)

Any thoughts/advice/experience with any of these airfoils?

 

Regards,

Duncan

[kasper]

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.

 

[duncan_rtfm]

OK, so the Fraser airfoil seems a poor choice.  The only thing I am hesitant about regarding the 747 is it's low Max Cl (1.36)  Both the 23xxx airfoils seem to have a max Cl of about 1.5  Is there any value in something like a 23115?

 

I'm busy researching Roncz, Horten and Hepperle at the moment.

 

Duncan

[duncan_rtfm]

OK, so the Fraser airfoil seems a poor choice.  The only thing I am hesitant about regarding the 747 is it's low Max Cl (1.36)  Both the 23xxx airfoils seem to have a max Cl of about 1.5  Is there any value in something like a 23115?

 

I might just play it safe, and go with the 23112...

 

I'm busy researching Roncz, Horten and Hepperle at the moment.

 

Duncan

[duncan_rtfm]

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

[kasper]

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.

[duncan_rtfm]

Done!  Cut the rear wing ribs using the NACA747A315 airfoil.  Nice and fat.  A CmMax of 0.012.  We'll see how it goes.  Also cut the rib jig.  Cooking with gas!  Photos tomorrow.

 

Duncan

[duncan_rtfm]

Well, all ribs cut, and all four rib jigs cut.

 

This is the first panel.  Unfortunately, the entire wing half won't fit on my build bench.  Mmmm.  But since they need to be built separately, that's not an issue - just that it would have been nice to see the entire wing - especially since the last panel sweeps up and backwards quite dramatically.  Oh well.  The jig holds the ribs nice and square.  One thing I still have to do is to angle the square cut-outs for the drag/anti-drag spar.  You can see the fancy cut-outs in the ribs to accommodate the drag spar.  Quite sexy. The CNC cuts them at 90 degrees.  But not a big deal.

 

I'll be sealing the ribs next.  I was planning on using West System - but that's a very expensive option.  So I got some Polyurethane sealer.  I'll do that tomorrow.

 

Fleas generally have the pivot at about 23 deg or so of chord.  But since this is a tapered wing, I had to calculate the AC first, and then work out 23% of the MAC.  Again, no big deal, but easy to miss.  I'll also be attaching the pivot masts to a variable attachment, allowing the pivot to be moved from 22 deg of the MAC to about 24 deg.  Final positioning can be determined during testing.

 

 

[cscotthendry]

Before you decidenot to use the epoxy to seal the ribs because of the cost, consider this;

Once you put the covering on and paint the wings, it's going to be a very long time before you can ever access those ribs again. Isn't it worth the peace of mind to apply the very best sealant to the things that are keeping you from plummeting to the ground unexpectedly?

[Blueadventures]

1 hour ago, cscotthendry said:

Before you decidenot to use the epoxy to seal the ribs because of the cost, consider this;

Once you put the covering on and paint the wings, it's going to be a very long time before you can ever access those ribs again. Isn't it worth the peace of mind to apply the very best sealant to the things that are keeping you from plummeting to the ground unexpectedly?

I agree and would ask advice from the few very experienced wood aircraft builders, restorers, repairs for example Bert Perrsons at Caboolture or Nigel Arnot Boonah etc. 

[kasper]

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.  

[duncan_rtfm]

As usual, a sane and common sense response.

Thank you.

 

Problem is, though, I plan to live well into my 90's (yeah, right...)

[spacesailor]

Be Very careful on the roads then !.

spacesailor

[FlyBoy1960]

On 01/07/2021 at 8:51 PM, spacesailor said:

A little clarification. 

AUF registered said 95-10-1103 Hummel bird no problem.

RAA Deregistered it, with out ANY correspondence at ANY time.

I was informed by L2 on final inspection.

RAAus has my particulars, but to this day have never , other than ' membership renewal ', sent one item of information to me.

spacesailor

I do believe you need some clarification here.

 

the RA-Aus will register anything, registration is only one of the processes of putting an aircraft into the air.  Honestly, I could register a wheelbarrrow with a plank across it but that doesn't mean anything it just gives it a registration number. If you don't progress to the next step in the regisstration process your registration will automatically expire after I think 12 months.

 

The next step after registration is to get a certificate of airworthiness. The registration doesn't mean anything at all, it is the certificate of airworthiness which is the document that allows you to go flying. The certificate of airworthiness is available to the owner of a new aircraft after inspection by the appropriate authority, these vary from what I understand depending on the category of registration and the origins of the aircraft (e.g. kit built from an approved kit, factory built or designed yourself)

 

Saying that the RA-Aus deregistered your aircraft is not true, if you did not proceed with a certificate of airworthiness within the 12 months or you did not pay for the renewal of the registration then your registration simply lapses just like it would give you registered a car for 12 months and didn't renew it.    Remember just like a car, it has to get inspected and signed off before it can be registered and in some states it needs to be inspected every 12 months or whatever it is based on the year of the car and the RA-Aus is exactly the same.

 

 

[spacesailor]

I did not get that ' air worthiness certificate because the L2 didn,t bother with a plane, not in the correct category. 

Then the registration on the RAA list was removed.

No correspondence by RAA what so ever, 

I only found out about category 95-10. From kasper, on this forum.

So much for RAA looking after its members.

spacesailor