Jabbies and 95 Mogas

[Wingless Nut]

Below is a copy from a (pdf format) letter sent by Jabiru, confirming that 95 Mogas may be used in Jabby engines. Les from Jabiru SA confirmed that it applies to 95 unleaded. All the while here was I thinking that those poor buggers flying Bantams had to use Avgas.

Australia’s Own – Light Sport Aircraft
A.B.N. 17 010 910 077
Jabiru Aircraft Pty Ltd Phone: (07) 4155 1778
PO Box 5186 Fax: (07) 4155 2669
Bundaberg West QLD 4670 Overseas: + 61 7 4155 1778
Australia Email: info@jabiru.net.au
http://www.jabiru.net.au
2nd September 2005
Ref # JL-21

To Jabiru Engine Owners,

For some time, Jabiru Engines have been approved to use automotive fuels with a RON (Research Octane Number) of 95 or above. This letter is intended to clarify which fuels are considered suitable in countries where AKI (Anti-Knock Index) is used in place of a RON number. RON can be approximated as AKI+5, so a fuel with an AKI of 89 would have a RON of
around 94, and would not be suitable for use in Jabiru Engines.

Jabiru Aircraft recommend using AVGAS in all models of Jabiru Engine wherever possible due to it’s guaranteed quality and performance. Where AVGAS is not available, automotive fuels with a RON of 95 or above, or an AKI of 90 or above may be used. However, operators must be aware that the quality and anti-detonation characteristics of automotive fuel is not guaranteed in the same manner as AVGAS.

Note that in addition to the above, operators of Jabiru Aircraft must ensure that the fuel they use does not contain an alcoholic additive (such as Ethanol) as these additives will damage
the sealant used in the fuel tanks of Jabiru Aircraft.

Regards,
Douglas Smith
Engineer, Jabiru Aircraft

[Thunderboy]

Its the other way to Rotax then if I understand correct.
With Rotax use normal mogas lead replacement and if you have to you can use Avgas

[Morph]

Its the other way to Rotax then if I understand correct.
With Rotax use normal mogas lead replacement and if you have to you can use Avgas

Thunderboy,

Rotax motors were never intended to be used for leaded and now lead replacement fuels. They were designed for Unleaded Mogas all along but can run of AVGAS with added costs and fouling of the plugs.

[justin.schoeman]

That is strange... I thought the mogas provision was only for the newer 'A' series motors? And don't most SA fuels have alcohol additives anyway?

-justin

[Wingless Nut]

Justin, I can't comment on the 'A' series motors, but the alcohol I would assume is considered harmful to the composite resin binding of the fuel tanks, in this instance. Most composite aircraft manufacturers make use of Two-pack cold cured vinyl ester/acrylic co-polymer resins, for virtually all components, including fuel tanks.

For info; Once chemically cured in the mould to the extent that the resin is touch dry (cured), the components are post-cured in autoclaves with heated air, or by means of infra-red baking. Post-curing is done at about 80° C for approximately 8 hours. Because of the limited curing window, post curing increases the chemical bonding between the base and the activator, by more effectively arranging these particles in the link-up chain ( the DNA chain of the resin, if you like). Similarly, Bulk fuel storage tanks at refineries and fuel depots are often coated internally by using the same technology to provide corrosion protection of the steel tank. The woven roving used is GRP (good old fibreglass textile), as opposed to Kevlar/carbon fibre used in aircraft construction. It is the post-cured resin in this case, that provides the resistance to chemical attack like alcohol in refined fuels and sulphates in sour crude. The alcohol content is supposed to be kept below 11%, if memory serves me right. Some refineries have been known to add as much as 20%. Post cured vinyl ester resin should withstand becoming a soluble, providing that the alcohol content remains within prescribed limits and does not exceed 60° C.

So it's fairly relative. Keep in mind that polymer based resins are also manufactured in various stages of refinement. Cheaper low-end resins are less suitable for purposes of chemical resistance.

[Morph]

Most composite aircraft manufacturers make use of Two-pack cold cured vinyl ester/acrylic co-polymer resins, for virtually all components, including fuel tanks.

Wow, next to my Silicon Coated, double laminar, syncopated valves that is one helluva description :D . But what does it mean

Are you saying that we are limited to the fuel that can be used in a planes engine because of the selection of materials used to manufacture the tank? Isn't that a bit like the cart leading the horse?

[Wingless Nut]

Yeah Morph, it's quite a mouthful! Simply put it's a 2-pack resin compound, whereby base and activator is mixed together to effect curing by chemical reaction. Much like the standard glass fibre polyester resins, but a whole lot more refined. Vinyl esters are generally more resistant to heat, chemical attack and mechanical damage. Co-polymers consist of more than one base polymer (in this case v/ester & acrylic) mixed with a single activator (which reacts with both) to effect curing. Depending on the critical nature of a desired composition (ratios), as well as to avoid self-polymerisation where 2 bases could chemically react, these co-polymer base materials are packed separately. This would thus be known as a 3-pack system (2 x base + 1 x activator). This term also applies to normal 2-pack systems, which require either a curing accelerator or retardant additive. Again, referred to as a 3-pack system.

If seen in the original context of this thread, yes the cart would be leading the horse here. Should one have a dislike for aluminium tanks due to potential corrosion problems, "plastics" would be the way to go. Employing glass reinforced composites for the manufacturing of plastic tanks is a heck of a lot cheaper than having injection/blow moulds machined. Blow moulding becomes viable if one produces these tanks in a "sausage factory" fashion by their thousands, as done for plastic containers, plastic jerry cans and fuel tanks of some cars. The sheer quantities justify the tooling (die manufacturing) expense. These tanks/cans are usually made out of polyethylene and is in no way affected by ethanol/ethyl alcohol.