Microlighters

Hi everyone,

Recently someone stated in a topic thread that the Bushbaby fuselage was fabricated from mild steel. Was this just a misundestanding or is it so?

Regards,

Henni

viewtopic.php?t=4973

"The only issue seems to be the extra 21 kg of mass on the nose of the 6 Vs the 4 cylinder Jab engine, given a 2 seater with a useful load of 300 kg – as per the Appolo fox (not sure about the Bushbaby – allegedly the airframe is a little heavier because its mild steel). Given that 100 litres of Mogas or Avgas weighs about 71 kg and I’m unlikely to fly with 2 folks weighing 200 kg total…this 21 kg would seem to not be a problem."

Yes the airframe is mild steel tubing and fabric. It is important to powder coat the airframe to enure no rust. The wings are aluminium spars and birch ply ribs and fabric.

The Kitfox uses Chrome-Moly steel on the the airframe which is much more expensive.

Hi Morph,

Thank you for your reply - now I know that mild steel is also accepted & approved for usage as aircraft construction material. (This sounds nearly too good to be true)

Keep well,

Henni

The BB is not the first plane to have a steel frame. It's been used for years. The Piper Tripacer/Colt is a steel tube and fabric plane and so is a Pitts Special

I am truly amazed! I always thought that ordinary mild steel cannot cope with the metal fatigue.

More questions please

1. Should any special welding process be used?
2. Who supplies such thin walled mild steel tubing?

Henni

Yes, the welding shop has to be an aviation approved welder. The Bush Baby is built in a jig and mig welded. It is a very neat job.

Monty at the BB factory also does do welding for non-BB clients as well (or he used to). He would be the best person to speak to and maybe he can tell you where to get/supply you some tubing.

The airframe is made up of a lot of triangular sections to give it strength. You must powdercoat it to protect against rust

This is my airframe

call him on 0ate2 seven54 340four

BTW what are you intending building

My eldest son has designed a two seater glider utilizing a steel tube/fibreglass body and wood spar/fabric coated wings. He is now scrounging for the money for the chrome moly or s/s tubing to start with the fuselage - man will he be exited about this news tonight which means he can start right away.

Thank you once again for the info Morph.

Regards,

Henni

Just a correction, the Bushbaby is welded with a Tig welder and not a mig welder. Huge defference. A decent one can be bought from Adendorfs or Unique welding supplies for arround R10.5k all inclusive.

Henni
Just make sure. Bushbabies are not made of normal mild steel that you get comercially. I stand corrected but 1010 rings a bell.
Pitts and Piper however use chrome-molly not mild steel. Huge difference in strength and weight between mild steel and chrome molly. Truely amazing stuff and understandable why it is so expensive.

MILD STEEL No. SAE 1010. Yep, sort of the same stuff all the old Pipers up to the Tri-Pacer is made off. IMOAHO perfect aircraft construction stuff. These Bushbabies are built like a bridge. As long as everything is properly tri-angulated, VERY strong. If you look at the way the BB frame is designed, all you see are tri-angles.

NOW. 4130 Chrome Moly tubing = BLOODY expensive. Reasonably difficult to work with, and much more prone to cracking on the welds. Also does not like to bend and the to be moered straight. No no, breaks or cracks.

1010, a little heavier, thicker walls to compensate, but a little more "Bendy" than 4130. So OK. We`re not going to be doing aerobatics in it, and we want to use local stuff to keep the cost down. Go for it :D

Henni wrote:Hi everyone,
Recently someone stated in a topic thread that the Bushbaby fuselage was fabricated from mild steel...

I wondered if anyone would pick up on that, I'm highly compressed Henni! Boet's exposition sounds quite reasonable, hell the triangles work for power line pylons and worked well for Barnes Wallace's WW2 Wellington bomber. Interlocking triangles being a well known, strength enhancing, engineering principle.

Does anyone know, what specifically is the weight penalty (or premium if you prefer) in actual kilos for the Busbaby's mild-steel vs the Kitfox's chrome-molly airframe?

Morph wrote:The BB is not the first plane to have a steel frame. It's been used for years. The Piper Tripacer/Colt is a steel tube and fabric plane and so is a Pitts Special

The Savage also has a steel frame as can be seen below.

Regards
John ZU-CIB

Hi everyone,

Thank you for all the feedback. Who sells this SAE 1010 stuff & is this also quite expensive?

Henni

Nick wrote:Does anyone know, what specifically is the weight penalty (or premium if you prefer) in actual kilos for the Busbaby's mild-steel vs the Kitfox's chrome-molly airframe?

Weight penalty I'm don't know but cost difference of R80K between the two kits Now that's a penalty

Jis, het julle ous daar in Gauties nog nie geleer van vuurmaak hout nie?? You can take that savage frame, have it sandblasted, replace all the missing components, and you have a flying aerie again :D Hell man, you can do a LOT of flying with R80k.










Now try THAT with a portaloo aerie. ( Hatcoatdoor&outahere......) :D