Postby MalcolmDouglasPorter » February 23rd, 2015, 11:46 am
Hi Phil,
If you have jumped the gun, then that would be my fault for not explaining the undercarriage in detail. Previous photos have not shown the aluminium tubes, so I have added a photo of the components as they are at the mo, and as you can see, the paper tube is not standing alone.
Perhaps I should step back a bit here and explain the process to you from my perspective. I started this project using my knowledge of model making from many years ago, realising that ideas, materials and methods have changed in those years. I produced drawings that are incomplete because there were many things that I was unsure about. As this project progresses, things will change, some my original ideas being unsuitable for a large flying model. One of those things that has changed is the undercarriage. When I say changed, the original concept on the real aircraft is being replicated here, only with ideas to suit a model. I had many things to consider, and that main thing was the ability to make this in several pieces for transportation and or storage. It is a big model, 16 foot wingspan and ten foot long, standing about four foot height at the fins. I decided it would be prudent to make the undercarriage detachable to reduce the width. The measurement across the main wheels is ITRO three feet, with these removed the width is just over 20 inches. This concept itself produces problems that need addressing.
Before I started any serious work on this project, I asked John Rickett (the inspector) to have a look at the drawings to make any suggestions etc, which he kindly did. From this meeting I changed the sizes of some bits that seemed too small. He questioned the integrity of the undercarriage and I suggested that these are parts that can be re-made to a higher spec at a later date. At that time I had no real idea of how I was going to tackle this. Later, at the AGM, I had a chat with John about this project and the subject of the undercarriage came up. What he suggested at that time was that I should make the undercarriage as strong as possible, he didn’t suggest how, just that I should make it strong. So this is where I am with it. Whilst I can understand why you should mention that the winglets are a structural feature with a fairing covering it, in reality, for this model and the winglets being quite small, there is a need to make them as load bearing as possible. The spars are made from birch ply, as is the fixing block on the outer end, and the rest is lite ply. There will be two ¼ inch dowels to give some support to the olio frames, and a 3/8 inch location dowel at the fuselage end. You mention the fact that there is no structure at the fuselage end, this is because it is not yet there. Unlike the wing roots, which was the starting point of the design, the undercarriage is worked in reverse because I needed to establish its actual position at the fuselage, and this was easier to do once the model had physically progressed. I made some mounting stretchers for the U/C some time ago. There are four of them each just over a foot long, and are located at the bottom of the frames. You can see in this picture that there is another aerofoil section loose fitted to the tube. This will be let into the side of the fuselage, and the 1.1/4 inch gap between this and the outer stretchers will be filled with a solid (balsa) block. There will be no movement on this winglet.
The concept is simple, but yet to be proven. The undercarriage is rectangular, a tube at the bottom passing through the fuselage and the winglets, the two olio legs at the sides, and another tube from the top of the olios passing through the wing roots. This top tube will have a boxing around it that will fit into a slot under the wings and will not be seen. The load will not be borne by the wings. We should also consider that there will be sprung suspension, so assuming a properly handled landing, these springs should absorb the weight of the aircraft gradually? In the event of a heavy landing, we must hope that there is enough strength there to prevent any damage occurring? I would prefer to think that these winglets are “well engineered” rather than “over engineered”? Perhaps we should also consider that it is the combined effect of all the undercarriage components working together that produce the required integrity, not just selected bits. However, should the design or structure of any component prove to be inadequate, then it can be re-made.
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Attachments
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- RH Winglet.
- P2230037 (600x450).jpg (89.44 KiB) Viewed 10854 times
