Jeremy Harris
Member
Some may have already read of my thoughts on the "balsa strip construction" thread (which drifted off-topic pretty quickly.........).
In short, due to the introduction of a new airworthiness deregulated aircraft category here in the UK, I'm looking to build something that meets the rules, but gets the best out of them, within my own constraints on size and cost.
The rule now states that the aircraft must weigh less than 115kg empty and must have an empty weight wing loading of not more than 10kg/m². MTOW cannot exceed 300kg. There are no limits on power, fuel capacity or speed.
Thinking this through, I've concluded that a design with a very low empty weight has some advantages, not least because it allows me to maximise the wing loading in normal flight. I've done a heap of trade-off studies and concluded that it's possible to get down to an empty weight of about 65kg, if I use a flying wing design fitted with a very light 20hp paramotor engine.
A flying wing is structurally efficient, particularly if I opt for a low aspect ratio (which will give me an induced drag penalty, but one I think I can live with). The small dimensions from such a layout will make trailering the aircraft sideways a realistic possibility, so meeting my requirements for low operating cost (hangarage here in the UK is expensive!).
I have done a couple of preliminary designs and have bought the parts to build a 1/5 scale flying model, correctly weighted and powered to give me an idea of the control and stability envelope (excepting the small (I hope) errors from the Re difference).
One thing that has occurred to me, both from a control standpoint and one of weight reduction (shorter control runs) is the idea of using a small all-flying, canard as a pitch control surface, rather than a conventional elevator in the central section of the wing. I can count the canard surface as lifting wing area, so allowing me to reduce the main wing area slightly. The weight reduction from the very short control run (the design is a pusher) is also useful. When you get down to designing at these very low weights even a few grammes saved from not using as many nuts and bolts gets critical!
I'd appreciate any observations anyone has on this as a concept. I know it's not new, but I feel that I'm really working in a light weight area where this sort of thing hasn't really been tried much.
Jeremy
SALISBURY
UK
In short, due to the introduction of a new airworthiness deregulated aircraft category here in the UK, I'm looking to build something that meets the rules, but gets the best out of them, within my own constraints on size and cost.
The rule now states that the aircraft must weigh less than 115kg empty and must have an empty weight wing loading of not more than 10kg/m². MTOW cannot exceed 300kg. There are no limits on power, fuel capacity or speed.
Thinking this through, I've concluded that a design with a very low empty weight has some advantages, not least because it allows me to maximise the wing loading in normal flight. I've done a heap of trade-off studies and concluded that it's possible to get down to an empty weight of about 65kg, if I use a flying wing design fitted with a very light 20hp paramotor engine.
A flying wing is structurally efficient, particularly if I opt for a low aspect ratio (which will give me an induced drag penalty, but one I think I can live with). The small dimensions from such a layout will make trailering the aircraft sideways a realistic possibility, so meeting my requirements for low operating cost (hangarage here in the UK is expensive!).
I have done a couple of preliminary designs and have bought the parts to build a 1/5 scale flying model, correctly weighted and powered to give me an idea of the control and stability envelope (excepting the small (I hope) errors from the Re difference).
One thing that has occurred to me, both from a control standpoint and one of weight reduction (shorter control runs) is the idea of using a small all-flying, canard as a pitch control surface, rather than a conventional elevator in the central section of the wing. I can count the canard surface as lifting wing area, so allowing me to reduce the main wing area slightly. The weight reduction from the very short control run (the design is a pusher) is also useful. When you get down to designing at these very low weights even a few grammes saved from not using as many nuts and bolts gets critical!
I'd appreciate any observations anyone has on this as a concept. I know it's not new, but I feel that I'm really working in a light weight area where this sort of thing hasn't really been tried much.
Jeremy
SALISBURY
UK