Head in the clouds
Well-Known Member
Hello all –
This is a design exercise that has come about because of all the wonderful research and discussion that has taken place on the ‘A Challenge to you all’ thread.
I have started a new thread for my own design exercise of an ‘improved’ ultralight to fit the US’s Pt 103 regulations which allows folks to build and fly their own plane without approvals or a licence provided that it meets certain weight and performance limitations.
Here is a link to Pt 103 and the Advisory Circular AC-107 which is associated with it - see posts #107 and #108 https://www.homebuiltairplanes.com/...ea/11041-challenge-you-all-41.html#post136915
For legal reasons I will be modelling up this new aircraft for my own purposes only, as I go about it others may want to use some of the ideas that come out of it and that is up to them of course, but I am not in any way suggesting that they do - it is a design exercise for my own amusement, nothing more.
I started by making a list of all the things I found beneficial from our research and polls on the ‘Challenge’ thread, and those are what influenced my decision about the configuration –
Taildragger – it’s lighter than tricycle and gives the aircraft more useability in terms of flying to/from unmade surfaces, and provides the pilot with the opportunity to hone their groundhandling skills.
Engine - A heavy engine means reduced performance in a category of aircraft that already has quite a restriction on its performance, so I can't bring myself to use the industrial engines, they’re not too bad with a redrive but still not remarkable. So I will be designing around the purpose-built engines, if someone builds something similar then they can use whatever powerplant suits them by making the nose longer for a lighter engine and shorter for a heavier one. I have chosen the MZ201 with 45HP at just 4500rpm, electric start and redrive for $4440 plus freight and 69lbs/31kg I don’t think I’ll find anything better, and its weight is midway between the lighter MZ34/MZ100 and the industrial V twins.
A variation on the theme with minimal change to the airframe would be to have twin wing mounted engines, probably using the MZ100s for about the same price and weight or the MZ34s for a bit more of both.
High wing, low wing? I like mid wing personally but the polls said high or low so I'm going for both high and low - biplane... because I have to have so much wing area that with two wing panels they are each very large, by stacking them one above the other the span is less for hangarage if/when it's hangared. Also the chord of each wing is less than a monoplane's would be, so the overall length of the fuselage is proportionately less, making for an altogether more compact airframe.
Fuselage - those profile type of fuselages are intriguing and as PTA so accurately pointed out, surface area is the killer as far as weight is concerned, the profile type is a great way to reduce that area and therefore the overall weight. But I also like the option to have the cockpit enclosed, and the quickest way of building a fuselage is the Winton style using square box section aly - Cab Wasp* Cadet* Cadet MkIII* Ca - scroll down to 'Cricket'. So I am going to use a hybrid of all three.
Undercarriage - can't beat the Drifter style and with rudder mounted tailwheel.
Getting in and out of a minimalist cabin biplane is easiest by going in through the windshield like the Hiperlight , but I am going to try and avoid or at least minimise the reverse wing stagger .
The ‘Challenge’ thread also determined that an improved ultralight would need to be ‘cheap, easy and cool’.
Cheap - Since it is an aircraft after all there are some unavoidable costs if it is to be safe, it needs good materials and engine, I think that it should be achievable for under $10K so that is my target.
Easy – I interpret that to mean that most folks, with ‘household maintainer’ skills should be able to build it with basic hand tools, allowing for a few components to be sourced and/or made up at local workshops.
Cool – well that’s in the eye of the beholder and I’m more structurally inclined than aesthetically so, so I won’t compromise the first for the second but we’ll see how I go.
In the ‘Challenge’ thread we all hung up for ages on the engine, that is why I decided that first. The price and weight for 45HP with a redrive (to spin a large prop for good thrust/climb rate) is as good as the Rotax 503 ever was, so that’ll do me.
The other hanging point was the type of wing structure. I’m going to use one that I developed 25yrs ago for strut braced high wing and with the reduced span and superior bracing of a biplane it’ll be even lighter and stiffer so the weight reduction should more than compensate for the increased drag.
I’ve started with the wings and a rough sketch of ideas for the fuselage which I’m going to model and reveal as I go along. It’ll take a while as I work full-time and am also building my LSA.
All and any constructive comment welcome – thanks!
The CAD images have come out a bit light, click on them for the larger version of course.
This is a design exercise that has come about because of all the wonderful research and discussion that has taken place on the ‘A Challenge to you all’ thread.
I have started a new thread for my own design exercise of an ‘improved’ ultralight to fit the US’s Pt 103 regulations which allows folks to build and fly their own plane without approvals or a licence provided that it meets certain weight and performance limitations.
Here is a link to Pt 103 and the Advisory Circular AC-107 which is associated with it - see posts #107 and #108 https://www.homebuiltairplanes.com/...ea/11041-challenge-you-all-41.html#post136915
For legal reasons I will be modelling up this new aircraft for my own purposes only, as I go about it others may want to use some of the ideas that come out of it and that is up to them of course, but I am not in any way suggesting that they do - it is a design exercise for my own amusement, nothing more.
I started by making a list of all the things I found beneficial from our research and polls on the ‘Challenge’ thread, and those are what influenced my decision about the configuration –
Taildragger – it’s lighter than tricycle and gives the aircraft more useability in terms of flying to/from unmade surfaces, and provides the pilot with the opportunity to hone their groundhandling skills.
Engine - A heavy engine means reduced performance in a category of aircraft that already has quite a restriction on its performance, so I can't bring myself to use the industrial engines, they’re not too bad with a redrive but still not remarkable. So I will be designing around the purpose-built engines, if someone builds something similar then they can use whatever powerplant suits them by making the nose longer for a lighter engine and shorter for a heavier one. I have chosen the MZ201 with 45HP at just 4500rpm, electric start and redrive for $4440 plus freight and 69lbs/31kg I don’t think I’ll find anything better, and its weight is midway between the lighter MZ34/MZ100 and the industrial V twins.
A variation on the theme with minimal change to the airframe would be to have twin wing mounted engines, probably using the MZ100s for about the same price and weight or the MZ34s for a bit more of both.
High wing, low wing? I like mid wing personally but the polls said high or low so I'm going for both high and low - biplane... because I have to have so much wing area that with two wing panels they are each very large, by stacking them one above the other the span is less for hangarage if/when it's hangared. Also the chord of each wing is less than a monoplane's would be, so the overall length of the fuselage is proportionately less, making for an altogether more compact airframe.
Fuselage - those profile type of fuselages are intriguing and as PTA so accurately pointed out, surface area is the killer as far as weight is concerned, the profile type is a great way to reduce that area and therefore the overall weight. But I also like the option to have the cockpit enclosed, and the quickest way of building a fuselage is the Winton style using square box section aly - Cab Wasp* Cadet* Cadet MkIII* Ca - scroll down to 'Cricket'. So I am going to use a hybrid of all three.
Undercarriage - can't beat the Drifter style and with rudder mounted tailwheel.
Getting in and out of a minimalist cabin biplane is easiest by going in through the windshield like the Hiperlight , but I am going to try and avoid or at least minimise the reverse wing stagger .
The ‘Challenge’ thread also determined that an improved ultralight would need to be ‘cheap, easy and cool’.
Cheap - Since it is an aircraft after all there are some unavoidable costs if it is to be safe, it needs good materials and engine, I think that it should be achievable for under $10K so that is my target.
Easy – I interpret that to mean that most folks, with ‘household maintainer’ skills should be able to build it with basic hand tools, allowing for a few components to be sourced and/or made up at local workshops.
Cool – well that’s in the eye of the beholder and I’m more structurally inclined than aesthetically so, so I won’t compromise the first for the second but we’ll see how I go.
In the ‘Challenge’ thread we all hung up for ages on the engine, that is why I decided that first. The price and weight for 45HP with a redrive (to spin a large prop for good thrust/climb rate) is as good as the Rotax 503 ever was, so that’ll do me.
The other hanging point was the type of wing structure. I’m going to use one that I developed 25yrs ago for strut braced high wing and with the reduced span and superior bracing of a biplane it’ll be even lighter and stiffer so the weight reduction should more than compensate for the increased drag.
I’ve started with the wings and a rough sketch of ideas for the fuselage which I’m going to model and reveal as I go along. It’ll take a while as I work full-time and am also building my LSA.
All and any constructive comment welcome – thanks!
The CAD images have come out a bit light, click on them for the larger version of course.
