poormansairforce
Well-Known Member
I am curious what the responses would be if a new cheaper design came out utilizing small twin 2 strokes....yea or nay?
Traveling with a twin engine 2 stroke airplane?
- Thread starter poormansairforce
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pictsidhe
Well-Known Member
Cheaper than what? An SR71, or VB?
poormansairforce
Well-Known Member
Well, most engine setups end up being upwards $7-10k so was just thinking about cost vs reliability. Also, with the design I'm looking at it would make sense to use 2 small engines.
Two off-the-shelf two-stroke paramotor engines like the Vittorazi Moster would give you 2 x 25 hp = 50 hp for 2 x $3,000 = $6,000. Then you need two props as well, call it $7,000. I would suggest a Grumman Skyrocket-style microlight for cool factor, but those engines are happier as pushers. so let's say you go with a podded rear engine layout like the Cessna ATPTB experimental Citation or that homebuilt with a business jet look and twin Rotax engines that I can't think of right now. So you end up with something about the size and performance of a souped up Fournier RF-3 motorglider that may or may not be able to maintain altitude on one engine. All very doable but what's the advantage over something like the Fournier that could get the same power from the cheapest possible 1600cc VW conversion?
poormansairforce
Well-Known Member
Two seats. And I would actually prefer a pusher which is part of the reason for the lightweight engines. Twins would increase the reliability.
Well...then you need a Fournier RF-5. What two-stroke engines did you have in mind? Much more expensive than the Vittorazi and a single four-stroke engine becomes cheaper than two two-strokes.
A twin does not increase reliability, it doubles the likelihood of an engine failure. The safety benefit of a twin comes from the ability to keep flying and ideally still climb on one engine. Without folding or feathering props, that can be a real challenge.
A twin does not increase reliability, it doubles the likelihood of an engine failure. The safety benefit of a twin comes from the ability to keep flying and ideally still climb on one engine. Without folding or feathering props, that can be a real challenge.
poormansairforce
Well-Known Member
Forgot about the RF-5, that could fit the bill. I guess I used reliability wrong, the point is to stay in the air to get to where you need to go. The odds of having two engine failures are pretty unlikely.
poormansairforce
Well-Known Member
On the other hand the RF-5 is not exactly cheap.
TFF
Well-Known Member
One or two two strokes really doesn’t matter. It’s all about care, and two strokes are a little more finicky, so you have to adapt yourself to what you got.
I deal with an Aircam with two 912s and it finicky with the four strokes. I have only seen two stroke AirCams never dealt with them, but if one fell in my lap I would be fine; give me a choice and I’m picking the four stroke.
I deal with an Aircam with two 912s and it finicky with the four strokes. I have only seen two stroke AirCams never dealt with them, but if one fell in my lap I would be fine; give me a choice and I’m picking the four stroke.
poormansairforce
Well-Known Member
mullacharjak
Well-Known Member
Nice excercise.You can get drawings from Fisher flying products if they have them for the Culite twin engine aircraft which used the 503 engine I think it was a two seater.
The norwegian Mikroflyprodukt Twin Stratus had two Rotax 447 or 503 engines on the wings. Great takeoff and climb performance, but not very fast (just like their single engined variants). https://saltenmikro.files.wordpress.com/2012/02/lww3892.jpg
pylon500
Well-Known Member
There was this modified Long Eze in England with two Hewland, three cylinder two strokes (75hp ea, so 150hp), and then two 90hp Norton rotarys.
I feel sure I also saw a one off single seat Vari-Eze clone with two Rotax 582's (65hp ea), but I can't find the info.
I had toyed with the idea of two 582's running direct drive to ducted fans at the back of a modified BD-5 body with a delta wing, but I guess I should have that in the 'Daydreamers' thread.
I don't deal with Lycosauruses, so I've no idea what sort of fuel burn to expect to get 120~150 hp, but a 'cruising' 582 will burn between 17 and 20 litres an hour...
Then there's the push/pull twin concept;
I feel sure I also saw a one off single seat Vari-Eze clone with two Rotax 582's (65hp ea), but I can't find the info.
I had toyed with the idea of two 582's running direct drive to ducted fans at the back of a modified BD-5 body with a delta wing, but I guess I should have that in the 'Daydreamers' thread.
I don't deal with Lycosauruses, so I've no idea what sort of fuel burn to expect to get 120~150 hp, but a 'cruising' 582 will burn between 17 and 20 litres an hour...
Then there's the push/pull twin concept;
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mullacharjak
Well-Known Member
Powers-Bashforth Minimaster push pull twin had similiar appearence.
poormansairforce
Well-Known Member
LOL This is a little bit where I was headed with one of the 2 designs in my head. BD5 meets Rohr 2-175 but probably without the ducted fans. My thought was to make the stabilizer do double duty as engine pylons. Think A-4 with engines at the outboard ends of the stabilizer. The fuselage could narrow down quite a bit and the vertical stab just becomes an extension of the fuse so it can be made plenty strong.
pylon500
Well-Known Member
THAT's the one I was trying to think of...
Oddly, the ideal behind my twin ducted fan is that, here in Australia, we have a multi tiered ultralight system, and all but our 103 equivalent are bordeline FAR23 and LSA design limited.
Our 103 equivalent, ANO95:10 (our first original rule set) is reasonably lax and limited at the same time.
We are limited to 300kg total flying weight (give or take floats and/or parachutes), and 30kg per Sq metre wing loading [661lbs/~6lb sq ft] and single seat.
Other that, no other limits on number of motors (Lazair), type of motor (elec, ICE, jet) or number of propellors/wings/wheels/etc.
As for engines on the end of tails, I think it would be better to have the tails outside the engines and keep them as close to centre as possible (just realising you're probably thinking props while I'm thinking fans?)
The manufacturer of Tucano does offer a twin configuration:
Armilite
Well-Known Member
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In General, most Twins have proved to be not any more reliable than Singles account they can't Fly on just (1) Engine when fully Loaded. Cheap and Twin Engine don't go together. You don't say what Class you're talking about.
One Cheap Twin that was successful, but now out of Production and could be upgraded and made again, is the Lazair Ultralight! It will FLY on (1) Engine.
Probably the Cheapest Production 2 Stroke Engines would be the Hirth F36, at 15hp@6000rpm x 2 = 30hp!
F-36 with Recoil Start & Re-Drive. $2,364.00 x 2 = $4,728!
F-36 with Electric start & Re-Drive. $2,964.00 x 2 = $5.928!
BUT, most people would prefer a 4 Stroke to Maximize your Sales! A Pair of Honda/Clone GX200 Type Engines upgraded for (15hp@5000rpm) each Cost total about $800ea x 2 = $1,600 for (2) Upgraded Engines. ACE Belt Drives for them run $669 each Shipped to the USA x 2 = $1,338 + $1,600 = $2,938 for Engines & Redrives.
The original Lazair had a low MTOW of 450 lbs.
- Max. takeoff weight: 450 lb (204 kg)
- Empty weight: 210 lb (95 kg)
- Useful load: 240 lb (109 kg)
Could you make a Cheaper Belt Drive, probably less than Half the Cost of the ACE, Yes! Like this guy did.
You don't have to reinvent the Wheel, we have so many Single Engine Planes we have lost over the Years, mainly due to Poor Marketing and Over Pricing their product.
As you know if you have a total of 50hp with two engines it is unlikely to maintain altitude on a single engine (with any appreciable weight) because of losses due to drag will make the effective power available closer to 37% than 50% so on single engine you will have effectively more like 18hp than 25hp. Also you likely don't cruise @ full power so being on one engine will be a judgement call, if in order to maintain some kind of glide path better than complete engine loss you decide to reduce power on the one remaining due to engine temps going up regards power setting and airspeed.
My crazy thinking is three engines are better. Usually with three engines one will be in the center and will not adversely affect yaw and therefor not be included to any appreciable degree in drag losses due to the failure of either engine mounted on the side. So worst case if you lose a side mounted engine on an aircraft with (3) 17hp engines (51hp total) then you would have effective power of 37% of the two side mounted engines plus the full power of the center engine so 37% of 34hp = 12.5hp effective + 17hp center engine equals 29.5hp effective which is over 10hp better than a twin with a engine loss and much more room to reduce some power a bit to maintain temps.
My crazy thinking is three engines are better. Usually with three engines one will be in the center and will not adversely affect yaw and therefor not be included to any appreciable degree in drag losses due to the failure of either engine mounted on the side. So worst case if you lose a side mounted engine on an aircraft with (3) 17hp engines (51hp total) then you would have effective power of 37% of the two side mounted engines plus the full power of the center engine so 37% of 34hp = 12.5hp effective + 17hp center engine equals 29.5hp effective which is over 10hp better than a twin with a engine loss and much more room to reduce some power a bit to maintain temps.
Glide of a triple engine on one engine would still be better than that of a twin on zero engines.
