Discussion in 'The light stuff area' started by MGriffin, Sep 11, 2016.
A direct drive V-twin is around 70 pounds without the flywheel or starter and alternator coils.
I used the manufacturer's specs on TBO and Fuel consumption, figuring they all pad their numbers about the same amount. The Big Twin has a bit less HP than the ½VW, and would therefore consume a bit less fuel (air cooled engine GPH is pretty predictable), but even at 2gph, the cost per hour to operate is under $8/hour, which is still a pretty good deal. If a 1,200 hour TBO equates to 10 years of flying, then the advertised 3,000 tbo on the Big Twin (an presumably most other similar conversions) would be about 25 years worth of flying.
But since we are on the subject of the Hummel ½ VW...
The Hummel ½VW's look like nice little engines. But when comparing to the Big Twin, we have to keep in mind that that 85 lb at $4,550 is with no prop, starter, or alternator. The Big Twin comes in at $5,500 and 120 lb, but that includes Prop, starter, alternator, and cooling fan (even though it does not have the fan in any of the pictures of the Backyard Flier). I'm not sure about the weights, but a quick search of the interwebs gives me $4,975± for a ½VW set up like the Big Twin - that Redrive has to cost something...
I only mention this to try to keep the comparisons as even as I can, not because I am a rabid fan of the Valley Big Twin. I think it's a cool idea, but I also like most of the other engines out there for various reasons (Cost, Weight, Reliability... cool factor).
But this is a discussion about "Low Budget Ulralights", so we have one more powerplant to consider... Electrics.
We have all hear the claims of $1/hour flight costs of electric planes, with an endurance of 40 minutes. What we're not normally told is that the batteries for such a plan will run at least $5,000. A 40ish HP motor will run about $3,500, and the controller will likely be another $1,000. That's $9,500. The batteries don't last forever, Earthstar says 3,000 hr TBO on the batts, and they don't get overhauled, they get replaced. No TBO was given for the motor, but we'll assume it's 5,000 hours (not as many moving bits to fail as on a recip engine). So, even with the not-so-often mentioned costs involved with an electric, you can figure about $3/hour operating costs, but you have to accept reduced flight time and range as a consequence. But it's kind of like buying all the gasoline up front. Still, there is always the chance that battery technology will improve just about the time you are ready to trade replace those batteries.
3,000 hr TBO on the batteries is also a little misleading. Sure it's something like 25 years worth of flying, but as batteries age, they lose some capacity (pep). So by teh end of the TBO, that 40 minute flight may be down to 30 minutes (or even less).
Why not get exact pricing on the egull powerplant. The eGull uses zero powertrain and there are atleast two eGull aircraft flying with Zero powertrain and doing well. It is a clean design and Mark suggests 70mph @~4KW power. So here is the powerplant that can be used:
Zero FX/FXS: 28/44HP @3700RPM(70 ft-lb) @ $7645 for entire motorcycle after rebate on 2016 model for 3.3Kwhr battery pack.
Zero DS: 54HP @ 4300RPM (68ft-lb) @ $9895 with rebate on 2016 model for ~10KWhr battery pack
The 2017 are due to be announced in 2 weeks and will most likely cost the same or less with at least 10% increase in battery capacity as has been the trend over the last few years for zero.
For a self launch sailplane or a clean UL the Zero powertrain makes sense today as is. Just buy the motorcycle and extract all the components. Without the battery pack the 44Hp motor is 30lbs and the 54 Hp motor is 40 lbs. Add controller and charger and you are 20 lbs more. The batteries can move to better W&B location.
I know no one around here that uses their UL for any kind of cross country flights but dont want electric powerplant due to the limited range .... :tired:
I havent seen a 1/2 VW or Big twin on any UL around here yet. Also everyone that I know who has 2 stroke is always tinkering with their 2 strokes too....:dis:
When talking electric motors, it's a little easier to use kW in place of HP. 1 HP = 0.75 kW (it's actually 0.7457, but .75 is easier), conversely 1 kW= 1.3 HP (1.34102...)
The 3.3 kWh battery pack in the Zero FX has a max capacity of 3.3 kWh and a normal capacity of 2.9 kWh, let's keep it simple and call it 3 kWh. It will put out 3 kW for 1 hour before running out of juice. So if the Zero's motor is 27 hp (20 kW), that 3 kWh battery will last about 9 or 10 minutes. You'll need a lot more battery - Zero sells them for about $2,900 for another 3.3 kWh pack... To get 30 minutes at 27 hp (20 kW), you'll need 10 kWh of battery, or slightly more than 3 of those 3.3 packs, running you $6,000 on top of the $7,600 for the bike, so a total of $13,600. Let's assume a 3,000 hr tbo on the batteries. So every 25 years you'll have to shell out $8,700 for "fuel".
Sounds like a lot...
Let's say you can fly on $1/hour of electricity, and let's assume you'll have to replace the entire drive system every 3,000 hours (batteries, motor, all of it). $13,600 ÷ 3,000 hrs = $4.5. 4.5 + $1 for electricity = $5.50/hour to go flying for a half hour at a time. If all you have to do is change the batteries, you get about $3/hour.
Sounds like an affordable plane, if you are okay with short hops.
I'm not saying Electric flight is bad or good. I'm just saying it has pros and cons. What I'm also saying is that there is more than one kind of "Low Budget". There is the desire for a plane with a low initial cost, but there is also a desire for low recurring costs.
The main problem with all the ½VWs is that you can't use a redrive, so you take a big hit in prop efficiency due to the high rpm / small prop. The main problem with the Big Twin is the weight... most ultralights can't afford the extra 35 lbs. Having a starter is nice, but far from necessary, and note the battery isn't included in the engine weight. But if you can afford the weight, there's a lot to like about it. I don't know if a Big Twin is feasible without a stater; hand propping an engine with a redrive isn't easy. 2-strokes with redrives have pull starters; you don't hand prop them.
Yup... the only legal UL flying on the Big Twin was designed around the engine (Valley Backyard Flyer). I think the same holds pretty much true for the ½VW (Hummel Ultra Cruiser and Legal Eagle).
It is not $13600 for 10KWhr battery but $9895 today...completely off the shelf. The DS has a 10KW battery today with 54HP motor (40HP continuous) and with the 2017 will probably increase this to 10KWhr usable.
Again UL like egull can fly on 4KW power @70mph. That is 2hr flying time with the DS powerplant. It is doable today... but is it cheap...no; definitely not for this thread on low budget UL.
I would love the idea of a electric beast, but the problems relate to range.
Yes it is possible but it best suits machines that are slippery and low drag. The Song comes to mind- very expensive.
The Song is more motorglider than normal ultralight. It can afford to be electric because you can cruise on very low power and even turn off the engine.
Most designs will not allow this.
So the golden rule at the moment I think is only for low drag designs.
As for the costs- I do not worry about the battery cost of replacement- they are getting considerably cheaper and more powerful. By the time it comes to replace them, the cost will be low and performance will be greatly improved. In 5-10 years the options for batteries will be plentiful.
The conversation in 10 years will be very different- when people decide to change battery they will discuss changing wing skins to augment with cheap lightweight and powerful solar cells printed onto the surface. Then the game will change completely.
The UL Gull?
Yes it has potential but is still on the draggy side compared to a sleek beast like the Song.
Something like the design of Scott Winton Opal would be great as would the Sapphire- a sleek little pusher, small frontal area and low cooling drag.
A sapphire will easily do 95 knts (vne) on less than 40hp. With electric and greatly reduced drag- it would use a lot less. And a cantilever wing would help.
We need to look at machines that fly well on very little power- they are out there just not like the backyard flyer etc.
Alright, that makes it a bit more affordable. :gig:
Of the two motorcycles you listed, the FXS is the most attractive at $7,500. But by the time you get it to a useful flight time, it's more expensive than just going with the DS. According to the videos I watched on this system, a re-drive of some kind is needed. In one, Mark had a Rotax B gearbox on the 54hp motor, but he said that a belt drive would work also (the Bikes have belts), and probably be lighter. The cost of that re-drive would have to be added in, but it's still a small amount when figuring the operating costs of the 3,000 hr TBO of the batteries.
Not sure about the 2 hr flight time off the DS's 10kWh pack. Mark said he was getting just over an hour out of it. He also said the whole setup had cost him about $13,000. That is bound to come down in the near future though. Batteries will get better, manufacturing techniques will improve, and factors of scale will help drive the prices down thanks to companies like Zero and Tesla. And at the end of 3,000 hours (25-30 years out) there will be better, lighter, cheaper batteries. In fact, I doubt many batteries will actually run more than 1,000 hours before the plane gets an upgrade to a lighter pack with more kWh.
Still too expensive to be considered "Low Budget" as far as initial purchase, but very "Low Budget" for recurring costs.
Batteries are still, and always will be, very heavy compared to a tank of gasoline, which is problematic for [artificially] weight limited ultralights.
When stuck with a silly 254lb limit, then yes.
But if under 661 lbs total rules as a class- then it can be a worthwhile exercise. That is a extra 407 lbs to play with- takeway a 180lb pilot- my weight. And 481 lbs is a reasonable amount of engine and battery and airframe. I am sure someone could design something that suited and was slippery.
A slippery motorglider type machine with a folding tractor setup is the answer for longest flight time and some real speed. The size of good spinner can hide the engine, they can be very compact. Here in Aus we are not speed limited so can have much more fun. As long as it stalls below 52mph in landing configuration- we are cool.
But I am not saying it would not have limitations due to the cost of building a smooth slippery machine but it could make sense.
When expecting the machine to weigh fully fueled at only 254lb electric that is a joke. But when it can be 481lbs plus pilot it gets very interesting. That 227lbs can be a lot of range extension. Even accounting for the greater mass of airframe needed for a 661lb machine you can have a substantial range and power on tap.
I don't believe in using a artificially low number as a good design point- it barely makes sense with petrol and makes none with electric.
Oh absolutely. The motors are very light for their power (as compared to a fuel-burning engine). The Controllers are a couple of pounds. But those batteries just kill you.
HOWEVER... I have read a an article or two, and seen a couple of videos (one on the eGull, one on the electric Lazair) that allude to the FAA seeing the batteries as "Fuel", and saying a 5 gallon volume of batteries is the same as a 5 gallon volume of gas (as long as the batteries are removable) - so their weight is not counted against the empty weight of the plane.
But then, this really belongs in a different thread.
No, that was suggested, but the FAA didn't buy it. Batteries are included in the 254# empty weight, you don't even get the 30# fuel allowance.
The 36HP Simonini and Polini paramotor engines are fairly inexpensive for what they are (modern technology that makes 2-stroke engines more reliable and very fuel efficient). Looks like $3750 https://aerolight.com/A/index.php/products/powered-paragliding/engines-parts/polini-thor-250
The V-twin is much less, maybe even half, but as mentioned the purchase price of the engine is not nearly the whole story here.
These Italian 2-strokers are a lot lighter for the power, and they already have working, reliable, "bugs worked out" redrives mounted on them, as well as electric starters and quiet neighbor-friendly exhaust systems. That's huge. A V-twin aircraft conversion kit or setup adds a lot of time or money to the purchase price.
The potential game-changer is that the weight savings from the Italian engines will possibly allow airplanes to fit into the Part 103 ultralight category that were always too heavy before. The engine weight savings balances the "little too heavy" airframe. A low-budget inexpensive airframe that was previously a little too heavy (many of the Texas Parasols and tube and gusset types) might now be possible to build and fly under Part 103 because the weight saved by the engine is available for the aircraft structure. I believe there were a significant number of perfectly good airplanes that were 20-40 pounds over with a 40-50HP Rotax or half-VW.
(More importantly, the 20 or more pounds of weight saved by these engines can be put into stronger, safer, and more robust structure for the existing "legal" ultralights, many of which were kind of marginal.)
As mentioned, "low budget" means operating cost, maintenance cost, overhaul cost every bit as much as component purchase cost. Development cost too: I love the V-twin engines and their high reliability and long service life. Again the catalog or website price is less (half of a Polini). But then figure out the value of the time, money, machining, design/development, pile of incorrect parts on the floor... to make that V-twin into a proper aircraft engine. I am very sorry to say that it will be well over the price of the Polini or Simonini of the same power rating. I believe that a small block Briggs V-twin needs pistons, carburetors, ignition, exhaust, fuel injection, and a redrive to put out the equivalent power of the Polini. Then when it's all done it's heavier than the Polini as well.
Airframe weight is financial too. The lighter materials (airplane quality 2024-T3 sheet, composites) are more expensive. The cheapest materials (non-aircraft wood, 6061 aluminum tube or angle) are not quite as light or "structurally efficient".
If you consider the total ownership / operational cost of the (new purchase) Simonini and Polini engines as being roughly equal to a (new) properly aviation-converted V-twin, and if the weight savings of the Polini allows you to build your ultralight out of heavier but cheap tube and gusset or riveted angle... there is a good chance that you may achieve the lowest overall budget with the Italian 2-banger.
One answer for low budget is direct drive V-twin for simplicity and low cost. It will take some creativity to fly on 20-30hp, but the English Electric Wren proved it's possible to fly with low power way back in the 1920’s.
Norm Heistand is working on a 36hp engine under $1000. Two 18hp single cylinder engines coupled to make 36hp under 80 pounds.
Mr. Heistand (nheistand) has not been active here at HBA for some time, and his YouTube account shows nothing about a Siamese V Twin in development. Can you go into more detail?
Norm has a recent thread on the yahoo group: https://beta.groups.yahoo.com/neo/groups/Small4-strokeEngines/conversations/messages/16387
This project is two singles, not V-twin. These singles are $160-300 each. V-twins are normally more than $1000 each.
I rescue and buy low end ultralight projects that are taking up hanger or garage space or otherwise headed for the dumpster.
Disassembled, wrecked, vintage, whatever.
If you guys come across any give me a heads up and shoot me an email here of what and where...
If you are someone looking for the same, give me a shout out, I'll keep my eyes out for something near your state; I can't buy everything.
Someone has found an assembled Dream Classic minus engine for $300 (not $3,000) I need to figure out a way to finance as my Demoiselle like modern ultralight.
Like I always say, "It's best to gather up and tuck away all the neat stuff that I can find, before the hoarders can get it!"
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