# $5,500 aircraft? ### Help Support HomeBuiltAirplanes.com: #### brehmel62 ##### Well-Known Member In the ultralight challenge thread, a$5,500 aircraft was mentioned. I thought this deserved its own thread. How feasible is that price point?

I considered that instruments might be a problem. I made up a list on Aircraft Spruce including Altimeter, Air speed indicator, thermometer, slip indicator, vertical card compass, hour meter, volt meter, tachometer, egt/cht, pitot/static, and stall warning that came to $1,050. However, I was able to create a budget version that was only$261. So, I don't think instruments would have to be a problem. This leaves the engine as the most likely limiting factor.

Hirth F36 w/redrive - 15 HP @ 6,000 rpm, 28 lbs, $2,483 Hirth F33 w/redrive - 28 HP @ 6,500 rpm, 40 lbs,$3,128
Great Plains Half VW kit - 38 HP @ 3,400 rpm, 87 lbs, $4,000 (with carburetor, manifolds and ignition, no starter) An engine that costs over$3,000 would make the airframe budget rather tight. The F36 at $2,483 might work. The obvious question is whether 15 HP would be enough. It could be if the weight stayed down and the span loading was low enough. However, I probably should point out that the original Quickie used 18 HP and the original Starlite used 20 HP. Unfortunately, the Limbach 275, KFM 107, Zenoah G25, and Rotax 277 are out of production. The 2si (Cuyuna) 215 is supposedly still being made but I haven't found anyone selling them. Let's look at what we know is available. There are 25-44HP engines from Zanzottera. These are used for RPV's so they probably are not affordable. There are Victor and Mini engines from Simonini. The 24 HP Mini 4 is$3,200.
JPX has a 14 HP D160 engine for $2,000 and a 20 HP D330 for$3,100. Their larger, 65-90HP four stroke engines appear comparable to VW conversions such as those from Great Plains. Great Plains charges for a long block VW about what JC Whitney charges so this appears to be the price floor for VWs.

Zenoah ZP 80 cc - 7.4 HP @ 7,500 rpm, 6.25 lbs, $950 ZDZ 360cc - 34 HP @ 8,500 rpm, 17.6 lbs,$3,895

The Zenoah is a twin cylinder RC engine and is based on Zenoah's experience with chainsaw units. The ZDZ is a purpose built RC engine. These might suggest a price floor since, if we had two of the Zenoah units and a redrive, the price and horsepower would be quite similar to the Hirth F36 while the ZDZ is similar to the Half VW.

DJ 80cc - 8.2 HP @ 8,000 rpm, 4.4 lbs, $280 JC 120cc - 12.5 HP @ 8,000 rpm, 6.4 lbs,$455
DLE 170cc - 17.5 HP @ 9,000 rpm, 9 lbs, $1,050 The Half VW is$105 per HP. The Zenoah is $128 per HP, the Hirth F36 is$166 per HP, and the F33 is $112 per HP. In contrast, the DJ runs$34 per HP, the JC runs $36.4 and the DLE is$60 per HP.

Let's imagine we are a bit adventurous and compare multi-engine configurations.

4 units DJ 80cc - 32.8 HP, 17.6 lbs, $1,120 3 units 120cc - 37.5 HP, 19.2 lbs,$1,365
2 units DLE 170cc - 35 HP, 18 lbs, $2,100 With this much horsepower, we could design a two seat aircraft if we were careful with the weight. It might even be rather novel to imagine hand-propping three or four engines before taking off. If we wanted to design a single seat craft and stay near 18 HP we end up with something like: 3 units DJ 80cc - 24.6 HP, 13.2 lbs,$840
2 units 120cc - 25 HP, 12.8 lbs, $910 1 unit DLE 170cc - 17.5 HP, 9 lbs,$1,050

This looks feasible however the problem with these units is not price or weight; it's rpm. There is no way that we are going to make good use of an engine that turns at 8,000 rpm. Tip speed would limit us to a 22" prop when even the smallest of these, the DJ 80cc with 8.2 HP, would need a 36" prop. Some kind of PSRU or redrive is needed. This subject can be rather intimidating if you have read Ray Stitts' efforts with the Skeeto. However, these types of redrives are fairly common today on VW, Simonini, JPX, and Hirth engines.

Let's come back to the issue of redrives in the next post. After all, these are RC engines and the first question should be whether or not these are basically junk. Specifically, are these engines running so hot that they are likely to fall apart?

There was an equation that was given by Colin Campbell in his book "The Sports Car -- It's Design and Performance" back in 1954 for determining safe rpm for engines. The equation is:

safe rpm = 450,000 / (bore * stroke)^0.5, bore and stroke in millimeters
safe rpm = 17,714 / (bore * stroke)^0.5, bore and stroke in inches

If you go to a website like ZENOAH MODIFIED ENGINES | ZENOAH ENGINE MODS you can find high output racing engines that go over these specs. It is possible to go over these limits but you need good engineering and development. Just porting an engine to boost the HP doesn't really qualify. Let's see how these stock RC engines compare:

ZP 80cc - 7.4 HP @7,500 rpm, 1.6 inch bore x 1.22 inch stroke: 12,679 rpm is safe, 41% under
DJ 80cc - 8.2 HP @ 8,000 rpm, 2.05 inch bore x 1.5 inch stroke: 10,102 rpm is safe, 21% under
JC 120cc - 12.5 HP @ 8,000 rpm, 1.77 inch bore x 1.5 inch stroke: 10,871 rpm is safe, 26% under
DLE 170cc - 17.5 HP @ 9,000 rpm, 2.05 inch bore x 1.57 inch stroke: 9,874 rpm is safe, 9% under

This is interesting. Even using a conservative equation from 60 years ago, each of these engines is running at a reasonable rpm. Personally, I would tend to leave out the DJ 80cc because it is one cylinder. Using a twin cylinder should help with at least some of the vibration and bearing loads.

I guess if we are looking at RC engines, we might as well look at RC instruments.

Suppose I wanted to work up an instrument list based on RC components.
GPS - $72 Hall Effect rpm sensor -$10
Optical rpm sensor - $14 EGT sensor w/probe -$81
Second EGT probe (sensor can handle two) - $30 CHT sensor w/probe -$81
Second CHT probe (sensor can handle two) - $27 Altimeter (0-20,000 ft, 1 ft resolution) -$32
Air speed sensor w/pitot tube (9 - 200 mph) - $32 Stabilization sensor (can generate artificial horizon) -$44
3 axis G sensor (+/- 7 Gs) - $18 Two channel analog to digital sensor (0 - 4 volts) -$90

I have to say that this is rather surprising. If you hooked the data logger up to, say, a netbook (which wouldn't be difficult since it has a USB port), you would almost have a glass cockpit for around $2,000. And, in terms of flight testing, everything is recorded. You could even use the A/D sensors (up to four) to record: rudder, elevator, aileron, and flap positions. Last edited: #### cheapracer ##### Well-Known Member Log Member Great post! I don't know why you guys are so shy of Japanese (Yamaha, Kawasaki, Honda, Suzuki) motocross engines, lightweight, bullet proof, 20+hp and 30+hp for 80cc and 125cc respectively and cheap as chips. Anything from the last 20 years will be suitable, buy a whole cheap bike off EBay. Cut the entire gearbox off or use one of the gears as a reduction while pulling the rest out and solidify the clutch. Young teenagers hammer the absolute crap out of these engines week after week all year round and they just do not stop, as they shouldn't after 40 years and billions of dollars of development put into them. #### 4trade ##### Well-Known Member I don't know why you guys are so shy of Japanese (Yamaha, Kawasaki, Honda, Suzuki) motocross engines, lightweight, bullet proof, 20+hp and 30+hp for 80cc and 125cc respectively and cheap as chips. Motocross engine life span is very limited because it have high piston speed. If you run these engines at high rpm level (where you find that hp) most of these engines wear out piston at 10-40 hour. Even worse, you must operate all time so high rpm (read: piston speed), that these pistons cannot tolerate any small cooling related issues. Even slight overheating will destroy piston right away. Motocross engines is design like any very high performance engines, close to thin line of total destroy at max hp level. High piston speed cause fatigue of piston, and that is the one what destroy piston, not overall wear of piston. Manufactures like Wiseco give 7,5 hour life span for their piston at 125 cc motocross engine, depending on company and overall hp/ cc combo. #### cheapracer ##### Well-Known Member Log Member Motocross engine life span is very limited because ........ Your post offers absurdly ill-informed information on modern 2 stroke engines. Sad thing is some people will believe your 1960's carry over mythology because, amazingly, dark clouds still hang over 2 strokes from stuff of 50 years ago. #### Jay Kempf ##### Curmudgeon in Training (CIT) Lifetime Supporter In the ultralight challenge thread, a$5,500 aircraft was mentioned. I thought this deserved its own thread. How feasible is that price point?[...]
There are threads on using Android or Ipad style screens with a single interface box and sensors for all instruments. It is very possible. The Arduino world has a whole host of single board computers as well with lots of daughter boards for sensors including rudimentary autopilots. Accuracy is getting better all the time.

Last edited by a moderator:

#### brehmel62

##### Well-Known Member
I don't know why you guys are so shy of Japanese (Yamaha, Kawasaki, Honda, Suzuki) motocross engines
Do you honestly believe that I would go to the trouble of looking up French and Italian engines and prices but ignore others? I've checked on the Chinese scooter/ATV/pocket bike engines, but these don't seem to be that easy to use. Some have integrated transmission cases and the ones that don't, seem about the same as the Zenoah engines. I don't see any reason to talk about these since I don't know who would work on them or if you could get parts. In terms of the Japanese motorcycle engines, I don't know of anyone who sells them outside of an actual dealer. And, I believe the book price is on the order of $4,000, which is higher than some other options. I'm open to discussing any engine that fits within the budget, power, and weight requirements. Just as an example, I can get a Briggs & Stratton 31 HP Vanguard V twin with electric start and a 20 amp alternator for$2,413. Unfortunately, it weighs 155 lbs.

lightweight, bullet proof, 20+hp and 30+hp for 80cc and 125cc respectively and cheap as chips.
I would be surprised if you could get 20 HP out of 80cc. Typically that would be 8 HP.

Anything from the last 20 years will be suitable, buy a whole cheap bike off EBay. Cut the entire gearbox off or use one of the gears as a reduction while pulling the rest out and solidify the clutch.
It sounds like you are talking about scrounging up a used engine. That's not what I'm looking for. I'm looking for what is available for anyone who wants one, not just a happenstance good deal.

#### brehmel62

##### Well-Known Member
There are threads on using Android or Ipad style screens with a single interface box and sensors for all instruments. It is very possible. The Arduino world has a whole host of single board computers as well with lots of daughter boards for sensors including rudimentary autopilots. Accuracy is getting better all the time.
Thank you, although I don't believe I had seen this with actual aircraft instruments before. Do you know of an aircraft application of this? Also, could you please not quote my entire post. I'm sure most people would prefer to suffer through it only once. Thank you.

#### brehmel62

##### Well-Known Member
Levil industries makes a device that replaces the "six pack" with an Ipad.
Levil Aviation - portable AHRS systems
Yes, that looks like it is along the same lines but quite a bit more expensive than the RC avionics. Look at this Point Of View display for an RC aircraft.

If you go to http://vimeo.com/3772235# you can see an example in use. Obviously from inside the aircraft, you don't need the video display. However, it seems like if you had a black background and a bright enough screen and could display the image backwards, you could use the reflection and have a Head Up Display.

Last edited:

##### Well-Known Member
In the ultralight challenge thread, a $5,500 aircraft was mentioned. I thought this deserved its own thread. How feasible is that price point? Not feasible at all. The cheapest ones (with a lot of looking for 2nd hand parts) are the Hummelbirds and similar for 8-10K. By the time you add up all the essential parts, you are up to that kind of money. Engines, whether meant for aircraft, or converted unavoidably are going to cost you a few grand, even if you take an industrial one and adopt it. Wheels that don't melt don't come for free. Instruments can be dead-cheap, but than they're inaccurate as HELL too. Invest a few hundred US$ in a speed dial and just forget about a radio, altimeter, vario etc.

If you can't afford that alone, take a partner, or buy a good "given-up" project. They usually sell for considerably less than parts value...

#### brehmel62

##### Well-Known Member
Not feasible at all. The cheapest ones (with a lot of looking for 2nd hand parts) are the Hummelbirds and similar for 8-10K.
Yes, I know that there are ultralights available for roughly 10k. They all seem to use the Hirth F33 for some reason.

By the time you add up all the essential parts, you are up to that kind of money. Engines, whether meant for aircraft, or converted unavoidably are going to cost you a few grand, even if you take an industrial one and adopt it. Wheels that don't melt don't come for free.
As I said, this was brought up in the ultralight challenge thread. One gentleman stated that one ought to be able to build an aircraft for $5,500. I thought I would look into it in detail rather than just dismiss the idea without any serious consideration. I am puzzled though about the melting tires comment. I've never heard that before. Instruments can be dead-cheap, but than they're inaccurate as HELL too. Invest a few hundred US$ in a speed dial and just forget about a radio, altimeter, vario etc.
I didn't include a radio. And, you can get an altimeter for $40. If you can't afford that alone, take a partner, or buy a good "given-up" project. They usually sell for considerably less than parts value... Thank you, but that has nothing to do with the point of this thread. It is not about buying a half-built project or getting partners to invest in an aircraft. It is specifically about whether it is possible to build an aircraft for$5,500. The truth is that someone can always spend more; the question is how little someone could spend.

##### Well-Known Member
As I said, this was brought up in the ultralight challenge thread. One gentleman stated that one ought to be able to build an aircraft for $5,500. I thought I would look into it in detail rather than just dismiss the idea without any serious consideration. If you have read that thread, you have seen that my comments aren't without "any serious consideration", but well founded in all sorts of considerations. I am puzzled though about the melting tires comment. I've never heard that before. Cheap tires, rims etc simply don't stand up against the beating of aircraft (unless you're flying an UL). Been there, wrecked two. And, you can get an altimeter for$40.
Yes, a ****ty one, that might very well be 2000 ft off. Been there too. Invest in quality, or don't buy it (GPS altitude is plenty accurate)

#### cheapracer

##### Well-Known Member
Log Member
Do you honestly believe that I would go to the trouble of looking up French and Italian engines and prices but ignore others?
Why are we suddenly at war? I'm trying to help and I wouldn't say ignore, I will just say there are quite obviously things I know that you don't.

I would be surprised if you could get 20 HP out of 80cc. Typically that would be 8 HP.
Try around 32+ for a Shifter Kart, but either side of 24 has been the norm off the showroom floor for a long time now, and I'm talking 20 years.

Here is a comparison between a stock Yamaha YZ80 with standard and aftermarket pipe - 18 and 19 rear wheel horsepower, around 24 -25 at the crank but we are more interested in running around 8500/9000 so with the right pipe mods (say add 50mm length into the header pipe for example) you are looking at around 20hp crank and around 40 to 50 hours for a ring set, maybe longer in the nice clean sky air ..

No carbon fiber.

#### brehmel62

##### Well-Known Member
I guess I should talk about the previously mentioned instruments list for $261 so that people can attack them properly. The first part is pretty easy. I can get EGT, CHT, tachometer, volt meter, and hour meter on Aircraft Spruce. However, these items are also common on ATVs and riding mowers and they work exactly the same. I have an hour meter on my Cub Cadet riding mower. If you have an EGT, you probably don't need a CHT so we can leave that off. I would use an ordinary marine compass instead of an aircraft panel compass. The function is the same but the price is less. The only downside of a bracket mount instead of a panel mount is that you could potentially bump the compass and break the bracket. We could however solve that by using a recessed mount. That brings us to the important instruments like altimeter, air speed indicator, and slip indicator. The slip indicator is similar to a bubble level but these are too twitchy in an aircraft. You want one with a ball so that the rate of movement is damped and it isn't bouncing all over the place. Fortunately, they make these for leveling trailers. You can get them in sizes from about 3" to 10". They work the same. The altimeter is a Liberty Mountain Sb-400 Altimeter. It only has a single arm so it is not sensitive. However, for VFR conditions, I can't see why it wouldn't be sufficient. I don't know of an inexpensive air speed indicator so you would have to use a Hall Wind Meter. These have been used on ultralights and hang gliders for some time. They cost about$25. I suppose if the top speed of 80 mph is not high enough you could theoretically use a partially restricted inlet with a second tube and extend the range up to perhaps 120 mph. That should be enough for any light application.

And, finally, we can use a Cessna stall warning reed which you can get from Aircraft Spruce for 75 cents. You need tubing and you'll have to fabric an adjustable inlet port on the wing but we would have to do that anyway since ports are only available for production aircraft.

M

#### Manticore

I did a quick cost analysis for a single seater a couple of years ago. Can't find the exact details but it was roughly: Airframe materials 20% Instruments 25% Engine + Prop 55% The total came to about $8,500 if I remember correctly. Think I was considering one of the JPX engines at the time. #### brehmel62 ##### Well-Known Member #### nerobro ##### Well-Known Member Log Member Okey, real post time. First, lets talk powerplant. Since that's the expensive bit. Davis demonstrated that you can fly, quickly, and well, on a B&S vanguard engine. That engine can be found for around$1500. I strongly suspect the modifications to make it airworthy could be done for less than $500. (remove flywheel, small extention shaft and a "5th" bearing... ) So that leaves$3500 left for the plane. I think that's doable.

Lets talk instrumentation.

From: http://www.faa-ground-school.com/library/VFR-regulations.pdf
Code:
Instruments required for
[/FONT]
[FONT=serif]day VFR flight include: [/FONT]
[FONT=serif](1) Airspeed indicator, altimeter, compass [/FONT]
[FONT=serif](2) Oil pressure gage, temperature gage, fuel gage
[/FONT]
[FONT=serif](4) Tachometer, and maybe a manifold pressure
[/FONT]
[FONT=serif] gage and maybe a landing gear indicator [/FONT]

1: Hall Brothers Manufacturing Co. | Hang Gliders, Paragliders & Ultralights for an airspeed indicator. I don't know of a cheap altimeter, and compasses are cheap enough. Lets call it $200 for the 1 category. 2: If we use a clear fuel tank, that's our fuel guage. Worst case, we can use a sight tube.$free. Temprature guage should be in the $20 range, and the same for oil pressure. We'll call that$40.

3: We can find a tach for $40. A MAP is easily found at your local auto parts store for$20.

So we can probably get through instrumentation for $300. Leaving us$3200 for the remainder. At that point, I think we could go either way, and go ultralight, or experimental. Whichever way we go, we'll need to have a decent design, because flying on 20hp, is very different form the typical ultralight practice of flying on 50hp.