# VP-21A Single Seat / Yankee Luciole

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#### Topaz

##### Super Moderator
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The DA-11 is physically too small for most pilots. Larger is probably necessary. Also, what do your numbers say about takeoff and landing distance on this level of power? Is 1200 feet still do-able?
I haven't run that set of numbers, but I'll try to do that tonight after dinner. That calc isn't in my spreadsheet, but I can run it manually from Raymer.

What airport are you flying from that's genuinely only 1200' in length? Even Skylark's shortest dirt runway is 2,250'. I know your home field. Its shortest runway is well over 3,500' long. Even Mountain Valley, a popular destination for both of us, is 4,890', albeit at 4,220'MSL.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
I picked 1200 feet out of thin air. Just to specify an airplane that isn't a ground hog. My home airport will support a C-130, but I can't afford one of those. I did take the 172 into Black Butte, near el Mirage, a couple of weeks ago, and that's 1400 feet... and was 100 degrees F by the time I left.

#### Topaz

##### Super Moderator
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Well, I'll tell you a realistic ground-run for the 22hp "version" I outlined above. It's not going to be a Navy catapult launch, no, but I suspect it'll be okay.

Gotta run. Post later.

#### Bigshu

##### Well-Known Member
Great article. I feel better about what's left to achieve at my age!

#### patrickrio

##### Well-Known Member
Great article. I feel better about what's left to achieve at my age!
Laminar Magic is also on my list of planes. I never found a listed gross weight for it- no listed stall speed or cruise speed either. It supposedly flew 127 mph in level flight. It looks like it was set up to carry a pilot as heavy as 220 though.

It's also a one off design, but a few people flew it and it is supposedly very good natured in flight. Plans are not available but lots of it's design features are discussed in Strojnik's publications.

It does not meet VBs desired construction method of metal/rivets.

#### rotax618

##### Well-Known Member
From reading Strojnik‘s books, I don’t think there is any unobtanium in the laminar magic airframe, the use of a ply web bonded to alloy angle caps isn’ my preferred method of building a spar - if you are looking for an already proven plans built airframe to give great speed and range using a modified lawnmower engine, all I can say is good luck with that.

#### Vigilant1

##### Well-Known Member
Lifetime Supporter
Topaz you caught me... but the airplane needs to be larger, and having the full 30-32HP from a small block engine would provide a much better realistic safety margin.
.... 22-26hp can most certainly fly a nice "Modern American" pilot safely and with no magic required. The issue is that nobody has really seen it before, because all those 1960's and '70's designers designed with really short spans. It feels "unnatural" to consider flying a "modern American" on this "little" power.
One handy thing is that there's no big difference in weight or cost between the available V-twin options from 24 HP to 30 HP (maybe 33+ HP). The base engines have a retail street price of $1300-$1400, the cost of parts needed to convert them to acft use won't be appreciably different, either. When done and ready for flight, they will all weigh less than 80 lbs. The shop work to convert the lighter, more powerful 810cc engine to a flying 30 HP engine will be greater (since the oil system needs to be adapted to run in the horizontal shaft mode). It has been done before and no exotic tech is required. If 33HP (+) is needed, or if a "heads-down" version is desired, then keep an eye on Tipi's efforts.

As practical matter, if a design was built assuming a 24 HP engine, but things changed (plane got fat, pilot got fat, need to take off in shorter distance, plane proved draggier than anticipated, moved home base to Denver, etc) no redesign would be required to change to a new engine. And, as has been noted, a 1/2 VW (without electrical system) weighs just 10 lbs more, so if a LOT more climb (for more money) was desired, that option is there.

But, IMO, it would be a mistake to use up the available "cushion" by designing for the bleeding edge best engine HP/LB from the start. Planes don't generally lose weight during the design and (especially) build process. Drag can be difficult for an amateur designer to accurately estimate, and it eats up HP. Design realistically but conservatively to keep options open and avoid disappointment.

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#### rotax618

##### Well-Known Member
I don’t know if any of the posters have had an in flight engine failure, I have had 2 in my over 50 years of building and flying aerial contraptions, it certainly gets your attention. Fact is if you are going to use a modified industrial engine you don’t want a stall speed over 25-30 kts Max. You should be aiming to design a powered glider, a wing area/span that gives a higher minimum speed is brave to the extreme.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
I've had a couple in powered airplanes, and maybe 75 in gliders (that kind of don't count because gliders are built for it). I am very much aware of the need for safe and reasonable landing speeds, but not every airplane has to be a glider.

My original request or challenge included US Light Sport Aircraft standards for stall speed, which are apparently safe enough for a 2 stroke powered airplane, so they will by all means be safe enough for a 4 stroke powered airplane.

Mass also has a very large effect on landing survivability, so I believe it's safe to think a lighter airplane that is a little faster (than a Super Cub) may well be as safe as a heavier airplane that lands at 30 knots.

#### Topaz

##### Super Moderator
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Okay, dinner done, calcs done. Using Dan Raymer's procedure from Aircraft Design: A Conceptual Approach Third edition, page 99, I get the following for the 22hp aircraft described earlier:

Takeoff ground roll for ISO standard-day conditions: ~1400 feet.

Takeoff ground roll for 5,000' density altitude: ~1600 feet.

These are distances for a paved or hard-surface dirt runway. Whether or not this constitutes a "ground hog" is a subjective opinion and up to you, VB.

... But, IMO, it would be a mistake to use up the available "cushion" by designing for the bleeding edge best engine HP/LB from the start. Planes don't generally lose weight during the design and (especially) build process. Drag can be difficult for an amateur designer to accurately estimate, and it eats up HP. Design realistically but conservatively to keep options open and avoid disappointment.
This is a valid concern. Fortunately, the large range of engines over a range of power ratings (22-30hp) available at about the same weight mitigates this quite a bit, as you mention earlier in your post.

#### Geraldc

##### Well-Known Member
I meant it generally, not specifically. Pick a group of engines. Pick SOMETHING.
Jabiru 2200 or go the 1/2 vw route and make a half Jabiru.
And put it on a Jodel D9 with mods.
In the time this thread has been running I have made all the metal fittings for a D9 except undercarriage and a fixed horizontal elevator.

#### rotax618

##### Well-Known Member
The Jodel is a good and proven airframe, I’m not sure there is much meat that could be safely removed or if it would suit a 6’+ 220lb pilot. There are features that could be borrowed from the Jodel, making the wing from three equal panels of say 8’ each, the outer panels removable, having say a 18” tip would give a 27’ span and let you to trailer it and store it in a domestic garage

#### Victor Bravo

##### Well-Known Member
HBA Supporter
Jabiru 2200 or go the 1/2 vw route and make a half Jabiru.
And put it on a Jodel D9 with mods.
In the time this thread has been running I have made all the metal fittings for a D9 except undercarriage and a fixed horizontal elevator.
Which is relevant to what?

We are in a worldwide discussion group, not a production facility. Discussions like this (and HBA in general) are very enriching to a large percentage of us.

#### Geraldc

##### Well-Known Member
Which is relevant to what?
Many people here are reluctant to make the first part.I am not a production facility.Just a bandsaw a tig welder and a few hand tools.
The reference to the Jodel is that except for the spar a build should not take too long.
We are in a worldwide discussion group
Hopefully some will be building something as well.

#### rotax618

##### Well-Known Member
I don’t expect that anyone would believe that they could get 70 reliable horsepower from a Predator 670, but this video gives a good idea of how well these engines are built - (plastic gears in the crankcase and pressed metal rockers).

#### Vigilant1

##### Well-Known Member
Lifetime Supporter
I don’t expect that anyone would believe that they could get 70 reliable horsepower from a Predator 670, but this video gives a good idea of how well these engines are built - (plastic gears in the crankcase and pressed metal rockers).
Yes, the Predator 670 horiz shaft engine (sold by Harbor Freight in the US) is at the low price end of the market. Hot Wings has bought one for examination and shared his findings in several posts.

OTOH, other engines are built to different standards. Here's a look inside the B&S (Vanguard) 810cc engine:

Tipi has also done a lot of work on these. He shares the good and the bad here:B&S 49-series (810cm3/49ci) - TiPi's conversion for aircraft use

They are all simple engines: 2 valves per cylinder, pushrods, magnetron ignition. No overhead cams, no VVT, etc. But, there are differences among them. Some very nice ones (Hondas) aren't ideal candidates for conversion for various reasons. Also, many of them are fitted with EFI systems that work well for their intended use (including engine monitoring with Bluetooth output of all key parameters), but aspects of those systems make them problematic for use in aircraft. It takes some research and discernment to work out the best path to a solid conversion. Others have done it.

One nice thing about the major brands of industrial engines is that the innards stay relatively constant over many years. This is an advantage compared to engines made for some other industries.

These engines aren't perfect, but the signs to date indicate that they are very dependable in their intended use and can also provide reliable service in the air if they are adapted properly.

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#### Michael Silvius

##### Well-Known Member
21st Century Davis DA-11, for a larger pilot, simpler construction, and with a 25-33% larger but similar engine... does that make it any easier to wrap everyone's head around?
Leon Davis did that already, he called it the Davis DA5A, plans are still available

• Length: 15 ft 9 in (4.80 m)
• Wingspan: 15 ft 7+1⁄4 in (4.756 m)
• Empty weight: 460 lb (209 kg)
• Max takeoff weight: 775 lb (352 kg)
• Powerplant: Continental C-65
• Propellers: 2-bladed, 60-70 , 5 ft 0 in (1.52 m) dia
• Maximum speed: 160 mph (260 km/h, 140 kn) at sea level
• Cruise speed: 120 mph (190 km/h, 100 kn) (econ. cruise)
• Stall speed: 60 mph (97 km/h, 52 kn)
• Rate of climb: 800 ft/min (4.1 m/s)

#### Vigilant1

##### Well-Known Member
Lifetime Supporter
Leon Davis did that already, he called it the Davis DA5A, plans are still available

• Length: 15 ft 9 in (4.80 m)
• Wingspan: 15 ft 7+1⁄4 in (4.756 m)
• Empty weight: 460 lb (209 kg)
• Max takeoff weight: 775 lb (352 kg)
• Powerplant: Continental C-65
• Propellers: 2-bladed, 60-70 , 5 ft 0 in (1.52 m) dia
• Maximum speed: 160 mph (260 km/h, 140 kn) at sea level
• Cruise speed: 120 mph (190 km/h, 100 kn) (econ. cruise)
• Stall speed: 60 mph (97 km/h, 52 kn)
• Rate of climb: 800 ft/min (4.1 m/s)
Well, that C-65/A-65 engine weighs about 170 lbs, so we'd lose about 90 lbs by going to a 25-30 HP V-twin. That brings the MTOW down to the 650 lb figure we've been kicking around. Then, give it a wing about 10 ft longer and that the smaller engine will let it climb just fine (though it won't be as fast as the DA-5).

#### Bigshu

##### Well-Known Member
Well, that C-65/A-65 engine weighs about 170 lbs, so we'd lose about 90 lbs by going to a 25-30 HP V-twin. That brings the MTOW down to the 650 lb figure we've been kicking around. Then, give it a wing about 10 ft longer and that the smaller engine will let it climb just fine (though it won't be as fast as the DA-5).
We keep talking about wing span all by itself, but isn't there a ratio of length to wing span that doesn't work? When I look at aircraft that are really short, like 15 feet, they don't look right with wings much longer than 18-20 feet. Is it just me? We get into flying wing territory at some point.