Showing posts with label Hoerner wingtips. Show all posts
Showing posts with label Hoerner wingtips. Show all posts

Monday, March 26, 2012

Fact Sheet on the WOW ultralight aircraft


Please note: James' blog has moved to a Wordpress site. To access it, please visit http://jameswiebe.wordpress.com/. All posts have been transferred to the new site, and all new posts will only be accessible via Wordpress. Thank you for your interest!


Ultralight Aircraft, WOW style, from Belite
High Res Photos of the WoW plane on our Flickr site.

Fact Sheet on the WoW ultralight airplane from Belite – in no particular order:

  1. NAME.  We call it the WoW plane because of the amazing paint scheme and the amazing combination of features it has.
  2. AMAZING PAINT SCHEME.  The aircraft is painted in Insignia White from Stewart Systems, with multi-colored dots of various sizes floating off the airframe.  I came up with the idea of floating dots.  If you think it looks like a bread wrapper, well… hmm.
  3. BASE AIRCRAFT KIT.  This ultralight aircraft is an example of many different ideas, all built into one Belite Aircraft.  Any skilled aircraft builder could make this airplane, starting with our base kit. 
  4. KIT PRICE.  Our base kit is priced at $7000, including a discount of $2000 at Sun N Fun, after show discount.  That includes just about everything required to build an ultralight airplane, firewall back.  (Regular price, non-show, $9000.)
  5. CARBON FIBER SPARS.  This ultralight aircraft has carbon fiber spars.   They are a $2200 option.  They save about 9 pounds and add considerable strength.
  6. HYDRAULIC BRAKES.  The aircraft has been fitted with hydraulic tip brakes.  From Grove Aircraft.  The tip brake design is ‘one-off’ (not documented in our build manual), but builders are encouraged to innovate and copy what we have done.
Hydraulic Toe Brake in Belite Ultralight Aircraft
  1. COWLING.  The cowl is constructed from fiberglass, and is optional in our kits.  The plane flies fine without a cowl.  It also flies fine with a cowl.  The cowl weighs less than 3 pounds.  We do not include it in our flying weight, because it is removable for flight. (BTW, the pictures don't show the cowl attached.  We just got it fitted on today, and we'll have more pictures tomorrow.)
  2. AIRCRAFT WEIGHT.  The plane weighs about 275 pounds, including parachute.  The legal maximum weight for an ultralight aircraft with parachute is 278 pounds.
  3. ENGINE.  The engine on this plane is a Hirth F33, producing 28HP.  It weighs about 47 pounds, including the muffler.  It uses premix oil/fuel, at a 90 to 1 ratio.
  4. PROPELLER.  The propeller is a 58 x 22 wooden propeller from Tennessee Propellers.  It is very lightweight and sturdy.
  5. FUSELAGE.  The fuselage is constructed from our 4130 chromaloy steel.  However, this same airplane could have been constructed from our aluminum fuselage option.
  6. MORE ON THE FUSELAGE SHAPE.  The rear fuselage and the bottom fuselage was ‘built up’ with a series of angle aluminum longerons to add cross section shape, then covered with fabric.  You can see the internal aluminum structure by looking inside the fuselage, from the cockpit.  This helps make the airplane look like any other ‘real’ airplane.
WoW Ultralight Aircraft from Belite, viewed from underneath.  Note wingtip detail (Hoerner style), note nav lights; also note underneath fuselage shape detail and elevator trim tab detail.
  1. STRUT FAIRINGS.  Notice that the struts are faired, providing a streamlined strut structure.  Very nice.
  2. LANDING GEAR ‘A’ ARMS.  These are also faired and covered with fabric.  So is the cross bar, under the fuselage, connecting the landing gear together.
  3. SPRING LANDING GEAR.  The main landing gear use steel springs, replacing bungees.  They make hard landings soft and also make taxiing a lot more comfortable. 
  4. INSTRUMENT PANEL.  The panel is made from ultralight weight Belite Electronics instruments and and the entire panel runs off of a single 9 volt battery.  Battery life is about 8 hours.  Current usage for the entire panel is about 55 milli-amps.  The panel could also run off any power source (including ship power) between 9 and 14 volts.  If you look at the plane, you can see the battery velcroed behind the panel.  The panel is completely removable by removing the wing nuts on the four corners.  The missing instrument is the airspeed indicator --- oops!  Sorry!  I frequently fly without instruments so it’s not a big deal to me.   The entire panel weighs about 12 ounces.  We do not include it in aircraft weight because it is removable and not required for flight.  I cut the panel aluminum on our ShopBot.  We can make nice panels in just a few minutes, from CAD on the computer to finished product.  Very cool.  Here's a pic of a similar panel, on display:
Instruments from Belite Electronics, for experimental and ultralight usage
  1. PANEL STRUCTURE.  In the WoW airplane, notice that the instrument panel is connected to a classic aluminum structure, built from bent aluminum sheet metal and faired around the cross bracing under the windshield.  Very nicely done.
  2. WING DESIGN.  All of Belite’s aircraft utilize an expanded span and chord (25’ 2” span; 40” chord).  As a result, Belite’s wing produces more lift at slow speeds, which makes it ideal for ultralight operation.  (But the wing in the WoW plane has even greater span, due to the Hoerner wingtips… see below.)
  3. FLAPERON DESIGN.  All of Belite’s aircraft utilize an expanded flaperon, with a 12” chord.
  4. HOERNER WINGTIPS.  This aircraft was built with a one-off Hoerner wingtip design.  This increases span and reduces tip vortices in flight, causing better lift and reduced drag.  In other words, better performance low & slow. A while back, I wrote a nice explanatory post on Hoerner wingtips.
Hoerner Wingtip on Belite Ultralight Airplane

  1. HORIZONTAL STABILIZER / ELEVATOR.  These control surfaces are built with an aerodynamic cross-section.  This gives better control and smoother flight characteristics, due to drag reduction.  The stabilizer has a 2024 T3 spar; the elevator spar is built from Chromalloy steel. 
  2. RUDDER TAB.  Note the ground adjustable rudder tab.  Very nicely done.  This is another ‘one-off’ feature which I would encourage our customers to copy.
  3. ELEVATOR TAB.  Note the inflight adjustable manual elevator tab.  The control lever is to the left of the pilot’s sight.   It runs to the rear of the airplane using a single Bowden cable.
  4. FLAPERON CABLES.  The flaperon cables are very low friction.  In flight, the aircraft feels like the control surfaces are on ball bearings.
  5. TAIL WHEEL SPRING.  Constructed from spring steel, we have them made for us by a local spring vendor.
  6. POSITION / NAVIGATION LIGHTS.  We’ve equipped this ultralight airplane with position lights.  This allows ultralight flight for 30 minutes after sunset.  
  7. ‘Y’ CNC MACHINED LIFT STRUT FITTINGS.  There are several machined parts which we make at Belite, on this airplane; the strut lift fittings at the base of the fuselage are a great example.  They are hogged out of solid aluminum.
  8. LIFT STRUTS.  The lift struts are constructed from 2024T3 aluminum, 1.00 x 0.035 wall, on this airplane.  This is a builder option.   It is lighter than 6061T6 aluminum.  (The lift struts are covered with the plastic extruded fairings.)
  9. FOR SALE?  Hmm.  Good question.  This was built to be our demonstrator and also to be James’ personal ultralight airplane.

Wednesday, December 21, 2011

More on "Hoerner Wingtips" in ultralight aircraft

Please note: James' blog has moved to a Wordpress site. To access it, please visit http://jameswiebe.wordpress.com/. All posts have been transferred to the new site, and all new posts will only be accessible via Wordpress. Thank you for your interest!


My previous post cited the work of Dr. Hoerner in the development of wingtips which produce smaller vortices, which consequently produces less drag, which consequently allows more speed (for a given thrust), and consequently a better rate of climb....

Clearly the Hoerner wingtips are a desirable thing.  While there are other ways to produce effective vortice reduction (for instance, vertical winglets or even flat plates), the Hoerner wingtip is more easily fabricated, and frankly, in my opinion, just looks darn sexy.

Soooo, it's worthwhile to spend a couple of minutes reviewing Dr. Hoerner's research, so we can guess what positive results these wingtips will give us.

Below is a basic illustration of a wingtip vortice, which I have copied from Dr. Hoerner's most excellent book, "Fluid Dynamic Drag".

Vortice at wingtip, from Fluid Dynamic Drag, by Hoerner
This illustration shows how high pressure air is spilling from the underside of the wing out of the wingtip, causing the vortice.  (The villain isn't the vortice, it is the fact that a vortice is created by the loss of high energy air from the bottom of the wing.  The evidence and creation of a vortice only proves the problem.)

Dr. Hoerner reviewed several different kinds of wingtip configurations, including square wings with sharp edges (which is exactly what our Belite ultralight airplane has), along with round rectangular edges, sharp rounded wings, sharp full wings, and more.  He also reviewed vortices and drag  reduction around wingtip fuel tanks (which are not in our current Belite innovation plans.)   With each kind of wingtip shape, he calculated and presented the effective span of the wing -- in other words, a longer wing is a better thing -- and if you get that length 'for free' (by using better wingtips), that is a really good thing.

The very worst wingtip is a rounded wingtip, with a round cross section.  The very best wingtips are ones which have a sharp cross section.

And interestingly, the square wingtip with a square edge is nearly as good as the very best wingtip, but not quite.  It is worthwhile to quote Dr. Hoerner on this topic:

"Theory predicts minimum induced drag for elliptical lift distribution across the span....   however, directly in one case... that a rectangular wing (with sharp lateral edges) does not have a higher drag due to lift than the elliptical wing."

Wow.  Score one for Belite, and the game of innovative improvement hasn't even started!

Back to Dr. Hoerner's writing:

"It is seen that the most effective plan forms are the rectangular, the moderately tapered ones and those which have a long trailing edge....   In other words, to make the span of the rolled-up vortex system, or the effective span of a wing of given basic shape, as wide as possible, it is favorable to keep the tip vortices apart from each other as far downstream as possible."

Now if I look back at his charts, I do see that sharp wingtips have an advantage over the square wingtip with square edges, and all of those have huge advantages over rounded  wingtips.

So the Hoerner wingtip is taking it to the next level.

Let's find some more interesting remarks from my new best friend, Dr. Hoerner.  He makes some comments about the most ideal wingtip shape, which I (and others) now call "Hoerner wingtips":

"In case of [Hoerner wingtips], which is the most favorable one concerning small drag due to lift as well as to minimum sectional drag, it appears that one additional effect is the bent-up shape.  Experimental data.... on a small-aspect-ratio wing, confirm that this feature is important.  Combination of [Hoerner wingtips] with a moderately tapered plan form is believed to be the most effective..."

So things get a bit 'guess-work-eee' from here.  But we think that we know the following:

 * sharp wingtips reduce the size of the vortice -- which is what the Hoerner wingtip is all about
 * the addition of the Hoerner wingtip spreads the trailing edge, adding span, and further separating the vortice
 * sharp wingtips have less drag at higher angles of attack, which is where ultralights spend more time at than higher speed airplanes

Hey, wait a minute.  I better provide some documentation for a couple of those points.  Here's another illustration from the book which helps:

Improvement shown with Hoerner wingtips -- with square wingtips not far behind!
The illustration shows, on the top right hand side of the curve, the slightly higher coefficient of lift achieved with the Hoerner wingtips.  Square (Belite) wings are close behind, with round wings falling off considerably.

Here's a final helpful illustration, showing the cross section of vortices with sharp vs round wingtips:

Decreased vortice size with Hoerner wingtips (a) vs round (b) or wingtip tanks (c)







Finally, some conclusions...



Q.  So what is all of this worth to a Belite ultralight aircraft?

A.  We believe the aerodynamic effective span will increase by a little over 2 feet.  However, we are cheating a bit, because the Hoerner wingtips will add about 20 inches of real span all by themselves.  The increase in effective wing area is 7+ square feet!  (with an original wing area of about 108 square feet).

Q.  What performance increases will result?

A.  Hopefully I'll see an improvement in climb rate, a reduction in stall speed, a reduction in takeoff roll, a reduction in landing roll (I'd like to beat my personal measured 100.5' landing record -- which I know I'll be able to do [because I've already done it in another Belite, before I even started talking about Hoerner wingtips   :-)  ])  and more...

Q.  What weight penalty do the wingtips entail?

A.  Substantially less than a 8 ounces per wing, vs. our existing square design.   Really!


Q.  What if they don't work quite that well?

A.  Then I'll get to figure out why, and I'll have the coolest looking ultralight airplane on the planet.

My thanks to Dr. Hoerner, and his wonderful book.  I believe my quotes and illustrations taken from his book fall under fair use doctrine.

I am also indebted to Mike, who is building this wonderful test airplane with Hoerner wingtips for me.

If you want an overview of what else I'm working on (and willing to talk about) you can read it here:

Upcoming 2012 Product Innovations at Belite Aircraft

-- James Wiebe, 2011 EAA August Raspet award recipient









Monday, December 19, 2011

Upcoming 2012 Product Innovations at Belite

Please note: James' blog has moved to a Wordpress site. To access it, please visit http://jameswiebe.wordpress.com/. All posts have been transferred to the new site, and all new posts will only be accessible via Wordpress. Thank you for your interest!


"Upcoming 2012 Product Innovations at Belite"

 an overview of what's coming...
 this post focuses on "Hoerner Wingtips"

One of the absolute joys of my pseudo-job is that I get to investigate, implement and test aerodynamic improvements to my Belite ultalight airplanes.  As a result, I have come up with a goal of decreasing drag on our aircraft so that our very smallest engine option will allow cruising flight at 62mph.  (And the larger engines will require throttle limitations in order to stay within Part 103 -- or registration as experimental aircraft.)

When all is implemented, this will provide important improvements to takeoff and landing performance, along with substantial improvements to climb rate, reduced stall speeds.

Because our aircraft is so similar to a conventional high wing aircraft, I have identified several opportunities for drag reduction which are already available on many 'commercial' certified aircraft.  These opportunities include:

a)  lift strut drag reduction via fairings  --  all airplanes should have this
b)  wingtip drag reduction via reduction of wingtip vortices
c)  increased Lift / Drag in wing airfoil via subtle improvements
d)  reduced drag due to improved cowling design
e)  And maybe there will be more.

(none of these future options have been made available, or even priced yet)

I've already implemented and test flown a Belite with lift strut fairings, and I will provide a full report soon.  Hint at the outcome:  It was awesome.

I'm also working on a changed cowling design -- it will take a few more months and I'll have that one ready for report.

I've been reading through a variety of aerospace engineering reports on wing airfoils.  I find that my engineering and math background are an excellent helper for me as I've learned more and more about airfoils.

As for wingtip vortices, lots of people already know that Dr. Hoerner tested many different types of wingtips, in order to select and document those which increased effective span and reduced drag by reducing or eliminating those nasty wingtip vortices.  I happen to have gotten my hands on a copy of a couple of his books (they were loaned to me by a friend at my Church) and they have been delicious reading for my ultralight aircraft aerodynamic engineering education.

So, here's some photos of a set of wings in construction progress, showing Hoerner wingtips being fabricated.  These will end up on a plane which is being built to exhibit at Sun N Fun in 2012.  No opportunity for improvement is being overlooked in this airplane.  The wings in question are carbon fiber spars, with aluminum ribs, and the Hoerner wingtips.  You may also notice that they are also being prepared for VFR night flight via the addition of wingtip lights.  (The airplane is being built with a heavy 4 stroke engine, and will be registered experimental, thus allowing night flight.  It will be also be flyable as a legal FAR Part 103 airplane, albeit with a different engine.).  (This particular set of wings is being built by builder Mike.  Mike is awesome.)

So here are the pictures:

Belite Ultralight Aircraft wing, under construction with Hoerner wingtip

Detail of Hoerner wingtip, showing nav light fairing

Front view of Hoerner wingtip, with much smooth work still to do


Quartering view of Hoerner wingtip


View of Hoerner wingtip, prior to adding foam to front cell


Trailing edge quartering view of Hoerner wingtip


View of Hoerner wingtip from outside rear