E7 by Jos Guggenmos

The E-7 is a hybrid rigid-wing model made by Jos Guggenmos. It is similar to, and obviously influenced by, the Exxtacy and the ATOS. Key difference from the Exxtacy is a lot lighter weight.

E7 DESCRIPTION

Note: The following comments about the E7 are made by Jim Zeiset, the U.S. distributor of the E7, as published in the OZ Report, Vol. 3, No. 65, on June 6, 1999.

"After accumulating 20 hours on the E7 I’m ready to report my impressions of the wing. I
can certainly respect Dave Sharp for waiting till he had accumulated some hours on the
ATOS to make subjective comment rather than spewing out meaningless chatter that a
twenty minute test flight might generate. As most experienced pilots know wringing
maximum performance out of a new wing requires some time in the control bar. We are
all looking for a glider that is lighter, safer, better handling, easier to set up, highly
controllable, sweet to land, easy to transport, and has the highest performance
parameters available. The E7 just might be the one to meet these requirements better
than any of the other contenders.

"The E7 is a cantilevered rigid wing of similar structural configuration to the Exxtacy but
that is where the similarity ends. It was designed and built by Josef Guggenmos et al in
Germany at his small manufacturing facility. He is fortunate to have in his employ a
composite structure expert retired from the European aircraft industry. With that
composites expertise and his 25 years experience of fabricating hang gliders (building
the Bullet series and RCS Topless hang gliders) he has developed the E7. Josef is well
known through out Europe for his attention to detail and innovative problem solving. As
pilots at the Nationals scrutinized the E7 the common comment was about how well the
sail was built and how clean the hardware looked.

SPECIFICATIONS OF THE E7

Claimed max L/D 18.5
Claimed min. sink 138 ft/min - 0.70 m/s
Weight 68 lb. - 30.8 kg
Aspect Ratio 10.43
Span 39.4 ft - 12.01 m
Sail Area 149 sq. ft. - 13.84 m2
Packed Length 18.7 ft - 5.70 m
Min. Hook in 154 lb. - 70 kg
Max. Hook in 264 lb - 120 kg
I estimate the glide ratio of the E7 to be very close to 18.5:1. I’m confident of this
number because of the amount of time that I glided with Exxtacies demonstrating a
slight improvement. Their glide ratio is pretty well accepted to be 17:1 Even Davis Straub
reported no significant difference that he observed in glide and he has been flying his
Ex for more than 100 hours while I had only an hour on the E7. Although I flew the E7
on the last day of the Nationals as did Dave Sharp on the ATOS we never had a chance
to fly together due to him getting a late start.

I established sink rate to my satisfaction on an early morning test flight the last day of
the Nationals. The air was very smooth and I was able to slow it down to 17 mph. This is
2 mph slower than I could fly an Exxtacy. I use a Flytec 4030 with a wireless air speed
mounted on the left downtube close to the corner bracket (same place on any glider I
fly). I was able to maintain a sink rate of 140 ft/min for a solid 3 minutes. It doesn’t fly
below 17 with my 235 LB hook in wt.

The night that I was able to get the E7 released from Customs I got in late. It was my
plan to go to bed early so that I could get up by 7:00 and cop a few test flights. That
wasn’t going to happen. Too many pilots wanted me to weigh it. It had been
pre-announced that the glider would weigh 68 lbs. Somebody found a 90kg hanging meat
scale. It came in at 32 kg. That’s about 70.5 lbs. I didn’t have any confidence in the meat
scale so I weighed it on my UPS scale when I got home. The scale only goes to 50 lbs.
but oh did I say that it comes in two pieces in separate bags. One side weighed 28-lbs. 4
oz. and the other side weighed 42 lbs. 4 oz., a total of 70 lbs. 8 oz. Close enough, it’s the
lightest modern rigid wing made.

THE E7 SET UP

Two pieces? Nobody told me about that. I was skeptical at first, but after assembling
the two sides by inserting a couple of Exxtacy like pins and pit pins I was sold. It pops
together real fast and when it was time to load it on the Suburban, Amy did it. It packs
up cleaner, no parts rubbing and no hassle at all to pop it together. Just assemble the
control bar with that half on its back in the unzipped bag then stand it up on its control
bar. Unzip the other half about 4 ft., slip the attachment dogs into the keel tie plates,
slip in the hinge pins and pit pins and your ready for the tip wands.

The tip wands are an engineering masterpiece. Pull the sail back from the outboard tip of
the spar/D-tube. The sail is only attached at the nose making structural inspection simple.
Slip the tip wand into the receiver on the spar being sure to place the wand stiffener
through the forward section of the outboard rib. Both the wand and stiffener seat
decidedly in there detents. Next pull the sail over the wand and attach it to the end of
the wand with a double purchase. Josef tells me that he will put a break over mechanism
on the end of the tip wand if I so desire. I told him I do and then fabricated one that
worked quite well from an Exxtacy retrofit part.

Starting with the inboard rib rotate each rib from it’s nesting position against the spar to
its approximate extended position. I have a mod that I did to my Exxtacy where I tied a
piece of #205 leech line close to the end of each rib allowing me to position all the ribs
on one side at one time. You are now ready to attach the sail at the keel. Instead of sail
hooks the E7 sail attaches by slipping small metal plates with a hole in each onto a pit pin
that sticks out the bottom of the keel. Remove the keel extension and zip up the top and
bottom sail zippers.

Open the wings as far as they will go and attach the turnbuckle using the provided pin
and safety. Since there is no whack tube protruding out the front of the nose there is no
ring attached to the turnbuckle to serve as a handle to rotate it. Instead a long bolt
passes through the center of the turnbuckle. Place your left hand on the right D-tube at
the nose and push straight down the keel as you turn the turnbuckle in half turn
increments till the turnbuckle tightens up against the double nuts with both ends. Check
out that keel. The forward half is a trapezoidal carbon fiber box. Hook up the front
flying wires with the keyhole tang and position the perfect fitting nose cowling. It really
looks good without that intermediate whack tube sticking out the nose. Some pilots have
expressed disappointment that it didn’t have a whack tube but I for one do not want a 2
inch diameter tube coming down on the back of my neck in a blown landing.

Walk around to the back, replace the keel extension and attach the top and bottom sail
surfaces to the ribs with the double purchase string. Press the trailing edge Velcro
together. Slide the metal tab in the bottom undersurface of the spoilers forward as far
as it will go and secure it by taking up the slack in the return bungee and securing it’s
end knot in it’s retainer. Insert the flap string pit pins into the aft corner of the flaps
and feed the flap string through its cleat. The only thing left is to attach the spoiler
control cables to the corner of the control bar with the stainless quicklinks. Go get your
harness.

GROUND HANDLING THE E7

I recommend setting up the E7 quartering tail into the wind. This will result in lower
loads on the structural parts of the wing than any other position. Do not hook in before
turning around. As usual it is better to have help on the up wind wing when rotating the
glider into the wind. However when every one is scrambling to get set up you will find
that because of its lightweight more effort can be placed in controlling the glider.

Tip inertia is really low and rotating it comes easy. Once you get it into the wind the wing
that was downwind is probably high. By pulling the bottom of the control bar away from
the high wing the spoiler is deployed. The E7 spoiler is located on the high point of the
airfoil and on a line that goes through the hang point. This does four things that are a
considerable improvement on previous designs.

One is it acts exactly like a speed brake on a sailplane causing the offending wing to
move rearward. This process decreases the speed of the wind and lift over that wing and
increases the speed of the wind and lift on the opposite wing.

Two is that it acts as a spoiler and spoils the lift on a portion of the offending wing
forcing it down.

Three is when the spoiler is activated it results in a minimum change of the pitch moment
of the glider. This feature is especially nice because the nose does not tend to go up
when the spoiler is activated during ground handling which always makes matters worse.

Fourth is that locating the spoiler on the high point of the airfoil allows the spoiler to be
folded up in the sail with out removing it.

Ground handling the E7 is easier than other designs because a single light bungee holds
down the spoilers. Because the spoiler return pressure is so light the spoiler actuating
cables can be located farther outboard where they enter the undersurface. This
decreases the amount of travel of the base tube necessary to get full deployment and
results in a very tightly rigged glider. That light spoiler return pressure and tight rigging
make holding the E7 on a moderately gusty launch a lot less of a challenge.

LAUNCHING THE E7

The E7 is one glider that is a pleasure to lift onto your shoulders. At 70 lb. It is
noticeably lighter than any of the popular topless designs. Static balance is perfect. Pull
the flaps on full for take off, as this is the highest lift configuration and it enhances roll
control. As you start your launch run you will be impressed by how quickly the E7 lifts
off of your shoulders. With dihedral similar to the Exxtacy the wing tips are about 7
feet above the ground. Check out how far above the ground the wing tips of your flex
wing are when you’re launching it.

Since the glider will fly at 17, low to no wind launches are easier to make happen safely.
The launch is performed with a slightly positive angle of attack, just enough to allow the
wing to fly. The hang strap tension will be much lighter than a flex wing because the E7
slips through the air with less drag. This feature allows the pilot to accelerate noticeably
faster. I get the feeling that I could run all the way to the LZ if I didn’t push out a little.
Once your weight hits the hang strap bar pressure kicks in and the glider wants to go to
trim. That usually means a strong climb back to launch level or higher. You can feel the
efficiency of this rigid wing right away.

FLYING THE E7

The trim position of the base tube on the E7 with full flaps is at about your chin and
results in a speed of about 24 mph at a hook in weight of 235 lb. This setting allows for
a lot of slowing down and works great for recreational thermaling. For competition I
would slow trim down to about 21. This can be accomplished by tightening up the
turnbuckle a half turn and loosening the rear sail attachment webbing ¼ inch. Trim moves
up to about 29 with the flaps off. Best glide appears to reach maximum at about 36 to 38
however speeds of up to 44 bring on no high sink rate.

Running at VNE of 65 for extended periods of time is no problem in reasonable air and I
don’t fly in smooth enough air to go any faster. I’m convinced that I could make it go 90
if I wanted to. I consider the flaps on the E7 to be high lift devices and fly with them
either on full or off. They are not very effective in glide path control. In fact when I
want to get it on the ground before a gust front I have been more effective in getting
down by running into the blue, flaps off, at 55 or 60 mph. Sink rates in the area of 800
to 1000 fpm are attainable.

Bar pressure is light enough in a dive to be sustainable for long periods of time but still
provides positive feedback. When trimmed at 24 the glider bar pressure is too high to fly
at sustained speeds of 18 or 19. In this configuration it does the same thing other fast
trimmed rigids do when slowed to stall. Laminar air flow breaks away from the upper
surface all across the wing except at the tips. The wing is not flying, there is no bar
pressure, you're pushing out with 20 to 40 lbs., the nose pitches up farther, you
experience an abrupt stall, the nose pitches down and you better start thinking about
bending at the elbows.

As I discovered with the Exxtacy you can mellow the stall characteristics by lowering
the trim speed as suggested above. By tightening the turnbuckle a half turn, more of the
wing is in front of the hang strap than before and the glider slows to a trim of 21. When
trimmed at 21 and the base tube pushed out to full arm extension the E7 slows to 17. It
experiences a soft, short drop of the nose and auto recovery to 17 or 18 and then
repeats the soft stall again. The glider will spin in the hands of a competent professional.

THERMALING THE E7

Getting to know the E7 and how it enters lift takes a little time for a pilot of 20 years
experience on a flex wing. The E7 exhibits a characteristic that is first perplexing and
then once you learn to use it, delightful. It is a quality I call verse yaw.

For years I’ve been flying hang gliders that have varying degrees of adverse yaw. I’ve
learned to counteract this undesirable trait by imparting body twist into my thermal
entry maneuver. In other words I point my toes in the direction that I want to turn
towards. It’s no wonder I’m exhausted after a four hour cross country flight in a flex
wing. It may be the most efficient way to enter lift but your body sure isn’t in line with
the air flow.

The E7 on the other hand turns by activating spoilers on the high point of the airfoil,
which act as asymetrical speed brakes as well as air deflectors or inverted split flaps.
Deployment of the spoiler yaws the glider in the direction of the desired turn as the
glider begins to bank. The nose does not pitch up so you must push out to reach the best
banked climbing speed. Because the glider does not pitch up on turning into lift it does
not slip off on the back side.

I think this verse yaw characteristic catches the new E7 pilot off guard and his initial
reaction to a yaw in the desired direction is to stop this yaw by signaling a turn in the
opposite direction. This is exacerbated by extremely light roll pressures on the base
tube and a pilot induced oscillation results for about two cycles.

All I can suggest is relax. Now that I have some time on the glider I have determined that
it is lighter in roll than any other glider that I’ve flown. It will turn 45 to 45 in about 6
seconds. When cranking in a little tighter or rolling out in an attempt to center up,
response is nearly instantaneous. I feel that this gives me a tremendous climbing
advantage.

The glider is tightly rigged so you feel more connected. The base tube travel to full
spoiler deflection is a fairly short distance with little resistance. Kind of feels like a
sports car. When thermaling I usually seek out the core and bank steeply and the E7 does
this well.

LANDING THE E7

When approaching to land with the E7, I recommend losing altitude up wind of the
intended landing field and then entering a downwind, leg base leg and final. I usually
enter downwind opposite the LZ at about 300 feet. This allows you the time to set the
flaps to the full on position while on downwind, turn twice and still make a long final
approach.

I land on wheels because of a 20 year old knee injury that causes me to suffer post
traumatic arthritis whenever I impact it. To do this I land the E7 just like I land my
Cessna 320, slowing to stall speed and touch down simultaneously. Once it touches down
I pull my weight over the base tube during roll out to prevent harness drag. Just as it
stops let the body move back till the keel touches the ground.

As the E7 is noticeably light the 11 pilots that have test flown it have landed on their feet
and with out exception have had great landings. The flare window appears to be quite
huge and the glider has a propensity to drop behind the pilot when he slows to below 17
mph. allowing for only a few steps to full stop (auto-flare in case you forgot). The
relatively light weight of the glider is really noticeable in a full stop flare. Carrying the
E7 off of the landing field to the breakdown area is a pleasure even after along day of
flying.

MORE ON THE E7

The fit and finish of the E7 is fantastic. No other manufacturer can compare in sail work
or hardware. There is nothing crude about the carbon fiber ribs and each rib is
fabricated with an adjusting device to set the height of the rear tip. There are only 6
ribs per side and that is all that’s needed to support the super tight wrinkle free sail. The
tip wand also has an adjusting device on its brace in order to maintain sail tightness over
its life. Set up and break down are faster than on its predecessors although it takes me
twice as long because of so many pilots looking it over and asking questions. It’s pretty
hard to find a glider whose nose cowling fits as perfectly as this one. At $10,200.00
you would expect no less.

FINAL COMMENTS ON THE E7

Many people have asked me what I’m going to fly and for now it will be the E7. Flying the
E7 well was more difficult than I thought it would be but after 20 hours I think I’ve got
a handle on it. On aero tow some pilots induced a yaw oscillation that was uncomfortable
but now it tows like an Exxtacy for me. It is still easier to tow than a flex wing. It just
took some getting used to the tight rigging and light control forces. It is the sports car of
hang gliders. Call me if you’d like to try it.

Some more info on the Ixbo

From: JimZgreen@aol.com [SMTP:JimZgreen@aol.com]
Sent: Tuesday, March 02, 1999 2:45 PM
To: airHOG@thinairdesigns.com
Subj: Guggenmos E-7, 68 lb. carbon rigid wing
The following information is provided to make you aware of this rigid wing breakthrough.
I have contacted my old friend Joe Guggenmos and have set up a North American exclusive on his in-production carbon fiber E-7. He makes the Bullet series of gliders and the RCS topless in a production system similar to Trampeneau of Seedwings but in Germany. He has an outstanding reputation throughout Europe for manufacturing the highest quality hanggliders with amazing attention to detail.

The E-7 is similar in configuration to the EX however it has a tapered wing (both chord and D-Cell cross section), control bar activated spoilers, 152 square feet, 10.43 Aspect Ratio, 39ft. span, spoilers and flaps fold up with glider, 18.5 ft in the bag, and only 68 lbs. Joe claims greater than 17:1 glide and a sink rate of 137 ft./min. I will make these wings available for $10,200.00 FOB Salida. Delivery is 8 weeks and I've ordered 4 now and 4 later. If you want to order one of these first 8 gliders get your fully refundable $2000.00 deposit in right away. If you don't think that this glider meets or exceeds the advertised specifications and after inspection you choose not to accept delivery your deposit will be refunded.

- Jim Zeiset
President/Pendulum Aerosports Inc.
13154 County Road 140
Salida, CO 81201
800-WE-FLY-XC
800-933-5992
FAX 719-539-3900
www.pendulumaero.com
jimzgreen@aol.com

Pictures will soon be available on www.pendulumaero.com or e-mail me for a copy.

Some pictures of the E-7 prototype

Jos Guggenmos with the E-7 

the E-7 at the Tegelberg launch 

the E-7 on the DHV test rig