SPORTPLANE BUILDER Tony Bingelis

Once in a while a builder will ex-press dissatisfaction with the type ofcanopy recommended for the partic-ular airplane he is building. However,more often than not, if he is buildingfrom a kit, he will usually go aheadand use the canopy sent him.

Rest assured, the canopy designselected by the aircraft designer isone he feels to be the best all aroundinstallation.

Without a doubt, the designer hasagonized over the options he hadavailable. He most certainly wouldhave considered the overall appear-ance, head room, ease of installation,safety of the installation in regards tocanopy security, as well as the easeof entry and egress to and from thecockpit.

Many builders who think they canimprove the designed canopy instal-lation are usually motivated by someimpulsive personal whim. More oftenthan not, that builder will not haveconsidered a number of factors al-ready evaluated by the aircraftdesigner in the first place.

This is not to infer that only onetype or style of canopy is the best fora particular airplane . . . would thatthe selection of a canopy design bethat simple.

I'm sure you realize that installinga canopy you can easily open andclose can be a problem ... for thatmatter, it always has been a problemfor builders.

It is not surprising, therefore, thatwe see so many differences in canopyshapes and in canopy installations.

Canopies In General

Canopies can be divided into twobasic categories.

1. The one-piece bubble canopyinstallation.

2. The separate windshield/canopy installation.

The spin-off from these two basictypes includes a variety of installationsthat are better recognized by themethod used to attach the canopy tothe aircraft structure. This, in turn, de-termines the way the canopy isopened, closed and secured.

Regardless of the type canopy youinstall, the most important considera-tion is that your canopy will allow yousufficient headroom. This is moreimportant than striving for that elu-

Would you believe it? A large front hinged canopy without a frame . . . on a 300 mphairplane? It's all in the design. I understand 6 latches are used to secure it in theclosed position.

sive long, low, streamlined look.Most large canopies are vacuum

formed, in an oven, of 3/16" plexiglassalthough some windshield sections forthe faster homebuilts may be as thickas 1/2" to provide additional safetyand to reduce wind noise.

Unfortunately, many large vac-uum molded canopies do not havethe excellent optics that mostsmaller free-formed vacuum drawnbubble canopies have. These minoroptical distortions are most often

picked up during the vacuum form-ing from a poorly prepared mold.

The localized distortions can bevery irritating to a few pilots, espe-cially when a blemish happens to bewithin the pilot's normal line of sight.

Fortunately, such distortions are,ordinarily, confined to a few very smalllocalized areas. They can, therefore,be dressed down and removed usingthe well-known Micromesh plexiglasspolishing kit (obtainable from most anyaircraft supply source).

This canopy swings up and backward on stilt-like supports. The idea is clever buttoo radical for most builders. That is a lot of canopy weight to raise and support.

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A Separate Windshield?

A canopy installation that utilizesa separate windshield is, by far, thesafest type of installation becausethe windshield also serves as aturnover structure. Furthermore, inthe event the canopy accidentallycomes open, or blows away, the per-manently installed windshield willprotect the pilot from the blindingslipstream.

On the minus side, a windshieldframe does obstruct the pilot's visionto a minor degree.

Some builders may consider aseparate windshield installation tobe a bit more difficult to fit and installthan a single piece canopy, but thisis not always the case.

The Front Hinged Tilt-Up Canopy

A one-piece bubble canopy is themost aerodynamically efficient in-stallation you can make for yourairplane. However, this efficiencymay be diminished by the time youhave figured out the best way to at-tach it securely and yet ensure easyaccess to the cockpit.

One way to do this is by hingingthe front end of the canopy so thatthe aft end of the canopy can beraised enough to provide the neededcockpit access.

Tilt-up canopies are commonly in-stalled on two seater side-by-sideaircraft such as the Dragonfly, Q200,RV-6, Swearingen SX300 and theVenture, to name a few.

The visibility in all directions frominside a one-piece tilt-up canopy issuperb.

Some builders may find this onetype of canopy easier to install thana sliding canopy because there is noneed to cut, fit and match a separatewindshield to the canopy frame.

However, fitting and aligning ahuge one-piece plexiglass bubble tothe fuselage, while installing the sup-port hinges is not exactly a picnice i ther . . . by all means, try to getsome help.

The tilt-up canopy has a couple ofdrawbacks peculiar to its installation.

The forward hinged position israther difficult to install so that itdoesn't leak.

Obviously, a leaky canopy ispretty hard to put up with. Even ifyour airplane is always hangared andyou don't fly in rain, sooner or lateryou will wash it and get water insidethe cockpit . . . and that can be justas bad for your radios.

A tilt-up canopy, like a few otherdesigns, can be readily hinged so

Canopy installation on a single seater is a simple matter with a variety of optionsavailable. One of the simplest is the fixed windshield and the side-hinged canopy.

that the canopy can be jettisoned inan emergency. Howeve r . . . it ismost unlikely that anyone woulddare jettison such a large canopy (oreven a small one) in flight because:

1. Most of us don't wear a 'chute.2. Cutting that big thing loose

from its hinges in flight will almostcertainly destroy the entire tail as-sembly as it leaves the aircraft. Evenif it didn't the pilot would be left withno protection from the high velocityslipstream.

A one-piece tilt-up canopy is anawesome sight when it is opened.This makes it very vulnerable to dam-age from winds and from thepropwash churned up by unman-nered pilots.

These canopies can also be diffi-

cult to raise in a strong wind.In flight, that huge bubble seems

to magnify the sun's rays, turning thecockpit into a hot box.

On the other hand, it is great inthe winter time because on sunnydays no cabin heat is needed . . . ifyou don't mind the cold feet.

Installing an automotive type com-pression strut on each side of atilt-up canopy will stabilize it consid-erably and reduce its vulnerability tothe effects of wind gusts while open.

The Rear Hinged Tilt-Up Canopy

There are very few examples ofthe rear hinged military style tilt-up canopy among homebuilts.However, this type of installation is

This huge side-hinged canopy was economically fabricated using flat plexiglasspanels. However, the Dyke Delta wing imposed unusual access problems whichthe builder overcame with the aid of a step ladder and a fuselage panel opening.

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an ideal solution for anyone buildingan amphibian. This is because arear hinged tilt-up canopy, whenfully opened, enables the pilot tohandle the docking chores moreeasily. Typical examples of the rearhinged tilt-up canopy may be seenon the Osprey 2 and Seahawker am-phibians.

Just about everything said aboutthe front hinged canopy applies tothe rear hinged installations.

The most important considerationfor this type of installation is that thecanopy latching system be positiveand foolproof. The canopy mustseal tightly so that no air can enterregardless of the airspeed.

Can you imagine what could hap-pen to that canopy on its first testflight if the front edge wasn't closefitting and latched tightly to the fuse-lage?

The Side-Hinged Canopies

This type of canopy installation isthe most popular, by far, withbuilders who are building singleseater aircraft or two seater tandemdesigns.

The side-hinged canopies arequite versatile in that they may be in-stalled as a one-piece unit or with aseparate windshield.

The one-piece canopy does resultin a more rigid installation althoughit, like the tilt-up installation previ-ously described, harbors a greaterrisk to the pilot in the event thecanopy becomes unlatched in flight.

If the fuselage sides are straightin the area where the canopy is to bemounted, the installation is simple tomake using a long piano hinge asthe means of attachment.

For access to the cockpit it will benecessary to restrain the canopyfrom swinging open too far, other-wise the hinge might be torn looseor the canopy plexiglass may bedamaged.

A simple restraining cord, or alight chain, is not a satisfactory wayto restrain the canopy in its open po-sition as wind gusts may cause thecanopy to bounce and self destruct.Some type of a rigid strut or a springloaded compression strut would bea better solution.

This same side-hinged type of in-stallation is not generally as effectivefor side-by-side aircraft.

The big wide canopy would haveto be attached to an equally widefuselage where there will undoubt-edly be considerable curvature. Thiswould make the use of a long pianohinge impossible.

A sliding canopy is the ultimate experience for the macho pilot. Imagine yourselftaxiing up to the crowded parking area with the canopy open and your elbow non-chalantly propped in the opening? Machismo!

One of the best forward sliding canopy designs may be seen on any Pulsar.

Here's a clever solution for a large tandem canopy to make it easier to handle.Simply make the front portion a flip-up installation and the aft canopy a flip-over,side hinged arrangement.

114 OCTOBER 1992

This rear hinged flip-up canopy is ideally suited for an amphibian as it permitseasier docking.

The large front hinged flip-up canopies are awesome when open and need the addi-tional support that can be provided by automotive type tailgate struts. This type ofcanopy should never be left unattended when open.

Gull-winged hatches are popular fixtures on some high performance aircraft. Thetwo point hinge design is critical. The frame and plexiglass must fit the openingperfectly to be assured of a leak proof installation.

The mounting of the canopywould then entail using two separateextra strong hinges to accommodatethe curvature of the canopy andfuselage. This, in turn, would pre-sent a greater challenge for securingthe large canopy in its open position.

One advantage to any side open-ing canopy installation is that entryto the cockpit must be from one sideonly. That means a protective wingwalk need only be installed on oneside.

The Sliding Canopy

This canopy is seen most frequentlyon Falcos, T-18s and is beginning toappear on RV-6s and RV-6As. Thebest example of a sliding canopy in-stallation on certificated aircraft is thatused on the popular 4-place GrummanTiger/Cougar.

Homebuilt aircraft, especially lowwing, are not the easiest to get inand out of. However, with a slidingcanopy access to the cockpit isabout as easy as it gets becauseyou simply step into it and loweryourself into your seat.

Although some sliding canopyinstallations are not designed to beopened in flight, they certainly canbe slid open immediately after land-ing to provide plenty of cooling airwhile taxiing on a hot day.

In the event of an electrical firewith smoke in the cockpit, slidingthe canopy open a bit would at leastgive you some fresh air to breath.

Actually, taking off with a slidingcanopy unlatched is not as seriousa matter as it is with other types ofcanopy installations. The reasonbeing that a sliding canopy will tendto slide shut by itself during takeoff.Actually, most sliding canopies aredifficult to pull open the first fewinches in flight because of the aero-dynamic shape of the canopy.

The worst thing said about slid-ing canopies is that when it israining the cockpit seats will getwet. Well, wouldn't this also betrue of any low wing aircraft regard-less of the way the canopy opens?

Another nice feature of the slid-ing canopy is that it may bequickly removed to provide unlim-ited access to the cockpit formaintenance. For example, a slid-ing canopy on the RV-6/RV-6A canbe removed by simply taking outtwo bolts and sliding the canopyback and lifting it off its rear track.When removed, you can also cleanand polish the plexiglass easily, in-side and out, without having towork on it upside down.

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The Forward Sliding Canopy

The installations, like those on thePulsar and the various Zenith mod-els, slide forward on tracks fitted tothe fuselage.

Other aircraft like the Lancairs uti-lize parallel struts which permit thecanopy to be raised up and swungforward.

In either event, the forward slid-ing canopies, like those tilt-up afthinged ones, do require a very goodfitting positive latching system tokeep the wind and wind noise fromgetting under the canopy and intothe cockpit.

Canopy Door Installations

Canopy doors are often not aslarge as one would like them to be.This may make entry into the cockpita bit more restrictive than it is withother installations.

Making and installing two sepa-rate beautifully contoured doors, asinstalled in the original Emeraudes,demands considerable patience andskill.

Having separate canopy doors isas much a nuisance as it is a conve-nience. This means that both doorswould have to be closed and se-cured for flight.

In flight, the bulged plexiglasswindows, like other bubble installa-tions, produce "lift" that tends tosuck the doors open. Speciallatches must, therefore, be devisedto cure this tendency.

On the ground, especially at fly-ins, there is the problem of lockingtwo doors to keep out unwelcome"investigators."

And last but not the least impor-tant, two doors are quite difficult toweatherstrip effectively.

On rereading this, I can only con-clude that installing two separatedoors in a canopy may be the leastdesirable option of all.

Gull Wing Hatches

Gull wing hatches are very muchlike having two doors that aremounted higher up on the canopy. Ifthey are large enough and open wideenough access to the cockpit is fairlygood . . . otherwise, a bit of squirm-ing will be required.

When a separate hatch is to beinstalled on each side of the canopy,a sufficiently wide space must beprovided between the two so thatboth hatches may be opened fully atthe same time. You cannot use aone-piece piano hinge to mount the

A forward sliding canopy or one that opens up front requires positive latches to en-sure that the wind will not get under it and force it open in flight.

hatch because the canopy roof iscontoured with a definite curvature.

On the other hand, if the roof linewas straight, you could install a pi-ano hinge - but the effect would bedouble ugly when the aircraft isviewed from the side.

Weatherstri ppi ng

Weatherstripping should alwaysbe installed in a single length toforce water to flow along its edgesand not take a short cut into thecockpit around the hinges.

Remember, weatherstripping willalso keep out wind noise.

Emergency Egress

In the event of an accident wherethe airplane flips over, mostcanopies and hatches will entrap theoccupants in the aircraft becausethe canopy cannot be opened.

The occupants will remaintrapped under the airplane until res-

cued or until the pilot, using somekind of emergency tool, can smashthe plexiglass or chip his waythrough the fuselage skin. A smallcombination axe/hammer/crowbaror a heavy handled hunting knifemight be just the tool for this pur-pose.

For the Sake of Creature Comfort

I believe all canopies, especiallythe larger bubble type, should havea sun screen of some sort. This maybe in the form of a painted centerstrip or a plastic sun shade stuck tothe canopy roof.

Painting a 12" wide center stripon the canopy is an effective way toblock out some of the hot sun. Thispainting may be done on the outsideor the inside of the canopy. Paintingthe canopy on the inside is a very ef-fective and attractive way to do it.Try it and see. However, since paintis not transparent, your vision will becompletely blocked in that area.

Lancair's up and over forward sliding canopy is effective and practical althoughsome builders admit that access to the cockpit is a bit difficult for some not sosvelte pilots.

116 OCTOBER 1992

The canopy doors as used in the early model Emeraude designs were very practi-cal. They afforded easy access to the cockpit and could be jettisoned if necessary.

A better way, I believe, is with theinstallation of a perforated blackvinyl Truck Blackout WindowScreen. It is removable andreusable. No adhesive is required asit clings to the static charged canopywithout help. Don't confuse this sunscreen with that ugly plastic stuffthat wrinkles when you try to get it tostay on curved surfaces.

The Truck Blackout WindowScreen will conform to your canopycurvature quite well. Simply cut it tosize and smooth it in place. If toomuch of your vision is obscured in abanked turn, simply trim off a bitmore with a pair of scissors. (It'scalled Truck Blackout WindowScreen and is sold by Wal-Mart andWestern Auto.)

Ventilation

The same kind of inflight ventila-tion system may be installedregardless of the type of canopy in-stallation you have.

Most of these ventilators don'twork too well on the ground becausetheir effectiveness depends on air-speed in most cases. It is thereforenecessary to provide for some extraventilation while on the ground.

Obviously, an opened slidingcanopy provides the best ventilationon the ground - but what about theother canopies?

The usual solution is to provide anintermediate latching position thatholds the canopy partially open while

To keep your canopy out of harms way during construction consider suspending itas shown. Because a large canopy will take up most of your bench space it will beconstantly exposed to possible damage.

taxiing. This, of course, calls for alittle more complexity in the installa-tion.

In Summary

The ideal canopy will have plentyof headroom. It will have good op-tics. The canopy will be installed sothat entry to and exit from the cock-pit can be made easily and withdignity.

The canopy should be leakproofand easy to weatherstrip effectively.

Finally,security in flight must beassured and a secondary fail-safelatching system is highly recom-mended.

If you wish to contact the authorof this column for additional infor-mation, please send a SASE to TonyBingelis, 8509 Greenflint Ln., Austin,TX 78759.

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