More Cowling Templates (Dec. 30th, 2006)

This shows the template is not perfectly symmtrical. This is not a big problem however. I will cut the large board in half and make an identical mirror-inverted part. After gluing together the halves these have to be symmetrical.

 

 

Cross-Section where nosebowl will (hopefully) meet cowling skin.

 

 

Siedview of nosebowl cross-section.
I purchasd three boards of blue styrofoam today. Using this stuff to make the positive mould will become a rather nasty affair (styrofoam fragments are statically charged and stick everywhere but the dustbin.

The cooling 'noseholes' will be as far apart as possible, firstly because this will be near the cylinder heads where most of the heat is produced, and secondly because as closer to the propellor hub the less airflow is generated.

Most probably in the center lower section will be the air inlet for the oilcooler.

Currently I'm goint not to use ram-air for the engine. I heared some bad effects from RV builders. If the airscoop is not properly designed the air pulses from the propellor do more harm than good. So probably the air inlet with filter will be located just in eont of the firewall facing forward into the high-pressure cowling section. An alternative might be an NACA-inlet or air-scoop on the left upper part of the cowling. This all is not finally decided yet.

=====================================================================

 

Engine Mount, Once More (Dec. 28th, 2006)

Today I cured the stuck drillbit. When I removed the engine mount the bit-fragment simply dropped out (now I have a single drillbit left for all the still-to-do 1/4" boltholes).

This is what I suspected: the lower weld seam dows not allow for a nut to be seated properly. This should be a case for my 'mission impossible' section.

 

My only cure was to grind off a good part of these two self-locking nuts. The self locking plastic insert is still intact. This is not a nice solution, but I don't know of a better one.

 

 

Now the partial nut at least sits flush in the steel frame.

 

 

 

Because I'm not satisfied with this questionable solution I drilled a third bolthole on each of the lower attachments. The attachment tab should not be weakened substantially by this.

As you can see I do not use the countersunk cross-recessed bolts as suggested by the plans. Countersinking this tab would still weaken it. Because I use 0.6mm aluminum sheet instead of the thicker composite for the cowling the boltheads should not be in the way. Otherwise I will press some small dents into the cowling.

 

 

Some interesting sidenote (Tony Spicer mentioned it some time ago in a mailing list):

=====================================================================

 

Cowling Templates (Dec. 27th, 2006)

My metal cowling will be of a traditionally horizontally split one (the original Sonex cowling is vertically split). The advantage of the horizontally split cowling is the smaller top part can easily be removed because it will be fastened by camlocks (the lower cowling is attached by piano-wires slipping into hinges which is a p.i.t.a. to remove and particularily to attach again). When the top part is off then all checkpoints of the engine compartment are easily accessible.

This is a rough cardboard template. Critical is the minimum distance between exhaust tube and cowling (however not as far as critical as it is for a composite cowling). Generally there schould be as few unused space as possible in the engine compartment.

The engine currently is not in the final position. According to the plans there have to be spacers of 35 mm between engine and mount to bring the engine this amount forward. Because I had to use thicker sheet metal in the tail I'll make the spacers 50mm at the beginning and eventually will reduce the lateron whatever the center of gravety requires.

The rocker covers will receive some 'cheeks' (however not the usual teardrop ones). The cheeks allow for a narrover frontend.

Actually this cardboarding is not very handy. Another idea came to mind: If I would attach a sheet of cloth on the fuselage sides and bottom, then make an oval board attached at the nosebowl intersection, then attach the other end of the cloth on this board I will get an cutting template muche easier.

 

 

The lower cowling will end about at the red line, where the nosebowl attaches.

Looks a sif the nosebowl-forming will be the most demanding job at this section.


 

 

This is the first template of a cheek (which will cover the rocker-box cutout). From the aesthetic standpoint I think this kind of shape fits much better to the 'edgy' Sonex body.

=====================================================================

 

I almost asked for it (Dec. 25th, 2006)

Today I did a lot of little unimportant stuff, grinded the powder coating away from the engine mount's gerled reception tube and also from the engine mounting 'fingers'. Actually I don't know why Sonex made them so tiny. The rubber bushings habe bores of 9mm. So I have to slop yet another tube ocer this tube - kindof a silly solutin.

 

After I pilot drilled and clecoed the engine mount I asked myself why not final drill, push some bolts in and hang the engine on. As usual if everything runs too smooth disaster is waiting on the next corner...

My disaster happened when I drilled the lower bottom bolt hole. This two holes go into this 'steel box'. Inside of the box is another 45 degrees tube intersection. When the drill breakes through into the box it will wander up the 45 degrees ramp, will stick and then break. I wonder how many Sonex builders ran into this trap.


 

Imagine, a washer and a self-locking nut has to be fiddled on the bolt inside of this box. The designer of this service nightmare should be forced to bolt on such a contraption at least once every day.

 

 

Anyway, I will try to cure this crap at another time. Let's hang the engine!

The perspectivic view is a bit misleading. The total width of the engine is a few millimeters less of the fuselage width.

 

Engine looks not that impressive. Actually I use the 'Diehl Accesory Case'. In that case the plans ask for an extender of 35mm to bring the engine forward for this amount (actually I don't realize why the AeroVee does not need this extension). This picture may give an impression how the cowling sides may look like. Actually I dont't like the aesthetics of the Sonex original cowling. Looks kindof 'fat' at the front end. When I wandered around in cyberspace recently I found this:

My cowling will be split approx. at the red horizontla line. This is necessary because the rocker-cover cheek has to be positioned just below.

This cowling looks sharp! The lower part forms a straight upward line -great! And most of the cowling is made of sheet metal - a big advantage (if you count all the fibreglass cowlings having burnmarks). The next few days I'll tailor some cardboard panels just to get a feeling how -my- cowling could look like.

=====================================================================

 

The Engine Mounting (Dec. 25th, 2006)

I hanged the motor mount onto the fuse today. Surprisingly the mount snapped in almost perfectly (such glory moments too rarely happened during this project)

 

the engine mount attach points are shimmed against the fuselage hardpoints. I used 2mm Aluminum on all four sides. I think explicitely adjusting of the thrustline is not necessary - everything looks quite well.

 

Not so nice: This is the tube where the titanium rod of the main gearleg slips in. The angle blocks the rod (same on both sides). The fuselage edges I made exactly according to the plans. Actually this corners of the engine mount could have been done better by Sonex. As you can see , this tube-end should not rest on this aluminum angle at all. This steel cage would be ideally suited to transfer loads onto the fuselage. Sonex only would have to position the gear tubes a few millimeters to the centerline

.=====================================================================

 

The Breath of Time (Dec. 24th, 2006)

The wings are complete (with minor leftover work like wingwalk, doubler) and stowed away in the workshop. Why not outside in a dry place you may ask? . Because of this:

This is a forward fuselage side. The fuselage was rested under the balcony for about three years. There never rain nor snow has touched the aluminium. The complete fuselage was vovered by a plastic sheet.

 

This is how it looked when I uncovered the fuselage. All formerly mirror-shining surfaces are covered with this kind of oxidation.

 

All this talk about '6061 is corrosion resistant' - forget it! The skin can be repolished but it is not a light work.

 

At left a cleco left out for three years, at right one from the toolbox

 

I should have waxed the aluminum after the polishing job, maybe this would have prevented the mess (and a lot of additional work).

=====================================================================

 

@!?&%-Endrib (Dec. 17th, 2006)

I even got bad dreams because of this endrib-problem.

The hole-duplicator did NOT work as expected. The unsupported end of the wingskin and the clips attached to this skin will bend away when I drilled throu the hole duplicator. While drilling all seemed fine, but when the rib is attached one of every three holes is out of alignment @!?&% (curse No.1).

I tried also the lamp-from-behing method but the hole shadows are blurred so that one cannot find the exact hole center @!?&% (curse No.2).

In my despair I returned to the paper drill-pattern method. If the lamp-from-behind method did not work, then maybe I can 'print' the holes. So I painted all tabs with blue lacqueur-paint then quickly, as long as the pint was wet, pressed a paper over it.

You can see the imprints faintly on the lower part - totally useless @!?&% (curse No.3).

Then I used this paper, picked holes through where the tabs were, inserted the screws, then used the cross of the phillips heads to precisely mark the hole centers (see 'X'es on top). This went quite well, but watch the paper waves. This paper is too thin for this purpose @!?&% (curse No.4).

 

So I did it all over again, this time used a stronger paper/light cardboard. Picked the holes, all crews in, mark center points, crews out, transfer to metal, centerpunch, pilotdrill, finaldrill, deburr, dimple, cleco on again (clecoing is faster, in case this attempt would also fail).

 

-Relief- all of the clecos found their nutplates behind!

 

The status on Sunday night. This is acceptable now. Some more screws, Strobelights on, finished is the left wing - hurray!

 

This hole affair took my attention for more than one week. For this left wing I made three scrap metal endribs, one good one and spend all my leftover 0.025" sheet metal. Lesson learned? -Never give up!

=====================================================================

 

Problem Solving (Dec. 11th, 2006)

Thanks for the ingenious contributors of the independend Sonex email list I received a few practical solutions for my problem:

 

I decided for the latter because such a duplicator can be made quickly using some scrap steel band.

This is the tool. The making took only 10 minutes. The lower part is dimpled and a pointed screw is glued in (I used medium-strength Loctite, will see if the screw will stay in place). The holes are 1/8", I think there's no need for pilot drilling here.

 

Application of the hole-duplicator. The new endrib is only roughly snipped out with about 1/4" oversize on all edges.

=====================================================================

 

Problems with the Left Wing (Dec. 9th, 2006)

Finally, after 8 weeks of waiting I have received my bag of 1000 CCC-42 rivets ( except of the row where the wingskins overlap above the sparcap, I only use flush rivets).

Today I have pulled the last rivets through the left wing's ribs and skin. Then only mount the stobe-lens, then store the wing away and start with someting totally different - engine installation. So I thought - how wrong I was!

The wing-endrib's dimpled holes do no more match with the mounting tabs! What the hell is going on here? The endrib is completely finished, primed, dimpled and all - and then such a mess!

I think I know the reason: when I match-drilled the endrib the wing only was clamped together using a few clecos. Most probably the wing frame was NOT square and true. So, now when the wing (hopefully) is perfectly aligned the holes are out of alignment (up to three millimeters - too much to pull and push them in place).

It very much looks as if I have to make another endrib. And to make things worse, the new one cannot be match-drilled anymore because the mounting tabs are alread in-place, nutplates riveted-on and the skins also cannot be opened anymore. What to do now?

 

After some headscratching this are my plans now:

These are my plans fo far. If there's someone out there with a better/easier method please contact me on the independend sonexbuilder's email-list or via 'ga at loeff dot de'. I'm frustrated, have to destroy a bottle of apple-wine now....

=====================================================================