RW19 – Oscar – Barcelona/Catalonia

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Joined
Nov 1, 2020
Messages
23
Location
Catalonia
A decades long dream of building my own airplane has finally come to fruition!. On November 1st. I did acquire online the constructions plans for my RW19. Some weeks went by studying the plans, doing some research and liaising with HBA fellow members asking for advice. By the end of the month, the construction video package was also ordered. December was fully devoted to prepare the documentation required by the Spanish Civil Aviation Authority in order to grant permission for the homebuilt construction. I wanted to have a clear and positive official statement before starting to buy the wood. More on wood election will follow in incoming posts...
 
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Joined
Nov 1, 2020
Messages
23
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Catalonia
Two weeks ago, I did complete the construction of my working bench. The final dimensions of the bench are 18Ft x 49" with a height of 32". It is important that your construction is sturdy enough to avoid the boards to flex out of true. The size of the resulting bench is long enough to build the airplane, but leaving not much extra clearance. I did my best with the limited available space of my garage, if I had a bigger place, I would have added some extra Ft.

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And immediately after finishing the bench, I started drawing the stabilizer and rudder in preparation for the wood to arrive somewhen...

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Joined
Nov 1, 2020
Messages
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Catalonia
My construction activity has been lately idling, as the lead time to source the required wood has been way longer than I anticipated. Finally I have opted to use Western Hemlock wood, as a local fellow had some surplus he was willing to sell. I have performed several tests to the chosen wood, and the MoR (Module of Rupture) was right in the middle of the values stated in the technical literature (Wood Handbook--Chapter 4--Mechanical Properties of Wood by David W. Green, Jerrold E. Winandy, and David E. Kretschmann). My airplane will thus be slightly stronger than a Sitka built one and hopefully only some 30 pounds heavier, I consider it to be an acceptable trade-off.


This is the clumsy press I assembled in order to test the wood, ugly but functional:

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As I will start with the laminated rudder, steaming will be required. I have therefore acquired a steam generator and assembled a steam box (actually a steam tube) by re-purposing some very affordable galvanized chimney sections. The tests I have performed with the assembly, throw very satisfactory results as temperature and humidity remain pretty high during the whole steaming procedure.

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Joined
Nov 1, 2020
Messages
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Catalonia
A quick update showing that I have been working on the tail of my plane. I had my doubts whether to post the pictures before or after having tidied up the whole assembly. I have finally opted to show how messy the parts look before being finished in contrast to how beautiful (I hope so...) they will look at the end of the process.

My working pace have been limited by the curing times of the epoxy. The slow process, on the other hand has allowed me to improve my woodworking skills, mainly regarding lamination which has been my first attempt ever. The attached picture shows the vertical stabilizer and the rudder still missing the beef up blocks, as well as gussets and reinforcing plywood.

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I'm planning to start working next week on the horizontal stabilizer and elevator.
 
Joined
Nov 1, 2020
Messages
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Catalonia
Recently, I have been dealing with the horizontal stabilizer and elevator. The stabilizer is a pretty straight forward construction, requiring mainly to pay special attention to the quality of the joints. I finished the basic frame less gussets in roughly one week.

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The elevator is quite a different story: compound curved laminations, huge dimensions and the logical requirement for a complete symmetry between the right and left halves. As I am gaining confidence in my construction capabilities, I am also taking more risky approaches. I have decided to build a single jig for only half of the elevator. The idea is to flip the completed half along its Y axis and reuse the same jig for the remaining half. Time will tell if this decision has been a wise one, but if no complications arise I will get a wonderfully symmetrical elevator

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This sharp radius was the main source of my concerns as I feared the outer lamination may splinter, hence extra jig reinforcement was foreseen. It seems it has worked out well as wood shows no sign of damage.

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Nov 1, 2020
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Catalonia
As I haven't updated my log in a while, I will just comment that my approach to flip the elevator and hence having just 1/2 of the required jig construction, has worked out perfectly. There are no flaws in the elevator construction which may be derived from the flip approach ;-)

I still need to attach some small corner blocks on the trim section and do the gusset reinforcements. My next post, hopefully will show all the tail components already finished and varnished.

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Joined
Nov 1, 2020
Messages
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Catalonia
Finally I can consider the tail section as almost finished. I couldn't apply the gussets to the elevator, as I ran out of plywood and the supplier won't deliver my order till mid August. Nonetheless I could complete the vertical & horizontal stabilizers as well as the rudder.

Overall I am satisfied with the achieved quality and I am quite confident, that the parts will look even greater once covered with fabric and painted.

I have finally opted to round the exterior profiles by means of a router bit with a 5/16" radius. I initially doubted between the 5/16" and 1/4", but found that the latter was still leaving too boxy an appearance to the profiles. As you can see, the profiles were rounded before applying the reinforcing gussets.

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Here you can see the rudder in the process of drying after application of the sealing nitrocellulose lacquer.
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Putting the parts together to check gaps and the overall assembly appearance.
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Leaving apart some minor cosmetic corrections that I will address shorty before installing the parts on the fuselage, the only flaw still to be corrected is a not fully straight beam of the horizontal stabilizer. It's flat when lying on a surface, but in the middle of the beam intended to carry the hinges, a slight belly towards the elevator can be observed. As the deviation from perfection ;-) is rather small, I will carefully remove some wood and hopefully this will leave the hinge axis absolutely straight.

Next post should already deal with the construction of the wing ribs...
 
Joined
Nov 1, 2020
Messages
23
Location
Catalonia
My forced idle period came finally to an end two weeks ago, when I finally got the plywood I ordered from the Finnish sawmill. I placed my order to a company called Koskisen (Koskisen Group - Koskisen) and I must say that I couldn't be happier with that decision. The plywood is virtually defect free and easy to work with. Moreover, the staff at Koskisen have all been really committed to assist me with my transportation requests in an attempt to keep forwarding costs at bay (the mill is located 2300 miles from my home!).

Here you are a picture of the whole plywood batch I've got delivered

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As anticipated, I have pursued my construction with the wings. I need plenty of wing ribs, which for my plane are all identical save the inboard and outboard ones which are blinded with a plywood sheet. That means, that I am almost working like an assembly line operator, cutting template gussets, trimming wood, gluing, etc... It's a tedious work, but somebody had to do it ;-)

Be it as it may, the jig I constructed eases the assembly. You may realize that sensitive areas have been wrapped with wax paper to allow for a somehow easier unmolding (still a pain to free the ribs from the jig though!)


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My first two ribs look acceptable to me. The more ribs I will construct, the better they should become.

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Joined
Nov 1, 2020
Messages
23
Location
Catalonia
It’s been a while since my last post and this time lapse deserves some explanations. Recently I have been really busy doing some home renovation work. I’ve been mainly acting as plumber, electrician and carpenter, cleaning lady and everything else it may come to your mind for such situations.

It shouldn’t be an excuse for neglecting my work on the plane, as obviously the home renovation tasks haven’t taken all my spare time (although most of my energy, YES!). Moreover, the always present menace of a computer crash had materialized in between. I do now and then back-up copies of my most critical files, but you guess what? the last back-up was three months old, so I have lost plenty of files relevant to my Storch project. Be as it may, the new Lenovo computer is now up and running at full power . I hope to achieve soon a good cruising speed with the construction of the wings.

I finally got all my wing ribs finished. The reinforced ones were given a final trim with the router and to my great surprise they all ended up quite decent. Right now, my garage seems a spare parts warehouse with plenty of airplane parts and none of them assembled so far.

Here you are the wall storage I have devised in order to save my scarce working space (ceiling may be next when storage for the complete wings will be required ;-)
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Picture of the progress done with the ribs with reinforced trailing edge, the ones where the brackets for ailerons and flaps will attach:

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In addition to the regular complete ribs, there are two «trailing-edge-only» ribs which you can see on top of the complete ones. Those fractional trailing edges are intended to allow some space for the bolts of the hinge bracket. According to the construction drawings, they solely attach butt end to the rear spar, but bearing in mind that they are supposed to take the lion share of the torque involved when lowering the flaps, I thought it would be wise to apply the same design used for the regular ribs, say enveloping the spar and adding a pair of gussets. It may well be over engineering but I needed some peace of mind if I have somewhen to fly that airplane.

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And last but not least, I have started to manufacture the nose ribs using a template and a copying router bit. Not an easy task though! Almost every time I use the router, I damage some parts and the nose ribs obviously were no exception... Be as it may, at the end it seems I have succeeded in creating my first four pieces (top corner slight damage included), which will soon be glued to the blue foam.

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Joined
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Messages
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I have been busy completing the different parts for my wings. So far, all ribs including the inboard & outboard plywood reinforced ones are done. Moreover, the regular nose ribs, the extended and the thickened blue foam ones, are ready to go as well.
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I am pending of sending the Aluminum raw plate to the CNC workshop to laser cut my bracket hinges. This is something that I could do by myself with my manual tools, but I am sure the improved finish achieved by the professionals (at its due cost!) will compensate. As I wish to assemble the brackets before the completion of the wings, I have started to work on the ailerons and flaps until the brackets arrive.

A word of caution regarding the construction plans: they mix (sometimes with a remark, sometimes without it) different versions of the parts to be constructed. Some drawings refer to the prototype, whereas others refer to improved versions. This is particularly true for the ailerons & flaps. The construction of my chosen Frise ailerons are poorly documented and some creativity on my side is being requested.

I have reviewed the plans plenty of times and due to contradictory instructions in different parts of them, I have ended up with doubts on how to assemble the ailerons. The prototype used a slotted rib and spar construction. The Frise version calls for either continuous spar caps with “patches/doublers” of plywood web adjusted between ribs or for continuous ply web with discontinuous spar caps adjusted between the ribs. After seeking advice from my friend and fellow builder MadProfessor8138 our views converged in what I call an hybrid version, say using the rib design of the Frise aileron but the slotted building method of the prototyped part. And as it couldn’t be otherwise, I have played God by redesigning a bit the rib (hope I won’t regret it though!)

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Mainly I have added some lightening holes, increased the main triangular one and provided the needed slots for the caps and spar web (the latter not shown, being still displayed the odd centered design for a self supported web). The RAST 1,6393 notice, is a reminder for me regarding the stretching factor I selected when doing the mosaic of plans using our European DIN A4 standard piece of paper. For that sake I found this webpage to be gorgeous: The Rasterbator

Meanwhile I am working on the spars, glueing the caps and waiting for them to dry before cutting them with my jigsaw (fingers crossed I don’t screw it up at the very last moment!)

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Joined
Nov 1, 2020
Messages
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Work on the ailerons & flaps have been progressing at a slow but steady pace. As I am ordering some accessories and tooling short before I really need them, any delay in delivery implies me being delayed as well. I don’t won’t to put too much pressure on myself as otherwise this project would turn from an expensive hobby to a tiring nightmare. I am aiming at taking it easy!

In order to cut and adjust the required slots on the spars and ribs, I opted exclusively for manual work, no power tools this time! I hence resorted to my trusty Japanese style pull saw and a set of miniature hand files (actually intended for steel, but working fine for final slight adjustments).

This two pictures display the quality of the finishing I was able to achieve (best ones depicted though...)

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The ailerons and flaps look good so far. What you see, is holding together without a single drop of glue. This is a kind of double check that my self-imposed tolerances have been met.

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Some of the ancillary parts have been already received, whilst during this week I have confirmation for the arrival of the balance, mainly the sinterized copper bushings and a reamer for the aluminum brackets.

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I commissioned the laser cutting of the 2024-T3 Aluminum brackets to a purportedly reliable workshop. I was upset when the foreman told me they screwed up two out of twelve ordered brackets (I had no spare material left for a second attempt). They made some sheet centering tests and instead of cutting a small diameter, they went crazy and cut a ½” circle. Obviously as dictated by the Murphy’s Law, those tests affected the most sensitive part of the brackets, say the hinging point.

I ended up having to reduce the length of the two affected pieces and will try to reinforce the attachment to the wing rib by changing the hole pattern and perhaps even drilling an additional hole for peace of mind.

Here the before and after:
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Joined
Nov 1, 2020
Messages
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Catalonia
Today I finally finished the two flaps and the two ailerons. I am quite satisfied with the accomplished quality. I am mostly proud of the soft and sexy curvature of the leading edge. All parts have been duly varnished and will await stored until finally being assembled to the wings at its due time.
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Initially I had in mind securing the hinge bolts by means of E-type clips. I though it would be the neatest possible assembly and taking into account that no lateral efforts where foreseen, it sounded to me the logical way to proceed. My joy lasted very little time, during the assembly checks and without any substantial load, one of the clips suddenly sprang up showing how dangerous my approach was. I suspect the material the clips are made of were to blame. Conventional clips are done with special spring steel, but the ones I used were made out of stainless steel whereas the required spring-back tension was obviously insufficient. I have now ordered replacement clevis and their corresponding split pins.

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A glimpse of the construction phases:
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On the very last moment, I have decided against my wildest instinct to cut a 1" maintenance hole for the easy of installing and/or removing the bolts. The first two surfaces where glued with the "unremovable" bolts and brackets already in place (not really advisable, though!)
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As of next week, I will hopefully start building the wing’s main spars.
 
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Joined
Nov 1, 2020
Messages
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Catalonia
I have finally finished the first main spar of my wings. I wanted to keep the spliced joints to the bare minimum and have managed to have a single joint per spar, owing it to the fact that I ordered extra long plywood boards. The webs have been cut slightly oversize (1,5 mm extra width) to allow me a final trim when the ribs will be assembled. Having to cut the plywood webs with a jigsaw is not an easy job, hence the oversize approach. In order to have the spars as straight as possible, I used a laser level to help me trace the contours (as the red light was really faint, no photos were taken, sorry).

Here you can see a set of front and rear spar already spliced and without further assembly

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Some considerations regarding the scarf joint: in order to increase the glueing area, the joint was cut diagonally (as and amendment in the construction plans suggested) and with a really generous slope. All work being done with an electric band sander and a manual wood file. Bearing in mind the limitations imposed by the tools used, I am proud of the achieved results.

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Here glueing the caps. Instead of nailing or stapling them, with the ulterior need for removal and the unavoidable damage ensuing from that operation, I opted for a overkill use of clamps. The alignment is tricky, as the cap is prone to slightly shift out of position when settling, but with some patience the wood can be convinced to stay where you want and the results are quite satisfactory.
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The construction videos call for reinforcement doublers on the scarf joint and over the swallow tail blocks for the spar strap attachment. Those doublers are not indicated in the construction plans though... hence after some cross checking I decided to go for them but using 1/8” plywood instead (main spar web is 1/4”). The back side, considering the proximity of the swallow block to the scarf joint, it seemed to be best solved by deploying a longer single doubler instead of two very close smaller reinforcements.

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The front scarf joint doubler, was cut to match the on end of the swallow tail block

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And here it goes the finished spar and hopefully soon, three more to go!

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Finally I have finished all four wing spars with consistent measurements and an overall good finished quality. They all are straight as should be. For the sake of taking the picture all four spars have been arranged parallel to each other, and to me it appears that a kind of Art Deco pattern has arisen.
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The spar root fitting straps deserve a word apart. They are being made out of 4130 steel and I can tell you I hadn’t ever drilled through such a hard material before. Even though I used extra hard drill bits, I really had a hard time drilling the holes through the steel and achieving something close to a circular form!
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Before attempting to glue the ribs onto the spars, I have made a dry assembly test. Only very minor adjustments were necessary.
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The attachment of the rib to the main spar is done with the usual epoxy and brass nails which won’t be removed after curing. As I was unable to find the brass nails in the size I needed, I have opted for using stainless steel mini brad finishing nails. The stick making part of the rib is 5/16” x 5/16” and during my tests I found that even when great care was applied, some of the sticks did splinter as I drove the nail through. My solution tested to satisfaction consists in manually pre-drilling 0,8mm holes which serve as guide to the nail. It’s laborious, but it works.
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And last but not least, my personal Hall of Horrors! The three big mistakes, which I’ll have to fix with blood, sweat and tears.

First one: applying the doublers before installing the ribs is not a good approach ;-) The aft part of the ribs do envelope the rear spar, hence to assemble them they have slide along the spar. I painfully removed the doubler which will be made anew once the ribs are glued on place.

Second one: if one increases the thickness of the outboard spars through doublers, your rib template does not work. I h ad to chisel out some wood, reinforce with an extra stick and glue all anew.
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Third one: the rear spar has a vertical offset of 5/16” to the main spar. If one does not account for this offset, a misalignment of the front and rear pivoting pin of the wing strut straps will occur. I will have to plug the wrong holes and drill new ones. To my defense, I must argue that the constructions plans regarding this point, are extremely poor and confusing.
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Progress is ongoing on my right wing. Ribs have been attached to the main spar using the mini-brads and the result is a tidy and strong joint.

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I did cut the compression and diagonal members to a very close tolerance. In order to avoid having them working on too steep a slope (due to the members being of a smaller section than the cap they attach to on the spar) I have opted to attach the members flush with the top of front spar cap, but on the other hand flush with the bottom of the rear spar. This implies that the gussets will have to be glued on top of the members for the front part but on its bottom for the rear part. This way the still existing slope becomes almost negligible. I don’t know whether so much care made sense, but it was the decision I took and I am quite happy with the result.
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The trailing edge is supported by three sticks per cell, which you can see here during the dry assembly test. Tolerance again if of utmost importance as shown by the sticks holding without a drop of glue.

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As usual along this project, the assembly of the nose section is a bit confusing. Depending on your source of information the method to follow varies substantially. If one obeys what the constructions plans call for, one has to use a continuous 168” long nose runner. If one watches the construction videos, the runner is cut to cell lengths and butt glued at both ends to the extended nose ribs.
I have decided to go for the one piece way! It implies no weight penalty, but construction is substantially more complicated, as the runner has to go trough the extended nose ribs and one has to manipulate a rather long assembled piece (14 Ft). I even introduced my personal bit of creativity in letting the runner go trough the inboard and outboard reinforced blind ribs. Extra strength wherever possible!
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During the next week, I am expecting to attach the whole nose section and form and glue the trailing edge in its nice curved pattern.
 
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I virtually finished the right wing, remaining only to varnish it. The slots deserve a special treatment as they were not included in the provided list of materials and hence I had to reorder some additional thin plywood and stringers.

Attachment of the nose ribs assembly went straightforward and despite its large size, the final result was according to my expectations. I found it was easier to work with and far more convenient for my back pain to place the wing in a vertical position. Moreover the setting of the glue was working with the gravity and not against it, hence running glue was avoided.

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The trickiest part of the wing construction though, was the curvature of the trailing edge. The plywood used was 1,5 mm as per the specs, but if it was to be my own design I would have used 1 mm instead. The radius of curvature was too small for 1,5mm plywood and it was almost impossible to avoid some longitudinal cracks. I did repair them to the best of my knowledge, but can’t say I am proud of the result. On top of that, the strain that the plywood produced when the glue was setting, induced some warping on the top stringers, which before assembly were straight as an arrow! I ended up accepting this slight upwards bowing, as once the wing is covered it will give even a nice oldie appearance to the trailing edge.
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Covering the leading edge presented no major challenges apart from having to deal with large pieces of plywood in tension. My first finished cell ended up with some slight ripples which I had to file down and smooth with wood putty (I know, again a not optimal solution but having ripples inducing turbulence where the slots will be placed would have been a far worse scenario).
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And here it goes the right wing completed. I even temporarily assembled the flap and aileron to check for accuracy. Only very minor adjustments will be necessary, which I will take care of once the wings are attached to the fuselage and the control cables are installed.
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As of next week, fun starts again with the left wing. With the experience I have gathered, I hope to achieve a better result.
 
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