Chpt 10 - Canard

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Working on Chapter 19

updated: 09/05/2022

 

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12/05/2008 - In this chapter the R1145MS Canard is constructed.  I have decided to stick to the Plans recommendation and make the shorter 142" Canard.  The canard core is made in 5 pieces. 1 centre core 39" long ( using C + C Templates), 2 inboard cores each 43" long (left & right using C + D Templates), and 2 outboard cores each 8" long (using A + B Templates). These are all cut out separately and then bonded together with micro. First the cores are cut using the airfoil templates (A & B). Then the centre and inboard cores have a trough cut into the middle of the top and bottom surfaces using Templates C & D. These troughs allow for the installation of the shear web and spar cap.

Step 1 Trimming the Foam Blocks & Cutting the Cores

I started off by cutting out templates A, B, C & D from drawing M17 and spray gluing them onto 3mm Masonite board.  They were then cut out on the band saw and finished off with a file.  A duplicate C template was also made and the Talking marks drawn on the reverse side of the templates.  The Canard is cut from 2 blocks 7"x14"x64", 1.6# Density Poly Foam (Wicks part No. F200-015) and 1 block 7"x14"x41", 1.6# Density Poly Foam (Wicks part No. F200-010).  I made the Hot Wire cutter as per plans and strung it with 0.8 mm Nichrome wire and hocked it up to a 24V, 5amp battery charger.  This seems to work fine and gives me a nice cut at about 1" per 4 to 5 seconds. I proceeded to cut out the cores with my better half operating the other side of the Hot Wire cutter.  There were a couple little mistakes with the wire being lifted off the templates, but this was easily fixed afterwards by sanding down the high ridges, before removing the templates.

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Step 2 Making the Lift Tabs, Inserts, Jigging Cores, Laying up the Shear Web & Installing the Lift Tabs.

I purchased the (2) CG-NC-CLT Lift Tabs and (2) CG-NC-LTNP Lift Tab Nut-Plate Assemblies from CG Products already alodined, with the (3) MS21047-L4 anchor nuts riveted into place.  Before cutting the leading edge off the centre and 2 inboard core sections, I made the 11 x 1/4" wooden dowel pins and pushed them into the foam to make the guide holes. The sharp corners along the shear web where the leading edges had been removed were than sanded to create a small radius.  I then proceeded with setting up the 2 x 8ft long boards on the work table and paid extra attention to ensure that they were secured level, straight & parallel to each other, exactly 3.5" apart.

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Using 2 string lines, one on the top & one on the TE, I then tried to shim the 3 foam sections so that they were straight and level.  I spent way too much time trying to get this right and after a lot of frustration & fiddling,  I decided to push the foam cores back against the back board and use this as a guide to ensure that all 3 cores were straight.  Then using the 2 string lines, all I had to worry about was getting them level.  I found that by using a vernier caliper to measure the height of the string line from the work bench, on both sides, it was easier to ensure that the line was level before shimming the foam cores.  Once I was happy with the setup I then proceeded with gluing down the nails in the centre core section .  The next day the 2 outer sections were then microed onto the centre section, aligned and secured into place. 

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The lift tab inserts were then set into place with dry micro using the jig setup described in the plans, ensuring that they were centred and perpendicular to the chord line.  I marked the location of the jigs, so that they could be refitted back into place, after fibre glassing the shear web, so that the bolts holes for the lift tabs could be redrilled.  With the canard setup on my work bench I didn't have enough bench space to rollout and cut the Bid & Uni cloth, so I decided to make a portable cutting table for my fibre glass stand.  The requirements were to make a table 1800mm long by 1200mm wide with folding legs and the ability to clip onto the stand as and when required.  A quick trip down to Bunnings to buy a sheet of 6mm thick MDF and a couple strips of pine, and a couple hours later I had the table knocked up.  The cutting table worked out great, I should have done this a long time ago.

I cut the cloth as per plans on Saturday and on Sunday with the help of my better half we finished all the glassing in about 4.5 hours.  Before starting we decided to made 4 paper templates of the canard, out of grease proof paper, for the 4 layups.  The 1st at the full length of the canard 125", the 2nd at 77" to fit the 38.5" BL location and 3rd at 57" to suit 28.5" BL. The 4th for the single Bid layup was cut at 39" for 19.5BL.  The 1st, 2nd & 3rd layups, 2 plies each, were each wetted out on the greaseproof paper templates and cut a little under size before being fitted onto the canard. This worked great and I had no build up of glass around the shear web joggle.

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After removing the peel ply, the lift tab insert holes were drilled by re-assembling the jigs I made earlier.  The plans method works really well here and the holes lined up perfectly. After floxing and bolting the tabs into place I used a string line to check the alignment of the 2 tabs, the height difference between the 2 tabs was within 0.5mm, which should be OK.

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Step 3 Jigging & Bonding the Canard Sections Together

I cut out template K from drawing M-17 and made 13 identical jig blocks from 3/4" particle board (3 extra as suggested by some builders), using the band saw to rough cut and the drilling machine clamped to the work bench to sand to the line.  The drilling machine worked great and was much easier & more accurate than trying to do this by hand.  I decided to use thicker board for the templates, as advised by other builders as it is easier to level and setup the canard later on.  I also cut out templates E,F & H,I at the same time.  The K templates were then setup and glued onto my work bench.

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At this point I deviated slightly from the plans by bonding on the leading edge cores onto the canard before putting the whole canard into the K jigs.  I used the canard core cutting template to make a couple new wood jigs. I then used those jigs to hold the leading edge pieces in the proper orientation while the micro cured. After bonding the cores I dropped the canard into the 13 K jigs, bonded the fishtail of the centre section with 5 minute epoxy and then pulled the two ends into alignment. Once they were lined up properly I bonded them to the jigs with small blobs of 5 minute on the fishtail and used drywall screws through the front of the K jigs to hold the leading edge tight onto the jigs. 

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Step 4 Spar Cap Layup

Ready for the spar cap lay-up, the canard bottom has been taped and has newspaper laid over the exposed foam sections. As usual on the larger lay-ups I solicited the help of my beautiful wife Bernardine for this lay-up. She has become extremely component at the art of fibre glassing, halving the time it would normally take on my own.

As per plans I ran a micro bead along the inside corners of the shear web, ensuring there was no excess micro on the fibre glassed areas. I also made a temporary roller stand on the end of my adjustable ladder to hold the roll of UNI spar cap tape, making it easier to pull off lengths of tape as needed.  Credit card squeegees are perfect for fitting into the spar cap trough and can be used to gauge whether the spar trough is filled properly, it lines up exactly with the foam on either side of it. I used normal masking tape along the edges of the trough and it didn't come off at all for this part of the lay-up, worked great.

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Here's the trough filled all the way, with a total of 9 layers. At this point I used the K template to double check for any low / high spots on the lay-up. For some reason I left the masking tape on and proceeded to peel ply the complete lay-up. This proved to be a big mistake as it took hours to remove all the masking tape after the lay-up cured. DON'T DO YOURS THIS WAY! TAKE THE TAPE OFF!

Step 5 Applying the Bottom Skin

Once the peel ply, newspaper and masking tape was removed I used a combination of razor blade scrapers and sandpaper to remove any high spots and bits of tape. I managed to do it this with only minimum damage to the foam. I think, when I do the top spar cap, I will definitely take off the tape before I peel ply and let it cure... At this point also sanded a 1/32" x 1" wide depression at the outboard ends of the canard (for when you attached the canard tips). 

Once all of the tape was removed, I was ready to apply the bottom skin. I started by turning the canard over and applying the duct tape called for in the plans along the leading edge of the canard.  I used 2" wide tape which was more than wide enough to stop any excess epoxy from running past the tape onto the top foam surface of the canard.  The UNI & BID cloth were cut as per plans.  I used 1" wide masking tape on the edges of the UNI as suggested in the plans to stop the edges from unravelling and just cut if off after the cloth had been laid and wetted out.  The plans say to use nails to affix a piece of 1" wide peel ply to the trailing edge on the canard.  Lots of people reported having trouble pulling out the nails or staples when removing the fish tail, so I used small dabs of 5 minute epoxy along the full length of the peel ply strip to hold it in place during the glassing process. This worked fine as the peel ply did not move and was easily removed later on during the prepping of the trailing edge in Step 6.

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I was happy with the final result and with Bernardine's help the complete lay-up took about 2.5 hours.  After cure I removed the canard from its jigs, removed all the peel ply, tape and newspaper and sanded the trailing edge straight as per plans. Double checked it with a Straight line, It's not like a ruler, but it's pretty good.

Step 6 - Installing Hard Foam Blocks for Elevator Hinges, The Upper Spar Cap & The Upper Skin

I purchased a 12ft length of 1.66" OD PVC pipe and made 5 1"x4"x8" long wooden blocks from a length of finished pine and proceeded to set-up the bottom jig as per Fig.45 on Page 10.6.  I used Bondo as stated in the plans to stick the board and pipe together, but found that when I tried to flip the canard over the next day, everything fell a part.  It took me more than an hour to remove the hardened Bondo from the canard and jigs, before starting again with the set-up, this time using 5 minute epoxy.  Before fixing the canard to the work table I proceeded to remove the "Fishtail" using a hacksaw blade and a mixing stick as a shim to ensure that I didn't remove too much foam.  This worked great and I finished off with a sanding block and template F.  The canard was then turned around with the leading edge overhanging the table as per plans, the table was re-checked for level and the 5 boards shimmed and glued to the table, ensuring the canard was 100% level.

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The plans are pretty vague about the actual size & exact location of the 6 foam hard points, so I followed the advise and sizes posted on Rick Maddy's website and made each foam block 1" wide by 1.5" long and 2.25" deep, placed .25" aft of the spar cap trough.  I also used the Canard E Template to obtain the correct shape of the 6lb Last-A-Foam blocks, Wicks part No. F400-090.  To make the 6 square holes in the canard, I used a utility knife and a small wood chisel to remove the foam.  The foam blocks were then microed into place, making sure that there was no excess micro on the blue canard foam, and left over night to cure before sanding down the excess to the same contour as  the canard top surface.

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The upper Spar Cap was then completed using the same technique used on the bottom, with a total of 9 layers.  I decided not to install any antennas into the canard for the Glide Slope and Nav as I plan to fly VFR and will be using GPS.  The final 4 top lay-ups were completed as per plans in about 4 hours, peel plied and left to cure overnight before trimming and removing from the jigs.  The finished canard at this point weighed in at 10.3kgs (22.7lbs), not sure how this compares with other builders?.

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