Airdrome Aeroplanes 75% Fokker Dr1

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flyvulcan

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As if I don't have enough on my plate (Komet jet build in Australia and Lightning Bug rebuild in the US), I've now started an Airdrome Aeroplanes 75% Fokker Dr1 triplane here in the desert of the Middle East to help pass the time here. I am building the aircraft in partnership with a fellow Ozmate who is flying for a local airline. To view information about the kit, check out the Airdrome Aeroplanes website at Airdrome Aeroplanes ~ Holden, MO

Our first build session only lasted 1 hour and we knocked up a jig for the rudder. We traced a full sized template onto a sheet of MDF and cut some small blocks which we screwed to the pattern to hold the aluminium tubing in place.

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The next day, we marked and drilled the required holes in the rudder main spar for the ribs and rudder bow. After drilling the holes, we filed them to tidy them up and removed all burrs in and around the holes. This took around 2 hours. Robert Baslee who sells the kit does this all in a much shorter timeframe, but we were being quite pedantic about alignment of the holes, and finishing/deburring of all holes. We want to do this build as well as possible.


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All holes are now finished. All ribs and bows fit nicely into their slots.

Next, we will bend up the bow and attach all ribs/bows to the spar.
 

flyvulcan

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Rudder

Today, we spent two hours bending the rudder bow. We started by making two wooden formers, one with a 24" diameter and one with 12" diameter. We then bent up the bow, making sure we kept the bend in 2 dimensions and not 3. There was a bit of too-ing and fro-ing as we had to make some parts of the bow with smaller and larger radii.

After bending up the bow, we trimmed the ends to slot into the holes we had cut into the rudder spar to secure the bow ends into. We filed a radius onto the ends of the bow so that the ends would snug up against the ID of the spar.

When the bow was sorted, we trimmed the 3 ribs to length and then radiused the ends to fit inside the spar tube at one end, and against the rudder bow at the other.

So after a bit of bending, hacksawing and filing, we now have all our rudder pieces fitting together and looking like it should. It's now ready to install the hinges and cleco together in readiness for pulling apart and prepping for final assembly.

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flyvulcan

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Rudder hinges and gussets

Today, I tidied up the four hinge fittings for the rudder. They came in the kit as pieces cut from stock and I had to file and sand the ends to remove the scarring from where the stock was cut. All four pieces are now smooth with no scarring.

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I then needed to cut a slot in one of the hinges that would mount to the base of the rudder spar. The slot is to allow the rudder bow to pass through the hinge into the spar.

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After that, I drew the gusset pattern onto the .020" sheet, then cut out the pattern using tin snips. I rounded the ends on a belt sander and then finished them off by filing and sanding the edges to remove all burrs and scarring from the tin snips. They are now ready to be drilled and bent.

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flyvulcan

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Rudder gusset and bellcrank

I started today with fabricating the gusset between the rudder main spar and the rib to which the rudder bell crank is mounted. This gusset is made from .020" flat sheet, about 6" x 3". I wrapped a sheet of paper around the rear spar at the rib location to determine the flat plate distance from one side of the rib, around the back side of the spar to the other side of the rib. I then marked this distance on the gusset plate equidistant from the centre of the plate. These two lines would be bend lines.

I wrapped the plate around the rear spar to get the correct diameter for the gusset, then bent the gusset at the two bend lines that I had drawn on it. Once bent, I then trimmed the gusset sides to shape using tin snips.

I then marked the gusset for where I needed to drill it to mount. I then clamped this gusset to the spar/rib, ensuring correct alignment of the rib and drilled the spar and rib, then clecoed the gusset in place.

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I next checked the location for the rudder bellcrank and drilled the mounting holes in the bellcrank.

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Then I clamped the bellcrank in place and drilled the mounting holes through the rib to mount the bellcrank.

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That was it for today. There was the usual deburring, filing, sanding etc. and it was a very pleasant 2.5 hours for me.
 

flyvulcan

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Rudder rib gussets

After yesterday's session, I decided I needed to figure out how to bend the gussets better and more easily. After a bit of thought, I came up with an idea (I should have simply asked someone experienced!). Anyway, I had a 4"x4" block about 15" long with a V shaped groove cut into it that I was using as a jig to hold tubing while I drilled it on the drill press. I used this block as a base for my "bending tool". I bought a 12" length of 1" diameter copper pipe to use to wrap the gusset around.

I simply clamped one end of the copper pipe into the groove and placed the gusset that needed to be bent across the groove in the 4x4 under the tube, making sure the bend line was parallel to the pipe/groove. I then pressed down on the free end of the pipe which pushed the gusset down into the groove and the gusset formed around the pipe. To finish the bend, I clamped the free end of the pipe into the groove, then used my hands to bend the gusset further around the pipe until the required arc was completed.

Here are some pics that might explain it better.

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Once the gusset had been radiused, I then had to put two small bends into it to complete its shape. I used two wood formers clamped into a vise with a suitable bend radius sanded onto the bending corner.

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With the gusset all bent up, I used the same technique as for the gusset in the above post to secure the gusset in place. I needed to ensure that the ribs were perpendicular to the spar and that all the ribs were aligned in the same plane. Here are the pics from that excercise.

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It was 2 more hours of fun!
 

flyvulcan

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Rudder spar and bow

I had a brief foray into the workshop yesterday. I share a buddies workshop and he is building an RV7. I ended up bucking rivets for him for longer than I worked on my own project, but hey, that's what this aircraft building gig is all about; camaraderie and helping each other out.

I disassembled all the ribs from the spar so I could lay the spar back into its jig and confirm the marks on the rudder bow where the bow will be attached to the top of the spar. Once I had done this, I placed a 1/2" drill bit inside the cutout in the top of the rudder spar around which I could bend the top of the spar to flatten it against the drill bit (which simulated the rudder bow). I initially placed the tip of the spar in a vice with some cloth to protect the aluminium and squeezed the sides together in the vice. This worked pretty well on a rough level but left a small amount of scarring on the aluminium which I wasn't pleased about. The cloth was supposed to prevent that.

After the rough flattening of the spar end around the drill bit, I needed to finish the bending of the spar sides over the drill bit. My clever RV7 builder mate suggested I use his rivet gun to tap it into shape. Well, that technique worked a treat and the top of the spar was bent nicely around the drill bit. Now I didn't make it a tight fit over the drill bit as I wanted to check the alignment of the bow through the slot, so I then placed the spar into its jig, slotted the bow into the slot in the top of the spar, installed the ribs into their slots in the spar (but without their gussets holding them in place).

It was at that point that I was sidetracked into the riveting job and I didn't get back to completing my task of finishing the join of the spar and bow. There is still a little tapping to do of the spar sides to bring it in flush with the bow tube, as can be seen on the following photos. That will only be a few minute job at the start of my next session.

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flyvulcan

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Rudder bow gussets

Today I fabricated the gussets that hold the rudder bow to the front side of the spar as well as the gussets for connecting the ribs to the bow.

As usual, the gussets started as sheet that I had to cut to shape, bend, trim, file, drill, sand and mount. Then came the dis-assembly and deburring. It was a little challenging in that the plans do not call for gussets on all these joints so we did not have drawings for the gussets. Some of the joints, according to the plans, call for a dowel to be inserted into the end of the rib or bow, and then a hole is drilled through the bow to put a wood screw through the bow wall and into the dowel in the end of the rib. In our opinion, this technique is not the best to hold the frame together, hence our move to gussets on all joints.

Here are the pics from today's work.

Firstly, fabricating the gussets:

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Then mounting them:

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flyvulcan

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Rudder

It was back to the project today after a couple of months break due to my family visiting for 3 weeks and a leg injury that is just recovering (man, I'm getting old!).

Anyway, today saw me fabricate and mount the last set of gussets to the rudder. These were located at the bottom of the spar and hold the bow to the spar, as well as hold the lower rudder hinge in place. It was the usual trace the pattern onto some sheet, rough cut using tin snips, drill, bend to shape, mount in place, remove, trim to final shape, file/sand edges, then remount to check I haven't screwed something up.

Here is the end result.

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After completing these gussets, I drilled all the 3/32' holes in the rudder out to their final 1/8" holes and clecoed it all together with 1/8" clecoes.

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Next, I removed the lower rib and clecoed the rudder bellcrank to it and drilled the mounting holes out from their existing 1/8" holes to 3/16" to accept the AN3-10 bolts that are used to mount the bellcrank to the rib. I also inserted the wooden dowel into the end of the rib where the bellcrank is bolted to which according to the designer provides both rigidity and crush resistance.

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flyvulcan

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Rudder

Today, I disassembled all the rudder components in order to prep them for priming and final assembly.

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I trimmed a couple of the gussets and then deburred all holes and edges of all the components. All the parts were then roughed a little using scotch brite in readiness for cleaning and priming at the next session.

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After the clean and prime will come final assembly and riveting. Can't wait to see the first finished component :)
 

flyvulcan

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Riveting rudder

Today I cleaned all the individual rudder components then primed all the parts where they join.

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I then reassembled all the components to check for final fit and alignment before riveting.

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Then it was time to remove clecoes and start riveting. 30 minutes later, I had this (sorry about the orientation, it rotated when I uploaded it):

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flyvulcan

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Horizontal stab

We've been getting on with the horizontal stab lately. On our last session, we jigged the stab and trimmed, bent, and shaped the tubing, cut and shaped the gussets from sheet, and drilled and clecoed half the stab together.

Today, we disassembled all that we had done, deburred all the holes, ensured all edges of gussets and tubing were smooth, then prepped and primed the joints. After the primer dried, we reassembled and riveted the half that we had done.

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After riveting one side, we trimmed all tubing for the other side. That's as far as we got today. We should finish it up at the next session.

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flyvulcan

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Finishing the horizontal stabiliser

Today, we finished the horizontal stabiliser. We started by fabricating the gussets for the second half of the stab. We then set the stab in its jig and drilled and clecoed the gussets to the tube frame. As usual, we started out drilling to 3/32" and then once it was all stable and clecoed together, we drilled out to 1/8".

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We then disassembled the structure and deburred all holes, tidied all edges, cleaned, primed, reassembled with clecoes, installed the elevator hinges, then finally riveted the structure.

We then trimmed the cross beam tube to size, fabricated the gussets, then the usual drill, clecoe, etc. etc.. We finally riveted it in place which then completed the horizontal stabiliser. It is all nicely aligned and surprisingly rigid. We are very pleased with the result of our work.

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Now all we need to do is the elevator to finish the tailfeather structure. So far, we have 56 hours in the build. Some may say that is a long time but we were learning the art of it all for the first 30 hours. Now we feel very comfortable with what we are doing. Robert Baslee would have finished what we have done in around 10 hours or less, but we have better fitting gussets, and we've been deburring, priming etc. which in general, Robert doesn't seem to do. We want to have complete confidence in the security and longevity of our aircraft so I'd like to think that we are taking a bit more care than is seen on Roberts construction YouTube videos.

That said, full credit to Robert for bringing these affordable and easy to build aircraft to all of us enthusiasts.
 

flyvulcan

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After a long break, Steve and I got back into the workshop to carry on with the Fokker build. Today, we fabricated the components for the RH elevator.

A few months back, we had bent up the tubing for both the elevators. Today, we drilled the holes in the RH elevator spar to mount the trailing edge ribs into. We also drilled the end of the spar to secure the tubing into. Once the spar was drilled, we rounded the end of the trailing edge ribs to insert into the holes in the spar and would nest against the inside wall of the spar tubing opposite the hole in the spar.

Once the ribs were inserted into the spar, we marked then trimmed the ribs to their correct length. We cut them around 2mm oversized so that we could round the end to fit flush with the 1/2" tubing that attaches to the end of the ribs.

I drew the shape of the gussets onto the .020" sheet provided then cut and filed the 6 main gussets for the ribs.

I filed the hinge brackets to smooth their rough finish which is how they come in the kit then temporarily mounted them on to the elevator spar. We then placed the completed horizontal stab on our elevator jig so that we could align the leading edge of the elevator horns with the leading edge of the horizontal stab. We needed to bend the leading edge of the elevator horn out a little to align it all. We then marked the location of the leading edge rib and drilled the main spar hole to accept the leading edge rib. We then rough trimmed that rib to length.

Finally, we jigged all our handiwork up to check that it would all go together ok. This is what we ended up with:

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It all lines up well so next session, we shall do the final trimming, put it all together with its gussets and rivet it up.
 

flyvulcan

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RH elevator construction

Today, we continued with the RH elevator.

We started by fabricating the last strap to hold the inboard rib in place against the spar. This involved the usual bending of the strap, followed by clamping, drilling and clecoing the strap in place, ensuring that the rib was fully inserted into its hole in the spar and perpendicular to the spar. This last trailing edge rib aligned quite nicely with the first two ribs that had been mounted.

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Once all 3 trailing edge ribs had been clecoed to the spar and their alignment was checked, we disassembled everything, deburred all components then scuffed, cleaned and primed all joints.

We then reassembled the structure using clecoes, then riveted the trailing edge ribs to the spar.

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Note the nice new pneumatic riveter. Wow, it makes it so much easier!!

And when all was finished, we jigged up the trailing/leading edge tubing to make it look like an elevator.

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Our next session should see us finishing the RH elevator.

I will admit that in our enthusiasm to rivet the ribs to the spar, we forgot to insert the elevator hinge between the outboard and centre ribs. Consequently, we had to drill out the rivets on the end rib, remove the rib, slide the hinge onto the spar, then reassemble/rivet the outboard rib back on to the spar. We wasted 15 minutes fixing our stuff up but hey, that's building for you.

Today, we spent 3 hours doing what we did. It was fun and we felt that we had made positive and visible progress.
 
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flyvulcan

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RH Elevator

Today, I fabricated and mounted the straps and gussets that go around the trailing edge tubing of the RH elevator and which hold it to the ribs.

I started by tracing and cutting the straps from .016" AL sheet then rounding the ends and smoothing the edges on the grinding/polishing wheels.

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I then jigged up the RH elevator and ensured the edge tubing was in the correct position in relation to the spar and ribs. With it clamped, I drilled and clecoed firstly the outboard rib, followed by the inboard rib to the trailing edge tubing.

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I then fabricated in the same fashion a small strap to hold the trailing edge inboard tubing to the spar.

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In addition to the strap shown above, next build sessions I will fabricate two gussets to supplement this strap.

The last gusset that I fabricated was for the very inboard short rib to trailing edge joint. It was made from the supplied small square .020" AL sheets. I trimmed the ends and bent the gusset then mounted it is place using a few clamps.

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I then drilled and clecoed this gusset in place.

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That was it for today. It was about 3.5 hours for me to do that. Ok, I'm not the fastest builder, but there was a lot of filing, smoothing, dremelling, fitting, disassembling etc...
 

flyvulcan

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RH Elevator

Today, I started with fabricating the two gussets that connect the inboard end of the trailing edge tubing to the spar. The plans do not call for gussets, only joining the tube to the spar with a strap. However, we have decided to use a strap and supplement the strap with gussets.

The gussets started as a 3' square piece of .020" AL sheet which I simply cut in half from corner to opposite corner using tin snips. I then trimmed off the corners where the flange mounts to the spar. Next, I smoothed the edges of the gussets on the polishing grinder (or whatever its called). I then bent a 9mm wide flange along one edge of the gusset and drilled some 3/32" pilot holes. I then clamped the gusset to the tube/spar and drilled through the gusset pilot holes into the tube and spar, clecoing as I went. Once the first gusset was mounted, I flipped the tailplane and did the other side gusset. I pulled off both gussets and removed all drilling debris and reassembled the gussets into place. I then drilled out the holes to 1/8" then pulled apart again, deburred all parts and then reassembled again. Those gussets were now finished.

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After finishing those gussets, I squeezed the ends of the spar where the tube passes through the cutouts in the spar end using a 12mm drill bit in place of the tubing and a wooden vise to do the squeezing. The vise got it fairly close but I needed to use a hammer to finish the squeeze.

Once the ends were squeezed, I reinserted the tubing and drilled and clecoed the tubing to the spar end.

I then fabricated and mounted the gusset that holds the leading edge rib to the spar. To do that, I had to attach the elevator to the horizontal stab using the correct hinges to ensure that the leading edge rib was parallel to the end of the stab. I then drilled and clecoed the gusset in place ensuring that the alignment of the leading edge rib was parallell to the trailing edge ribs.

I then fabricated the leading edge gusset which joins the leading edge rib to the leading edge tubing. The usual steps were taken to do this.

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I still have to drill out the leading edge gussets to 1/8" and deburr etc. which wont take too long. I will then clean, prime and rivet the entire RH elevator structure. Can't wait!!
 
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flyvulcan

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Right hand elevator riveting

Today, we drilled out the last of the holes to take the 1/8" rivets then took the whole assembly apart, deburred all holes, scuffed, cleaned and primed all mating joints then spent a very pleasurable 20 minutes riveting it all together. We love that pneumatic riveter. So easy to use and a good solid consistent pull.

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Now on to the left elevator which will go together a lot faster since most straps and gussets have already been fabricated.
 

flyvulcan

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It was on to the left elevator today. We started by jigging up the elevator to the horizontal stab to ensure symmetry between left and right sides and to ensure that we had the same gaps between the elevator horns and horizontal stab on both sides. The spar was trimmed to length, again ensuring that the size of the elevator horns was identical on both sides. While the elevators and horizontal stab were jigged to each other, ensuring that the right hand elevator was parallel to the stab, we marked the front and rear face of the main spar where the ribs would be mounted and ran a 90 degree angle along our table to mark the exact front and rear face of the spar where the ribs would be attached.

After the spar was trimmed to size, we accurately marked the location of all 4 ribs (3 trailing edge and one leading edge), then placed the spar gently into a wooden vise and used a hand drill to drill the 1/2" holes into the spar to slot the ribs into. We started with a 3/32" drill bit then worked our way out using around 10 incrementally larger drill bits to enlarge the size of the holes. They turned out very neat. The holes were deburred and were ready for the ribs.

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We then trimmed the ribs to length and rounded/hollowed the ends to allow the rib ends to fit snug up against the inside radius of the spar and around the outside radius of the elevator bow. After overlaying our LH elevator bow over the riveted up RH elevator bow to ensure their shape was identical (a very small amount of additional bending was required), we trimmed the ends of the LH elevator bow to the final size. With all ribs/spar and bow then jigged up together, we left it there for tomorrow where we will finish and fit all gussets and get it all clecoed together.

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flyvulcan

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LH elevator gussets and straps

Today, we completed fabrication of all gussets and straps for the LH elevator then drilled and clecoed them all in place. We had to ensure that all ribs were set at 90 degrees to the spar and that all ribs and the bow were parallel to the right hand elevator. i.e they are both on the same plane.

It all worked out quite nicely.

We need to check a feature of the plans with the designer, Robert Baslee before we can rivet the structure. I expect that by our next build session that we shall have the answer from Robert so that we can complete the fabrication and then do all the prep for riveting.

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