CriCri MC-15 in NZ

Discussion in 'The light stuff area' started by MadRocketScientist, Jun 19, 2009.

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  1. Aug 8, 2010 #201

    MadRocketScientist

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    Got taken for a short ride in the Dynamic shown in the first pic, it has lots of get up and go and flies like its on rails. Very impressed and a big thanks to Kevin for the demo flight.:ban:

    I took a break from dimpling etc and machined the taper on the spar web doublers. I used double sided tape to hold them down while machining. The MDF block is packed up at one end to provide the taper. It is quite tricky to get the taper to end in exactly the right place, but any small difference should be filled with epoxy when the spar is bonded together.

    I then used sandpaper on a block to sand the machining marks off while it was still taped on the jig.

    Shannon.
     

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  2. Aug 8, 2010 #202

    PTAirco

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    The more I look at the Cri-Cri, the more I think it deserves an award as the most complex aircraft design ever, pound for pound, of anything out there. While I appreciate nice engineering and drool over your project pictures, I am glad I did not choose it as a project - it would have driven me insane very quickly.

    My own design looks almost crude in comparison, but I strive for simplicity in everything. You really need to produce kits for yours after all the time and effort you put into the CNC work!
     
  3. Aug 12, 2010 #203

    MadRocketScientist

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    Here is another file that will be a benefit to any builders out there, it is a much better fitting cockpit border. The original gave me headaches with the fit so I tried changing the curve, worked pretty good on the third try. There should be around 2mm of overhang on the outer edge but this will depend on how accurately the fuselage frames have been made.

    You guys using solidworks might be best to redraw this as a spline using some of the points in the curve. My CAM package converts it to tiny line segments for cutting but once its CNC cut it is not noticeable. The holes in the file are for 6mm bolts to clamp the MDF formers together and to align the border for forming. The holes could be drilled out to 1/4" and things would still work fine. The blue line shows where the lower edge of the border sits when being formed.


    Shannon.
     

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  4. Aug 13, 2010 #204

    MadRocketScientist

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    Cut some more parts today, a new false fin spar, the fin skin and a couple of nose mounting bands.

    I had already cut a false fin spar but the width was slightly out once it was folded so a new one was the order of the day (not pictured).

    I also have the fin skin cut and formed, it fits reasonably well. Most of the flying surfaces have their skins formed from single pieces of metal making it necessary to form the leading edges to fit the ribs. This is done by squashing the skin down to a stop therefore giving the sheet a leading edge shape. Naturally the stop height varies for each skin. The forming distance can change with things like temperature and the orientation of grain in the metal.
    The instruction manual didn't have any measurements for the tapered stop for forming the leading edge of the fin skin so a little testing with scraps was in order. Once the testing gave the correct curves my tapered mdf stop varied from 20mm at the top to 14.7mm at the base of the fin (this is due to the fin having a different chord at the top and bottom). A bit of jumping up and down on the mdf board formed the skin just fine :gig:.

    I also folded the nose mounting band to suit the engine mounts. The plans show a bolt and nut for mounting the nose to the band but I thought it would work better with a nutplate for a small change:).

    Shannon.
     

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  5. Aug 14, 2010 #205

    MadRocketScientist

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    Flanged the fin base today (sorry no pics yet) and then onto the rudder. The rudder skin is rolled around a 32mm diameter tube or bar to allow for springback so it fits to the correct curve. It also has more curve at the top so it has to be rolled with slight taper from each side towards the middle. I had to roll the middle more as there isn't quite enough wrap around room once the first side is rolled (the sides get in each others way:ermm:)

    I CNC predrilled the skins to make it easier to fit the upper and lower bearing plates, worked a treat. I also used the safety rivet holes to set things up square.

    I'm starting to look forward to the Divinycell foam arriving, should be any day now.

    Shannon.
     

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  6. Aug 19, 2010 #206

    MadRocketScientist

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    Folded the trailing edge of the rudder on a folder at the airfield the other day (Thanks again Pat:)) Now the rudder is pretty much ready for the divinycell ribs and the final assembly process.

    Today I started forming the aileron ribs, seems I missed cutting about half of them. There should be 16 but I only have 8:ponder::hammer:. Works out alright though as there are two types of ribs in the aileron halves. The end ones don't need the doublers in them so the flanges are slightly different. I will cut the other 8 without the wide parts on the flanges.

    The plans show the ribs without then but I prefer to flute the ribs as it is easier to get the shape right. I now have two sizes homemade fluting pliers but only the very front top flute on the ribs needed to be attacked with the larger ones. I also cut a slot in the flange where it is sandwiched between the reinforcement and the skin as a flute would get in the way there. This is all glued together when the doubler and nutplates are installed so I can't see it being a problem.

    It took me a while to work out the best process for a consistent rib but got it sorted in the end. First flange the rib in the form block to give a rough flange and mark the flute locations. Then I remove the rib from the blocks and flute with the fluting pliers. I give them a good hard fluting to make the outer surface sit reasonably flat bt it does overbend the rib somewhat. Once it is back on the former it sits flat and is ready for the final planishing to give crisp formed flange. I think they will need a little bit more attention for a really good fit into the 0.016" aileron skins but they are really close now. The fit does need to be as good as I can get it as the quality of fit will show through the thin skins.

    The MDF formers are a bit on the soft side but they work well when saturated with thin CA (Cyanoacrylate glue). I would use a harder material like phenolic or aluminium for the smaller and more commonly used formers in future.

    I need to fold all the spar web stiffeners in the last picture, only 60 or so. I will make a jig to fold them on to make it easier.

    Some of the divinycell also arrived today, I only need about 1/3 sheet of the 20mm thick stuff but now I have a whole sheet due to minimum sales size...enough for 3 CriCri:gig:

    Shannon.
     

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  7. Aug 19, 2010 #207

    Insane

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    Hi Shannon,

    You may have mentioned it be fore, but would like to confirm that you are building off plans only and not from a kit??

    The reason being that the quality of workmanship and attention to detail amazing.

    Fantastic!!

    Calvyn
     
  8. Aug 19, 2010 #208

    MadRocketScientist

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    Well I could have a kit, I am making the kit as I go along:gig::gig:.

    There were a few kits of a 'Cricket' (ripped and butchered CriCri copy) available in Nth America years back but they don't come close to the parts I am making;).

    If I ever get to making kits available you have an idea of the quality to expect.


    Shannon.
     
  9. Aug 20, 2010 #209

    MadRocketScientist

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    Finished off making the aileron ribs, sometimes you get lucky and a mistake turns out for the best. The other 8 ribs have a slight variation and go on the ends of the aileron halves... eventually. I will alodine everything closer to final assembly.

    Shannon.
     

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  10. Aug 21, 2010 #210

    MadRocketScientist

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    I thought I was doing well in getting on top of the part numbers... I checked my spreadsheet and I still have over 500 parts still to make. A lot of them are the foam ribs and stiffeners but its still heaps:depressed

    So... I cut some more of the little bits today and made some aluminium formers to fold them on. I also tried making a piece of black acrylic for testing the fit of the aileron ribs. Works out well apart from that I can't see the gap clearance without holding it up to the light. I will make another one out of white acrylic and see if its any better. The aluminium on shiny black looks very arty (not that it helps get the plane built:gig:.

    Shannon
     

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  11. Aug 21, 2010 #211

    MadRocketScientist

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    Pile 'O' brackets all folded, These all have a slight curve to the flange and need to be formed carefully for a good fit. I need to remove yet another flute to allow the inner brackets to fit in to the ribs. There will be nutplates on the inside for bolting on the aileron pivots.

    Looking at the doublers on the inside of these ribs, they seem to be way overkill for what they need to do. The rest of the surrounding structure is 0.020" or less and the doublers are 0.040":ponder:. These are only pivots and even the control horn on one end doesn't have a doubler. I'm not going to change anything but it does seem to be a bit excessive.

    Some of the brackets also yet to be folded.

    Shannon
     

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  12. Aug 21, 2010 #212

    Dauntless

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    Good God, man, how many pieces are in that thing? :dis:

    Seriously...how many pieces are in the basic Cri-Cri structures? I have in mind an eight-foot canoe made of a thousand pieces.
     
  13. Aug 21, 2010 #213

    MadRocketScientist

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    The 8ft canoe is about right but the parts count is a little low:gig::gig:.

    The completed airframe less engines and avionics is a tad under 2300 parts (the number changes as I work out what is actually needed) plus around 4000 rivets. Of the 2300 parts there are 1225 to actually make, the rest are purchased (as my spreadsheet stands so far:gig:).

    Now try and tell me I don't have OCD:roll::roll:

    Shannon.
     
  14. Aug 22, 2010 #214

    Dauntless

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    Oh, sorry about the low parts count...it's even worse than I feared, eh!? :gig:

    I recently replicated a racing car's front wing. The original aluminum wing had 57 pieces, but I duplicated it with 5 pieces total in fiberglass. My version weighed 15% less and was 30% cheaper. That might be too much to expect from a composite Cri-Cri, but unless one simply wants to bend aluminum sheet for years on end, why go through that?

    Stan
     
  15. Aug 22, 2010 #215

    scooter1948

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    I AM LOOKING FOR A SET OF BUILDING PLANS FOR THE CRI CRI AND I UNDERSTAND THAT THE DESIGNER WILL NOT SELL THEM TO AMERICANS. DO YOU HAPPEN TO KNOW WHERE I CAN GET A COPY EITHER NEW OR USED?

    SCOTT MORROW
    MYRTLE BEACH,SC USA
    843-236-3522
     
  16. Aug 22, 2010 #216

    steveair2

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  17. Aug 23, 2010 #217

    MadRocketScientist

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    Sorted out the acrylic for the rib fit test widget, the clear works much better than the black.

    Folded the internal aileron brackets for in the wing. Again the plans specify a very tight bend and fresh tempering of the alloy is needed. Some of the parts do have a tendency to want to crack and need another tempering halfway through forming:ponder:. I didn't help any not having the grain orientated the wrong way. Will get it right next time:gig:.

    Shannon.
     

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  18. Aug 30, 2010 #218

    MadRocketScientist

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    Cut the aileron jig on the CNC, quite slow but it beats making cutters for a spindle molder. Also CNC cut the leading edge fold former for the ailerons too. The ends of the skins overhang the jig 1mm to allow for mounting the control horns and aileron joiners. I can cut the skin back and rivet the horns on with the jig holding them square while the glue sets.

    I had cut and predrilled the aileron skins early on and forgot all about the fact that they have a 1.5 degree twist in them. I was more than a little worried that the twist would mess up the hole alignment and I would have to cut new skins. Turns out to be a non event with the ends being offset less than 1mm due to the twist. The fit of the skins on the ribs is very good and everything looks like it will fit exactly as planned.

    I have yet to put the fold in the trailing edge of the skins.


    Shannon.
     

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  19. Aug 30, 2010 #219

    Mac790

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    Shannon,

    After you finish this one you should build second one but this time without CNC, if you start next summer you would have big chances to finish it before 2020.:gig: Just kidding.

    Great work as usual, thanks for updates.:)

    I was wondering about quality of drawings, did you find many errors in them, do parts fit nicely eachother, or did you have to make some major changes. If I remember correcly you said it took you few hundered hours, to convert those drawings into CAD format, did you make some 3D too, or only 2D?

    Looking at number of parts in this little bird, now I understand why Mr. Colomban design one aircraft every 10 years :roll:.

    Keep going and keep us posted.

    Seb
     
  20. Aug 30, 2010 #220

    Lori

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    Hello, all members!

    Shannon, tell (in ideal with photos), how you formed the aileron skins please.
    Thanks.

    Andrew
     
    Last edited by a moderator: Aug 30, 2010

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