Discussion in 'The light stuff area' started by MadRocketScientist, Jun 19, 2009.
Ah, it must be heaven to have CNC machinery around....
Just a small update, I almost have my CAD drawings completed, progress should be much much faster once they are finished.
Today I made the fold jigs for the cockpit border. I had cut the border pieces when making parts for the spars, now they are folded. I think they are going to need a small amount of stretching on one face to fit correctly. That can wait till later.
The CNC kicks out a lot of dust when cutting MDF, but the vacuum makes short work of the cleanup.
I folded the 0.020 2024T3 with careful use of a rubber mallet.
More progress, still very slow due to changes in the way I am making parts. A lot of the holes are designed to be drilled with parts in place so the holes line up. I am drilling a lot of them on the CNC so if they don't line up I have drawn something wrong:depressed.
Before I started cutting the flapperon and elevator skins, I had to check that pre-drilling the holes would work out. The skins also had to be test folded using narrow strips. The MDF rib patterns worked well and the skins tests fitted correctly. I did shorten the flapperon skins by 3mm to correct an overhang on the trailing edge
I cut all the 0.016" (0.4mm) parts today, flapperon skins, rudder and elevator skins, nose vent and the rudder pedal rail supports.
Feel free to add comments or questions etc.
More visible progress, the rear fuselage is cut out and assembled. I didn't take any pics of the cnc cutting the panels out. To me thats all in a days work and the white doesn't show up too well when cutting.
I still haven't finalized the air holes in the front skins, gotta keep the pilot cool for when the fans on the front stop. I have started making the frames for when they are ready to cut. they should go together really fast too, having match drilled holes makes life easy (as any VANS quickbuilder can attest)
Some of my folding skills need practice, I get most of them right but one particular part I have folded twice and got it wrong both times :mad2::mad2::dis: Hopefully third times the charm. The side for the rear have turned out really well, I think the bend radius could have been a little tighter but the sizes are spot on (overall when clecoed within 0.3mm) I made some little extensions on the folded skin so that I could line the folds up when folding(first pics in row 3)
What looks like oversized hobby pins is just some 1/16" TIG wire. I use it in the 1/16" pre drilled holes to hole the alignment when drilling for the clecos. I haven't drilled out all the rivet holes but did just enough to get a feel for how well thing s line up. I intend to use solids and flush rivet the entire exterior.
Re: CriCri MC-15 in NZ***MUGSHOT WARNING***
Well I ran out of picture spaces in the last post, so here's some more.
The plane looks smaller and smaller as I get more of it made, it is really a tiny aircraft.
I am still reasonably confident of finishing the airframe by Christmas:devious:, all the details are drawn in and predrilled like the shots of the small cable clamp and rudder fittings, pretty much everything I could think of that is shown on the plans. I also studied all the photos I have of CriCri's from on the internets.
I do like the CNC for making crisp cut alloy:ban:
A W E S O M E ! !
Thank you so much for keeping us posted.
Beautiful. You're going to be a very happy airplane owner!
Great pictures, thanks Shannon. I'm really looking forward to seeing this plane go together.
I did a little more on my CriCri tonight, I shaped and fitted the reinforcements for the underside access panel. The angle has to have the outside corner rounded to allow it to fit into the fold on the 0.020" side skins. The ends had to be shaped slightly, the disk linisher and file took care of that. I also drilled the rivet holes for the nutplates.
I also dragged out the parts for the fin spar, the caps need to be cut to shape and then drilled to match the web while the holes for the elevator pivot are held in perfect alignment. I have a lot more work to do yet.
The last two photos are of the fuel cap I have on borrow from the Aircraft Logistics at the Rangiora airfield (Great guy that Steve). The cap is from Aircraft Spruce but its too heavy for my liking. I have sourced some smaller O-rings so that I can make a smaller and lighter cap. The CriCri is very sensitive to too much weight and most end up built heavier than recommended.
I finally found time to run thru your blog-EXCELLENT!! Nice to see your mug as well-I think pretty much as I imagined, even though I did not know what I imagined. Love to see how fast you are rolling along on the project. Just such excellent reference for the rest of us who are building. The CNC is obviously an excellent asset. Probably isn't hurting your programming skills any, either..
Thanks for documenting-You are an inspiration to me, as I am sure you are to everyone else reading along..
-Christian von Delius
Kalispell, Montana, USA
Thanks for the great comments guys, I have more parts made today but I will wait until later today to put up more progress pics. Its back to the workshop for more aircraft construction today.
Today I refolded the new parts cut to replace the bad folds from yesterday. Managed to get them folded spot on only to realize there is a mistake in the drawings and two of the parts needed fixing. Cutting replacements was fast as I had left the sheet of aluminium on the machine. Now I a up to 3 parts that I have folde more than twice :gig: makes for good folding practice. I am actually quite surprised at the low amount of drawing errors so far. Usually it is quite hard to get things without errors on the first try when using 2D CAD.
I folded the rear seatbelt fitting and match drilled it to suit the rear fuselage. I have removed the PVC from under the fitting when it was drilled, although it might not be immediately clear in the pics. The fitting has a tab that gets welded on to bolt the seatbelt to.
I also started to assemble the forward fuselage frames, and check them for sizing. Frame 2 has a slight curve to it as it sits at an angle inside the fuselage. The outer side needs to be shaped on a form block (or two). I cut the forms on the CNC and hand sanded a small radius onto the edge of the block. I made the fold using a rubber mallet and a skinny block of wood to fold the edge as evenly as possible. Having the fold in three parts makes it easier too.
Its not very visible in the pics, but I cut large holes in a sheet of 3mm mdf to sit the frames in for drilling. This should hold them to their final sizes. The last two pictures are of frame 4. This frame makes up the spar box and has to be assembled around the complete wing spars for a close fit. I will only be partial assembling it at this point.
Pretty neat wood fixtures!
Nice work Shannon !
I like the use of milling an indentation in the MDF to set the frames up
Some questions ?
On longer bends are you using a press brake to bend the flanges ?
Using wooden blocks for bending do you allow for some springback ?
Do you mill the drill holes slightly smaller to allow for the final drilling and alignment ?
Will you be bonding some of those frame joints before you rivet ?
I have some Banbi MC100 plans and they suggest using Araldite 420 what about the Cri Cri ?
I have been using a folder out at the local airfield for all the folds. The first picture in post 44 is of the side skin in the folder.
The folds I have done on the wooden blocks so far have been angles larger than 90 degrees so the springback hasn't been a problem. I will see what happens on the 90 degree angles. I may need to sand the wood to allow for springback. The 0.020" 2024 is also thin enough to be able to finish the fold by using your fingers. I will let you know how I get on.
I have been drilling all the holes at 1/16" and then drilling to final size on assembly. I may drill some of the holes to final size on the next CriCri. I have been cutting some of the bolt holes to finished size.
Yes I intend to bond most of the airframe, I would have to look up the plans about the Araldite 420, I think there are a few different primer/epoxy sytems available to use. I have yet to decide which one I will use.
Just A sneak pic of current progress, will put a longer post up sometime. Things are really going together fast now. The best bit is all the holes ensure that everything is square. And yes the workshop now needs some tidying:gig:
Looks like a certain Russian Ekranoplane, maybe I should name it The Caspian Cri Monster:lick:
Just briliant! Beautiful job, I can't even imagine making all these parts without CNC, no way. I'm still a little bit scare about a number of parts, do you count them? Last picture is just marvellous love it, are you going to sell kits in the future? I believe you could find some customers. Thanks again for sharing with us.
There are 2200 parts counting washer,bolts, etc:shock: and then about 4000 rivets. I haven't got around to working out how many parts there are to make, there are around 300 parts in the wings alone that need to be made. I would guess around 1000 parts to make. I have an excel file with the parts and numbers of each, I just need to go through it and add up all the parts that are to be made.
If anyone wanted a kit or even parts they can email me, although I do run the CNC as a business the CriCri side of things is more a hobby. I would just do the kits or parts if/when someone wanted them.
Here are yet more pictures, the fuselage has FINALLY come together. I have a lot of drilling, countersinking and dimpling ahead of me.
I bent the corner angle aluminium for the front fuselage half using a rubber mallet and a custom formed wood jig (custom formed as in was lying around and fit the purpose:gig The manual says to pull the angle section through a shaped block of wood to get the bend in it. I didn't think the former blocks would be as accurate as I liked and hammering stuff:hammer: has its therapeutic side to it:devious: I think I may have to do it all over again once the angle is drilled and countersunk due to more internal stresses being released (what a pity more hammering :gig::gig The angles were then drilled to fit the skins, first the sides and then the bottom. I also cut out the notches in the angles to fit the spars, both lower angles are cut like this.
I had a few trial runs at fitting things together and pinned the parts with the 'T' pins. once I was sure things were lining up I started drilling and holding it with clecos. I have only drilled about every third hole or so. I will go back over it later and drill all the holes.
Everything lines up really well and not having to check anything for square as I go makes it much easier.
More progress today, I think the biggest parts of this plane are about tacked together. Most of the remaining parts won't be as fast to go together and will be smaller.
Today I started to put in the spar box together inside the fuselage, as I mentioned earlier it wont be completely assembled until the spar is glued and riveted.
I started to fit the cockpit side rails, very disappointed with the fit:dis:, I creased one side trying to get it to conform to the correct shape. The parts need about a 10mm deeper curve on on them than what the plans show, I think I will redraw it and make a new set including a new fold former. The curve is matched to the fuselage side where it may be easier to match it to the top edge. Its easier to stretch the 20mm wide flange in 0.020"2024T3 than it is to shrink it.
I also fitted one side of the control column mount.
I FINALLY remembered to take my soldering iron to the workshop. It comes in very handy for removing the PVC from on the parts when they touch and still leave it where it protects the aluminium.
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