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Old Jan 24, 2013, 04:39 PM
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PeterF's Avatar
United Kingdom, England, North York
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Quote:
Originally Posted by thedeuce View Post
Great work, what sequencer did you use for the doors?

Cheers
The sequencers are from SM Services, a well known company here in the UK that have been making on board units of many types for a long time with a good reputation. See SM Services then look under on board units.

I have a SM25 type 1 sequencer (door open - gear down / gear up - door closed) that is operating the main gear retracts, main gear doors and nose gear front door.

I have a SM26 type 2 sequencer (door open - gear down - door closed / door open - gear up - door closed) operating the nose wheel retracts and the nose wheel main door.

This means I have to have the time delays carefully as I have no direct link between the nose wheel retract and nose wheel front door as they are on independent sequencers. However, as the nose door has to wait for the mains to retract I should always be OK.
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Old Jan 28, 2013, 07:11 AM
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Main Gear Door Installation

Onto the main gear doors, and has been pointed out in a few posts these needed some thought because the bottom of the plane is curved in this location unlike the full size, so a simple hinge set up could not be used.

I have come up with some home built hinges, with an offset hinge line. I needed the front of the doors to open and lift away from the body of the plane quite a lot to allow for the curvature. However, I did not need the rear of the door to lift away from the body of the plane. I wanted the bottom edge of the doors when open (inboard long edge when closed) to remain relatively horizontal when open so that I retained a good ground clearance. I was also after a hinge layout that would allow more than 90° opening to again increase the ground clearance, I know that is not scale, but as noted previously, this is only a “scale like” plane.

I tried to design my own complex hinges like those on kitchen cupboard doors that would keep the forward hinge vertically in line with the opening but move it away from the surface. I gave up when I realised how complex and fiddly these would be.

I decided to go with a simple rear offset hinge location but with hidden hinges when closed, I did not want to have visible cut outs in the sheeting. The hinge rods are 2mm wire threaded into ball joints, bent to clear the sheeting, but bent just enough to clear the door to give room for the wheels. I have used ball joints so I can be a little sloppy on the hinge line running between the two hinges and do not need to get them both lined up perfectly – a pragmatic cop out. The other end of the 2mm (5/64”) rods is inserted into some very hard 6mm (1/4”) balsa, glued to the door sheeting with some extra support. I had to add some extra formers onto the doors because they were very floppy being only soft balsa. The balls are screwed into 2.4mm (3/32”) ply which is then glued onto some hard mounting blocks. These will be glued along with the reinforcing strips to the rib / sheeting corners but for the time being are held in place with some balsa scraps.

The front hinge site a lot further back than the edge of the sheeting so that as it opens the door moves well away from the planes surface. The rear hinge is offset a much smaller amount to give some lift. I could have arranged less offset at the back and more at the front to keep the door closer to horizontal when open, but the offset hinge at the front move the door away from the opening quite a lot, so I put some offset into the rear hinge to make that move away at the same time. The result is not properly scale but does look reasonable in my opinion, is functional, looks better than not having doors and gives me some good ground clearance.
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Old Jan 28, 2013, 10:54 AM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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that sorts looks like the real deal ...they have 4 hinges and when open they are closer to the hinge line ...i dont know how they do it ,door is a bit flater than what you have .but hey you got the right idea going there,you can bend and tweak those wires to get the fit you need.this is not an easy door to do ,but i think you'll get it
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Old Jan 28, 2013, 07:53 PM
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United States, MO, Warrensburg
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The full size B-2 has a flatter and wider under side near the gear doors and weapon doors which allows for the straight gear door line.
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Old Jan 28, 2013, 09:26 PM
deltas are cool
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Tehachapi ,CA.
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well there semi straight doors they have some curve in them ....this kit must have a different airfoil which i would expect.hmmm it would appear that plane is missing a jack pad cover
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Old Jan 29, 2013, 01:33 AM
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Jetnfast, that is an interesting photo, I have not seen one looking straight up before, and their is no way I could have got the doors to open at 90° on the hinge line without complicated hinges, or hinges standing proud of the planes underside. The model has a flat bottom on the centre of the model out to what would be the centre of the bomm bay doors and then starts to blend this into the airfoil shape of the wings so at the outboard hinge edge of the gear doors the underside is fully curved. With a lot of fore sight the ribs at this locations could have been flattened out before the build. Some of the photos on the first page show how the rib profile changes.
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Old Jan 29, 2013, 09:14 PM
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No worries Peter! Your B-2 is a work of art no matter how close to the real thing the details might get. The curvature on the botton would be hard to mimic exaclty without sacraficing all the other details and airfoil design like you mentioned. The curvature is hardly noticeable on yours anyhow. In fact, you can thank Air Sally for pointing it out!!
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Old Jan 30, 2013, 01:42 AM
deltas are cool
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Tehachapi ,CA.
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my bad ...i cant help it . just your stucture build along is a work of art ,cant wait to see how this flys .im going to try and do a smaller B-2 ...im sure there will be a lot of things that wont be scale either .i've been told the full scale airfoil would make a lousy Model airfoil.
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Old Jan 30, 2013, 03:38 AM
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Colchester UK
Joined May 2004
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Peter

Interesting problem. It is exactly the same on the Horten except the Horten doors are longer and need more hinges. I used home made hinges similar in action to yours so they standoff to make the hinge line behind the edge of the door. I made a jig up from balsa to get the action right before I made them. As you can see the Horten doors are shaped like bananas!

John
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Old Jan 30, 2013, 11:01 AM
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United Kingdom, England, North York
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John,

I do not envy you that, but it loloks good, are the hinge plates from glass fibre sheet and if so what do you cut it with, I have never had much luck trying to use it.
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Old Jan 30, 2013, 11:56 AM
deltas are cool
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Tehachapi ,CA.
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thin diamond wheel is best for cutting C/F or glass sheets
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Old Jan 30, 2013, 02:04 PM
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Colchester UK
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Peter

Yes they are from fibreglass sheet. I use a scroll saw, fret saw. It is easy to cut out but you do not need it to run too fast. I find the blades would last to cut out all the hinges.

John
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Last edited by John Wright; Jan 30, 2013 at 03:05 PM.
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Old Jan 30, 2013, 04:14 PM
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Thanks for the info on cutting the sheet, I will have to see about getting a diamond blade for my Dremel as I have some carbon / glass sheet to cut for the fan moutning lugs.

I have spent some time fiddling about with the hinges and got my servo in to open and close the door, all working well as per the video. The servo is not screwed in properly yet, that will come next. Also not tried it with the sequencer yet.

RC B2 Stealth bomber main gear door test (0 min 13 sec)
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Old Feb 01, 2013, 05:23 PM
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the doors are awesome. then again, the whole build is awesome.
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Old Feb 03, 2013, 11:08 AM
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Completion of the main gear doors

Once again thanks for the compliments on the build from everyone.

I have now copleted the second main gear door and got the sequencer working on the mains as well as the nose wheel. There is very little extra to add from last time. The gear door servos had some hard wood mounting blocks glued into place and that is about it.

Tokk a dispropotionate amount of time but it looks worth it. The main doors open much wider than scale so that there is more clearance between the bottom of the doors and the ground and that is about the only difference, the outline of the doors is reasonably scale.

I now have to move on to the fans, there will be quite a bit of work setting those up, balancing them, building the mounts etc. so there may not be much of an update for a while as this involves 4 of everything.

Retracts test on my RC B2 stealth (0 min 22 sec)
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