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B-36 build thread and free plans

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Old 02-16-2008, 05:27 PM
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Default B-36 build thread and free plans

This is an extension of a previous post named: I have free plans for a 114" B-36 How do I share

That post has photos and some good (??) information. Look it over if you have an interest.

It was suggested that I rename the post to a building thread but I don't know how to do that so I am starting this one.

The 3 bladed 9x7 pusher Master Airscrew props arrived today.

I did manage to get the retracts set in to place.

The first photo shows where I decided to cut in to the ribs and the second shows the retracts set in to place.

I still need to box it in and create a retract mount that grabs hold of the carbon fiber wing spars.

Mike
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Old 02-16-2008, 06:29 PM
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Default RE: B-36 build thread and free plans

Nice build of an interesting subject Mike.

It brought back bad memories reading about your trouble with the paper templates you used to cut out the parts. I forget who told me about it but here is a neat trick. If you lay a photocopied page upside down on balsa and saturate it with solvent (like lacquer thinner) the image will print directly onto the wood! Not only do you not have to deal with the paper, it will also label your parts at the same time. The solvent evaporates too fast to distort the wood like water can. The first time I tried it I was blown away at how well it worked.

Also, if you have to make 4 identical parts you can stack and pin three blank sheets to your printed wood and cut/sand them all at once. I gather all my 2x's and 4x's together and lay them out on a phantom sheet of balsa within the CAD program. When I print the file I line up the corners on the piece of wood and do the print trick.
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Old 02-16-2008, 07:01 PM
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Default RE: B-36 build thread and free plans

Mike are the wheels you are using those super light wheels Dave Brown makes? They look familiar.

Mike
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Old 02-16-2008, 09:48 PM
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Default RE: B-36 build thread and free plans

That is an interesting suggestion about transferring the print from the paper to the balsa. This is the third wing that I have built for this plane. I keep getting a bit closer to what I am looking for. I will definitely try your suggestion if I go for a fourth wing or if I just build another B-36. Where was that suggestion when I needed it :-)

The wheels are the Du-Bro Super Lite foam wheels. The 2.0" wheels weigh in at 5.2 grams each. When you have 10 wheels, you gotta go lite. The proper scale for the wheels should be 2-3/8 inches on the main gear and just slightly under 2.0 inches for the nose. Century Jet built a custom set of retracts for my B-36. They built them large enough to hold 2-1/2 inch main wheels. It seemed ok to me. When I designed this plane about 10 years ago I didn't have any thoughts of putting in retracts. I was focused on eliminating weight anywhere possible due to heavy brushed motors and NiCad batteries. With 2-1/2" wheels on the main gear, the wheels don't fit between the carbon fiber wing spars. I started by taking an inch of length out of the rectangular aluminum bar that holds the main wheel axles. This almost fit so I bought 8 of the 2-1/4 inch wheels. They MAY have fit because the foam wheels could rub slightly on the spars and the wheels might flatten slightly when retracted. I didn't like that so I just bought a set of 2 inch wheels and they fit fine with a little room to spare. The 2" wheels are a little narrower than the 2-1/4 or 2-1/2 wheels so now I need to shorten the axles a bit for the main gear. That's ok, they won't protrude from the bottom of the wing quite as much. FYI, the wheels protrude on the bottom of the full size plane so I will still be pretty close to scale.

I didn't know there was so much to say about wheels......



LOOK HERE.... LOOK HERE....LOOK HERE....LOOK HERE...

IF YOU WANT TO DOWNLOAD THE PLANS, HERE IS THE LINK : http://rapidshare.com/files/92497326...First_Pass.zip

There is an option at the bottom of the page to download it for free. The download speed was quite high and I downloaded it successfully myself.

I feel that I must apologize a bit. I started out with the idea that I would post the plans and then kind of walk away until I got around to posting another zip file with the updates for retracts and so on. This zip file is not as organized as I would have liked and it does not have all of my documentation, it has no Unigraphics CAD files, no parasolids (for those who know how to use them, and finally it has only pdf versions of the part drawings, no postscript versions). I removed this info in an effort to get the size down. I will get all of that stuff in an updated file.

Be sure to download a virtual reality viewer so that you can view the files with a wrl file extension. I really like the virtual reality files. I referenced them from time to time when I was building. Virtuall reality viewers are available free for download. You should be able to get one from www.download.com I have used SolidView Lite which is easy to use, but the displayed assembly isn't quite as nice. My favorite is Cosmo Player. Cosmo offered a freeware version when I downloaded mine. I am not sure if they still offer that version. If not I can share my copy of this freeware version.


There, now the plans are shared out. I will be sure to post when an updated set of plans are ready for download.

My email address is mikeroerig@gmail.com

Contact me if you have questions. If there are Unigraphics users out there, I would enjoy a conversation with them.

So from here on it will be back to a build thread.

Mike
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Old 02-17-2008, 05:45 PM
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Default RE: B-36 build thread and free plans

I had a couple of emails about the program needed to view virtual reality CAD drawings.

The program is SolidView Lite. It is free and is available direct from SolidView with this link: http://www.solidview.com/download.html

Mike
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Old 02-18-2008, 08:24 PM
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Default RE: B-36 build thread and free plans

I didn't get too far tonight, but I did get the main retract fitted in to the left wing.

I wasn't sure how to secure the retracts, but it seems to me that the strongest structure in the wing are the carbon fiber wing spars.

I used 3/8" basswood to make a a couple of pieces similar in shape to center of the rib. I then made spacers of very light balsa and put them between the ribs and retract mount pieces. I epoxied the basswood pieces to the spars and used CA on the spacers. I think this is the only epoxy in the plane so far.

It didn't come out all that pretty, but it is very solid and should withstand a rough landing. It took quite a while to get it all fit in place. I still have to box in the rib area where I cut out for the oleo strut and wheels.

These are Century Jet retracts. In order to fit them in this slender wing, I had to rotate the retract cylinder 180 degrees. That means that one of the air fittings is between the cylinder and the retracted oleo strut. The nylon right angle air fitting was .4" tall. I only have .3" of space when the gear is retracted. Does anyone know where I can get a low profile right angle air fitting? I sent an email to Century Jet but they haven't answered back yet.

Mike
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Old 02-19-2008, 03:57 AM
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Default RE: B-36 build thread and free plans

What you have done is tie the supports for the retracts to the spars but there is no structure, besides the wing skin, between the blocks at the front & the back. Any twisting motion by the retract will be carried by the wing skin.

Whilst the wing is open I'd suggest some extra good quality 1/8 ply ribs from the front to rear spars glued to the existing ribs to bridge the gap. Of course the inboard rib will need a slot for the leg & cylinder. With the rigid legs the retract mounts will take a real pounding. - John.
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Old 02-19-2008, 05:32 PM
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Default RE: B-36 build thread and free plans

John,

At first I was going to defend the way I mounted the main gear. There are 2 carbon fiber wing spars that that are the backbone for support. I created 1/2" basswood 'short ribs' to screw the retract mount to. I added balsa spacers to put between short ribs and the remaining portion of the wing ribs. I used epoxy and CA on each side of the retract mount blocks to make it solid. All of the wing ribs and the basswood short ribs are adhered to the wing spars. It all seemed very solid and I thought that I had done an alright job on it. So I decided to think about your comments before responding.

I still believe that I have created 2 solid pieces for mounting the main gear retracts, but I think you have a right about twisting. The pressure of a hard landing would cause the short ribs to try and twist the carbon fiber tubes. I doubt that the tubes would break, but I think it would cause them to break loose due to the twisting. If a mount breaks away from the wing spar there would be very little support and it could punch through the wing skin.

So I thank you for your feedback and I will add the plywood support as you suggest. This is my first design and my first scratch build so I will take help whenever it comes along.

Thanks again and feel free to add your constructive criticism. As you mention, it is best to make corrections while the wing is still open.

Mike
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Old 02-19-2008, 10:59 PM
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Default RE: B-36 build thread and free plans

Quote:
This is my first design and my first scratch build
That's the spirit, start at the top & work your way down! I usually scratch build as it gives me the most pleasure & challenges my model was my first attempt at an electric scale model. I was building an IC powered B-29 when I first suggested to my scale buddys I was thinking about an electric B-36 even bigger than the B-29. As they were still convinced the B-29 would not fly an electric model was science fiction.

My main U/C legs are piano wire with a coil in it so little twisting motion is transferred to the undercarriage mounts although the legs bend a bit on bad landings. My wheel bogies are very simple & as narrow as possible to fit in the thinner than scale wing. Even so I had to make the gear doors more bulged than scale. Check the photos of the full size, there are blisters on the top surface of the wings for the undercarriage as well. - John.
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Old 02-23-2008, 08:10 AM
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Default RE: B-36 build thread and free plans

I haven't had much time to work on this over the last few days, but I did take a previous suggestion and strengthen the retract mount. I added 1/8" ply to both sides of the retract mount (see before and after photo) though most of the plywood was cut away on one side to make room for the air cylinder.

Mike
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Old 02-23-2008, 08:46 AM
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Default RE: B-36 build thread and free plans

I had a math teacher who was an engineer on one, and he figured out that they could t/o with light fuel and refuel in the air like they had to with full fuel, faster and get to the refuel plane with the same amount of fuel left. It did not pay to lift all that fuel. I guess I need to find a copy of SAC now.
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Old 02-23-2008, 02:07 PM
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Default RE: B-36 build thread and free plans

I received a couple of emails to provide a more complete set of plans for the 114" 6 motor electric B-36.

Here is a link to those plans: http://www.megaupload.com/?d=AHJ56N2X

The download is free.

The zip file is 87MB

Mike
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Old 02-24-2008, 12:53 PM
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Default RE: B-36 build thread and free plans

I received an email from someone that had a problem downloading from megaupload.com

Here is a different link to the larger set of plans for the b-36 http://rapidshare.com/files/94565987...n_2nd_Pass.zip

I have tested both sites and they both worked for me.

I am installing the second main gear retract and I will post another photo, though it will look just like the first retract.

Mike
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Old 02-27-2008, 10:59 PM
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Default RE: B-36 build thread and free plans

I promised to post some photos of the fuse build when I found them and I just found them. Most of the jpg photo files that I have are too large to post here. I will add them to a download file and provide a link for downloading. Perhaps I can figure out a way to reduce the file size so I can post more photos here. For now I have found 2 photos that are small enough to post here.

I have long days on the job this week so I didn't get much done. A little bit of work on the retracts, and I have a new plan for the wing mount.

Anyways, here are the 2 photos.....

Mike
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Old 02-28-2008, 03:16 AM
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Default RE: B-36 build thread and free plans

They are certainly big beasts. It's interesting to see an alternative method of construction to the one I chose. It's looking good! - John.
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Old 02-28-2008, 05:16 PM
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Default RE: B-36 build thread and free plans

Your B-36 looks good. I can only hope that mine will look as good.

I'm not sure about the alternate method of construction. My goal was to keep it light, because it is very large, it would be easy to get some weight. The fuse weighs exactly 3.0 pounds in the previously posted photo of me holding it. I believe that is an acceptable weight. I think the wing with retracts is currently between 3 - 4 pounds. I am using very light balsa whenever possible. Any thoughts? Is this light or not so light?

I will post a link to the fuse build photos later tonight. You will see more of my alternate method of building in those photos. Ignore the part of the photos that show a messy shop when I am building.

In an earlier post I showed the cad image of the tail section. There are photos showing the tail built prior to applying the skin that will be in the zip file tonight. I would send the photos now, but I am not at home.

Mike
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Old 02-28-2008, 08:25 PM
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Default RE: B-36 build thread and free plans

Here a link to the photos that I took while building fuse: http://rapidshare.com/files/95619462...hotos.zip.html

There is a button at the bottom of the page to download it for free.

It will ask you to type in the 4 letter code that is displayed. That stops automated downloads from overwhelming their site. The download will start about 2 minutes later... watch the timer.

I put the zip file together rather quickly. I just took a look and there are a couple of photos of a car part in the zip file. Ignore them. There are also a couple of photos of my first attempt to build the wing that didn't turn out. Soon I will start to organize the photos and add some descriptions.

For those who don't want to download the zip file of photos, I will show one here of how I did the fuselage nose. Originally this was going to be a XB-36 which has a different nose.

That's it for now,

Mike
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Old 02-29-2008, 01:26 AM
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Default RE: B-36 build thread and free plans

I'm taking mine to a flying display next weekend so I'll weigh the bits & get back to you. It had another 4 flights last weekend & it was good to get it back in the air.

Mine was built as light as possible to fly on the limited power of the speed 400 motors & some compromises were made. For example, your tail surfaces are a symetrical section as per full size & sheet covered, mine are flat & film covered. Likewise, my wing does have some open bays which are covered in film, yours are fully sheeted.

For all my hard work though battery & motor technology has advanced so far yours may be stronger & lighter with lipo batteries. Mine carries 2 1/2 pounds of nicads which will not be hard to beat! - John.
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Old 02-29-2008, 08:53 AM
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Default RE: B-36 build thread and free plans

So I guess procrastination paid off. I had originally planned on light fixed landing gear and approx 3 pounds of NiCads. With the lighter LiPo batteries I was able to add retracts. I believe that I have the retracts down to 1.8 pounds now. Century Jet made them to handle four 2.5 inch wheels on each main gear, but I handn't measured the space between my wing spars and I didn't know they wouldn't fit. It was my mistake, not theirs. I shortened the axle bar and the axles for the 2.0 inch wheels. Now it all fits and is lighter as well.

I am curious.... Does your B-36 fly similarly to a large glider? Also, the wing extends far beyond main gear. How is landing? You must have to keep the wing very horizontal...

I don't recall the wing span on yours, what is the span and do you know the wing loading?

You may find it interesting to look over the fuselage build photos that I posted. I put a link in my previous post. Correction: there are no car part photos in the zip file. When I made that statement I was reviewing the wrong zip file. My bad.

Mike
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Old 02-29-2008, 09:56 PM
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Default RE: B-36 build thread and free plans

Blast! I typed a reply & the 'session timed out'.

Span is 110 inch & the wing loading is about 23 oz per sq ft.

Occasionally a prop will clip the ground on landing but it's no drama, they are still the originals & 13 years old.

It's a strange device to fly, like a cross between a glider & a ship. Everything seems to happen very slowly & it's not difficult, just different. Yes, it will thermal. - John.
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Old 02-29-2008, 10:58 PM
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Default RE: B-36 build thread and free plans

Boomer,
If you time out just hit your back button, highlight and ctrl C your text and then cancel the reply. Open a new reply and ctrl V your original text into it. I time out a lot too...
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Old 03-01-2008, 03:37 AM
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Default RE: B-36 build thread and free plans

Thanks CC, my head was getting sore from banging it against the wall! [:@] - John.
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Old 03-01-2008, 08:27 PM
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Default RE: B-36 build thread and free plans

I found some of the photos of building the B-36 fuse. I will place a few posts with a couple of photos in each.

The first photo shows the fuselage framed up but not yet sheeted. You can see carbon fiber tubing used for fuse spars. The 2 spars on the bottom run the full length of the fuse. The top spar runs from the nose to wing saddle. Behind the wing saddle I switched to a pair or balsa spars that will straddle the leading edge of the fin.

In the second photo you can see that it was not possible to have the carbon fiber fuse spars support the 2 front fuse formers. My solution was to incorporate 4 notches in the 5 front fuse spars, and place 1/8 x 1/4 inch balsa sticks in the notches to hold it all in place until I could sheet the nose. You can see that one of the fuse formers does not have an opening in the center to lighten it up. This is a plywood former that will be used to support the front retracts. You can see that it is tied in to all 3 carbon fiber tubes. I have also built a temporary support that holds all 3 fuse spars during building so that this long cigar shaped fuse comes out straight.

That's it for this post. Mike
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Old 03-01-2008, 08:37 PM
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Default RE: B-36 build thread and free plans

Here is the nose a bit further along. I used a Master Airscrew balsa stripper to make the strips and then soak them in a container of water for a few hours. They wouldn't break when bent and CA worked just fine.

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Old 03-01-2008, 08:44 PM
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Default RE: B-36 build thread and free plans

In the first photo you can see that the nose is nearly completely closed in. The second photo shows the nose complete and the front support removed. The combination of sheeting and carbon fiber fuse spars makes this a very solid structure.

Mike
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