PeterF's Chris Golds Northrop B2-A stealth bomber - Page 4 - RC Groups
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Dec 19, 2012, 11:52 PM
deltas are cool
AIR SALLY's Avatar
man that is a lot of parts,keep at it looking great.
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Dec 22, 2012, 10:54 AM
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PeterF's Avatar
Complete Misellaneous Airframe Bits & Pieces

The last few building sessions have been covering a lot of small bits and pieces as I finish off the woodwork before I start to add the hardware. It really has been a case of doing everything I can as I try to put off the point of installing servos, landing gear or the fans as each of these 3 activities are going to need some forward planning and thinking.

Things that have been completed are

1. Sheeting the upper surface of the outer wing panels from the leading edges back to the main spars, again adding stiffness to these panels.
2. Adding leading edge strips on both the fuselage and outer wing panels. These are not on the plan as such but my leading edges were too deep to contour so I have added an extra strip on the front.
3. Adding outer edge strips to the wing panels, making the wingspan 25mm (1) wider.
4. Adding small bits of balsa around the wing joints so that the joints have the same shape and do not have a large uneven gap.
5. Hinging the control surfaces. I have used the fluffy surface Mylar type hinges that glue in with cyano. Whilst the B is an EDF it is hardly a speed demon and this type of hinge has done me good service on previous models. This has meant adding extra blocks onto the 6mm (1/4) rear edges to give more purchase depth for the Mylar hinges. I will probably pin them as well once they are permanently glued in place.
6. Removed the building trestles from the underside of the body.

I am quite amazed at how stiff and rigid the fuselage section is and the upper surface sheeting has not been completed yet. I had wondered about adding shear webs to the main spars, the plan does not show these and now I have got the front upper sheeting on I can now see that the plan is right, none is required. I suppose as the fuselage is much deeper than a normal wing it will be stiffer.

It is now time to stop prevaricating around the bush and make a choice, servos, retracts or fans.
Dec 22, 2012, 06:24 PM
deltas are cool
AIR SALLY's Avatar
man there are almost as many parts as the real one i cant tell if it is the rhoto or not ,but the rudders looks shorter than the full scale ,and the elevons are not as wide as the full scale .but that should'nt matter as the full scale were made that way for a reason thats a lot of area your balsa bill must be huge
Dec 22, 2012, 06:29 PM
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Jetnfast's Avatar
Originally Posted by AIR SALLY
man there are almost as many parts as the real one i cant tell if it is the rhoto or not ,but the rudders looks shorter than the full scale ,and the elevons are not as wide as the full scale .but that should'nt matter as the full scale were made that way for a reason thats a lot of area your balsa bill must be huge
You have a good eye! Exactly scale or not, this has been fun to watch the building progress....and yes that is lots of balsa!!
Dec 22, 2012, 06:49 PM
deltas are cool
AIR SALLY's Avatar
Good eye .....???? i better have a good eye after living with that jet for the last 26 years
Dec 23, 2012, 04:12 AM
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PeterF's Avatar
Thanks for the ongoing interest and support.

I have looked at some 3 view drawings and photos of the real plane and these show that the rudders and outer elevons are about the same length, i.e. both take up about 50% of the outer wing panel. On the model the rudders are much shorter than the outer elevon taking up about 35-40% of the outer panel. The attached photo of the plan / ribs shows this clearly.

The model is scale-ish not scale, Chris Golds wrote that he designed it with the correct planform and side elevation but made other features simplistic, almost cartoon scale as it was designed during the early days of EDF. My aim is to keep the model close to the design as that is a proven flyer but make it more scale like on the upper surface, I will not touch anything flying related becasue I know that set up wrong this model will not fly (or it will fly once for a limited time).

The balsa bill grows, I reckon it is now around 140 = $230, possibly larger as I have been using some wood I already had left over from my previous models. I could have saved some if I had cut all the ribs myself rather than buying a laser cut short kit, but that would have sucked.
Dec 23, 2012, 02:24 PM
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PeterF's Avatar
Nose Gear

I finally plucked up the courage to start installing the landing gear and started with the nose gear because the mounting plate for this was installed earlier in the build. The landing gear is from E-Flite and is the electric self actuating trike set for 10lb models. I may have been able to get away with the slightly lighter set in retrospect.

Before I started installing the gear I needed to cut out the doors. I have decided as with the rest of the build to have them scale like, i.e. they will look and work like the real ones but possibly will not be the exact correct size or in the exact correct location. I made up some templates of the correct size, then pushed a series of pins through the sheeting from inside the plane to mark the limits of the landing gear bays. From the pins I could locate the templates on the outside of the body and then cut out the gear doors.

The nose leg was cut to length and a Robart nose wheel collar attached. This needed drilling out, the E-Flite struts may be metric and the Robart collar imperial. I then made up a 1/8 axle (3.2mm), drilled out my wheels to 1/8 (3.2mm) and made up the nose wheel assembly. The wheels are held on with Starlock washers that grip the axle and are very thin, much thinner than bushes with grub screws. I then added a Robart strut cover, again not scale, but scale like. The chosen wheel diameter is reasonably close to scale and may end up being too small, I have enough room to increase the from 1 (30mm) to 1 (42mm) if required.

Video can be seen below, it sounds very loud because the whole of the fuselage is acting like a sound chamber like a guitar.

RC B2 stealth nose leg retract test (0 min 13 sec)
Dec 25, 2012, 03:15 PM
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Jetnfast's Avatar
looks great, I love the scale gear doors!
Dec 25, 2012, 07:24 PM
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edf nut's Avatar
Fantastic build
Cant wait to see it flying
Dec 29, 2012, 05:05 PM
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PeterF's Avatar
Complete Nose Gear and Start Main Gear

Fitting the steering servo was the final part of the nose gear installation, a Hitec HS-85 metal gear. The bend in the pushrod is not ideal, but it was that or move the servo as the sliding steering arm mechanism was not as smooth as I liked when the nose leg was retracted.

I then moved on to the main gear, I had to cut the mounting plates for this as they were not in the box of laser cut parts I received. Not too much trouble from (6mm) light ply. I spent a lot of time measuring these up accurately and then determining where they needed to be mounted by setting the plane up level of using dummy balsa legs of the right length to get the vertical position of the plates correct. I then flipped the plane over and again set it level and adjusted the pitch and roll angles of the plates to ensure that the legs where vertical in both senses. There is nothing worse than seeing a well executed plane apart from the gear being at wonky angles.

The main plates were then glued into position, pinned and clamped and the angles checked once again. The various bits of reinforcements were then added to spread the load around the model. The retract legs were then cut to length and installed into place.
Dec 30, 2012, 02:23 PM
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PeterF's Avatar
Complete Main Gear

My aim of making a more scale like model continues with the main gear. I did not want to follow the original model design and use just two wheels on a single axle per leg and have gone to 4 wheeled dual axle trucks / bogies (I do not know what the proper terminology is). However, I was not going to spend ages finessing an ultra scale set of gear as the rest of the model does not justify this, so I have scratch built a basic symmetrical 4 wheel bogie set. From photographs the real plane trucks the leg is not central between the two axles. The real plane also has the front wheel of the bogie hanging lower than the rear wheel when it is not in contact with the ground, not something I would contemplate on my flying field so the bogie has a small spring built in to keep the rear wheel the lower of the two. This also necessary because if the front wheel sat lower, then when retracting it could catch on the lip of the stalling the retract mechanism. By having the rear wheel lower, if this catches on the lip of the hatch the truck / bogie will merely rotate to clear the lip.

The photos show the make up of the bogies. I could not get a Robart collet set for the wire size on these retracts so I have made up may own block from 3/8 (10mm) aluminium. This is then pinned to a (12.5mm) aluminium channel with an inside width of 3/8 (10mm). Axles are all 1/8 (3.2mm) piano wire using starlock washers. The whole thing will look better when painted white as per the real plane, including the starlock washers.

The only hassle I have is that the wheel does not disappear completely into the hatch and stands proud by perhaps 1/8 (3mm) because the outer rib is a lot shallower and I miscalculated this. I have two options, add a bit of an angle onto the retracts body by adding a wedge between the retract and the mounting plate (easy) or configuring something from the retract servo to rotate the trucks / bogies a little as the door closes (difficult).

Video can be seen below.

Retracts test Chris Golds RC B2 Stealth Bomber (0 min 15 sec)
Dec 30, 2012, 04:51 PM
jean-claude Terrettaz
bidule's Avatar
Fantastic work
Dec 30, 2012, 07:28 PM
deltas are cool
AIR SALLY's Avatar
looks good the real boogie pivots and hugs the strut ,but the way you did it is a lot simpler. the clam shell door is tricky as it is curved, so hinging is going to be fun,the full scale main doors seem wider/taller than what you have ,but that may be a function of ground clearance,they are pretty close to the ground on the real thing.make sure you have a bit of AOA on the nose setting on the gear it will help it rotate easier. it's coming right along.
Dec 31, 2012, 04:17 AM
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PeterF's Avatar
Air Sally,

You are right on the doors, they are narrower and shorter, narrower because I want some ground clearance, I may arrange the doors to open more than 90 to increase clearance, which I know is not scale. I am limited by length, the leg position sets the rearward position so that it is not too far behind the CoG to give easy rotation. The front of the door is limited by the location of the main spar.

I have been thinking about packing the nose gear to give the plane a positive incidence when sat on the ground or swap to a larger wheel size as I am not sure the small scale ones are practical. You have given me the impetus to look into this some more.

And yes, hinging and actuating the doors is going to need some thought, this is he trouble with modifying plans and making it up as you go along.
Dec 31, 2012, 10:58 AM
deltas are cool
AIR SALLY's Avatar
the real ones had to have the main doors modded to open a few degrees more also when turning tight while taxing the trucks would twist and the wheel balance lugs would hit the door.yeah i always am looking at that clam shell door to see how they hinged it.the front hinge is different than the rear one .yeah your on your own when you start modding stuff .but you are really doing a great job just being too scale crazy due to being so close to the of the reasons i have not tried to build one yet

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