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Ziroli 1/7 (120") B-25 B scale build

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Ziroli 1/7 (120") B-25 B scale build

Old 09-20-2014, 08:38 AM
  #51  
rossmick
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Default

Tim

Thanks for the comments and the reference on the book, I will get it ordered ASAP.

Yesterday was a bust as the truck was in all day with a mandatory EGR filter change and system cleanout, something to do with the Cummins diesel and $700 - OUCH.

Today I hope to spend the majority of the day working on the B-25. I have changed the design on the extension and will use 1/4" balsa in place of the top 1/16 ply. I think it will provide a better glue connection to the side member and allow for more sanding to curve the upper corner to match the full scale drawings and photos. I just have to make sure there is good clearance for the linkage and horn.

Additionally, I want to get started on the fabric covered ailerons. As they use the same structural "D" shape LE with the ribs joined to that and ending at the TE. I will use the same technique as I did on the elevator and rudders. Also the aileron TE is curved at the outboard end where it matches the curve on the wing tip and is not straight as the plan shows so that will be some changes there as well.

I have not decided just how to hide the connection from servo to the aileron. I have used Sam's idea of the sliding tubes between servo and aileron on the Corsair and it works fine - funny when I designed the linkage on the Corsair using brass square tube I thought I was the only one to think of it - I SHOULD HAVE KNOWN BETTER. Seeing Sam's use of round Nyrod tube made more sense and gave me more confidence that the idea would work. I am also considering RDS but have never used it. I don't like hatch covers on the wings and maybe I can put the servos at the inboard section of the outer wing panel and run the long rod out to the aileron. I am afraid there will be too much twist over that length - still thinking. I have also seen guys just bury the servos but I don't think I can live with that - Ah the joys of scale building.

I'll post photos late tonight as my daughter in law is having us over for dinner to thank me for fixing two computers that I had to reinstall Windows and programs because of virus problems - kids playing on the internet.

Last edited by rossmick; 09-20-2014 at 08:49 AM.
Old 09-20-2014, 10:37 PM
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Default continuation of elevator, rudder, stab



Photo 1 - Chiseled out the cut out for the attached tab which will be glued in. Photo 2 - attach tab in place. Photo 3 - First try at extension missing top member.

Photo 4 - completed extension in rough form. Photo 5 - left side extension trial fit.

Photos 6 - 9 shows servo connection to aileron planning using sliding tubes. The layout looks a little close and may not be able to get the 3/4" travel required.

Photo 10 - Aileron center web lay out. Rib spacing above the trim tab are a different spacing than the rest of the rib spacing. Laying out the "D" LE section comes next and the sliding tube interface with the hinge looks like a problem. Going to use the gold Nyrod with the 1/16" wire hinge pin. Also need to layout the hinge locations, looks like there are three of them.
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Last edited by rossmick; 09-20-2014 at 11:10 PM.
Old 09-23-2014, 08:28 PM
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Default COntinuation of elev, rudder, stab



Photo 1 Stab extension prototype on right fin

Photo 2 extension modification of rudder so extension passes through central web with inboard travel.

Photo 3 Closer view of extension prototype and rudder.

Photo 4 - 8 With the opening in the central web for the extension the attach area for the control horn is now too weak and the first of many re-dos are in order. The existing balsa re-enforcement had to be removed so a hardwood replacement can be glued in. A high quality wood chisel cleaned up this area very well. This hardwood member will now have blind nuts installed in the recessed area to bolt the control horn to, and a balsa filler will be glued on top to make the area flush. The hardwood should now provide an adequate structure to move the rudder from the action on the control horn. The bolts will have to be the correct length so as not to penetrate past the blind nuts.
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Last edited by rossmick; 10-03-2014 at 07:56 PM.
Old 09-26-2014, 10:52 PM
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Default rudder, stab, ail



Photo 1, blind nuts installed, control horn bolted in with double lock washers for depth in blind nust, balsa cover sheet glued in.

Photo 2 - 3, stab extension prototype in place and max travel is available.

Prototype can now be use to create the actual stab extensions, one left and one right. Note, that extension can not go past fabric on outboard side of rudder, so I may set up a physical stop rather than depend on a servo adjustment.

Ailerons

Photo 4 - 5, 'D' shape leading edge and center web with Nyloc hinge gluing up.

Photo 6 - 7, Leading edge sanded to shape and aileron cut to fit wing.

Next is gluing in ribs and trim tab and sanding to shape.
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Last edited by rossmick; 10-03-2014 at 07:54 PM.
Old 10-01-2014, 08:49 PM
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Default Aileron



Photo 1 - 2, Standard square ribs glued in. Square shape allows for aileron to be clamped down to work bench to maintain a straight center web and TE while glue sets up - done on both sides.

Photo 3 - 5, Sanding done on power belt sander to rough shape and then hand sanded to finish shape. Make sure the dust collector is running during the power sanding so you can see and breath.

Photo 6, Initial positioning of aileron to wing. The trailing edge of the ribs had to be adjusted so as to maintain a straight line for the LE of the aileron.

Photo 7, Hinge plates made of G10 (more photos to come). Slots cut in aileron for the hinges, made first cut too wide and will have to shim in for tighter fit. Trailing edge of wing top stringer removed so hinge plates could be inserted for trial fit. Inboard hinge had to go under 1/4x1/4 hard wood stringer so it is not as tall as I would have liked - shaped balsa blocks to come to hold hinge plates.

I have not made up my mind on just where I will mount the servo, as you can see from the various sketches on the wing. I can't go to far out or there is not enough height for the servo arm to swing, some trial and error will have to be done here as I would like to be as much toward the center of the aileron with the servo as possible. More than likely I will settle for about 1/3 the way out from the inboard side.

The hinge pin Is 1/16 dia. wire and fits very well in the aileron and the hinge plates showing no sign of any slop. At least one rib will have to be realigned, maybe more.
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Last edited by rossmick; 10-03-2014 at 10:04 AM.
Old 10-03-2014, 07:35 PM
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Default Aileron continued




Photo 1, G10 hinges, notice the step cut that catches on the trailing stringers so hinge can't pull out of wing. Also drilled 6 glue holes so Hysol can get a good bond once in the mounting block.

Photo 2 - 3, hinges installed in ailerons with hinge pin in place and rough fit in the wing.

Photos 4 - 5, Mounting blocks for the hinges, They are cut so as to stay just under the bottom skin once applied. Slot is cut so as to have a snug fit with the hinge, all of this done on the band saw.

Photos 6 -7, Dry fit of the mounting blocks in the wing. Did a little re cutting to make sure blocks stayed inside the skin to reduce hand sanding before applying the bottom skin.

Photos 8 - 11, Show the mounting blocks glued in. Titebond used to glue mounting blocks to skin and Hysol used to glue hinge in the mounting block slot. I used plenty of each glue to insure block and hinge won't come loose. I will use Hysol around the mounting block once the Titebond has completely dried. I mounted the outer wings on the center section and then took a good look at the alignment of the ailerons to the total wing. All looked pretty close and just needed a little adjustment to be correct. Thank goodness for Hysol as it gives you time to make the required adjustments.
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Last edited by rossmick; 10-03-2014 at 07:58 PM.
Old 10-20-2014, 10:16 PM
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Default Ail. redo and servo linkage



Well, I would like to say the ailerons shown in the prior thread were prototypes but the simple truth is they are just wrong. Wrong width, wrong length on the trim tab. "D" section was too thin and when slot was cut for the hinge the section became weak. New "D" section has an added 1/8" layer behind hinge pin section followed by the 1/4" beam on the center web. Aileron corrected for width with the curve to the tip not cut in at this time. Trim tab is .75" by 5.5" and tapered roughly following the LE.. The hinge pin concept is that it would be removable and this causes a change in the servo linkage position which is now on the inboard end of the aileron.


Servo bracket is made from a 1 x 1 alum angle with 4-40 taped holes for attaching the servo and 5/32" holes for mounting the bracket. The 3/8" 4-40 Allen head bolts for mounting the servo are hard to fine and now have a bunch ordered. I have chosen the dual arm as recommend by Sam with the included 4-40 ball link. I have tried the black & yellow Nyrod system that I have seen and for me it showed some slop and I was afraid that the ailerons would flutter. I then used the same system as I did in the Corsair using brass square tubing. I use a 1/8" round tube that is inserted in to the ball link after drilling out the 4-40 tread by using a 1/8" drill bit. The fit is so snug that the tube has to be taped in. The round tube in then slid inside, with a snug fit, the K&S #152 5/32" square tube where a 1/16" hole is drilled through and a small screw is screwed through to hold the round tube from pulling out. I cut the round tube just short of the length of the square tube for the reason that it makes the linkage very strong over its entire length. Then this assembly is inserted in the K&S #153 3/16" square tube which is glued and trapped between plywood on the aileron. Here the #153 tube is cut so that the hinge pin can be pulled once the servo is removed allowing for the aileron to be removed for repair or replacement. Note, the ailerons are fabric covered and not balsa as per plan.


Mounting the servo in the wing is done so that the centered arm is at the center position of the rib and then the #153 tube is positioned in the slot in the aileron. The aileron is then aligned with, and held, on the bottom line of the rib, Now Hysol is applied around the #153. After the glue is dried, the plywood trap pieces are glued and screwed in place (be careful not to pinch the #153). Be certain that you have 3/4" up travel and 1/2" down travel. This is accomplished by the position of the servo from the hinge. The aileron is 3 1/4" at the inboard tip so at 3 1/4" forward of the hinge you would need 3/4" travel down inside the wing. As you rarely have that much room you would need to move the servo closer to the hinge line so that with less servo travel you will get the 3/4" at the tip. This is a tight fit in the wing here and the hinge block had to be trimmed back to get the servo in the correct position. The ball link is also critical because with the square tubes you would never get the alignment correct without binding.
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Last edited by rossmick; 10-28-2014 at 07:31 AM.
Old 08-03-2017, 05:38 PM
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Default Starting the build again.

Well, it has been some time since my last post on the B-25. Many issues stalled the project and thank goodness I had built the jig for the fuselage so that it is still straight and true. I'll share several photos of the parts completed to date and now must regroup my thinking and reorganizing all the parts in all the remaining boxes. It has been so long that I must relearn how to use RCU. Spending plenty of time reviewing Sam's B-25 build to get back in to finishing this build. I was so sad when his beautiful plane went in. It was one of the many reasons I really let this build slide, also there were some health issues and way too many other planes in between.
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Last edited by rossmick; 08-03-2017 at 09:01 PM. Reason: add photos
Old 08-07-2017, 10:06 PM
  #59  
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Well, looks like one more furniture project needs to be done before I can get started on 25. Hope to be done in about one week.
Old 08-10-2020, 09:41 PM
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Default Lets finish the B-25

Well here I am with many years that have passed. The B-25 was put up on the shelf and many other projects and planes have been produced. The big change for me was getting into electric power. Started small and ended up with the T-28 from E-flite and trying to make it scale. Spent many hours and experiments learning the ins and outs of electric. Each step let me learn a little more about scale building, fiber glassing and flite metal application. I also have been using a sound system in the T-28 which drives the other flyers crazy but it does get a lot of attention. I also picked up the smoke system and just plan to use it in the start sequence. The T-28 is the Air Force version and I have poked in way more rivets in the flite metal than I care to think about. I now also have a 83” giant stik that is electric as well. Long story longer, I never thought I would get in to electric, however, after reading multiple “single engine out” crash stories I am seriously considering going electric on the B-25 rather than gas. Also, I have had enough issues with electric gear that I may go back to pneumatic gear. I have built a 12’ X 20’ shed for my lumber storage and converted the pump house shed to store airplanes as there is no room in the shop. I have just installed an air conditioner in the shop so now I can work out there in the 109-degree heat that we have been having here in Tucson. With the virus situation flying has become problematic as too many members are not following the sensible guidelines. That coupled with having to fly at 0600 using electric only to avoid the extreme heat makes is much more difficult to get out there. So now I have decided to just build, stay isolated and safe and get back to finishing all the unfinished planes. I will start with the B-25 and not be so driven for the perfect scale aircraft. I would rather finish the bird and fly it rather than to get stalled out on perfection which I really don’t have the experience to do right now. In looking at the completed sections I can see where there should be some improvement and I will start there. One issue is that an electric B-25 will be even heavier that the gas verson, so I am not sure I can stay under 50#s. Thinking of skipping the FG and just sealing the balsa and putting the flite metal on that to save some weight??

So here we go.

Last edited by rossmick; 08-10-2020 at 09:47 PM.
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Old 08-12-2020, 08:44 PM
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Default B-25 Build

Over the last several days I cut in to an 8” solid block wall an opening for an air conditioner for the shop. Today I managed to seal the outside block wall to the air conditioner with aluminum strips with silicon caulking. I also sealed the unit on the inside with caulking and an ½ “MDF frame around the unit.

It is a cool 105 degrees today, so it is the first test of an all-day work in the shop with the air conditioner running. As it turns out it the unit holds the shop (about 500 sf) at 77 to 78 degrees which is a welcome relief from the past having to work in the heat.

Today, I just wanted to finish the repairs to the old Senior Falcon I built 55 years ago. I converted it to electric from the Enya 60 engine I had in it. This choice was driven by wanting to fly at 0600 to avoid the heat. We cannot fly gas before 0730 so electric is the only choice. Believe it or not, the Falcon flies quite well after all these years. It’s kind of like flying a glider on final, but it flies well with a long gentle final approach.

Photos tomorrow on the air conditioner, Falcon, T-28, Giant Stik, P-51, Hempel’s Super Decathlon, unfinished Corsair, a second P-51 bought as a favior to a fellow member, Storage shed, and plane hangar building (pump house). All of these has led to now getting started on the B-25.

Last edited by rossmick; 08-12-2020 at 09:01 PM.
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Old 08-14-2020, 08:19 PM
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Remind me to not say tomorrow as something always seems to come up. Did get yard irrigation working in 109-degree heat, great time for the underground feed pipe to spring a leak. Also, decided to install a TV in the shop now that it is air conditioned. All I need to do is install a rocker recliner in there-just kidding. However, I will be spending much more time out there in its new configuration. Next post I will try for the photos and get the B-25 on the bench. Does any one know how to get the spell checking to wortk?

Last edited by rossmick; 08-14-2020 at 08:24 PM.
Old 08-18-2020, 08:51 PM
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Off the shelf and on the bench. Found damage to the tail section of the fuselage and many other issues that will have to be reworked or repaired. Thank goodness for the jig as alignment of the long fuselage has been maintained. A twist or bow would be a disaster on the maiden flight.

Must make the decision as to how to handle the wing center section in the fuselage. Considering making it mounted solid to the fuselage with a removeable section over the top to handle equipment.

Just bought a 12’ trailer to handle this plane as my smaller trailer was too short for the length and the width of the center section would just fit inside. I will pick up the trailer tomorrow.

Wow, need to resize these photos before putting them on the site.

Fuselage in jig minus damaged tail section

Outboard wing sections, finished one side only to add servos and electric lines for lights.

Wing center section and the most masive of all the other modules with with the gear installed.

Tail section re-ttached and reinforced.

Last edited by rossmick; 08-18-2020 at 08:55 PM.
Old 08-20-2020, 09:51 PM
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Default Fuselage Build

Decisions, decisions. Decided to permanently mount the wing center section in the fuselage and not make it removeable. To be removeable the whole area above the wing would have to be made into a hatch. It just did not look like there was enough structure remaining in the fuselage to have good fuselage integrity. Did make a smaller hatch much higher up the side, so I used two spruce stringers running over the top of the wing before the hatch to give it more strength. I will leave the area where the wing goes through open until I get the rest of the stringers and the skin applied. I don’t like skinning too soon without laying out all the equipment, air lines, air tank and electric wiring inside.

Stringing the bottom of the fuselage will take it out of the jig so I will have to apply some skin to keep it straight and true. Most likely won’t get back to working on the bird until next week, maybe sometime on Saturday.


Last edited by rossmick; 08-20-2020 at 09:56 PM.
Old 08-25-2020, 09:04 PM
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Default Wing center section / main gear

Cleared the work bench of the fuselage and moved the center section over. As I had the gear modified to electric from air and now after much experience, I have decided to go back to air. To rebuild the gear, they need to be removed so the nacelles need to be skinned to get the gear doors off. One interesting thing about the B-25 is that there are three different sized gear doors per main gear. This is slow going with all the curves, so I have been using a paper template to help shape the skins before gluing them in place.

Another decision is to go electric for the power. This requires cutting in an access hatch in the nacelle behind the firewall to be able to handle the in-series 6-cell batteries. This space will also handle the esc and will keep the wire leads as short as possible to the motor.

Forgot to reduce the photo size, next time.









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Old 08-31-2020, 10:07 PM
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Default Wing center section / main gear 2

This is very slow going. Object is to get the gear out so they can be converted back to air from electric. Sheeting is tough enough but cutting out the doors is a real choir. Also slow going on getting the hatch built and opening created. Got one of the gears removed, now for the other. Matching nacelle sheeting to the wing will be next undertaking. Could have done a much better job preparing the nacelles for the gear door cut out. Learning as I go.

Doors removed

Hatch

Slowly cutting doors out

Doors and gear removed.
Old 09-01-2020, 08:32 PM
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Default Center section to wings

Gear doors cut out and gear removed.

Access routing tubes installed, just so happens that the tubes from mono coat fit perfect. Just needed to correct two rib holes to feed it through.

Wing rotation pins installed. Wing tab installed to hold outboard wing to center section.


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Old 08-21-2021, 09:06 PM
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Default

Well, it has been just about a year since the 25 was put up on the shelf one more time. As I had decided on electric for the 25 due to numerous gas engine failures and lost aircraft, I made a serious effort to get to know the plus and minus of using electric power. What I have determined is that a large aircraft has a real problem with the battery weight that is required for the larger electric motors (10s or 12s 5500 mAH minimum). So after modifying several larger aircraft to electric, I am now planning on going back to gas for the 25. This time using twin cylinder engines to reduce the vibration of the original larger single cylinder DA 50s, which I now have two still in the box. I have just finished my first flight with my test bed aircraft using the RCGF 40 twin and I believe it will be the engine of choice. It is lighter than the 50s, will fit inside the cowls and runs very smooth. Will also start watching my overall weight of the build for the slight reduction in total power.
The doors I cut in to the nacelles for batteries will now be used to hold the refueling points and ignition switches for the engine and access to the fuel tanks.
Shop was also upgraded to an air-conditioner in the wall and the second build table relocated so I can work from both sides for this large build.
The virus cancelled flying for me for almost a year as I had fellow members who were not abiding by the simple safety rules set by the club which made flying problematic. I am 76 and would like to go to 106 so staying away and getting the shots was the answer for me. Luckily, only lost several members over the year, but did have five additional fiends and neighbors die from the virus. However, not flying allowed the many home projects that needed to be done get accomplished - I would rather be flying.
So the build resumes, hopefully by next spring, or summer, the 25 will be in the air.
Old 06-25-2022, 09:28 PM
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Default Commitment to finish B-25

I restart the build on the B-25. Since the post last year there has been changes in my design and power ideas. I decided to run some testbed planes using electric power. What I have decided is that for a large plane the weight and cost of using electric was not going to work for me. It was in early May that I, once again, got the B-25 off the shelf and began the build with the return to gas engines. In this case, and after an additional testbed aircraft, I will be using the RCGF 40cc twin. I have now made the decision to use all twin engines and get away from single cylinder power. What I found was the extreme reduction in vibration using the twins and with little cost in weight. In this case the 40cc even fits inside the cowl with room to spare. The 40 has performed extremely well on the testbed and has all the other members asking what is that engine. Also, I can get the engines just down the road and it is the repair facility if required.
I will start posting the photos from the start in May and try and catchup to my current build status with more photos than words. After looking at what I had built, I decided to rework many of the areas to improve my prior work. Amazing what you can see when you spend some time away from a project that needs to be changed or improved. So here it starts with the idea to finish the plane and not get diverted off on other projects.
Goals: Gas twin engine, keep weight a low as possible, relax on total scale demand, return to air powered retract from electric (that was an expensive mistake), design mid-section above the wing to be a more structural element of the build, trying to not use fiberglass to cover the skin and use oratex colored covering with drawn panel lines and rivets.
As of 10 May, Photos where it starts.

Fuselage in jig with center section. Thank goodness for the jig to keep it straight and true.

Stringers remove to straighten them.

Tail section without vertical fins.
Old 06-25-2022, 09:37 PM
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Default 14 May


Begin center section rework

Stringers added

Side view
Old 06-25-2022, 09:51 PM
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Default 15 May

Idea on center section is to make it bolt in with added structure to strengthen the area above the wing. In my opinion this is a real weak spot even with the added ply sides from the earlier work. Then I want to make a hatch in the top to have access to electrons and air equipment.


Starting some skinning

Center section skin

Hatch skin

Center section in place, hatch skinned

Hatch removed from center section.
Old 06-25-2022, 10:01 PM
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Default 17 May


Fuselage out of the jig for the first time in 8 years

installing stringers
Old 06-25-2022, 10:09 PM
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Default 22 May


Nose gear door structure.

Skinning bottom of fuselage

Last edited by rossmick; 06-25-2022 at 10:23 PM.
Old 06-25-2022, 10:20 PM
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Default 23 May


Mistake in gear door layout, follower door and opposite door resized to clear struct.

Gear doors modified and now clear struct.

Bomb bay doors cut out.
Old 06-25-2022, 10:31 PM
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Default 3 Jun


Bomb bay door installed

Found front former was not held correctly and had to have skin removed and repositioned.

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