New 78" Vulcan for twin 90mm DF

[PeterF]

Martin,

Luckily the ESCs sit right at the front of the battery trays so no lengthening of the leads required. I have had to increase the length of the ESC to motor wires about 15cm, which should not be an issue. I have a Brian Taylor 81" Mosquito and chose the put one battery in each nacelle to avoid this issue. I did have a Topflite DC3, again about 80" span, batteries in the front of the fuselage and I did add a capacitor pack due to the large extension on the battery side of the ESC.

[Martin McIntosh]

Thanks Peter. My battery pack is miles from the intended esc position so when the wire arrives from HK EU I shall do some testing before making a decision.

[PeterF]

Continuing with the build, following the instruction pack sequence pretty much. The covering has been added over the fan ducting, it is not scale but it does not look too out of place. This includes the front of the covering and marking out the fan hatches. The spars have been added to the top and bottom of the the air inlets.

The cockpit has been planked and how I hate planking. I trim each and every plank down at the front of the cockpit to get a good finish with minimal stepping, but it means that it i s a laborious process of trial and error trimming the planks. I use white glue on the plank to plank joints but glue the planks to the formers with thick cyano to speed up the process. It gives a good finish and is worth the time and effort, but it just drags on and on, it probably took less time to sheet the top and bottom fuselage that it did the cockpit. Ho hum.

[PeterF]

I was continuing the build today and going to fit the turtle deck formers and noted on the plan that these are all vertical on the plan, so I decided to chock the model up to the same reference angle as the plan. It was then that I noticed a discrepancy between the left and right hand sides, the left hand side has a slightly higher angle of attack than the right. The photos show that I have the rear of the plane sat level, but when measured at the front, the right hand side is lower than the left. I have measured the angle between the two wing joiner tube holes on both sides using a digital inclinometer and some aluminium angle. This shows an AOA of 1.5° on the right and 2.1° on the left, but this is I believe a bit error prone depending on how well the aluminium angle sits etc. I measured the height of the rear of the ribs from the building board (the board is level confirmed by digital inclinometer) and these were equal. I measured to the top of the front spar, 146mm om the right and 151mm on the left. A 5mm difference over the 822mm length from the rear of the rib to the front spar is a difference in AOA of 0.35°, which is more palatable than the inclinometer results.

I have obviously built in a bit of a warp as I have gone through the sheeting process. The question is, what to do about it. Are there any real gurus out there who could tell me if this is significant or not or suggest the best way forward.

The options that I can identify are are
1. Continue building and hope it can be trimmed out during initial flying if it is felt to be small enough to ignore.
2. Strip off the sheeting from the right hand side, rejig the right hand side firmly and resheet.
3. Continue the build, but move the wing joiner tubes up a bit on the right hand wing and when the wing panel is attached, add some soft balsa sheet and blend this in to hide the step between the fuselage and wing.
4. Start again.

Rear of fuselage sat level

Front of fuselage sat right hand down

AOA measured on left hand side

AOA measured on the right

Front spar heights on the left

Front spar height on the right.

 

Edited By PeterF on 27/11/2019 14:44:28

Edited By PeterF on 27/11/2019 14:51:26

[Greg Minden]

i posted an answer on the Groups page

[PeterF]

I have done some more measurements and found that with the trailing edge flat as per previous post the nose, ribs around the fans and u/c bay are all tilted. When I set the front spars at the same height on both sides and let the right hand trailing edge lift everything else comes into line. I expect the front to be true because all of the formers around the fans keeps this area solid.

My belief now is that when I started the top sheeting at the rear, which is much less stiff than the fan area, I have allowed the rear of the fuselage to distort. The top of the fuselage is slightly higher in the middle and I made the first 4 sheets as 1 piece across rather than cutting them at the spine into 2 pieces. I think that this has flattened out the rear of the fuselage and as the sheeting has progressed it has locked this in. Your photos appear to show that your sheets were split in this area and Craig's are on the UK forum.

I am going to have a good think about releasing the upper sheeting on the right hand side at the rear and seeing if I can get the trailing edge to relax down. Then if that does not work 100%, I will lower the rear wing tube a little on the right hand side and pack and fill with some soft balsa to hide the offset.

[Martin McIntosh]

I would not worry about it on a model of that size. You would probably do more harm than good removing the sheeting ( if even possible). The wing sections on the small TN Concorde I am building are, shall we say, not quite the same on each side but I cannot see this making a significant difference to it. I have found in the past that even a small amount of trim will sort out what appears to be a large warp. Best of luck.

[Craig Carr]

Hello Peter,

I did all my top sheeting as separate pieces, your theory may well be the cause.

im wondering, if you used a straight edge and scalpeld through the sheeting along the centre line/spine would that help a little bit to “relax” the frame back into true?

I do fully understand the desire to have it “just so”. However, I think martins right if you just proceed as it is?

Craig

 

Edited By Craig Carr on 27/11/2019 22:49:17

[PeterF]

Craig,

That is a good idea about slitting the 1 piece sheeting so I have done that. I have had another suggestion to wet the sheeting and weight the model down with some over correction, the sheeting is soft balsa so I am also trying this. With the cut down the spine the sheeting may be able to give a little easier.

Peter.

[PeterF]

Update a couple of days later and it is all sorted, slitting the offending sheeting down the spine, soaking the sheeting and weighing the corners down has worked, the two sides are now about 0.5mm out instead of the 5mm, which is well within the accuracy of my measurement equipment. Thanks for all the help. The build continues with the tail cone and the framing for the turtle deck.

Rear of fuselage mounted flat

Right hand side a simdgen below 151mm to the bottom of the front spar

Left hand side a simdgen above 151mm to the bottom of the front spar

Tail cone frame

Turtle deck framing

[Craig Carr]

Well done Peter. Nice one

its all progressing really nicely. Are you glassing the model ?

[Greg Minden]

coming along nicely Peter

[PeterF]

Yes I will probably glass it, but I have not done any glassing about 15 years and that was not a great finish so I will have to practice first. The last 2 sheeted models I built were covered with tissue and Poly-C which is light but not hanger rash proof. I believe that glassing is a good idea with this given how the fuselage is built up.

[PeterF]

Now the fuselage is straight I have continued with the build per the instructions. The tail cone has been planked and the turtle deck sheeting added. The templates for the turtle deck sheeting were very good, they were a little oversize so could be neatly trimmed down to fit. Before I added the turtle deck sheeting I put some extra formers in place for where the battery hatch is going to be cut, putting in a top hatch because I am not keen on the idea of taking them in and out in the underside. Thanks for the idea Greg.

Tail cone planked

Extra formers for turtle deck at battery hatch

Extra formers for turtle deck at battery hatch, ink markings ran when I wetted the sheeting

Turtle deck sheeted

Edited By PeterF on 07/12/2019 13:35:50

[Mark Kettle 1]

I'm glad you sorted it PeterF, watching with interest.

[Greg Minden]

Peter - you will be so glad you made it this way. Also helps immeasurably with routing the wiring. I believe i have about 35 ft of cabling in this model.

[PeterF]

Progress has been a bit slow in terms of the amount of wood added to the plane. I have tackled the rudder and done this according to the plans and all has gone well. It is quite large, larger than the wings on some of my models so it has taken a bit of work.

The main reason is I have bought a basic 3D printer, my son has a model making business (not RC - wargame models) and he has a number of 3D printers, but he has been inundated with Christmas orders plus he had a special promotion on a new range of kits so he has not had time. Anyways, I have done a pair of pilots, taking the cue from Craig's build photos, pilots were 1/12th scale of Thingiverse and I believe the TN model is about 1/16th scale so printed them at 75%. These are the pilots with visors raised, hopefully more detail will show of their faces when painted. I have used the nose cone and tail cone supplied by Greg, spot on, thanks. I have not sanded the nose or tail cones until I got these. I have designed by own exhaust nozzles, I will post a little bit about these later.

[PeterF]

The exhaust nozzles on the plan are just some thin ply wrapped into a short tube. The advantage of these is that they have a minimal impact on the air stream flowing out of the thrust tubes. I have built the 3D model of the rear former and the air stream and original nozzles to show this.

Greg has then gone on to make a 3D printed version of these.

However, I wanted ones with some conical shape on, but the trouble is that these will interfere with the air stream, so I have made the cone quite small and angled the two cones 3 degree inwards to reduce the impact on the air stream in the middle of the thrust tube. This does mean that the gap between the cones is reduced, but needs must. They have also been angled down 3 degree compared to the outlet former. The 3D model shows the limited impact on the air stream.

If anyone wants the file for the conical version pm me with your email address and I'll happily send it to you.

Edited By PeterF on 23/12/2019 11:23:24

[Greg Minden]

Looking good! Instead of painting my nozzles , i used a silver sharpie pen to color them. Gives a kind of metalic, steel finish.

[PeterF]

I have completed the skeleton of the right hand wing, spars, ribs, leading edges, trailing edges, shear webs and wing tubes and this fits well with the fuselage. I mainly followed the photo pack. One thing is the photo pack does not exactly stipulate how to set the ribs up and I could not find a note on the plan either. One photo shows the trailing edges all set on the building board, so this is what I have done. I also put the front spar in place as a positioning device whist the ribs were fitted, then lifted it up and glued it in place later in the build. I also added the shear webs before lifting from the board in an attempt to keep everything more rigid once lifted from the board.

Ribs glued in place with the spars.

Rear of the ribs level on the board.

Front spar only used for location at this stage.

Front spar lifted up once top spars, LEs and TEs have been glued in place

Shear webs added

Wing removed from building board and trial fitted.

[PeterF]

Second wing skeleton completed and test fit. This is getting quite large now and will be too long to fit when the nose and tail cones are on. I need a considerably bigger workshop or I might have to take the doors of the wall cupboard.

[Greg Minden]

looking good!

[PeterF]

It has been a while since I posted but I have been working away and making good progress.

The topic of this post is how I have designed the wing retention on my model as the plans are silent on this issue. Ideally this should be decided upon before the wings are sheeted, otherwise you will need to cut patches out of the skin.

I have glued ply plates onto the wing tubes either side of the wing joint and reinforced these with triangular stock, all glued on with lashings of epoxy. Threaded inserts had already been glued into the ply plate using before gluing them to the wing tubes. The outside of the inserts is knurled to give a good grip when glued in. Slots are then cut into the root ribs and a short 3mm aluminium bar with holes in the appropriate locations is then screwed to the inserts in the ply plates using cap head screws through small holes in the upper sheeting. By appropriate use of shims, the head of the bolts is relatively flush with the wing surface.

The main aluminium wing tube (the rear one) needs some form of stopper to prevent it migrating in and pressing against the exhaust duct from the fan as this is flexible and will deform allowing the tube to move and the fan performance to be reduced. During the wing attachment, a small piece of sheeting needs removing so you can glue the wing tube to short rib WS1. I took advantage of this and glued 2 sheets of ply between WS1 and the exhaust duct, the first sheet of ply was 2.4mm and had a hole in to match the wing tube so that the wing tube could pass through WS1 by a small amount. The second sheet of ply was solid and this stops the wing tube moving inwards towards the exhaust duct.

Pictures may explain things better.

Ply plates glued to the wing tube shown from above before sheeting

Ply plates shown from below with triangular reinforcement from below after sheeting the top surface

Wing section removed showing aluminium tubes and aluminium strip to lock the wing in place

Upper sheeting showing the two cap head machine screws

Two layers of ply between short rib WS1 and the exhaust duct with a hole in the first additional ply layer

[PeterF]

The first wing has been completed and this followed the photographic instruction sheet and the plans. Sheet the upper surface, add strengthening blocks at some corners, add the elevator and elevon hinge blocks, add the servo rails, sheet the lower surface and cut off the wing, which is shown in the post above. The only area I have deviated is to mount the servos into plastic covers because the plan calls for the servo tops and horns to be exposed. I have 3D printed some servo covers and I have gone back and reworked the rudder servo to match. The second wing is coming along now that the first one is completed.

Wing skeleton being glued into place on the fuselage.

Top surface sheeted.

Servo rails / hatch for the inner elevator.

Servo in 3D printed cover.

Servo for the outer elevon mounted in position before sheeting the lower surface.

Bottom surface sheeted.

Rudder servo reworked so it is not exposed.

[Craig Carr]

hello Peter

all looking spot on I did the same but used some commercial slec ones