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New 78" Vulcan for twin 90mm DF

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Greg Minden05/11/2019 01:45:02
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34 forum posts
34 photos

looking good! seems nice and straight. Here'img_20180222_184026391.jpgs where i was at that stage

PeterF12/11/2019 08:47:54
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452 forum posts
619 photos

Greg, Thanks for that picture, it got me thinking that putting the ESCs in at this stage was much better than waiting.

I have continued the build sequence as the the TN photo build document, inserting the battery tray, but as noted above, I have also fitted the ESCs at this stage whilst I have good access to wiring the ESC to the fans. The bottom of the fuselage has then been sheeted and the radio hatch marked on. I will plan to use this radio hatch per the plan. I will add some small air scoops to bring some air flow over the ESC heat sinks in flight. I have marked out a battery access hatch in the top of the plane per Greg's build because I do not want to be flipping the plane over to install the 4 battery packs, a because turning such a large plane over is a hassle and b, the access hatch will be larger on the top for better access. The nose has been fitted, once again with various straight edges and clamps to check it is in line, use 30 minute epoxy to give lots of chance to tweak it straight. The only issue was that W1 and S1 did not match in front of F6 and a small wedge was installed. Everything else lined up per the plan so I concluded this was the best thing to do.

Battery tray and ESCs installed, radio hatch marked on and bottom sheeting commenced.dsc08476.jpg

Bottom sheeting completed to the fansdsc08479.jpg

Battery hatch marked onto the upper sheeting. ESCs just visible.dsc08469.jpg

Gluing the nose onto the fuselage with straight edge.dsc08478.jpg

Small wedge between W1 and S1.dsc08482.jpg

Greg Minden12/11/2019 16:53:04
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34 forum posts
34 photos

img_20180517_182541.jpg

Greg Minden12/11/2019 16:53:53
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34 forum posts
34 photos

you will very happy that you put the battery hatch on top. Here's where i put in the esc air scoops

Martin McIntosh12/11/2019 20:01:25
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2970 forum posts
1090 photos

I shall not be attempting this design but am following your excellent build with interest. One question, do the battery leads to the esc`s need to be lengthened and do you propose to take any measures to prevent the latter from blowing up due to eddy currents (I think) in the extra wiring? The reason I ask is because one esc on my TN Mosquito failed on take off on the second flight despite low Z capacitors being added. Currently building the Concorde and Tony says that long wiring has never caused him a problem.

PeterF12/11/2019 20:32:33
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452 forum posts
619 photos

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 McIntosh13/11/2019 09:04:09
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2970 forum posts
1090 photos

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.

PeterF23/11/2019 21:10:24
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452 forum posts
619 photos

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.

dsc08494.jpg

dsc08501.jpg

dsc08497.jpg

dsc08506.jpg

dsc08510.jpg

PeterF27/11/2019 14:41:05
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452 forum posts
619 photos

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 leveldsc08524.jpg

Front of fuselage sat right hand downdsc08525.jpg

AOA measured on left hand sidedsc08528.jpg

AOA measured on the rightdsc08527.jpg

Front spar heights on the leftdsc08522.jpg

Front spar height on the right.dsc08520.jpg

 

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

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

Greg Minden27/11/2019 16:20:38
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34 forum posts
34 photos

i posted an answer on the Groups page

PeterF27/11/2019 17:14:44
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452 forum posts
619 photos

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.

dsc08428-2.jpg

Martin McIntosh27/11/2019 18:35:30
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2970 forum posts
1090 photos

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 Carr27/11/2019 22:48:42
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677 forum posts
430 photos

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

PeterF28/11/2019 10:30:41
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452 forum posts
619 photos

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.

PeterF29/11/2019 14:16:04
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452 forum posts
619 photos

Update a couple of days later and it is all sortedsmileyyes, 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 flatdsc08533.jpg

Right hand side a simdgen below 151mm to the bottom of the front spardsc08535.jpg

Left hand side a simdgen above 151mm to the bottom of the front spardsc08534.jpg

Tail cone framedsc08516.jpg

Turtle deck framingdsc08532.jpg

Craig Carr29/11/2019 14:32:36
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677 forum posts
430 photos

Well done Peter. Nice one thumbs up


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

Greg Minden29/11/2019 16:14:52
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34 forum posts
34 photos

coming along nicely Peter

PeterF29/11/2019 16:36:14
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452 forum posts
619 photos

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.

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