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New 78" Vulcan for twin 90mm DF


Tony  Nijhuis
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Now that it is building season I was looking around for this years build. I have a full set of gear (Fans, motors, ESCs, radio kit, servos, retracts) for a twin 90mm EDF from a former model and I was undecided between this and a couple of other options. Seeing the results of Greg's build has prompted me to choose the 78" Tony Njhuis Vulcan. I saw these flying from time to time as a child. My wife grew up in a small village north of Lincoln and needless to say seeing Vulcans in flight was a day to day occurrence for her. A huge box turned up today and I only ordered it over the weekend, soon had the contents spread out on my workbench.

dsc08317.jpg

As other people have commented, it is called a 78" model, but the wingspan on the plan is actually 83" (211cm) with the fuselage being about 75" (190cm) long.

I have one question for people who have built this, I can not find any use for the large vac formed part circled in red. I assume it is an optional cover for the end of the jet pipes, but the plans and photo build instructions make no mention of this.

dsc08319.jpg

Not sure if I will keep adding to this thread or create my own build log for this.

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Craig

Thanks for the info and photo of the smaller model showing where they belong. I have found the album containing your build pics of the 78" version, they will make a handy resource, your build is coming along very nicely. I wondered why you had so many weights on the ribs when building the fuselage. Now I have released mine from the sheets of lite ply I know, they have all taken on subtle curves.

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Yes the ribs in my kit were shocking once released..... they were all over the place.

fair play to Slec they changed mine free of charge because they were so bad. I also asked if they would do the 2 wing ribs which are the face ribs on the fuz and wing out of birch rather than light ply. They were much better

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  • 2 weeks later...

Luckily, whilst my light ply ribs are a little warped they are not too bad so I have started the build. I will add to this thread as a sort of build log, but I am not going to make it super detailed. Tony provides a photo based instruction document which covers most of the step by step stages.

One thing I have learnt after building a kit with CNC routed parts is the router can not cut sharp internal corners there is always a small radius of 1mm or so from router bit. Therefore, I always go over all the internal corners on jigging tabs / spar slots / half joints with needle files to remove the radius, otherwise the tabs / spars / half joints do not always press home fully.

The central spine of the fuselage has gone together easily, with ribs 1 & 2. To keep them all straight and spaced during this process because of the slight warp, I have added some temporary 6mm spars from scrap along with pins, packing pieces under W2 because that sits above the building board level and set squares etc. Luckily no need for heavy weights to keep everything in place.

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Posted by Martin McIntosh on 27/10/2019 19:40:31:

Sounds just like the SLEC cut cnc pack for a 72" Spit. I built. Whatever the ribs were made from it was not what I would call lite ply.

Martin,

You are right, the outer sheet of the lite ply is something with a very porous open grain structure, it really soaks up the glue leaving little hanging around the joints. Whenever I have bought a kit with lite ply before, the outer layers of the ply have been similar to normal ply, with a light softer wood in the core. Quite odd, but onward with the build.

I have got most of the ribs and spars together to make the frame for the fuselage section including the fan mounts. Once this lost is together it creates a relatively rigid box structure. Whilst gluing all the spars and formers into the ribs, I have used some carbon fibre rod to keep the ribs straight.

A couple of things on the plan if you are reading this before building one of your own. The plywood spars FS1 need to be notched at W2 as W1, W2 and W3 are not uniformly sloped at this location, it is not noted on the plan. Secondly, the rear tabs on the ribs WS1 were a bit long and they fouled FS2 / FS2A, sand them down and it all goes together. The final thing, the front 9mm x 9mm spars should be hard balsa, the plan does not state so I started building them in obechi and then found that there was not enough obechi in the wood pack to complete them, so off the the LMS to buy 2 more strips to complete the spars and replace the wood I had inadvertently used. Oh, well, check next time the plan is not specific on a point before applying the saw and glue.

Fuselage section ready for sheetingdsc08382.jpg

Carbon fibre tube to keep the central spine straightdsc08379.jpg

Notch on FS1dsc08361.jpg

Rear tab of WS1dsc08364.jpg

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Greg, thanks and checked it out, very useful as more detail than on here. I like the idea of the top access hatches, I'll have to think about that. I have had one plane with the battery access underneath and it was a real pain and in this case with 4 XT90 connectors to make each time!!!!.

I have completed sheeting the top of the fuselage section to the fan mounts and built up the nose section. This is relatively straightforward as it uses interlocking pieces, but being light ply, you need to make sure everything is straight before gluing. Not quite ready to glue the nose onto the fuselage yet, but it was a quick win in terms of progress.

Top sheeting completed to fansdsc08428.jpg

Top sheeting completed to fansdsc08434.jpg

Nose section under construction and checking for straightnessdsc08376.jpg

Test attachment of nosedsc08435.jpg

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Last few days have been spent wrangling the fans and thrust tubes into place but they are now in there and work OK. Thrust tubes from Mylar from a craft shop used for stencils and Gorilla tape. I made the thrust tubes parallel because the change in shape to an obround at the outlet will cut down the cross sectional area close to the FSA of the fan. For a plane like the Vulcan where speed is not of the essence there is no point in reducing the thrust tube outlet to smaller than the FSA to increase the efflux velocity. In fact the obround holes in the outlet former were larger than the thrust tube, so I put some infill strips of balsa to close the gaps up and stop the thrust tube deforming at high throttle.

Fans and thrust tubes installeddsc08467.jpg

Fans and thrust tubes installeddsc08456.jpg

Outlet former larger than thrust tubedsc08449.jpg

Outlet former with balsa infill to match thrust tubedsc08452.jpg

Balsa sheet to control the obround shape of the thrust tube at the outletdsc08453.jpg

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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

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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.

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