Mark's TN Hawk Build

[Mark Elen]

Hi Chris,

I now have all of the ingredients, I will post up a write up once the deed is done👍

Been working away fuselage side building, not much to say, except the CNC routing on the light ply is excellent, absolute perfect fit on the doublers.

I always like to lay out the two fuselage sides as per the last photo, it makes sure there is no chance of two of the same.

Cheers

Mark

[Martin McIntosh]

Took my version of the Hawk to the field today for taxiing trials. The grass was cut short yesterday but lots of cuttings left on and the ground underneath is still quite soft. Anyway, with those small wheels there was no way that it was ever going to reach take off speed assuming that the fan was running at maximum. One of the wheels actually fell off when taking the model apart because a grub screw came loose. The model was also leaning to one side due to an oleo leg sticking up. Easily fixed but this does not bode good for even a pristine grass field. I need some tarmac.

Wish that I could transfer this post to my own Hawk build blog but don`t know how to do it.

Edited By Martin McIntosh on 05/05/2018 20:34:04

[Mark Elen]

Hi Martin,

That doesn't sound good. I'm in the same boat as our field is grass. I think it's going to be a summertime only model. I may have to look into somewhere else that has Tarmac.

I have copied your post onto your build log👍

Done a little more this morning, drawn all of the former positions onto both fuselage sides and cut and fit one of the first pieces of 12mm triangle. I had to saw in a few cuts to get it to bend around the curve. Once it was glued into position, I let some Superphatic capillary into the cuts.

Cheers

Mark

[Martin McIntosh]

Thanks for doing that Mark.

Grass take offs certainly do not hold much promise. Our patch is probably as good as they come but it is early in the year and the ground still has a lot of drying out to do. Not yet cut quite as short as it usually is but I was expecting a faster test taxi. It would seem that the nosewheel is the main problem so I may have to change this for a none scale type. I had to use almost full revs to start it rolling. Must also check that the fan is still drawing the correct amount of power.

I also took my 48" Dalotel up and had the same problems. It is normally OK so all is not lost yet.

[Mark Elen]

Hi Martin,

Our field is similar, on Friday the ballerina wanted to nose over on landing the field was so boggy, yesterday was totally different, the field had dried out a lot, but was still soft in places. I'm hoping by summer it will be a lot harder.

The fuselage is coming along.

Cheers

Mark

[Mark Elen]

Here are a few more pictures of the fuselage going together. The fit of all of the parts is excellent. Unfortunately, there was not enough of the 12mm triangle in the kit - only 2 lengths, that's enough for the 2 pieces on the bottom each side, leaving not quite enough for the top front piece.

Fortunately, I had a length of 1/2" in my stock so I'm using that for what is left to do.

I also changed my mind with the jig and have built it directly over the plan

Cheers

Mark

[Mark Elen]

Got home from work early today, so got a bit more done.

Now ive come across the first snag with the CNC cutting. F8 fits perfectly in that it's a nice sliding fit at the back - this is one of the hatch formers, so no worries with this one.

F4 and F5 are both 2mm short in that they don't reach the sides. F4 needs gluing in. I'm going to have to get creative with this.😂

Cheers

Mark

[Martin McIntosh]

After the diabolical parts cut by the same people for my 72" Spit I would not entertain buying anything similar from them ever again. Sorry if this offends anyone but it is fact. CNC cut bits should be spot on every time and there is really no excuse for them to be inaccurate.

As with ARTF`s etc it would not seem unreasonable for someone to actually assemble one before sending them to market. No excuse for this considering the high cost.

[Mark Elen]

Hi Martin,

Sorry to hear that. You are correct though, there is no excuse for CNC bits not fitting, I can only assume it is my poor building that has caused the issue with these. 😁

I've bodged them to fit. I cut up a strip of .8mm ply and made up 4 short pieces to extend the formers. It has worked a treat, they are also now a sliding fit.

I also got the rear fuselage sides made up tonight and fitted:

Cheers

Mark

[Mark Elen]

Tonight I have got the rear top section of the fuselage done, I glued the first section on this morning before going to work. I have gone a little 'off piste' as I didn't like the large triangular hole at the rear and it looked to me like the filler bits would sand away to pretty much nothing, so I made up a couple of triangular fillets to help here.

Not looking forward to planing that off, but more to do before I get to that.

Cheers

Mark

[Mark Elen]

Done a bit more today, beginning with the upper fuselage/hatch. I cut up a couple of spacers out of acetate to both space f8 off the rear sheeting and to stop the glue from contacting the rear decking, you can just make them out on the first photo. You can also see the block I had to use to straighten the former at the front, the light ply was warped quite a bit.

I also got started making up the steering servo mount using scrap 1/4 ply.

Cheers

Mark

Edited By Mark Elen on 10/05/2018 23:13:01

[Mark Elen]

Hi all,

It's my birthday today, so have taken the day off work and have spent most of the morning working on the Hawk. I've made up the steering servo mount and fitted the retract. I normally don't enjoy making up linkages and hooking them up, but I've enjoyed this. I made up a small bracket to guide the pushrod from some Ali angle scrap that I had from work.

I was going to y lead this servo with the rudder servo, but I found that when retracted on full deflection of the rudder one side, the servo was stalling, so I decided to give this its own channel and i have programmed up the tanaris to only operate this servo whilst the gear is down. By doing this it will allow me to reduce the throw in programming if it needs it after taxi testing.

I've pretty much decided that I'm going to make up a little hatch to be able to get at this servo, rather than following the plan and boxing it in.

Whilst I was doing this, the postman turned up with a nice Birthday Present, a cheque for PPI. 😎

Cheers

Mark

[Mark Elen]

I've not really done much the last couple of days, although I have got the top sheeting finished and it is now ready for the razor plane.

I have have also got the tail plane pieces glued together

They are going to need a little notch in the leading edge where they meet the inside of the fuselage, as I have made the first sheet on the top of the fuselage a bit too long.

I have decided to cut up a couple of mini servo mounts to fabricate the small air intakes on the top of the fus.

Once I get them positioned and the holes cut for them, they will drop in from the bottom and the flat section at the front will be gluing area.

I decided to do some destructive testing to decide what glue to use for these, the photo below shows a couple of strips of balsa glued onto the scrap piece of plastic, the one one the left with superphatic, the one on the right with CA.

Neither of them wanted to separate very easily, but the CA definitely won this test.

I'm currently formulating a plan for the nosecone, At the moment, I'm leaning towards not gluing it on and making it removable with 2 or 3 little dowel pegs and a couple of neodynium magnets. I don't know, is it going to be a load of work for no real gain?

Cheers

Mark

[Martin McIntosh]

I should forget the dowels and magnets. My GRP version is fixed with a few No.2 self tappers into plastic cowl mounts. Unless you are being very fussy the screws are hardly noticeable. Mine has to be removable because of the rather over complex steering system.

I found that in order to get the annhedal tail to fit, a lot of material had to be removed from the fus. inside top. Not easy.

[Mark Elen]

Hi Martin,

Fussy is my middle name😂 I like to think through the various ways of attacking things and I had thought about screwing the nosecone on and discounted it. More thought needed.....

I have attacked a little job that I've been putting off for a while. I don't like the elevator servos poking out of the rear fus, so I got a pair of slim wing servos to hide here. It then became a 'how do I make this look neat' job. After going back and forward thinking I'll make up a ply plate, I ended up deciding on using a couple of standard mini servo mounts, butchered about a bit.

Im still going to stick the servos on with the foam sticky pads, but those little blocks of Cyparis are rock solid glued on with CA.

Now all I need to do is cut the rear fus for these to fit into.

Cheers

Mark

[Martin McIntosh]

Why trust your luck to sticky pads? I know that there will be no oily fuel around to attack them but these days nobody uses them. Whatever the mount is made of, that c.a. will probably not really be glued permanently to it. Birch ply mounts will look the same in the end.

[Mark Elen]

Hi Martin,

You are correct of coarse, I wasn't totally happy with this, and I have managed to break off those Cyparis blocks. They took a bit of breaking. To be honest, I don't know what I'm messing about at, there is loads of room to use the mounts as they are intended. The ruler below is on the line of the fan duct, the mount is flush with the fuselage side.

Cheers

Mark

[Mark Elen]

Hi All,

I've taken a break from building tonight, as my goodies turned up today. (Thanks PPI😎)

I had a bit of a quandary regarding the flaps and the elevators, in that one of each of the servos were going the wrong direction. I was going to open up the servos and reverse one of each by re-soldering the motor and pot wires. But then when it came to it, I thought, 'you've got 16 channels on the tanaris, why not use them'

I was just going to get another X8R, but for the small additional cost, the RX8R redundant receiver was available, although, only with non-EU firmware. The EU was out of stock. So tonight, I've uploaded the EU firmware and set up the 2 receivers.

I now have 16 channels to work with. Each servo can have its own channel and be programmed in the radio.

I also decided not to use either the NIMh or the SBEC. I have gone with a pair of Life batteries and a Powerbox Sensor.

I got the whole lot set up and working on the bench and am pretty happy with the set up, although there will be loads of lovely wiring to tidy and sort.

I'm getting concerned about the weight adding up, but I'm going to be happier knowing it's not relying on just one battery or receiver. I'm thinking I'll split the elevator, aileron and flap servos one to each receiver.

Cheers

Mark

Edited By Mark Elen on 15/05/2018 22:23:52

[Martin McIntosh]

Same as I have but with the HK failover switch of which I use several already, and just 2x 700 LiFe packs, not the nanotech things. Every nanotech pack I have had, (Lipos) have swollen after only one flight. Not just me either, one club member got through nine of these (lipos) in a similar way. Cannot speak for the nanotech LiFe ones though.

I also have a Taranis set which is great if only I persevered and got my head round it. Why the RX8R and not just another RX8?

[Mark Elen]

Hi Martin,

I may get a couple of smaller packs if weight becomes an issue. I got the RX8R because with it set up as the master as I have it, if it looses the signal to its antennas, it will use the signal from the slave RX antennas to drive both receivers. They connect together with the SBUS. (At least that is my understanding after watching the video on the website)

I could have just used another X8R but then if one looses signal, you loose all of the channels connected to it.

Both receivers get bound one after the other, you just need to disable telemetry on one using the jumper (I jumpered pins 1&2 on the X8R to set it as channels 9 to 16 with no telemetry (telemetry is carried on the RX8R which was bound with no jumpers - channels 1 to 8)

It does seem strange binding two receivers to the TX without changing any settings at all on the TX though. - just hit the bind button one after the other.

I have got a pair of fvlss Lipo voltage sensors that I'm planning to use to give cell voltage on my pair of 4S flight batteries, I have one of these set up on my foamie viper, it took a bit of setting up, but now I've got it set to call out low voltage when the lowest cell reaches 3.7v and to start calling out the actual voltage below 3.6. It works well, and I find that set like that, when I get the battery out and on the tester, without any load they come back at around 3.75 v

Cheers

Mark

[Chris Walby]

Mark, Very nice build you have going there, thanks for posting.

Just noticed on this photo you have a small L bracket on your steering rod, I assume its to stop the ball joint end sliding down oleo steering arm pin and changing the nose wheel direction.

Have you used this setup before and is it tricky to set up regarding aligning it all in the up and down positions?

Thanks for your time and keep on posting

[Craig Carr]

Hi Mark,

Re chris’s Post I was wondering the same thing as well about the L bracket.

When I’ve set those type of steerable nose wheels up in the past I’ve just use a direct connection between servo and the slider on the steering arm without issue. Like on this model here:-

[Mark Elen]

Hi Gents,

Many thanks for your kind comments. On Tony's build photos, he shows this bracket (although in a different form) and it's also shown on the plan. I did wonder if it was necessary, so I initially made up the linkage without it. I found that without it, with the leg down, the slider is free to slide up and down on the arm and due to the geometry of the linkage, it allows a fair bit of lateral play in the steering. The bracket has reduced this significantly.

Regarding fitting Chris, what I did was to hold the bracket in position next to the linkage with the nose leg up and marked up the hole, then just drilled and fitted it.

Cheers

Mark

[Chris Walby]

Craig, Apologies as off topic, but this may become an issue for some.

Sorry to say I have had the complete opposite experience with my foam EDF. It needs high ground speed to get air over the control surfaces to take off and mine has a forward C of G (due to the canards!) plus the nose wheel is was directly below the 6S4000 lipo in the cockpit

The original plastic U/C self destructed on the first launch run and I am now up to version 2c as it did very good impressions of a high speed "Reliant Robin Roll" or mad ground squirrel. The issue (I think) is too much ground clearance (I lifted mine by 15mm on V2, but lower on V2c) and sloppy steering.

I have added a ball joint and extra bracket on the oleo pin and got rid of all of the play, but one issue as that the rod that connects to the oleo pin could slid up and down, but that changes the steering direction !

IMHO its down to power to weight and technique, I can't pussy foot about on grass with a long winded acceleration down the runway, its up to full power, charge down the runway and gentle climb out to get air speed up (grass can be very high drag even with larger than standard wheels). This means that when it goes pear shaped it does it really fast and the result is not pretty, but its the only way of getting EDF's off the deck.

My forum post is under "Steering nose leg does it need trail" if you want to take a look.

Mark, Thanks for the comment, I am interested due to the geometry change between retract positions (up vs down) and if there was any rotation of the oleo + how the steering servo copes when the oleo is retracted as the ball joint end needs to slide along the oleo pin. 

Edited By Chris Walby on 16/05/2018 09:14:09

[Craig Carr]

Hi Chris

Yeah I know what your saying. Since that picture was taken I’ve also sleeved the piano wire with slop free/interference fit carbon tube to help against “flexing”. The model did prove to track true and straight on take off with no squirrelling (it needs a fair run as well - the TN 49” Vulcan)

It’s just in shot on my pic but I also used a barrel type connector on the oleo sliding bit which had an in built thread on the head (I think it may have been a multiplex connector type fitting) set with just enough play for smooth transition up and down the slider.

It does mean as the nose leg retracts it slightly “turns” the wheel. I obviously set the wheel up and “true and straight” when the retract is in the down position so that the twisting only occurs as it retracts back into the nose (which I’m not fussed about because it’s only marginal and still easily fits in the nose well)

Sorry to drift off your topic mark. Your hawk looks great, some lovely workmanship there.

Craig

Edited By Craig Carr on 16/05/2018 11:05:05