Martin`s Hawk

[Martin McIntosh]

Not knowing at the time that TN was about to publish a 50" one, I decided to draw up a 9:7 scaled version based on the original 42" plan.

Mine works out at 53.75" span which is 7.5% larger than Tony`s.

Looking at the new plan I am glad to see that the construction is nearly identical to mine so this could help any would be builders.

Having cut out the parts, I purchased Tony`s mouldings when I was at the Nats hoping that I could persuade them to fit. Nose cone and intakes were not a problem but the canopy has had to be extended a bit. Not sure how this will work out as yet. My home vac. forming leaves a lot to be desired.

Anyway, some pics. The fus. is in the process of being glass skinned using HK 18gm/sq m cloth and epoxy. Wings and tail are done in HK bright red film. I took a swatch to a paint supplier but the white reflective film on the reverse side confused their scanner so had to settle for a (hopefully) close match which is Ferrari 323 Rosso Scuderia.

As previously mentioned on the other post I have had to use two nose wheel steering servos. I am also using two rudder servos because it was the neatest way to do it. Other servos are slim wing types so that the elevator ones fit totally inside the fus.

[John Laverick]

I'm thinking of doing the 50" TN hawk for a winter project Martin, so will be watching yours with interest

John

[Mark Elen]

Hi Martin,

I'm watching this with interest as I've purchased the full set from TN and have just received the fan from HK. Waiting now for the ESC from HKs global warehouse and I have all of the bits and it's ready to start. Just need to finish the Ballerina and clear the board. (I ordered the fan and ESC before seeing that 4-max are stocking them)

Interested to see how you are doing the servos, as it would be nice to get them all hidden away.

Regards

Mark

Edited By Mark Elen on 04/10/2017 22:22:29

[Martin McIntosh]

Thanks for the replies. Other than the TN Vulcan this EDF stuff is new to me so I am in unknown territory since I only flew it once from the hallowed Barkston runway. My local patch is now much better so it will go again no doubt.

I have not bothered with a build blog since this has now been done by Tony.

Looking forward to a video of his in the air.

If you intend to do this then be careful with the chosen retracts since mine use pull pull on the nose leg, not the steering slider, which is giving me problems since it needs to retract forwards. The geometry on some of my previous HK units with a slider leaves a lot to be desired. They tend to twist on retraction.

Having glassed the fus. and fin I am now coating it with sanding sealer to fill the weave prior to spraying with white primer. Not tried the sanding sealer bit before but it seems to be working and adds very little weight. Lots of sanding down to do here.

The GRP horns have been made and fitted along with the linkages on the wing.

The fan tube is made from an A3 sheet of card and can be fitted after the rest of the construction.

[Martin McIntosh]

Please transfer to Mark`s TN Hawk build since these threads may as well be combined.

[Martin McIntosh]

Pics will still be on here, so a couple more.

[Geoff Gardiner]

Hi Martin.

That's looking very nice.

I am still plodding along with my TN Mossie but would like to have a crack at the Hawk at some point in the future.

I have just clicked 'buy now' on the following EDF unit which is currently on sale at Hobbyking:

DR. MAD THRUST 90MM 12 BLADE ALLOY EDF 1000KV - 5200W (10S), SKU 9107000335-0

Is this the one that you are using?

Geoff...

P.S. Have you got your Mossie back up in the air?

[Martin McIntosh]

Hi Geoff,

Yes, that looks to be the same one. Just where they get that 5.2kW from I really don`t know. Mine is nowhere near that but should be more than adequate.

The Mossie is at the back of the repair queue.

A couple more pics.

The vinyl masks have been made and fitted and I hope that when removed will leave the white lettering. Not tried this before so fingers crossed.

I sent a pic of the tentative installation. Ever gone into the shed the next day and wondered how you could have done something so dumb? No way to remove the fan, so the ESC/switch tray has been modified to screw on.

The red water based paint seems reluctant to fully harden on top of Halfords white primer despite being in the airing cupboard for some time so I decided to try the clear lacquer on a test piece, with and without cellulose thinners added. No adverse reaction so so far so good. It is Sadolin PV67 which to all intents and purposes is Tufkote.

[Martin McIntosh]

The water based paint is a total disaster despite spraying easily and covering well. It refuses to dry! The test pieces I did first seemed fine. Maybe it does not like the Halfords white primer although if it was used as intended on a vehicle then this would surely be a normal base coat. The ABS parts were sprayed directly and do not dry much quicker so perhaps they intend you to bake it on which I obviously cannot do with a model.

Worse to come. When I removed a little of the masking tape, the paint had not only crept under the edges but had gone right through. Same quality brand pf tape that I normally use and having done this what seems like a zillion times before thought I knew the answers to all the likely problems.

Maybe I should have used acrylic although what the difference is I do not know. I believe that the paint is the same as Tony used on his ABS parts. Will just have to wait a long time and see what happens. Shame because there is otherwise very little else left to do on the model.

[Martin McIntosh]

Just reading the thread `Build logs,-a dying art?` where people like to see some of the warts and all bits, so here are the warts I was speaking of above. The cure I have come up with is to mask alongside the areas of paint which have crept, carefully remove as much of the red as possible using IPA, remove the tape then re apply then brush on some white primer after squibbing some into a cup then allowing to thicken for a few minutes. It takes a lot of coats to do this.

Only a few bits done so far so this will be a long job. The red is still tacky but dry enough to handle the model. When finished I shall test spray, say, the rudder with two part clear lacquer which should give a hard surface.

[Martin McIntosh]

Here is the first part with the masking removed.

[Geoff Gardiner]

I hate it when that happens.

My EDF has turned up - it's bigger than I had assumed.

It came in 3 days from Hobbyking Europe - £44 no other charges.

Did yours come from the Global store, as you got stung for Duty costs?

[Martin McIntosh]

You are lucky, they were only on sale from Global when I got mine. Heavy, arn`t they. Is that the 10 or 8S?

 

The repairs to the paint job are actually coming along not too badly now.

 

 

Edited By Martin McIntosh on 22/10/2017 16:47:20

[Denis Watkins]

Quoting " Jaws " Geoff

" We are going to need a bigger boat "

Have been there and done it, and finished up with an experimental EDF with the big lump under the main wing spar

Thankfully, I managed to sell it.

Hope you have more bottle than I.

[Geoff Gardiner]

It is the 10s version

[Martin McIntosh]

My model is now nearly finished bar the nose cone which I melted trying to get the pesky paint to harden. No success as yet in trying to buy a new one from TN and really do not fancy carving a balsa one to take a mould from since it would be difficult to match up at this stage.

The paint has been retouched and the PV67 lacquer added which has hardened it fine.

Crunch time. On the scales with 2x 5S 5800 it is 10.25 lb, not unreasonable (this is less nose leg). An 8S fan with 2x 4S 5200 would have been 1lb lighter.

Pics to follow later.

[Geoff Parkes]

I built Tonys smaller Hawk a couple of years ago, the same spec. as Tonys, Dr. madthrust,fan, 6 s battery etc,etc, built as light as possible,and it turned out heavy, I think this is the plane Tony made a mistake on the finished weight of his plane, I had just finished his Vulcan and it flew superbly approx. 15 oz. per sq. ft wing loading, launched off the bungy at 8 kilo. pull and just floated around and totally convincing in the air, the hawk on the other hand was totally opposite, I increased the pull on the bungy , but the wing loading was around 35 oz. per sq. ft, not enough pull on the bungy and the plane virtually fell off the end of the ramp, but I think the wing loading on both of these Hawks is to much, if you do build either cut as much weight as poss. go for 6 s batteries, and Chain Sun 12 blade fans, these are a lot lighter than Mad Thrust and with Cyclone motors will give 3 kilos of thrust, available from RCCastle in Hong Kong, the last one I purchased was assembled and balanced it was just over £100, and I paid £12 to the post office.

[Piers Bowlan]

That is interesting Geoff. I have a Lander fan unit as well as a Chan Sun, which I though I might press into service in this model 'one day' - I have a three other builds to finish first! Thanks for the heads up on the motor, I will check it out. I was planning on 6s, 4500mAh LiPo as that is what I have. No landing gear, flaps, or rudder, (so only 3 servos) to keep the weight down. Won't be as impressive without the landing gear but where I fly the grass is too long anyway. Martin's model should go well on 10s. The paint problems sound like a bit of a nightmare.

[Martin McIntosh]

Remember that my version is 54", not 50 which I hope accounts for, and should handle, a bit of extra weight.

The alternative is to use an 8S fan with the lighter batteries but I have spent enough money on it already.

[Geoff Parkes]

I thought the alternative fan option might be interesting, the 90 mm Chain Sun comes with a Cyclone inrunner, and is designed for 6 s . My experience with EDF is go for the largest C rating batteries you can afford, I go for 65 - 130 c, more expensive but you get more power, if you can build light and use a bungy to lauch you save a lot of battery by not dragging a heavy plane off the ground using retracts. Regarding the paint issues , the last 3 planes I have built (BT Mosquito, Chris Golds Deffiant and an English Electric models Canberra ) were all covered in tissue, doped and then sprayed with polyester car paint, any good car paint supplier who mixes paint will mix to suit colour swatches you supply or match from their library of colours. it goes on well with any spray gun, you can get in 1/4 litre batches, which is enough for the 70 inch size planes for approx £8, and is obtainable in matt finish, not certain how fuel proof it is as I only fly electric, but I have not had the paint creep problem under the masking tape, I use 6 mm fine line tape backed up with normal masking tape, never had a problem, hope this helps.

[lightning 759]

as much as I love the red arrows why does every one go with this scheme when there is quite a few to choose from , just wondering that's all , great building by the way

andy

[Martin McIntosh]

Hi Geoff, the reason I went for the water based car paint was that people kept recommending it. I have a feeling that the supplier could have omitted a drying ingredient. The adverse reaction with the masking tape adds weight to this idea. I have masked up very, very many models over the years and rarely had a problem with paper tape. I never use the outer edge but cut it into crisp strips. One trick is to coat the tape with very thin clear dope. Never tried it before but I did on parts of the canopy and it worked great.

My scale models are built for my local club competitions for one. The flight scores 25% take off, 50% flying and 25% landing so bungees are out of the question. The patch is very near bowling green standard.

Thanks for all the comments so far.

[Martin McIntosh]

Bar the nose cone I got it all assembled today to check out the functions and above all the fan.

On full power it nearly blew the fence down with a huge blast from the rear end, but on checking the amount of thrust with some scales placed against the nose it registered a disappointing 1.8 kgf. This may not have been a fair test but it was all I could think of to try it. Considering that it is on a 10S pack and drawing the expected power I was surprised. I shall have to try a fast taxi test at the field but the grass is now rather wet and lush.

[Martin McIntosh]

The pics. Anti spin bits yet to be glued on and some more cable tidying to do but bar the nose it is very nearly there.

Could have done with a second coat of lacquer but this could be done later. The main batteries will need to be much further forward than anticipated so the fixing strap slots will have to be re cut.

Pics show the wing connectors which are a 12 plus a 10 way and the home made LED flasher with its Rx controlled switch. The front lamp will be an ultra bright 10mm LED.

Please excuse the rather unusual nose leg steering set up. It works fine on the ground but make sure that you do not buy this pull pull type even though it is advertised by HK for a 90mm Hawk.

I assume that the elevator travel is 18mm each way and full flap about 80deg.

[Mark Elen]

Hi Martin,

Hope you are well.

That looks great 👍

Not sure about the elevator, but I'm sure the flaps are shown as 45 degrees on the plan. (the plan is at work at the moment)

Cheers

Mark