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RC Mercury Marauder?

A conversion of a very old kit

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Simon Chaddock28/04/2019 12:58:16
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A very, very long time ago (61 years!) I hand a hand in building one of these, a Mercury Marauder with its unusual 'diamond' fuselage orientation.

inflight

Not having the space or the knowledge to fly it properly it only ever undertook hand launched 'test' glides so it ended up on the top of a wardrobe in my parents house.

Skip forward 30 years. I took pity on it and rebuilt it to a 2ch (the only RC kit I had!) glider with a new fuselage, an all flying tail, interlinked rudder and ailerons and the wing extended to 72" from the original 65".

Intended for the slope it did do so once but not very successfully as the conditions were not favourable - almost no wind!wink 2

Life then got in the way so it spent the next 31 years in various lofts.

This is what it looks like today.

72inchold

The doped tissue is now incredibly brittle!

My intention is to get it back in the air but this time as a powered glider so it can be flown safely in my tree lined field if only to prove to myself that the original concept was aerodynamically sound, particularly that all flying tail plane! wink 2

The original Marauder, with the required nose weight, was expected to weigh 11 oz. (312 g). Using modern micro RC gear I hope it will not be too much heavier than that even with a motor and LiPo.

I spent a couple of hours stripping the wing.

stripped1

To my surprise the balsa and perhaps more importantly the joints are all in surprisingly good condition.

It will nevertheless still be quite a long job.

Simon Chaddock29/04/2019 12:38:03
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The air frame all stripped.

allstripped

In this state it weighs 197 g (just under 7 oz) so a target of 400 g (14 oz) 'ready to go' looks possible. This would give a wing loading of 4.2 oz/sqft.

Dwain Dibley.30/04/2019 01:02:32
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Blimey Simon, that's a good old girl..........A bit of TLC needed there old bean.

Looking forward to the updates.

D.D.

Simon Chaddock01/05/2019 23:25:35
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Before any covering can go back on the "electrics" have to specified and installed.

First the motor. In order not to rip the wings off just a modest 24 g 1500kV Blue Wonder brushless in a printed mount.

motor1

The mount allows cooling air to pass through the motor.

motor2

With an 8x4 slow fly the motor draws 9.5 amps generating 65 Watts. With an 1800 mAh 2s that should give about 10 minutes at full power and I expect/hope considerably longer at "cruise"power. wink 2

Elevator and rudder servos next.

brokenenglish02/05/2019 10:14:02
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Looking at this model and a real Mercury Marauder, I can't see any resemblance at all!

It's absolutely unrecognisable.

Paul C.02/05/2019 10:21:38
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Hi Simon, a daft question just popped into my head (again) presumably the wings will be tissue covered as per original. The only tissue that I have seen has been in small sheets no where near long enough to cover the wings in one piece, are there rolls of tissue covering available or do you join it in some way? Probably an obvious answer somewhere but I just can't see it 😨

Paul.

Simon Chaddock02/05/2019 13:55:43
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brokenenglish

The complete 61 year old Marauder wing is included.

The polyhedral tips have been reset to match the wing dihedral and the tip balsa trailing edge is cut away to allow for an aileron. In addition an 8 inch centre section has been inserted to increase the span but otherwise you are quite correct there is nothing else of the original left except the length of the rear fuselage!

In my defence the Marauder shown in the picture I included is not original either! Its wing tips are square cut whereas the original plan shows a curved tip.

Plantip

Paul C

My tissue sheets are 76 cm long. This would be adequate to cover each panel of the original 65" polyhedral wing which you would have to do in any case..

I will just have to do the same on my wing although each half could be done with single sheet if it was long enough!

The tiny 3.7 g elevator and rudder servos are almost "lost" inside the fuselage.

Fusesrvos1

The rudder servo has an extended double arm as it will use pull/pull lines to the rudder horns. The elevator servo will use a HK lightweight plastic snake. As an all flying tail plane the extra friction of a snake should help reduce the possibility of the surface fluttering.

It is perhaps worth pointing out that in its first RC conversion the fuselage was sized to accommodate two full size servos and Rx box along with some big dry cell batteries! wink 2

Edited By Simon Chaddock on 02/05/2019 13:57:01

Colin Leighfield02/05/2019 15:43:59
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Fascinating stuff. Years ago I ordered a kit for the Marauder from Replikit and for some reason I can't remember finished up with two! These are in my build queue (lengthening) with a Contest Kits Inchworm kit to replace the one that I had sixty odd years ago. I always liked Mercury Models.

Simon Chaddock03/05/2019 20:34:54
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The initial set up of the pull/pull rudder using 15 lb nylon mono filament.

Surprisingly it is much to stiff.
It works rather better with thinner 5 lb line as it can be significantly pretensioned without putting an undue load on the bearings.
I need the elevator snake from HK before I can go much further.
Simon Chaddock07/05/2019 19:58:32
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The 'glued in' 3.7 g aileron servo.

Ailsrvo

It looks a bit sort of ' hanging in mid air' but there is not much structure to fix it to.

Note the small printed piece to allows a slot to be cut in the tissue for the servo arm to poke through.

The tip tissue covered but not yet water shrunk. That will have to wait until the rest of the wing is covered.

Tiptissue1

Thus the aileron servo is permanently sealed in!

Next the servo wires have to be extended and run through the wing. I do so hate soldering together 32 AWG servo wire! smile o .

Dwain Dibley.08/05/2019 00:41:06
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She's coming on Simon. I especially enjoy the covering part of a model build/refurb.

I like the clever printed tissue support.

D.D.

Simon Chaddock08/05/2019 20:26:36
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Just a bit further, the ESC installed and tested in situ with the motor.

ESC1

It has a 'fingered' heat sink poking through into the airflow.

ESC2

I have a suitable micro 6 ch receiver.

6chrx

At least with 6 channels I can use the 'differential ailerons' option.

Edited By Simon Chaddock on 08/05/2019 20:30:12

Simon Chaddock14/05/2019 09:45:13
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With the rear part of the fuselage covered, doped and painted the tail plane and rudder final installation can be tested.

Just the fuselage to finish, then the wings.
Simon Chaddock16/05/2019 22:51:40
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The fuselage complete and painted.

fusecmplt.jpg

Apart from the motor on the front it is visually almost indistinguishable from its original form.

The aileron is hinged with 'two way' cloth hinges again as before.

aileron2.jpg

I had originally intended to paint the whole wing yellow but it does add quite a bit of weight so just the tip to contrast the black aileron.The rest of the wing will left doped tissue.

Simon Chaddock17/05/2019 21:12:26
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Now complete.

Complete1

With its 1800 mAh 2s it weighs 425 g (15 oz).

At 75 W/lb it will not have 'rocket' performance but with its sail plane roots it should be quite adequate..

Simon Chaddock19/05/2019 11:57:34
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No rocket but it certainly floats like a butterfly!

An edited video of this morning's 9 minute flight.

Not the neatest of landings but reasonably accurate for a no power circuit and approach.
Never used full power even for the launch! wink 2

Edited By Simon Chaddock on 19/05/2019 11:59:06

Simon Chaddock23/05/2019 11:18:01
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Well I found out one of the problems with 61 year old balsa - it gets very brittle!sad

22may19

It was rather turbulent so it was being tossed around a bit and just a bit too much elevator recovery action and ........

Little point in repairing it but nevertheless interesting while it lasted.

All the electrics will be salvaged for something else..

Dwain Dibley.23/05/2019 11:27:34
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Awwwwwwwwwwwwww Simon........................broken heart

i just watched the video and was thinking how great it was................Next post............BAM !!, all over.

Feeling for you man, was sweet while it lasted, and a great blog too.

Onwards and upwards......................not too hard to build a new wing B.T.W. ?????

D.D.

Simon Chaddock23/05/2019 14:07:12
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2818 photos

Dwain

Actually the damage is more serious than perhaps the picture suggests..

When the wing folded it was initially retained by the aileron servo wires but they soon unplugged from the Rx leaving the fuselage free to 'lawn dart' straight down. The impact damaged to the motor mount, snapped the fuselage just ahead of the fin and RH tail plane.

The only completely undamaged bits are the ailerons, LH tail plane and the rudder.

Just to complete the picture, the salvaged 'electrics'

salvage

They will return in something.

Dwain Dibley.23/05/2019 15:39:47
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Ahh....................Right...............I'll give you that one Simon.............frown

Still............It's a crying shame matey.

D.D.

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