Northrop X-4 Bantam Build thread - RC Groups
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Jan 05, 2004, 10:31 AM
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Northrop X-4 Bantam Build (and fly) Thread

To encourage me to complete the build, finish and flying my X-4 Bantam I will share it.

Please feel free offer advice.

Please note.......I am building my interpretation of an aeroplane I have never seen for real or seen video of it flying.

This will not be a perfect scale model with the correct wing sections etc. Hopefully I will end up with something that flies.

Many thanks to everyone who have got me this far.

Here is the picture that diverted my attention away from building An A-6 intruder
Last edited by Robert May; Nov 21, 2004 at 12:56 PM. Reason: It works
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Jan 05, 2004, 10:48 AM
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3 view

this is one of three 3 views that I found or were sent
Jan 05, 2004, 11:04 AM
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once scanned it could be enlarged to a workable size.

The side elevation and a half plan drawn to give a wingspan of 35"

Originally it was going to be 32" but the slight increase in span means that the single Wemotec Mini fan will fit with near scale intakes and outlets.
Jan 05, 2004, 11:17 AM
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with no section details available only photographs I decided to loft the section myself. I hear that there are some very good CAD systems available that will do the lofting. But I decided to have a go at the manual way.

Mark on a piece of folded card the Half plan and elevation points for the given section.
Jan 05, 2004, 11:19 AM
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plot reference points and draw the section as it appears on the photos
Jan 05, 2004, 11:23 AM
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repeat for all sections and cut out.

you will notice a cut out which fits over a 9mm x3mm (3/8 x1/8) reference spar pinned to the plan.
Jan 05, 2004, 11:30 AM
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I couldn't visualise the rear ducting so made a simple model out of scrap (to scale) and lifted the duct sections onto the inside of the Fuz sections.

The inlet ducts were done in the same way.

I allowed 110% inlet volume and 80% outlet.

the rear duct will have a separator up the middle to split the flow to the two outlets
Jan 05, 2004, 11:35 AM
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The card sections were reproduced in 3mm (1/8th balsa) and pinned to the plan.

.4mm splines are then used to highlight the dips and bumps in the individual sections.
Last edited by Robert May; Jan 05, 2004 at 12:16 PM.
Jan 05, 2004, 11:47 AM
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I have now got a half model of the fuselage which I can now use to plan how to mount the fan unit, batteries servos etc.

I don't want the wing spars going through the ducts so my thoughts are to attach the wings to the fan plate.

If this is all too much like teaching Granny to suck eggs let me know and I can post photos of the milestones.

If not I'll carry on with an illustrated guide to NARTF.

Progress might slow down as I'm back to work and that means 3 nights away each week, with jobs to do at the weekends
Jan 05, 2004, 12:13 PM
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Inspirational photo.

Dream.......low, close pass.

Nightmare......... wrong Cof G, not enough power, duff launch,
wrong wing section, tip stall.......

On the subject of wing sections.

Right hand Clark Oxford size 9 1/2 or something more scientific.

10% NACA 63a010 at the root with 6% tip, 3 degrees washout?

the real one had NACA 0010 64????? this appears to have more reflex than the 63a010

Steve Savoies Slope soarer used an EH 2.0/10.0 which is much flatter but was intended to slope soar and termal

Thoughts please. (in real simple terms)
Jan 05, 2004, 01:34 PM
EDF rules... :)
AirX's Avatar

There are a lot of us that have built in balsa but there are a lot more that have yet to experience the scratch building experience. Your tutorial is enjoyed by both factions. I myself in paticular love this technique and enjoy reading the little details for there is much to learn from them. Than you.


Eric B.
Jan 05, 2004, 01:35 PM
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Gordon's Avatar
Hi Guys

I've seen Robert's model in the flesh and you can be sure it's a super job.

Robert - my Vector uses the EH 1.5/9 , tapered in thickness from root to tip. That should be a good start.

Jan 05, 2004, 01:41 PM
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Gordon's Avatar
Dunno if this will come out
Jan 05, 2004, 01:46 PM
thulizulu's Avatar
Very nice project! It´s quite a fast pace you´re on.
I was wondering why so many Luft 46 planes are covered these days, where some great designs showed up from the other side of the pond. Obviously, these fine planes took to the sky, where others not even made it to a wind tunnel model.
Keep up the good work.
May I ask what fan you´re about to install?
Jan 05, 2004, 03:18 PM
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Thanks for the section Gordon, that beats drawing around my shoe.

The fan unit is the Wemotec Mini with a Kontonic fun 400-36 motor. This should give max 32oz trust on a fresh pack of 11x 1950 FAUP's dropping down to 28 average. Should be plenty

Target weight is 50 oz max. There is not much plane behind the Centre of gravity so fingers crossed no ballast. I would like to get down to 45oz but I know the last ounce always weighs 8.

I am desparate to keep this simple and just use elevons, but the words Retracts, Rudder and Flaps keep jumping into my head. Its a good job Spring Air don't make a micro set of trikes!

When I was looking for some wall plugs in B&Q (hardware store) there were some very nice Toggle plugs (metal) designed for cavity doors which would be ideal for the "Dive Brakes".

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