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Old Oct 13, 2006, 11:42 PM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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Yet another Peter Rake IPS design!

I was reluctant to climb on the IPS express due mainly to eyesight-and-thumbs syndrome, but Peter had a Duigan biplane that no-one else wanted to build (it's Australian) so I volunteered. A lightweight indoor-ish model had always appealed to me and I will try to keep this as light as I can (and still have fun with external detail). Here are some pictures of the real thing.

The original is not well known as it was a one-off and crashed on its first flight (not an omen I hope) never to fly again. There is a fair amount of 'Avro' in it as Duigan worked with A.V. Roe in England prior to this design.

Pat
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Old Oct 13, 2006, 11:54 PM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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After reading the fuse rigging discussion earlier, the rig-while-building method was tried and it works fine. 2.5mm square hard balsa longerons and softer crosspiece stuff was pre-stained and assembled over the plan. Cross pieces were slit on the ends and the kevlar line fitted into the cuts. After pulling the bracing tight, a drop of CA secured the wood and the line. Easy

Undercarriage is very complicated with wood struts and braces, skids, aluminium tube braces, wire wheels etc. The wooden struts are incorporated into the fuse sides at the start as in the photo.

I only have an IPS motor with the very tall gearing - ex GWS foamy and usually pushing a 10X4.7 prop on 7.2V. This model will physically accept nothing bigger than a 6" prop but at 6.6:1 gearing, may be ok on 3S LIPO.
If not, I'll try and find some different gears.

Pat
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Old Oct 14, 2006, 02:50 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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I stuck the basic fuselage 'tub' together and checked the rear part for fit.

More akin to boat-building than aeroplanes

The top deck will be 1/64 ply, with the centre panel removable for battery access. (It will have to be small one!)

I'll use white Airspan for covering - I tried it on my Bleriot tail surfaces with no warpage - that used 1mm ribs as I intend here. It wont get any finishing either - just dirty white. (look at the original pictures) . Airspan is a bit lighter than Litespan as it doesn't have the water/fuel proofing (I think).

Pat

PS - the 2000mA LIPO holding the tail is NOT destined for this model!
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Old Oct 14, 2006, 08:08 AM
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Norfolk, England
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Pat,
Looks great mate. Love the way the stained rear frame has come out.
I simplified the u/c slightly from the 400 size version. That was fine for laser cut kits, but a bit of a pain if you had to cut all the parts yourself.

Pete
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Old Oct 14, 2006, 09:05 AM
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East Anglia, UK
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Quote:
Originally Posted by maltone
I only have an IPS motor with the very tall gearing - ex GWS foamy and usually pushing a 10X4.7 prop on 7.2V. This model will physically accept nothing bigger than a 6" prop but at 6.6:1 gearing, may be ok on 3S LIPO.
If not, I'll try and find some different gears.

Pat

Mm. 6.6:1 isn't a stock IPS ratio...thats a 350 ratio..

The 10x4.7 sounds like the B ratio - 7:1. That's best on an 8x6 on 3s LIPO.

You want S1 gears for a 6" prop - 4.1:1..that suits a 6x5 prop allright on 3s LIPO.

Or use LPS A gerabox for even less weight.

Having said that, I LOVE what you are doing with pre-stained balsa and the kevlar..that is a technique to file away for future reference.
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Old Oct 14, 2006, 02:17 PM
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Looooeeee!'s Avatar
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A good start Pat, I'm finding the L/G has a uniqueness not like the typical AVRO set-up. The skid arrangement on my 2 ships tends to be a pain unless the take off strip is absolutely smooth and debris free. I think it was Dereck who suggested that the skids for models of the early AVROs be just for show, demountable, in other words. I can see his point, especially at this size.
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Old Oct 14, 2006, 04:35 PM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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Vintao - you are correct (as you often are ) it is not 6.6:1 - I was remembering something else - the ips has a C ratio - even taller! Mind you even on 2S and a 7X6 - it makes a lot of wind

I may be able to get an LPS A setup. I need to sort it out unless I can mod Pete's design to remove the motor/GB. Hmm.....

Pat
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Old Oct 14, 2006, 06:10 PM
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Pat,
Make the motor plate liteply and bolt the motor post to it. Not only does it become interchangeable, it adds nose weight.

Pete
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Old Oct 15, 2006, 03:19 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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Motor Mounting

A removable motor stick as per Pete's suggestion was fitted and set at 2/2 deg offset. The cover plate had an extra bit cut to take the IPS C main gear. The motor will be completely hidden under the dummy water cooled V8 engine.

I was ready to glue the 1/64 ply cockpit surrounds and realised I'd not fitted servo rails yet As shown, the model is about 1.5 oz so far - not super light but as I want to make this as much a display model as a flyer, this is not a major concern.

For those keen-eyed types, the rather battered plan in the background is from 1957! - a 38" free-flight Supermarine/vickers Walrus. Designed for .75 - 1cc diesel, it would make a great electric candidate for a small bell outrunner.

Pat
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Old Oct 15, 2006, 05:01 AM
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It's a shame you are not closer Got a few S2 gearbox units here..That's probably the one, or the S1.

The C ratio is a 9x7 on 3s ...and that's for a VERY slow plane indeed.
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Old Oct 15, 2006, 10:40 AM
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Pat, I know it's a big country but you need a new gearbox. Dave at Aircraft World would, I'm sure, send you an appropriately ratio'd box very easily and quickly. I get stuff from Japan in about fove days and you;re a lot closer than I am.
These are the aluminium IPS replacement boxes, the mount acts as its own heat sink. Inexpensive and good, available in the ususal ratios.
http://www.aircraft-world.com/shopexd.asp?id=3454
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Old Oct 15, 2006, 04:02 PM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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WIP - thanks for the link - those aluminium GBs look good. I've got a finned heatsink on my IPS motor but there is a weight penalty.

I'll order a couple while I build the rest of the plane - I promise

Biggest problem with these little prototypes is fitting the gear in - the accesible area is only 43 X 70 mm - to fit the servos (5gm) Rx, ESC and be able to slide the battery in. But others have done it ok.

Pat
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Old Oct 15, 2006, 06:05 PM
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That is a storming little gearbox. Get the 4.14:1 ratio. That suits a 6x5 prop perfectly.

It's not exactly expensive either..the biggest problem is putting ne pintions on the IPS motors..there is no shaft to push against - just the plastic endbell, and if you aren't careful the rear end gets pushed and the brushes smash. Hot pinions and a careful pushfit probably work better than tapping with a hammer which I did - and wrecked a new motor.

Be careful and arrange cooling for the ESC as well. 2 small servos should be OK but BEC's get hot on 3s LIPO.
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Old Oct 15, 2006, 06:58 PM
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Pat,

Very nice little build. Now, where are you going to fy it without ripping the LG off?!?! Not at your 'normal' field I hope

Vint,

Thanks for the idea about 'hot' pinions. If you try it and it works let us know. Have struggled with that for a while. After botching one I just went out and bought another complete setup with the gearing I wanted.

charlie
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Old Oct 18, 2006, 11:35 PM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
6,963 Posts
With the warm weather arriving in Oz, I seem to be spending far too much time in the garden and house renovations/restorations so progress on this little bit of Aussie history is slow.

The cockpit sheeting is done in 1/64 ply with teak stain, and the engine section is clad with craft shop Al. foil - very hard to keep uncrinkled but with care......and doesn't add much weight. I stuck it on with a thin layer of contact adhesive - I've found this the best thing for aluminium-to-balsa fixing. White Airspan covers the sides - it will get grubby but so was the original!

The 5 gm servos are mounted, and with the motor/GB, I'm up to almost 2 oz - this is not going to be as light as I'd hoped with the rather complex undercarriage bound to add weight. But it'll look nice in the study

I've ordered a metal GB from Japan as recommended by WIP. The little HD prop is 6X3 - not enough pitch for flying but may be trimmed and painted for show.

Next is the UC and tail bits. Pat
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