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The Ohmen

My first electric powered aerobatic model

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Peter Miller25/05/2018 18:29:24
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Did some more flying today and got some better data.

I had two flights. The model is aerobatic on half throttle and only needs full power for things like square loops and they really are nice and square.

A flight of eight minutes left me with 11.4 volts in the battery.The first flight was slightly shorter at 7 1/2 minutes and I didn not use full power as much. that left 11.8 volts.

Tim Ballinger25/05/2018 18:41:32
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Looks like a ‘funster’ . I’ll add it to my list .

Tim

Peter Miller25/05/2018 19:38:28
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Hi Tim

It is light,very agile, easy to build and as you say, just good fun.

kc31/08/2018 18:24:36
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The October 2018 RCME is now in the shops and has the Ohmen as a pull out ( 'free' ) plan.

It looks to be what many many modellers want - a plan for a moderate size plane already designed for electric. So no need to redesign for a battery hatch etc. Realistic looks, a specified motor that is actually available, simple construction, aerobatic - could be a very popular model and RCME could easily sell out quickly!

Peter Miller31/08/2018 18:41:39
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THanks KC

I must say that I like it a lot.

Geoff S31/08/2018 20:05:08
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I'd promised myself that I'd concentrate on building only sport scale models in future but when I saw this in the RCME that dropped through the letter box earlier this week I'm tempted to build it even though it's a bit smaller than my usual lower limit of 1.5metres (60" ) wing span.

In the article, Peter comments that it's reduced version (87%) of a slightly bigger design so I wonder which one.

Geoff

Edited By Geoff Sleath on 31/08/2018 20:05:36

Peter Miller31/08/2018 21:00:38
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It is a smaller version of Miss Alliance.

It could easily be made to lok like a Magister or a Moth

kc02/09/2018 11:03:21
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I had expected that the Ohmen might have been a smaller simpler version of the Pee Tee Sportster (Crossbreed) due to the styling but obviously I was wrong.

However the family similarities to other Peter Miller designs are apparent in the wings - it seems virtually the same wing as Alley Cat (RCMW Feb2014 MW3678 not the Harry Gilkes Alley Cat ) and almost the same as Swamp Rat but that lacks all dihedral. So anyone with a wing from those models might utilise the old wing. Luckily i have a spare Swamp Rat wing acquired at Wings and Wheels........

Peter Miller02/09/2018 11:29:32
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Yes, kit is a fairly standard wing but designed specifically for Miss Alliance.

With slight modifications to the wing seat it should take others.

This is one reason I am doing the MAK 15 MP. Just to be different.

Got a date for my first cataract operation so am hoping to get the model ready for air tests on the 16th of this month or I wil have to wait or let Stuart do the test flying.

Piers Bowlan02/09/2018 12:08:35
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Posted by kc on 02/09/2018 11:03:21:

I had expected that the Ohmen might have been a smaller simpler version of the Pee Tee Sportster (Crossbreed) due to the styling but obviously I was wrong.

However the family similarities to other Peter Miller designs are apparent in the wings - it seems virtually the same wing as Alley Cat (RCMW Feb2014 MW3678 not the Harry Gilkes Alley Cat ) and almost the same as Swamp Rat but that lacks all dihedral. So anyone with a wing from those models might utilise the old wing. Luckily i have a spare Swamp Rat wing acquired at Wings and Wheels........

Here is my Alley Cat wing laid on top of the Ohmen plan.

img_4327.jpgI didn't get around to building the Fuselage for the Alley Cat (with OS 30FS) due to my house move. Might as well use the wing in an Ohmen build. I'll do the Alley Cat IC Fuselage later using the same wing, as it is virtually identical. Thanks Peter!

All the best with your cataract operation Peter. You will be building/flying again in no time.

Edited By Piers Bowlan on 02/09/2018 12:23:26

Geoff S02/09/2018 12:09:28
3578 forum posts
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Posted by Peter Miller on 31/08/2018 21:00:38:

It is a smaller version of Miss Alliance.

It could easily be made to look like a Magister or a Moth

You've set me off, Peter. I'd forgotten about the DH94 Moth Minor and it was a plane I thought would make a nice model. It was kitted a few years ago IIRC) The wings are different though with a bit of taper. I may build the Jerry Bates 1/8 th scale (54" ws ) . I'll see.

Geoff

kc02/09/2018 13:03:50
6417 forum posts
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Piers Alley Cat wing looks a bit non standard - seems to have shorter ailerons than the plan shows. Plans for both Alley Cat and Ohmen have similar aileron lengths. The wing seat does not need to be adjusted because the airfoil seems exactly the same on all 3 plans. Wing fixing might need slight change.

My Swamp Rat wing and the spare are slightly shorter span than the Ohmen due to tip being slightly different shape. Interesting to know what difference the tip shapes make- probably very little except in appearance and the ability to be able to stand a wing on end for storage!

There is some conjecture in another thread on whether the Ohmen would be a good design for the Mass Build. Ohmen builders might like to comment there.

Piers Bowlan02/09/2018 14:35:26
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You are right kc Alley Cat and Ohmen have the same length ailerons. Naughty me decided to fit flaps to my Alley Cat, then I changed my mind so the ailerons are a bit shorter, (can't see it making a vast difference). If I decide to do it as per the plan I only have to fit new trailing edge stock. The section is very similar as is the planform (Alley cat chord is 3mm shorter but that may be down to the TE stock I used. Rib spacing is slightly different.

Ideal for a mass build I would think, at least this may be one I actually finish!

Peter Miller02/09/2018 18:20:22
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Hi Piers, Thanks for the good wishes. Maybe it will stop my model dissapearing every so often which is worrying!!

All the wings were designed separately for each model believe it or not. Now you know why I suddenly feel and urge to produce something really different.

Most of the effect of the ailerons is out at the ip. so the reduced aileron length will not make much difference.

I have never really noticed that tip shape has much effect but that could be down to me not being a precision flyer.

I have jjust spent a perfect afternoon throwing "The OHmen" round the sky with only the odd moment when it vanished.

Well as a subject for the mass build.IT is easy to build, cheap and electric.

One modification I would make is to take the 1/32 ply wood doubler another inch further back. Also use hard strip for the tailplane if not using sheet.

A little while ago I got completley dissoriented. The model was coing down verytically at speed. I hauled in full "UP" and the model hit the ground dead flat. Bounced into the air with only one prop blade and ended up in the wheat.

The only damage was a clean break from the rear of the hatch to the rear of the wing cutoit and a crack or two in the cowl

Half an hour with glue and it wass back as good as new and has flow a lot since.

The doubler was short because I was using my last scraps of 1/32" ply.

Edited By Peter Miller on 02/09/2018 18:22:52

Former Member02/09/2018 20:47:31

[This posting has been removed]

Peter Miller02/09/2018 21:24:30
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Of course you could shrink the Oodalally wing down a little to make the Ohmen more moth minor like

kc10/09/2018 09:27:45
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173 photos

I have noticed that the plan as printed in the magazine does not show any bracing for the 1/8th ply motor bulkhead to the sides or battery tray. The photos of Peters model clearly show triangular bracing to the fuselage sides. Experienced modellers will automatically brace with triangular but this type of plan will appeal to new builders who may not realise this is needed, especially with only a thin 1/8th bulkhead. Only a very thin line of glue holds the motor on as per the plan!

Peter Miller10/09/2018 10:29:09
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OOPs I missed when proofing the plan. Sorry.

If anyone would like PGF files of my original plan. PM me with your email address.

Edited By Peter Miller on 10/09/2018 10:30:05

Piers Bowlan10/09/2018 11:35:31
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2118 forum posts
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Well spotted kc. Yes, I would have used triangular section stock as reinforcement myself. A point that could be mentioned if it was voted the 2019 mass build. Also, if it was selected, better the MB voting starts sooner rather than later as it would give Sarik/SLEC (or whoever) time to produce a CNC set of parts for those who might want that (in time for Jan 2019 start). I think the availability of a CNC kit encourages more participation whatever the model selected.

I wonder if there are others on the Forum who is, or planning to, build an Ohmen?

Trevor Crook10/09/2018 12:13:15
937 forum posts
67 photos

It's a "probable" for me, once I've finished the current project. (Sorry about the accidental pun!)

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