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The Ohmen

My first electric powered aerobatic model

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Martin McIntosh08/10/2019 14:09:47
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I would have liked an OS26FS in mine but both the ones I have were already spoken for.

I would say that for a B test something like balsa Wot4 may be more suitable since you may have a problem with stall turns. The model also tends to bounce around a bit on a windy day.

Peter Miller08/10/2019 14:53:54
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Never having taken a B test I don't know but Martin may wellbe right, it is small and light for windy days.

Trevor Crook08/10/2019 16:59:59
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Stall turns shouldn't be a problem, but yes, it's steadier in a light breeze. Having said that, I took my B years ago with a .20 powered lightweight aerobatic model.

Martin McIntosh08/10/2019 18:45:45
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Trevor, I found that before I modified the rudder angle it pushed the tail up, especially noticeable if a lot of rudder was needed for a crosswind take off. Do not really wish to criticise the design because it looks and generally flies pretty good.

A bit off piste but I originally gained a B about forty years ago in order to enter competitions. After an enforced lay off I joined another club and they accepted that I had a B, but I had lost the certificate. The BMFA, as the SMAE now is, could find no record of me whatsoever, so on a day when a couple of B tests were being run I volunteered to do it again. It was windy and to the surprise of the examiners elected to use a very light OS 20 powered funfly. Worse than taking your driving test again.

Peter Miller08/10/2019 21:05:37
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Feel perfectly free to criticise the design. If something improves the handling everyone should benefit from the added knowledge.

Alisdair Sutherland once oonted out that where the rudder is completley behind the elevatror Knife edge flight is much easier.

I stil forget to incorporate that in my designs.

chris larkins10/10/2019 23:26:44
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We are going to have a winter 'Mass build' at my club and so far we have 6 members that have signed up, we are going to build 'The Ohmen'.

In the spirit of being 'Green' does anyone have a copy of the plan that they would be willing to post? Cost of postage paid of course. I could go along to the local copy shop and have a run of 6 printed but would rather use a plan that has already been printed if possible.

Chris Walby11/10/2019 07:35:43
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Chris,

I'll bring the drawing and build article up tomorrow afternoon to the flying field...discuss between flights or tea

Chris

Peter Miller11/10/2019 08:35:18
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I am sending you a PM

Edited By Peter Miller on 11/10/2019 08:36:13

Martin Harris19/10/2019 01:57:42
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As Chris Larkins mentioned above, our club has decided to run a mini mass build this winter and so far, 14 members have verbally committed to the idea - and no arms [except mine] have yet been twisted!

While I have little interest in building an electric powered model, I do have an OS 20FS which I've been looking for a home for - so as a committee member who ought to make the effort to show willing and join in, I have hatched [or as will be apparent a little further on, perhaps more correctly de-hatched] a cunning plan.

I have had the plans scaled to 40" wingspan by the second Chris and after taking various measurements I've drawn up slight changes to them to accommodate engine bearers to mount the engine inverted. By moving F2 slightly forwards, a blue SLEC tank [shouldn't be any lack of duration!] will fit at a perfect height allowing space for a receiver battery under it if it needs to be forward for the C of G. I will delete the spruce rails and the removable hatch and use 1/16" ply doublers to help absorb any engine vibration.

Not having done any comparative calculations, I'm not sure yet whether the tail will need the "heavying" mods so I might retain the built up tail or just go for sheet surfaces and add lightening holes as necessary.

Hopefully the less than fire breathing but very cute little engine should swing a 9 or 10 inch prop with sufficient authority for decent performance - time will tell on that but Peter's observation that a 26 will power a full size version adequately gives me reasonable confidence.

P.S. As it's a minimised glow powered Ohmen, I intend to name mine The Gloamin'

Edited By Martin Harris on 19/10/2019 02:23:06

Peter Miller19/10/2019 08:27:31
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That sounds very good.

I think you will find that 1/32" ply fuselage doublers are fine, I use them and 3/32" balsa sides on everything up to .52 fourstrokes and .40 two strokes.

I will be most interested to see the finished model and hearing how it performs.

Martin Harris21/10/2019 23:53:00
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Just a little taster Peter...

20191021_232230.jpg

I've gone all traditional using hardwood bearers - mainly through laziness in leaving F1 in its original location.  The engine mounting bolts will be either side of F1 and I've extended the bearers to the front of the cowl to help support its construction blocks.

Edited By Martin Harris on 21/10/2019 23:55:55

Peter Miller22/10/2019 08:33:12
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An interesting approach but it should work well.

Of course you save all the hassle of the separate top hacth too.

Chris Walby22/10/2019 10:16:11
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1001 forum posts
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Martin, at this rate yours will be finished for the Christmas dinner fly-in!

Will it have a floats/skis options?

Nigel R22/10/2019 10:45:38
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Glowmen, surely?

The little OS is a thing of beauty.

Martin Harris22/10/2019 11:25:46
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I haven't finalised the spelling yet - I was also thinking of Glohmen to maintain the direct link to the original name. In fact the idea of Gloamin' only came to me while I was typing the first post and thought the spelling looked a bit odd...

I'll bear the suggestion in mind but there's plenty of wood to cut and glue before I make any final decision.

I took a photo once of the 20 sitting alongside my ASP 180 which is a direct relation through its clone origins and it looked like a model of a model engine...

Edited By Martin Harris on 22/10/2019 11:30:46

Martin Harris28/10/2019 21:52:29
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Hi Peter,

Just wondering why you went for the separate spar depth wing joiners instead of the more conventional single piece full depth version I've seen in one of the pictures of your prototype?

Peter Miller29/10/2019 08:38:55
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Posted by Martin Harris on 28/10/2019 21:52:29:

Hi Peter,

Just wondering why you went for the separate spar depth wing joiners instead of the more conventional single piece full depth version I've seen in one of the pictures of your prototype?

Do you know, I can't remember why...but then it was several models ago!! I probably had a good reasondont know

Martin Harris29/10/2019 11:07:36
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I hope you don't mind then, but I'm intending modifying mine to incorporate a single piece joiner which seems easier to assemble than 2 small joiners and [no doubt quite needlessly] stronger across the join, only resulting in adding a tiny extra amount of 1/16" ply close to the C of G. Assisting this was the fact that the joiners are drawn in their correct position relative to each other on the plan so simply needed filling in between them before cutting them out!

Peter Miller29/10/2019 11:43:47
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I never mind what people do to my designs. It is their choice.

Also by modifying designs people start to get interested in designing and that is so good!

Martin Harris07/11/2019 23:27:35
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The GLOhmen is taking shape with just a couple of small jobs to complete the woodwork and fitting out but I may deliberately put it on hold soon until nearer our club exhibition in the spring - the temptation to fly it over the winter will be just too great and I'd like it to be in pristine condition for the event. I've yet to decide on a colour scheme and on top of which, as we're trying to encourage less experienced/new plan builders in the club, it may help to be able to show the more intimate details in answer to any questions arising.

20191107_105857.jpg

I'm strongly considering making a canopy which I think might set it off rather well - a quick preview with a somewhat too small one from my spares drawer looks rather attractive to my eyes...

20191105_174433.jpg

We've already got at least half a dozen Ohmen builds under way and are actively trying to encourage others to join in. At least one other is being reverse engineered to IC - in that case a 30 FS at normal size rather than my 85% version.

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