1/5 scale Cessna 182 - which power unit ??

[Ben Kenobi]

A recently obtained and am planning the build for a TopFlite Cessna 182 (81" span) potential TOW of 6.5kg approx.

There are two topics high on the planning agenda - the first of which is what power to use. Recommendations are for a .61-.91 2 stroke or a .90-1.20 4 stroke OR a Rimfire 540kv electric.

For me the IC choice is fairly simple - most likely an O.S GT22 or a Saito FG21 (read quite a few posts about the smaller sized being borderline in this model) but in both these cases fitting the motor into the available cowl space and providing a suitable exhaust will be 'problematic', cooling will be a problem I think too - I also don't like how various components become totally inaccessible if you build as per plan and add things such as a cockpit.

On the other hand the electric recommendation is flawed - connecting a 3S and a 2S in series is a really bad idea (you should never connect two dissimilar batteries in this way) giving a 5S config - but in any case Electrifly state a 6S as the minimum for the recommended motor in any case, and having studied the drawings I can't see any way to fit such a battery where it won't mess up the COG completely and retain a cockpit - there is also a good chance that such a battery will put the model over the 7kg limit.

So I'm leaning toward the petrol engine but making the bulkhead detachable, is petrol going to limit or restrict the places I can fly though. I've had nothing to do with IC engines for 35 years - any tips for getting exhausts fabricated if I go the petrol route - and are there any bits available to remove the need to put your hand so close to a 15" or 16" propeller to set choke etc, I've watched a few fliers now with their hands mm away from a spinning prop and it makes me cringe.

So Electric? or petrol? which will allow the best scale, anyone have experience of a large Cessna?

The second topic is whether to use 'Monokote' or to use glass tissue (17g mer sq metre) I've a preference for the latter but it will require much more effort re painting etc. Not decided whether to replicate an existing aircraft or freelance at this stage.

[Rich too]

If you are going to tow, I would go for a DLE 30 or similar. I have a Cub designed for 10cc ic and it flies great on a Zenoah 23, with a beefed up bulkhead. There no problem with spinning props, my Zenoah uses a squirt of fuel Jan the carb (no choke) and my DLE a manual choke operated via a bell crank system exiting down the fuselage side well away from the prop.

What your concern with 7kg?

 

Edited By Rich2 on 02/10/2015 19:30:02

[Ben Kenobi]

So I could go up to 30cc with no adverse effect? I'm not looking for non scale handling, a Cessna isn't rated for racing or aerobatics after all.

I read that 7kg is the limit before permission is needed to fly in regulated airspace. Where I live is in the approach to Manchester airport - I have the ATC chart for the airport and I am right in the approach for 23R and 23L, I am well inside the 'A' zone.

I also noticed that many clubs impose a 7kg limitation, I'd be happy to visit one that doesn't if it isn't too far. I realise that I could fly outside this zone but it is large and would eliminate a lot of potential flying spots. I've been reading the terms and conditions of a few clubs and I find them a little off putting.

I know that nobody is going to pull up with a set of scales but should the worst happen ... I'm just a coward I guess.

I don't really want to tow but perhaps being able to top people's gliders for them would be cool, never thought of that.

Edited By Ben Kenobi 1 on 02/10/2015 19:47:16

[Rich too]

Build thread here

http://www.modelflying.co.uk/forums/postings.asp?th=63321&p=4

[Ben Kenobi]

The DLE30 is a good price - no doubt would get raped by the VAT man but still half the price of a Saito - the DLE's are a good engine I take it I confess I have only been looking at 4 stroke because of noise but I haven't read anything bad yet about the DLE.

I'm definitely leaning more towards a gasser than electric, I've been flying electric a couple of years and always frustrated by the flying time - LiPo's only charge so fast but a gallon of petrol will go a long way and be cheaper in the long run I think.

Thanks for the link - I shall study it some.

[Rich too]

yes, DLE's are great value. If you're not towing a 20 would be fine and it sips fuel!😉

 I used to fly ic 35 years ago, got into electric a few years back, but missed ic, and I'm hooked on petrol now!

I don't belong to a club so rules hit a concern, and 400 ft is pretty high! I always use a fail safe anyway.

Ps if I had the money I would prefer 4s, but at DLE prices its a no brainer

 

Edited By Rich2 on 02/10/2015 20:09:28

[Rich too]

My Cub is 80" so very similar in size, so I think the OS you suggested would be a great choice.

[Ben Kenobi]

Yo, similar specs, my last IC flight was in 1975 !!! - been flying electric for two years as I've only really just got back into having hobbies that didn't empty my fridge, my cupboards and my pockets - now it just empties my pockets.

I think the 400 feet is a general thing, over 7kg in controlled airspace the ceiling is zero, it is 400ft outside the controlled zone - isn't it ????

Phils thread is interesting, pity Martin seems to have disappeared before finishing - last on here in 2014.

This is what I'm 'planning' for the bulkhead to make access to the fuel tank and servo's sensible ... whether it will work out is too early to tell

**LINK**

I'm currently selling off a multirotor, all the funds will be for the propulsion system - I have receivers / batteries and flight controllers coming out of my ears - all open source (OpenTX).

At those prices though it wouldn't hurt to have one in the box, I'm not really interested in 'glow plug' ... noticed that you can even get a starter motor for the DLE30 - how cool is that

 

Edited By Ben Kenobi 1 on 02/10/2015 20:24:16

Edited By Ben Kenobi 1 on 02/10/2015 20:26:16

Edited By Ben Kenobi 1 on 02/10/2015 20:26:39

[Dave Hopkin]

By the way there is nothing wrong with connecting a 3S and a 2S in series, as long as they have the same capacity - A 3S is simply three single cells in series........

[Ben Kenobi]

Ah so it is OK as long as the mah is the same - that makes sense - and of course both must be LiPo.

Still doesn't get around the manufacturers recommendation for 6S, I've been trying to get an answer from TopFlite but so far nothing.

I actually have a 6S on the bench and have been playing with it on the drawings - petrol is looking more like the sensible choice. I've made no final decision yet but obviously need to before certain things get assembled.

[Dave Hopkin]

Yes both must be the same chemistry and the same capacity and discharge rate

You mention that most clubs have a 7kg limit due to CAP Article 166 where they are located in restricted airspace (which is most of the populated areas of the country!) , we are on the south side of Manchester about 8 miles from Manchester Airport so we have that 7kg limit, but you would be welcome to visit (club website **LINK**

[Ben Kenobi]

I may just pop along and say hi in a couple of weeks - day job has me stuck in Dublin the next two weeks (weekdays but I fly Sunday afternoon). I'm not so far from you. I am trying not to exceed 7kg, I'm reckoning 6.5kg but we will see over the coming months if I manage it. I take it that physical size is not an issue.

On the weight issue I think that the petrol is the best option for weight, I like the electric because of its convenience and relative simplicity but not so much the endurance. By the time I add a decent battery / pair of batteries, ESC, TX and servo battery it's getting heavy.

 

Edited By Ben Kenobi 1 on 02/10/2015 21:18:24

[Dave Hopkin]

We fly on Sunday Afternoons after 1:30..... (other days the times varies) Feel free to PM me when you want to visit

Physical size.....   never been an issue.....  but for obvious reasons it would probably be better to turn up with something smaller for the first visit as well

I hate to agree (as a electric flyer) but the law of diminishing returns with current battery energy/weight ratios as the model gets bigger... Next generation of Batteries should cure that though!!!!

Edited By Dave Hopkin on 02/10/2015 21:24:02

Edited By Dave Hopkin on 02/10/2015 21:25:11

Edited By Dave Hopkin on 02/10/2015 21:26:13

[Ben Kenobi]

Yup - my concern isn't that I couldn't get it off the ground with a sub 7kg TOW but how long I could keep it there. I found out pretty quick with a DJI 550 that 3S doesn't cut it - woefully underpowered and tragically short flight times as a result - ended up on 4S but the weight increased by 0.5kg ... get 20 or so minutes in the air now though. The time I get with the Align 450 is dire - barely 5 minutes 'safe' flying (I don't do 3D either it just doesn't appeal).

Unfortunately my flights back to the day job are at 17:00 on Sundays so it will be a couple of Sundays till I can come and see what you guys do - your field looks huge !! - I will drop you a line.

I hope you don't mind people that fly Mode 2, OpenTX equipment (Taranis X9D) and use LiPo's ..... although I shall refrain from bringing anything initially ... my helicopters in bits currently to replace some bearings, I've all but quit the multirotor game - too much hassle / BS that I can do without and my boats don't work so well on grass

[Dave Hopkin]

Mode 2 most people are mode 2, just a couple of "left footers" on mode 1

I fly on Taranis

Electric is probably 70% of the club these days....

Helo/MR - the flight line is in the centre of the field, so planks fly on the side away from the sun (when you can see it in Manchester!) Helos/MR fly on the other side concurrently so not a problem - Boats we have a couple of boaters too (sail at Platt Fields) in a wet winter you might get away with a air boat on the field!!!

The down side I can see for very large models (size not weight) is the goal posts... you have to learn to manage approaches to avoid them (limbo dancing is not encouraged!)

[Ben Kenobi]

I guess the only issue with the goal posts is the approach angle that it forces on you or are they rugby H's ?? making alignment a test of depth perception too. I've never flown such a large aeroplane, so I'll be into the ribs of those that have - not about to rap 6 months building round a post, in fact I don't feel confident enough to do the initial trim flight - but I've got to build it first, time enough to practice with a little FMS Cessna which is puny by comparison.

As far as 'wet' goes that's standard Manchester but I'm very much a fair weather hobbiest, I tend to maintain and build from October to March - basically when we are GMT not BST, then fly etc during BST, that and I can't stand the cold on my hands - not even with gloves - I'm in this for fun not self abuse - to be honest I get almost as much if not more fun out of the building etc.

[Dave Hopkin]

The Rugby H's are down at the bottom of the field (away from Princess Rd) the goal posts have more of a physcological effect rather than physical, there is plenty of room but they do prey on the mind!!!

[Ben Kenobi]

I decided on a Cessna to model and it's a 182T, it uses a three bladed prop. I'm really struggling to select a suitable prop / engine combination and can find no efficiency data on the three bladed props found so far.

I'm also now committed to 4 stroke / Petrol because of noise - I just don't like high revving 2 stroke noise.

The Cessna worst case will have a 28oz per sq ft wing loading, stall speed 29.5, max speed required 79. It's looking like I need a 16x10 which seems OK and matches the scale for a 182T ( 79" ) but it pushes me into a bigger class of engine than I expected (recommendation of TopFlite is for maximum 1.20 four stroke but that's a bit borderline on such a prop).

Any ideas?

Edited By Ben Kenobi on 26/10/2015 19:43:02

Edited By Ben Kenobi on 26/10/2015 19:44:21