Plans and Weights

[Rob Cope]

Handley Page Halifax 79" (RSQ1767)

I have bought the plans, (myhobbystore) and they're great. However, there is no target weight or parts list, etc. As I'm new to aeroplanes, I wonder if anyone has built this aeroplane and what weight was achieved (wood+covering only.) I have two books on building (one from scratch) and they have no discussion of target weight and how to achieve it.

I expect 0.1 hp/lb for scale flight and want 0.3 hp/lb available for more dramatic flying (bombers flew rather straight dull missions.) I also want to know what wing loading to aim at. ARTF seem to have 23oz/sq' or so, but with scale wing area, a weight of (say 12lb) all up will give me 38oz/sq', which from research here and elsewhere sounds impossibly high. Can anyone help me find if this an "OK" loading for a 79" span aircraft? Other than buying all the wood and glue and weighing it (allowing for packaging and some waste), how can I find if I'm even anywhere near on target before rashly commencing?

I'm planning 4 x OS 52 FS, so the weight will be high, but I do need to be able to land the thing.... We have a medium/short strip. Each engine weighs 14.2 oz, so I'm already up to 4lb on engines and flight pack alone!

I need to know what wood selection would be sensible in order not to go too overweight - but provide enough strength for this "power" warbird...

Thanks in advance, and do tell me if this is too much to hope for..!
Rob

[Alan Gorham]

Rob

 I have this model - didn't build it but bought it from a chap who had lightened the structure to make it suitable for electric flight circa 1996!

 The original was meant for 4 x 15 2-strokes (or at worst 2 x 15's outboard and 2 x 25 inboard - I'll have to check the plans).

The thought of putting 4 x 52 FS in is truly terrifying - plus I'm not even sure there is room in the nacelles for suitable size fuel tanks to run these engines for very long.

 IIRC, the plan protoype weighed in at 11lbs - doubt you'd get near this with your planned engines!

 Not sure why you want to make a rocket out of a WW2 heavy bomber...

I think if you build the model from the plan as it stands, plus follow the power guidelines therein, you won't have to woory too much about wood selection or wingloading and you will have a pleasant flyer.

If you go down your original route you will end up in a wingloading/power trap that you can't get out of and the model will be unpleasant to fly.

Mine has 4 x speed 400 motors in it and now weighs 5.5lbs all up. It flies delightfully - very scale like speeds and lovely gentle landings.

Actually I've just read your first line again - new to aeroplanes! Forget something this complex for a little while. Build a trainer, fly the heck out of it as often as possible and then the experience you have gained will stand you in great stead for a project like the Hali!

[Rob Cope]

Thanks Alan,

11lbs sounds quite heavy for those little engines. I am surprised. I admire the 5.5lbs. That's amazing. I expect I'm looking at around 9-10lb then given that "the gear" will weigh in at about 5lb - that only leaves 5-6lb for a "strong" airframe and retracts.

Sorry I wasn't clear. I have a boomerang trainer I assembled ARTF with an Irvine 53 2st in it I've been flying on average every week since March and it's great fun. The Irvine is a bit over powerful for a 40-size aeroplane, but gives lots of options and makes it a little aerobatic. Although I can't yet string a routine together, I can pull off individual manouvres pretty well more often than not now.

I've also acquired a second hand "Sportsman Aviation" 64" spitfire with a Thunder Tiger (51?) 2st too. Getting this running will keep me occupied at the field whilst building away - and will give me "low wing experience. "

What I mean by new to aeroplanes is building. I've built a few boats before and had some success, but with boats there's less planning and calculation involved, and if it's a little heavy, then no worries, you paint the waterline a little higher.

I know I'm going to be overpowering the Hali. It's just I've been advised (local model shop proprieter) that 4st smaller than about 50 get unreliable and with four of them to keep running I need reliability. I would also like enough power to have speed options even if one engine should stop. I would also like enough power to do non-scale things. It won't be climbing vertically all the time, but I'd like to be able to have fun with it as well as coast along at half throttle for scale... you know...

Rob

[Tony Nijhuis]

Rob,

At 79" the target weight should be no greater than 9lbs. My electric 72" Lanc and B-17 came out at 6.5lbs AUW.

If your plan is to go with IC then I would strongly suggest 4x15 size 2-strokes (OS plain bearing are the best)..... and use the supplied silencer. Don't use non OS silencers (ie in-cowl type) as these do effect the reliablity of the engine. Run the engines on a quality 10% nitro fuel which give better low end responce and reliability. Keep the engines either top or side mounted and make sure the fuel tank height is as per engine manufactures advise.

OS 53- 4strokes current over-power my 11 foot B17 that weighs 38lbs and as for reliability, the 53 can be a Bu**er too. 3 engine flying is therefore quite common.

Tony  

[Alan Gorham]

Rob

 Good to know you have experience!

 To back up what Tony is saying (and he is the absolute expert at multi engined models since he's designed and built so many!) his advice about engine size and setup is spot on.

 I note that you want to add retracts. IMO the model at the 79" size is too small to accept retracts that will stand up to the AUW you are proposing.

 My solution would be to scale up the Halifax to around 11 foot span as Tony suggests with his B17. Then you can use 52 four strokes and have retracts and have a model with a much lighter wing loading that will fly like a dream.

 If you build the model at 79" span with 52 FS and retracts I can practically guarantee that you will have a heavy, overpowered brick that will be a pig to fly. Plus the Engines won't fit under the cowls and it'll look awful!

[Tony Nijhuis]

Going back some 20years (1987), I designed & built my own version of the Halifax and at 75" I managed an AUW of 4lbs, speed 300 motors on a 7:1 gearboxs and one 7 cell 1200 scr nicad pack. Duration was 2mins of near stall I seem to remember  

I feel a Halifax plan coming on to exercise a few ghosts

[Alan Gorham]

Lol!

The bad old days of electric flight Tony!

Gone forever.

[Rob Cope]

Well,

Thanks very much for the input chaps. I'm new, but I have seen your name around a lot Tony - and talking a lot of sense. I'm coming round to the smaller engine view now, especially since reliability (or unreliability) seems to be such a subjective matter. I've seen comments to the positive and negative about the same engine so many times - for lots of different engines.

I expect "following the rules" is a good thing to do with the (lack of) experience I have at building. Hey! I can always try other engines later after selling on the 15s, 20s, 30s, whatever it turns out to be. There'a a Canadian (Mark) putting 4 x OS 30 FS in there you see. He's well on the way for 2008 season. He thinks that'll be plenty of power.

I understand (from forum postings) that 18oz/sq' is a good loading. Given the 8.8sq' for the Hali, this comes out at 9.9lb build weight. I think to aim for 9lb is therefore the right thing. Thanks Tony. So, once I've weighed up the engines, tanks, lines, gear, radio, servos, etc... how do I go about building an airframe to fit the remainder. Do I just build to the plans and accept any discrepancy I should get? Can I use CA glue/ PVA glue instead of epoxy to reduce the weight? Do I just need the "right" book? I need to be able to know if I have the choice of that lovely ply keel I've been thinking about, or whether to go for balsa as per the plan. I know electric guys are saving weight wherever they can, but I want a strong airframe for IC manouvres and landing resillience you see...?

The OS 15 LA seem to be around £50 each = £200 rather than the £560 I was going to be paying. That's a distinct advantage. However, I was looking forward to the thing "rumbling" through the skies (engine note) rather than sounding like four jetskis!!! There is the SC 30 FS at £74, so £296 the set... Hmmm.

I'll do more research.

Thanks again

Rob

[Tony Nijhuis]

Rob,

bearing in mind you are going the IC route, weight is not partiually criticle. The key to building light is wood sellection so make sure ALL the wood you use is light grade balsa and glass cloth the model to give it the 'knock' protection required.

Tony

[Barrie Cook]

I used to fly in the full size. Bristol Hercules engines, The Mk.111 not the taylors chalk fin type. Lovely aeroplane.

[Rob Cope]

Thanks Tony,

I'll have to research that glass cloth technique... not finished reading my book yet, so it may be in there.

Barrie,

Great you chipped in. What did it "feel" like in a Halifax? Noisey no doubt, but was it lumbering, rock-solid, even spritely for a craft of that size? Did it really feel like 250 MPH when cruising? How was take off and landing, dramatic or smooth as silk?

regards,

Rob.

[Rob Cope]

Hi Tony,

Do you really mean it about a Halifax? They're so under represented considering what they did and they're actually quite a graceful shape. I know some must be sick of warbird after warbird, but perhaps a meterological model in silver - like PP285? It might relieve the dizzying camoflage pattern patchwork in the hangar!

I know electric is the thing these days, especially for multi, let alone four engine planes, but it would be good if you could scale it for possible electric or 4-st glow. That would be superb! Oh, and one more autocratic demand...! Please make it as scale as possible... None of this clustering the engines near the fuselage. It just doesn't look like a Halfiax at all....

I'm thinking of dope rather than glass. Yes, I know "suits you". My reasoning is that dope forms a tough skin over balsa and is much lighter than glass, so I could get away with more as a beginning builder... Double-layer in places of course! Is this a good idea? I'm thinking non-shrink dope would be good for this as otherwise I might end up with a stellate balsa decoration for the tree in December...

Regards,

Rob

[Tony Nijhuis]

 Rob,

Always thinking a few projects ahead! You'll be suprised at the number of modeller who love war birds and just can't get enough of them..... The DC3 I planned a few years ago was done in Finn Air colours and the model just did'nt sell...I think because it wasn't in the drab green with invasion stripes.

Keep tuned and you should see one appear next year......about 85" for 4x.15 IC or electric and of course 'spot-on' scale.

Tony 

[Rob Cope]

Hi Tony,

I see you've produced an amazing Short Sunderland!!!   It looks spectacular from the photos.

Does this mean the HP Halifax came second place?  I wonder as I'm in the middle of a rethink on the 79" span (or 73" for scale) plans I've just started building from.  I'm being advised that for comfortable flying I ought to move to 100", but that means a split wing (for carriage) and more expense and bigger engines than the nicely priced Saito FA 30S... Hmmm.

I'd really love to build from a true scale plan you've drawn.. so please let me know... If it's on the back burner for a few months/years yet, please tip me off so that I can go do my own thing. The plans I have need adjusting for true scale, so I will either need to stick to the original (non-scale) or draw up some more pieces by cribbing bits and shapes from what I have. 

Regards, Rob

[Barrie Cook]

Hi Rob,

I meant to answer your thread of 31st Aug. but I seem to have been busy ploughing my local flying club with a succesion of models. The Halibag was a nice aircraft to fly in, especially from my point of view, that of a Flt. Eng. Landings and take offs, depends who was sitting in the front seat some of them hairy and some very smooth. I suppose I am biassed. I think they had more character than the Lanc. Have been catching up on the replies from Tony, you won't go far wrong with his advice. I think your dealer telling you to get 53 4st. had a look of pound signs in his eyes. I have the plans for the 79" Halibag, but seem to spend more time on my local hills with PSS models. At 77yrs of age, I am packing in as much stick time as I came. Best wishes Barrie. 

[Rob Cope]

Ah hah! Tony!

I spy a reference on your shiny new site...   At 85" it the wing should split either in two or three for transport.  I notice you say petrol/electric.  I hope this doesn't rule out methanol...!?

Regards, Rob