Bonified Wingnut

I am getting ready to build a Handley Page HP 42 from the Aeromodeller plans.

http://www.outerzone.co.uk/plan_details.asp?ID=465

I got a short kit from Laser design services.

http://store.laser-design-services.c...roducts_id=221

I am still debating on whether to go glow or electric. I already orders a set of electric motors but I still don't know if I want to go that route. The glow engines I would go with would be either Thunder Tiger 07 s or AP 061s. I have not ran anything under an OS 10la in decades.
My question is that does everybody here think that 4 of those would run reliably enough to fly consistant. And if so which would be the most reliable.
Thanks in advance.

Boomerang1

Even if they were perfectly reliable you would still be left with the noise, the mess, the
fuel & the hassle of fuel proofing the finish, the hassle of filling, mounting & plumbing
4 fuel tanks, accessing the needle valves for tuning, setting up throttle linkages, hiding
the engines, hiding the mufflers, accessing to connect glow plug batteries .....

I guess you can see where I'm coming from!

I've been flying multi engine models for years, modern electric power is a dream come
true for these models! - John.

Pond Skipper

Yea if you want easy peasy hassle free with little to do but charge n fly than go with brushless wonders with great output and light weight solid service.

If you want to be more mechanical in nature then ode to the engine whisperer - your reward is four humming engines syncing in tune off the deck and over the pea patch she goes ticking away like no other. Windex and paper towel is your friend or exhaust diverters.

.061's should be ok just tach them all to a easy max carry plenty fuel on board, set the low end air bleeds and throws to give you same low tach readings and enjoy!

049flyer

My Feedback: (18)

What is the projected flying weight?

Bonified Wingnut

Thanks for the replies.
Project weight is unknown. I think it has about 750-800 sq inches of area and I am guessing at 3 1/2 to 4 lbs but I am not real sure. I know there isn't any room for a prop of more than 6" although I can go 3 or 4 blade and probably will. My concern is reliability. Am I going to end up losing an engine or two every flight on glow? I know my OS 10LA will run all day at whatever rpms I wan't.

049flyer

My Feedback: (18)

Duplicate post

049flyer

My Feedback: (18)

If your primary concern is reliability then do as Boomerang suggested and go with electric.

Personally I would install glow engines all around, BUT I'm a small glow engine type and have operated both of the engines you mention. The fact that you are even asking questions about these particular engines tells me you may not be too familiar with them. With this in mind I believe that you are likely to have continuing problems for quite awhile and will have numerous inflight engine failures. Small glow engine are not impossible to get to run reliably but they do take some practice, patience and tinkering.

The question comes down to this: How much of a challenge are you willing to take on? If you are the "I can make ANY engine run right" type, then go for it. However if you are the "I like OS engines because they are easy to run" type, then go electric.

049flyer

My Feedback: (18)

By my calculations your projected weight and wing area will result in a wing loading of 21 to 24 oz per sq ft which is a bit on the heavy side for my taste. Plus with 4 small glow engines of the type mentioned you are very likely underpowered, add the fact you will possibly use 3 bladed props which are usually less efficient at low speed and you appear to be running the risk of encountering significant problems in my opinion.

If you can build the plane to weigh 2 1/2 to 3 lbs max your odds of success will be much higher. Weight is many more times more critical on 1/2a planes than larger planes (except 3D planes).

APC makes a 5.7 x 3 prop that works very well on 1/2a engines and may fit your application better than 3 placed props.

Bonified Wingnut

I have a Dragonfly 049 I have not ran in a long time. I have ran a lot of different engines OS 10 and 15la ...OS 35 bushed...GMS 32...Evolution 36...Tower 75...Magnum 30 and 52 4 stroke...Quadra 35...Zenoah 23...Dle20 and 30. I usualky have good luck and not many dead sticks. But I am wondering if the reliability of the smaller ebgines is any where in comparison.

airraptor

My Feedback: (66)

The AP61 with a APC 1/2A 6x4 prop is a good combo. great on gas and still provides good thrust. some on here will say its too much prop but it was enough to pull my 19 ounce honker straight up not very fast but it did go till I stopped it.

I would run 2-3 ounce tanks and set your timer so you can land with all running.

Bonified Wingnut

At 4 lbs the wingloading would only be abou 12 oz/sq ft

049flyer

My Feedback: (18)

I guess I have been figuring it wrong all these years. I'm not a math whiz and might be a bit old and slow besides. I would appreciate a little help so I can learn. Here is how I figured it:

I took the total square inches of 400 and divided that by the total square inches in 1 square ft which is 144 to get a total square ft of the wing of 2.7. Then I took 4 lbs and multiplied x 16 oz per lb to get total oz of 64. Then I divided 64 oz by total sq ft of 2.7 to get 23.7 oz per square ft.

Please help!

Sounds like with all that glow experience, you are well equipped to get the little jewels purring jut fine. Please post some pictures as you build so we can admire.

There is a youtube video of a guy with a Howard Hughes Spruce Goose model with I think 8 ea 1/2a engines. Flew great till they all quit one by one (no throttles), landed safely. Neat video.

Bonified Wingnut

800 sq in

airraptor

My Feedback: (66)

I thought it was 750-800 square on the wing not 400

049flyer

My Feedback: (18)

Well that would account for the difference! 800 sq inches changes things, don't know where I got the 400 sq inch number. My apologies.

Wingnut you are right. Should be great flyer at 12 oz per square foot.

The cool factor would certainly be much higher if you went with glow.

Bonified Wingnut

Boomerang1 you brought up something I hadn't looked into yet. Throttle servos. I will Probably have to make my own tanks but I will also have to make sure I have room for servos. The engines would sit in the open though. Not really worried about winning any scale contest.

So with the possibility of glow still up in the air which one does everyone think would be better for a four engined plane. Ap 061 or Thunder Tiger 07 and why? I don't want to start anykind of arguing because it isn't that important. For me I would go the cheap route.
If anyone is interested in building along get a short kit from LDS it comes with the plans for $75 I can give you the list of other stuff needed or you can find it on the plans at Outerzone on a pdf. I will be probably making a thread as soon as I get started in a few weeks.

Thanks to everyone for the replies.

Boomerang1

Quote:

our primary concern is reliability then do as Boomerang suggested and go with electric

Reliability, yes of course. But also convenience. Multi enginemodels are rare for 3 main reasons.

Multi engine models are a much bigger commitment in time, money & brainpower, few people are committed enough
to build one & if, by some chance they do build one, there's the ongoingcommitment to keep them flying.

Engine reliability is an absolute must, engine failure & the subsequentincorrect handling of the situation is the reason
most of them end up in a bucket. Generally the larger the engine the morereliable it is. You plan on using?

Convenience, a day at the field becomes a big job making sure everything is okon the model, at the very least four times
the hassle of a single engine model. So the model is flown less &less because of the hassle & leaving the model longer
between sessions results in more problems like gummed up engines, blockedneedle valves, oil not cleaned off from the
previous flying session eating into the paint, etc. In the end they endup just hanging up in the garage because it's all too hard.

I'm not a 1/2 A engine fan, I'm a model aircraft fan & flying them is thebest part. If a giant size, multi engine scale model was
available that I could take to the field, assemble in minutes, start withabsolutely no hassles, not have to clean oily goop from it,
do practically no maintenance to it, then repeat literally more than 300 timesfor almost 2 decades I'd have one. John.

Rendegade

At first I was going to poo-poo Boomerangs thoughts, as it would be a serious modelling acheivement to do a multi engined 1/2a.

Any time I see it I take my hat off to the modeller.

If you're not a complete whiz with motors (I'd like to think I am, but even so I'd not attempt it), stick with electric.

You'll either get frustrated with never flying it from engine problems, or worse you'll end up frustrated picking up the peices of the model you used to have.

combatpigg

My Feedback: (3)

I would use 5 x 3 props. Figure that each engine is capable of 12 to 13 ozs of thrust. Keep the engines as inboard as possible. It's really important to have real good rudder authority and to be proficient as a knife edge flyer doesn't hurt.
The worst case is to have both engines on the same wing quit, then allow the plane to spin before reacting in time to shut the opposite engines down or to bank the plane against the side that still has thrust. It's fun to KE fly against the assymetric thrust till the tank[s] run out.
With all of this in mind, I'd make a crude foam prototype to test some ideas before committing to a finished product. The plane needs to be large enough in both length and span to easily cope with engine problems [assymetric thrust].
Syncing the engines isn't super critical, but get them singing fairly even. You might find that having four 4.2 x 4 props is easier to manage if / when odd combinations of flameouts occur.
It would also be handy to have 2 guys pitting the 4 engines, at least during the initial fire up

BMatthews

If by some chance both engines quit on one side the MOST IMPORTANT THING is to keep your flying speed up even if it means having to maintain a shallow dive as you come back to the field. Let the speed drop and the rudders will lose their grab and the model will turn into the dead engines and there's nothing you can do about it once you have full rudder already. All you can do is speed up by diving to the point where you can fly straight with full rudder used to hold it.

There's one way to find out if using 3 glow engines is for you or not. Just simply set up four engines on a board that sort of simulates the same setup and have at it. If you can get them all warmed up then stop them with a rag in the props, top up and get them all running again within a minute than you could be a candidate for a 4x glow powered Hannibal.

I'm thinking that this thing will be a bit of a hot rod with 4 .049's though. Look at it this way. A 200 square inch 16oz model would be a hotrod with one .049. Now you're flying four such models that happen to be locked in formation.

If you are good with the engines and want to do this with 4x.049 I'm thinking that it would be good to bump it up to an honest 6 ft wingspan.

Boomerang1

Well, thank you!

The Short Stirling has 4 x Cox Medallions & the Lancaster has 4 x OS 10 FSR's.

BUT, it's like banging your head against the wall. They say that doing the same thing over
& over again & expecting a different result each time is one of the first signs of madness.

I'm not totally mad, I just I looked for a softer wall!

THAT's multi engine electrics. - John.

Bonified Wingnut

What is the wing area and weight in those two planes Boomerang1? The short kit is already bought and I am sure the 4 x 061 would not be overkill. It is a bibe with a ton of drag. Size and weight of a 40 size trainer. I would go with .10s but I don't think the nacelles would like it. My plan was 2 or 3 tanks 1 for each top and bottom pair. It will be rc...not control line engines.

Boomerang1

Both these planes have RC engines, the Cox engines have a sleeve throttle on the cylinder.

The Stirling was about 700 sq in & weighed about 6 pounds. It later ended up with the 10 FSR engines.

The Lancaster was about 8 pounds & around 1000 sq in, a bit heavier as it was fitted with retracts.

The total engine displacement on multi engine models can be lower for a particular size model due to the
greater combined propeller area.

All of my models used a separate tank for each engine. - John.

Rendegade

Nice models John, I take my hat off to you! I've considered doing something similar with a pile of OS 25's that I have lying around but yeah, like you say, it's banging your head against a brick wall!

BMatthews

Keep in mind the wing loading and scale like flying speed too. For the Hannibal I'd want to pull out the stops for making it light so it'll fly slow and stately like the original.

Also keep in mind that folks fly 6 foot to 2meter gliders with reed valve .049's all the time. Granted they don't so much CLIMB as they "glide uphill". But by the end of the 2 minute engine run or so they are typically up around 400 to 500 feet high. The point being that there's LOTS of room for flying something like a 65 inch Hannibal biplane on low power.

To cut down on the engine starting duties another option would be two OS.10s on the lower wing only. It would also avoid the nose down pitching that would occur with the high mounted engine pair if they were running instead of just being free wheeling props for decoration.

AND..... This should make you smile at the possibilities..... Can you imagine if you could size it up to the 72 to 80 inch size and fit it with a pair or quad of OS .20FS engines? The sound would be magical.