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Aerotech B-17

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Matt Yorke05/10/2017 19:56:10
14 forum posts

I've got a kit to build of an Aerotech B-17 and am pondering power. I want to go with 4-strokes - but was debating whether 40 or 52's would be a better bet. Saito 40's are lighter and smaller, but ASP 52's are still available too.

I'm debating whether 4x 52's would be overpowered and heavy or the Saito 40's would be a bit underpowered - does anyone have any thoughts/experience.

Many thanks

Matt

Denis Watkins05/10/2017 20:39:53
3597 forum posts
166 photos

Is it this one Matt


Scale 1/12
Engines 4 x .40 2 stroke
4 x .40 - .70 4 stroke

Wingspan 103 3/4
Length 74 3/4
Weight 13 - 15 lb
Control Min 4 CH.

Jon - Laser Engines06/10/2017 08:27:31
4570 forum posts
168 photos

I think the originals flew with 25 2 strokes so even the 40's would offer more grunt. A friend has their lancaster fitted with 4 52's and even though the engines are totally shot, and the model a complete brick, it cruises around no problem.

Matt Yorke06/10/2017 08:43:16
14 forum posts

Thank you both. My confusion is that it says on the box 25-40 2-strokes and 26-40 4-strokes. And then, as Denis notes above, some other sites have it listed for up to a 70 4-stroke.

I also managed to find a gentleman who has built & flown one - he had Saito 40's fitted and said performance was good. It's of course easy to put a bigger motor in, but the 52s add 0.62kg - 8% more weight to lug round. Shorter stroke also means less engine sticking out of the cowls!

I'd better order the Saitos before they become NLA.

Jon - Laser Engines06/10/2017 08:49:24
4570 forum posts
168 photos

70's are way ott. This chap (link below) in the Netherlands has 4 of our 70's in a 158'' monster B17 and has no shortage of power. If you run the 40's on something like 12x5 or 13x5 props you will have loads of thrust but not much speed, which is exactly what you need. 

I also had the ASM Hercules and flew that on 4 asp 30 4 strokes. They ran 10x5 props and while very ponderous (ie, scale) it flew very well. 

http://www.janhermkens.nl/

Edited By Jon Harper - Laser Engines on 06/10/2017 08:50:37

Matt Yorke06/10/2017 09:18:19
14 forum posts

Thanks Jon.

Percy Verance06/10/2017 17:22:11
avatar
7918 forum posts
152 photos

It would probably fly perfectly well on two .52's, with freewheeling props on the outers. At least that way there would be slightly less complexity and fiddling with engine starting/mixture setting. Mind you, those Aerotech jobs were no lightweights.........

I once flew with a chap whom had an Aerotech WW2 job - an ME109 iirc - and that posessed all the gliding qualities of a manhole cover.

Edited By Percy Verance on 06/10/2017 17:26:36

Denis Watkins06/10/2017 18:06:27
3597 forum posts
166 photos

Matt, the Saito 40s are more powerful than the published figures portray, but are very expensive. The model is 15lb, and a .52 will fly 6lb, so you are in the ball park there.

So the choice is to blow the expense and 4 stroke the power plant

But I would be tempted, to fit the .40 2 strokes, just to get to know the model in the air.

Matt Yorke06/10/2017 18:22:29
14 forum posts

The whole purpose of the project is "just" to run a real 4-engined aeroplane.

I guess it's sad but true that IC motors, especially smaller ones, are dinosaurs. Personally, all my vehicles are just containers/transport for the engines - I think electric is awesome for ducted fan applications, but a prop driven aircraft needs an engine. IMVHO.

I don't think I've ever got rid of an engine - somewhere there's the merco 35 I had in my Super Trainer as a kid (and the Sprengbrook Sportsman 27Mhz RC) - and I've still got the scar from the 11 stitches in my finger it gave me.

But it was start - I've just come in from the garage where I'm building a 9.1 litre motor at the moment.

Percy Verance06/10/2017 19:09:33
avatar
7918 forum posts
152 photos

I'd have to respectfully disagree there Matt. I think EDF models tend to be a tad on the noisy side. Much of the idea behind electric flight is surely to lose the noise, or have I missed something? And there are now sites at which i.c. models cannot be operated for that very reason. But hey, a lot of people do love their engines.

I still have two Mercos I flew with back in the 70's. Only 11 stitches? Eighteen was my grand total in an argument with one of my (smaller) engines....... I don't have many engines since I sold 40 odd of them a little while ago.......

 

Edited By Percy Verance on 06/10/2017 19:13:32

Matt Yorke06/10/2017 19:23:43
14 forum posts

That's a fair point regarding noise, Percy, and certainly a strong argument for electric.

But I still like engines....

Denis Watkins06/10/2017 20:54:58
3597 forum posts
166 photos

Am just the same Matt, the planes are just a vehicle for my IC motors

But as you know, the challenge is to add electronics and mechanisms in such a way

That beautifully shaped balsa, supports a skin long enough to get airborne

Jon - Laser Engines06/10/2017 23:08:45
4570 forum posts
168 photos

setting the engines on a 4 engine model is much easier than a twin. just run each one on its own, tune it so its happy and turn it off. do the same for its 3 mates then refuel, start the lot and go fly. don't bother checking if they are in sync, just get on with it.

if one is a bit fast the effect is nowhere near as pronounced as with a twin, and if one stops just ignore it and fly on the other 3. don't cut the opposite engine to the one that stopped as you are then down to two engines and not 3 which is much more dodgy.

Paul Marsh07/10/2017 15:14:03
avatar
3605 forum posts
1007 photos

I bought a kit years ago, but never built it. I reckon I was going to use 4 x 52 four strokes. I have built the wing and fuz, but needs repairing, but never did.

I have a full set of ABS parts I might sell, if anyone's interested, and/or the remains of the kit I started.

Matt Yorke07/10/2017 18:27:47
14 forum posts

Having spares would be handy - where are you based?

Paul Marsh08/10/2017 10:59:44
avatar
3605 forum posts
1007 photos

Cheshire. Nr Stoke-on-Trent.

eflightray08/10/2017 15:43:27
avatar
560 forum posts
127 photos

I have a scratch built B-17 at 100" span and electric powered.

b17-42.jpg

Foam core wings covered in brown paper, the rest is balsa, 10lb - 2oz flying.

 

Fairly old video, but she's still flying. -- (click on the title to see it on Youtube)

 

Ray.

 

Edited By eflightray on 08/10/2017 15:45:41

Matt Yorke12/11/2017 07:44:26
14 forum posts

Thanks everyone for the input. Quad Saito 40s are on order......

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