104 inch B-17 Identification

[Chris Walby]

Hi guys,

I am helping out another club member with a B17 that a late club member built and nearly finished.

I am after a set of plans and thought it was a design by Aerotech, but looking at these plans there are a number of things that are different, namely:

Now its possible the builder modified things, but I don’t think he did as my wing has working split flaps. Other differences are even more fundamental like:

• My wings are two piece, the Aerotech looks one piece
• My wings have two vertical tabs that go into the fuselage and bolt together
• My wings look fully built rib/balsa sheet, the Aerotech look like foam core
• The drawings show pins (into fuselage) and screws near the TE which mine does not have

Big question…any idea if there were any other B17 104 inch models available running 4 x SC52's.

There is of course a chance that he had it re-scaled but the ribs I can see are laser cut as they have ID number on them.
If any photos would help I can post

Any suggestions warmly welcomed as to where I can get a set of plans and a couple of cowls.

Thanks for your time

[eflightray]

Aerotech used to do a 1/12 (104" span) scale B-17 kit, but it was a while ago.

.

[Martin Harris - Moderator]

It was obtained from the USA if that's any help.  Mick E had quite a lot to do with this model - have you asked him?

Try searching for 12th scale or 103".

It was built from a (laser?) cut part kit.

Edited By Martin Harris on 12/03/2019 20:24:09

[eflightray]

Just spotted this thread -- Aerotech B-17

.

[Chris Walby]

Hi,

I obtained a set of Aerotech plans....see my OP as its not at all close to that....I suppose Brian might have changed the wing material, flaps, wing to fuselage mount and main spar design, but it would seem a lot of effort unless Aerotech made two versions with the same wingspan model?

Rib numbering is different, could have been a resized and laser cut, but then I don't know if he used the plastic parts on the fuselage. Two of the cowls are the right size!

 

 

Edited By Chris Walby on 12/03/2019 20:27:59

[Martin Harris - Moderator]

Aeropak B17?

[Chris Walby]

Martin, could be...not sure about spending $60 just to get a set of drawings...

Edited By Chris Walby on 12/03/2019 20:41:03

[John Duncker]

Keep posting here Chris.

I would love to know if it flies.

I helped out with some of the changes he made but I do not recall if he made the changes to a split wing, I know we did discuss this when he was in the planning stage and we both thought that split wing was the way to go purely to make it easier for him and Carol to handle.

I know we did look at the possibility of a Royal B 17 kit and I think I tried to steer him away from this as he had a tendancy to build heavy.

But there has been a lot of water under my keel since then and my memory may be playing tricks.

[Chris Walby]

John,

Thanks for the information as even the odd snippet of information is useful. Martin suggested I talk to Mick as he assisted Brian as well.

I was surprised at how light the wings felt with a pair of 52's in them compared with my IC Seagull Mosquito, 3kg compared to 2.7 kg and its 20 inch less wingspan. Although I don't know the fuselage might come out as it could be on the heavy side!

I can see the logic as the Aerotech looks a one piece wing and must be a real issue transporting it about at 104 inches if the had gone for that.

Can you remember when Brian started the B17?

We get Brian's Vulcan flying on special occasions and that has marginal power and high wing loading, but its just great watching it take up the sky as Dave hauls it around for another Farnborough pass!

As you can see hopefully there is not that much left to do in 11 weeks if I get a move on as the fuselage is apparently complete its just finish off the wings!

[eflightray]

Nice model the B-17

My scratch built, (no plans), 100" span, foam core wing covered in brown paper, the rest is balsa. Plug in wings, and horizontal stabs for easy transport.

Electric power. The video was shot when she still had brushed motors, Olympus belt drives, and Nimh cells. She was eventually upgraded to brushless and Lipo, and shaved 2Lbs of the weight.

Current flying weight is 10Lbs - 2oz, Still fly her occasionally.

Ray.

[cymaz]

This is any good ?

[Chris Walby]

Thanks cymaz, looking at some of their build photos it looks the closest so far although I am not to sure they would do a special 12th scale version with the cowls etc.

I'll see if Mick's about at the weekend...not likely to be much flying!

[John Duncker]

2005 would be about right for a start date. When I last saw him at his workshop he had both wings complete and we did a trial fit of the joiners and that would be the summer of 2007.

I am glad the Vulcan is still flying. It was marginal off grass but once airborne flew very nicely.

Did Mick get his Hunter flying? I am blown away by the performance of these lecky fans.

[Chris Walby]

JD, Thanks for the info, hadn't realised he had been at it that long with the B17, still have some time with my DC3 then! The Vulcan I have (Brian's) is twin electric pusher as he had a IC prior to that. Marginal is an understatement as it takes 20 yards of bungee at over 50 lbs of pull to get it into the sky and about four major rebuilds to iron out the issues.

I understand the Hunter went in on its maiden, not sure the cause as I was not there.

[eflightray]

Build light. they fly much better.

Sorry the video is so poor, I forgot to check and clean the lens.

82" span, 8Lb - 15oz flying, under 600 watts total.

Ray.

[Chris Walby]

Progress is almost completely good news, regarding missing bits etc.

A club member had the missing cowls and better still Brian has detailed the Starboard inner cowl (no3) so that makes life easier.

I have obtained the glass sheet to finish + 2 of the 4 silencers.

Made a wheel spindle and fitted some 100mm wheels

Dave found the ailerons and they are covered so that's good

Found a photo of the fuselage from a couple of years back (I haven't seen it since) but it looked good then.

Only sticking point at the moment is getting hold of four sets of Robart U/C air line quick connectors (white) that seem to be out of stock in the UK.

If anyone has any please PM and I'll arrange suitable payment

[Chris Walby]

Getting ahead of myself as I don't have the fuselage, but was wondering what people suggest as RX set up for something this size/complexity

It will have dual battery, dual switches or switch with fail over.

1. Throttle
2. Rudder
3. Ailerons
4. Elevators
5. Flaps
6. Gear - air

Now my mosquito I have engines and gear (mech with servos) set up on separate channels as it makes life easy adjusting each if necessary.

So could go for as I have a 8 channel TX (DX8 g2)

1. Throttle (engines 1 and 4)
2. Throttle (engines 2 and 3)
3. Rudder
4. Ailerons
5. Elevators
6. Flaps
7. Gear - air

Now someone mentioned using two 6 channel RX's, but I can't see the benefit unless to use two TX's (and have a helper).

Ideas anyone?

 

Edited By Chris Walby on 19/03/2019 22:50:25

[Jon H]

Keep it simple. The more complicated you make it the more likely something is to go wrong. Although the model is big its not heavily loaded and will basically just float about. it is only as complicated as you make it.

I had an ESM Hercules of 100 inch and it had one rx, one battery (a good one), one switch and then y leads to the dual elevator, aileron, flap servos. Throttles were done with y leads into y leads.

Each throttle was as close to mechanically identical as possible but i didnt loose sleep over it. On a 4 engine model the effects of one engine running slow/fast are not as big as on a twin. Indeed i lost one on the herc once and didnt even notice until i did a flyby.

In the instructions for the herc it recommended to set up the throttles on two channels so the inner and outer engines could be controlled individually. The theory was that if one engine stopped you would kill its best mate. This struck me as daft as you are turning the loss of one engine into the loss of two. If another drops you are really screwed! The only time i would consider killing the engines on a 4 engine model it would be if i lost two engines on one side. I would try and keep it flying, but i would be prepared to cut it.

If you do use dual rx's make sure the throttles are on a different rx to the rudder. The reason for this is that if you throttle rx drops and you have to wait for it to run out of fuel you can guarantee one engine will keep going longer than all of the others. In this case you will need rudder control to keep it pointing the right way. Equally, if you have throttle control rudder is less of a concern.

[Dickw]

Posted by Chris Walby on 19/03/2019 22:49:07:

Getting ahead of myself as I don't have the fuselage, but was wondering what people suggest as RX set up for something this size/complexity

It will have dual battery, dual switches or switch with fail over.

1. Throttle
2. Rudder
3. Ailerons
4. Elevators
5. Flaps
6. Gear - air

Now my mosquito I have engines and gear (mech with servos) set up on separate channels as it makes life easy adjusting each if necessary.

So could go for as I have a 8 channel TX (DX8 g2)

1. Throttle (engines 1 and 4)
2. Throttle (engines 2 and 3)
3. Rudder
4. Ailerons
5. Elevators
6. Flaps
7. Gear - air

Now someone mentioned using two 6 channel RX's, but I can't see the benefit unless to use two TX's (and have a helper).

Ideas anyone?

Edited By Chris Walby on 19/03/2019 22:50:25

I am guessing they may be doing that to gain some redundancy using two 2 Rx each with its own power supply. e.g :-

throttles 1 and 4 on 1. Rx1, with 2 and 3 on 1. Rx 2

Rudder on 2. Rx1

Split the ailerons between 3. Rx1 and 3. Rx 2

Elevators – use two servos on 4. Rx1 and 4. Rx2

Flaps 5. Rx2

Gear 6. Rx1 or Rx2

If either Rx fails you still have throttle on 2 engines, plus one half of ailerons, and one half of elevator. Rudder, gear, or flaps, either work or don’t depending on which Rx fails.

Dick

[Chris Walby]

Jon,

I see your logic and agree with keeping it simple. The Dual Ace has two batteries and a single fail over switch, the mossie single battery and no switch (as its easy to open the canopy to connect) and the hurricane single battery. All only have one RX.

Sounds like one good size RX battery with switch (of darn good size), one RX and keep it simple.

Struggling to see the benefit of only two throttle channels for setting up as either 4 channels would help (but don't have that many free) or a Y and a Y as a little unbalance does not seem to be an issue.

I'll knock a drawing up see how things go down.

PS Quite like the Hurricane power box arrangement as it has a fail safe switch.

[Jon H]

If you want true redundancy then the twin rx method is the best way. Dual batteries are great in theory but you still have a single point failure in the rx.

Twin rx's with a battery each is a better way to go and as Dick rightly points out you can split things. I would go right aileron left elevator, the two outboard engines and rudder, and gear on one rx and everything else on the other.

That way you have throttle control in both cases, but if you loose the inner engines and have to run them out of fuel you might need rudder to balance the outers as they have more yaw impact.

You also get undercarriage or flaps for landing.

In all honesty though i would go for a normal single rx setup and just make sure its all good stuff. Most failures come from poor maintenance and while there are unexpected failures they are rare.

Just for info, i have lost 3 models to radio gear failure in 25 years of flying. Two were swash servo failures on my heli, and one was a rx failure on a galaxy mustang. None of these were predictable and only the rx failure could have been covered off by a dual rx system.

[Martin Harris - Moderator]

Posted by Jon - Laser Engines on 20/03/2019 08:44:42:

In the instructions for the herc it recommended to set up the throttles on two channels so the inner and outer engines could be controlled individually. The theory was that if one engine stopped you would kill its best mate. This struck me as daft as you are turning the loss of one engine into the loss of two. If another drops you are really screwed! The only time i would consider killing the engines on a 4 engine model it would be if i lost two engines on one side. I would try and keep it flying, but i would be prepared to cut it.

Maybe they meant that you could idle the remaining engine rather than kill it, preserving balance while keeping the good engine in reserve?

I think Chris's question really pertains to the number of functions available from his transmitter. In this case, I could see a case for a co-pilot operating flaps, undercarriage, lights, bells and whistles via a separate transmitter.

From experience of twins, it is good to have isolation for the throttles for starting and ground running - you don't really want all the engines roaring away while you're making adjustments on one of them. Sadly, Chris's transmitter is unlikely to be able to accommodate that even if the non-flight functions are given to the co-pilot.

[Jon H]

Idle or off, its still turning a 4 engine model into a twin when it could be a triple. Is just a strange thing to do. Why give the power away? All that is likely to happen is you will slow down, try to bring the sleeping engine back into play and then crash as you are too slow to control the yaw by that point. Its better to leave it.

I have never used individual channels on my twins, and i personally have never found an occasion where it would be an advantage as any problem engines get run in isolation. Im not saying its wrong to mix them, i just have not found the need.

As you rightly point out though mixing 4 is likely to be a problem!

On the Herc i started each engine and set it up. Then set up its best mate and so on. I then started all 4 and went to fly. I didnt bother checking revs and made no effort to match them in any way other than the original mechanical setup. Its just not as important as on a twin, and both the herc and B17 have massive fins/rudders so directional stability is likely to be very good.

At 100 inch i think its a bit small for copiloting to be considered. 20 feet maybe  

Edited By Jon - Laser Engines on 20/03/2019 15:44:07

[Chris Walby]

Thanks Dick, that answers my question + everyone else who has contributed to the slightly wider discussion.

Benefit of dual RX, failure of one RX or failure of a servo (short circuit) shouldn't take the other RX out

Down side, more complexity with split wiring and extra pre flight checks

Everything else looks like a single point of failure will result in an inconvenience (loss of one engine) or uncontrolled loss of the model (TX failure).

This just leaves me with a personal question, would I spot two engines not responding (full, partial or dead) one aileron not responding and partial elevator control before I intervene and save it. For me I would go for single RX and just make sure everything is double checked before flying (PPPPPP )

Dave can have the final word as he'll get to do the maiden, just now I fully understand the rational for twin RX

Thanks for everyone's time.

PS until you can have full duplex redundancy, dual TX all the way through to a fully controllable model following any single point of failure I am not convinced doubling up some parts add benefit without complexity/greater risk of failure.

Think I'll go and have a look at the LMA's +20kg requirements and see how they deal with it, but for this its OTT.

Edited By Chris Walby on 20/03/2019 18:40:00

[Jon H]

I helped out with an over 20kg spitfire. Dual Rx's with a battery each was deemed totally acceptable.