Retract Angle - Electron Retracts

[Ariel]

Eyeing up some Electron retracts for what will be a 72" wingspan Spitfire Mk1a. I was wondering what the correct angle and Turnnion pin hole size would be? At the moment I think 95 degrees and 8mm for the hole but obviously dependent on what size legs I come up with. What are the implications of using 95 rather than 90 degrees? I think 90 degrees will splay the legs out due to the dihedral but will 95 be too much 'correction'. Trouble with being in France is that I can't easily go and look at a Spitfire!

 I'm hoping to come in under 8Kg which would suggest the ER-30 but there is an argument for going for the ER-40 (8 to 17Kg) to leave some wiggle room just in case. I'm in France for a few more weeks so now would be a good time to buy them to avoid being fleeced by the couriers for sorting out the import duties.

Any thoughts? Thanks.

Graham

 

https://www.electron-retracts.com/product/er-30evo-seta/

https://www.electron-retracts.com/product/er-40evo-set-a/

 

[Nick Somerville]

I have Er 40’s in my BT P46 which is just under 8kg and they are bullet proof. I am sure the 30’a would be more than adequate at 8kg. The benefit of the smaller units is that you have extra wriggle room to adjust the mounts by 5 degrees to achieve the correct angle. 

[Jon H]

Full size Spits are 95 degree and that is the right angle. You might just get away with 90's but only if the pivot point was right at the wing skin. Buried in the wing as it will be 95 is the way to go and its what i will have on all my Spitfires. I agree with Nick that the 30's will be fine as long as you are not landing in a ploughed field or touchdown in a manor that would make a carrier deck landing look tame. 

 

 

As a curiosity, which 72 inch Spit are you building and which powerplant are you intending to use? I ask as not all 72 inch Spits are created equal and some end up very heavy. 

Edited August 23, 2023 by Jon - Laser Engines

[Paul De Tourtoulon]

There are a few Spitfires in France, where do you live ?.

[Nick Somerville]

Have you tried asking Electron if they can supply a set with 95 degrees rotation 

[leccyflyer]

Looks like Electron provide 95 degrees as an option. I hadn't heard of them before, but their units look the bee's knees, with a lot of options available.

[Jon H]

Electron are very popular with the jet boys i believe. A customer of mine has 95 degree evo40's in a fokkerc 1/5 Spitfire (88 inch) and he is very happy with them. Dont you have some electron gear Nick?

[Jon H]

If you want to get real fancy there are some very detailed angular drawings here https://forum.il2sturmovik.com/topic/56682-alert-need-spit-mkxiv-info-for-landing-gear-bay-and-struts/?do=findComment&comment=931978

 

Most of the detail is useless for our purposes, but its interesting none the less

[Ariel]

Thanks for the replies. 95 degrees it is and good to hear positive things about the EV-30. I will ask Electron as I think they are back from the annual shutdown now.

I absolutely loved the detailed undercarriage drawings. Thanks for the link Jon.

I'm thinking about the Laser 155 for power. I will call you to discuss and order when I get back to the UK. Assuming you think that is the way to go. Pity the 120 is no more. It absolutely has to fit inside the cowl.

As to which one it is......well, it's my one! I'm drawing it up from scratch. Yes I know it will probably end badly but faint heart and all that.

There is a wealth of knowledge in this forum and lots of folk prepared to help so why not? 

I'm near Brantome in Perigord (24.) If you know of any in the area I would love to know. Otherwise it's Hendon in November.

Thanks all for taking an interest 

Edited August 23, 2023 by Ariel

[Mike T]

I bought the 40 series 95° units with 10mm trunnion bores for my Aviation Design (83") Spitfire.  They are 'Rolls-Royce' units for sure and you need to buy the bespoke controller to operate them.  I intend to machine my own scale(ish) oleos for them 😱

 

Edited August 24, 2023 by Mike T
degree

[Nigel R]

Ariel, this may be useful reference?

 

https://outerzone.co.uk/plan_details.asp?ID=4644

[Ariel]

Mike, good to know you are pleased with them and the trunnion size is useful too. I was thinking about whether bigger is better or less is more. Did you get one of the 200 series controllers or do you mean the manual control unit for setting up without the radio?

 

Nigel, thanks for that, it is useful. I'm using this as my reference at the moment  http://soyuyo.main.jp/spit1a/spit1ae.html He's a plastic modeller and does seem keen on detail so I am inclined to think it's accurate in terms of shape and the best Mk 1a drawings I have found so far. 

I'm drawing it up in Fusion 360 and driving myself quietly nuts trying to get the curve of the nose/ rocker covers right. After the wing it's what makes a Spitfire a Spitfire to my eye.

Thanks for the info guys.

 

[Jon H]

Nothing wrong with an own design. Spits are generally well behaved as models in my experience. I know that is contrary to popular opinion but i think the waters were muddied by the old/heavy 55 inch class Spits of days gone by and an expectation that they would fly like the wot4 or acrowot the pilot had just come from. 

 

Assuming a span of 74 (74 being exact 6th scale) and a weight of 14-16lbs a 155 would be spot on. You could even try our 160 or 200 inline 😉 

 

Cowl fit should not be a problem for any of the engines. A 155 is shown plonked on the Mick Reeves 6th scale plans below. The plastic box is my pretend fuel tank and shows where the tank needs to be installed. The wing will need some mods to accommodate it but its hardly a big job. If the inline is your preference, imagine everything forward of the wing leading edge chopped off. Engine on the front, cowl on top. Internal mods needed for cooling, tanks etc but the details of that can wait for now. 

 

 

[Jon H]

1 hour ago, Ariel said:

I'm using this as my reference at the moment  http://soyuyo.main.jp/spit1a/spit1ae.html

 

These drawings are great, i have used them for reference before 

[Mike T]

6 hours ago, Ariel said:

Mike, good to know you are pleased with them and the trunnion size is useful too. I was thinking about whether bigger is better or less is more. Did you get one of the 200 series controllers or do you mean the manual control unit for setting up without the radio? ...

 

I got the ER-40 units and the 200 controller only.  It was expensive enough without adding on 'luxuries'! 😄.  Mine is far from flying (the units are still in the box, though the controller and peripherals are all plumbed-in).

[Ariel]

It's a lot closer to flying than mine is Mike! Was thinking the basic controller would suffice as there are no doors or anything to contend with. Is it the RS200 you have and does that allow you to slow the retract speed and add  delay between the two legs? I believe it's 2 seconds to cycle from up to down but I can't imagine what that looks like in reality. I will email Electron and see what they say.

 

155 looks perfect Jon and thanks for the picture too. That gives me some guidance. I'm working on the principal that in the ideal world you would start with the engine and tank and hang an aeroplane off it. If I can think about cooling and wing mounting at the same time it  may well save all the hacking about that seems to be an issue a lot of the time. The advantage at the moment is that it's all in a drawing so I can change it to suit.

Speaking of fuel tank position, as many do, is there any reason not to have a wider, longer and flatter tank i.e same volume less depth? I haven't really thought that through but if it's not a total non starter for some reason then I will.

Don't know where 72" wingspan came from. I have it as 1871mm or 73.664 inches in my drawing. The discrepancy  could be from scaling the Canvas in Fusion. Now that really is a steep learning curve!

 

[Jon H]

3 minutes ago, Ariel said:

I'm working on the principal that in the ideal world you would start with the engine and tank and hang an aeroplane off it.

 

Yep, pretty much. In the model world we tend to do things the other way round and that causes issues. As you are working from scratch, you could design it to mount the wing to the fuselage on the main spar and not the leading edge as is most common. This means you can chop out the leading edge under the fuselage and use it for tank space, cooling etc. 

 

a wide/flat tank is sometimes problematic as you can have loads of fuel left but its only a few mm deep across the wide tank and the clunk struggles to pick it up without also drawing air. A tank that is wider than it is tall is good though as it minimises change in fuel head so there is a balance to be had there.

 

A long tank can be an issue if the clunk is at a back of the tank and you are nose down with say 1/3 tank of fuel left. The clunk is high and dry so the engine stops....ask me how i know. You could shorten the clunk tube but you then risk the clunk running dry in a climb instead/as well. Again, a balance needs to be found. 

 

Given the space available in a 6th Spit fuselage i doubt you can make a tank wide enough or long enough for it to be a major concern. 

 

If you use a 155 12-14oz of fuel is all you need. Especially with the new low oil juice we recommend. 

[Ariel]

That's pretty much what I was thinking, hence the interest in retracts now rather than when I have built a wing. I want a strong light box that mounts the engine, tank, wing and retracts with a Mk1 Spitfire around it. How hard can it be???! I'll let you know.

What you say about the wide flat tank idea makes sense when you see it written down. Useful to know about the tank size too. That's another thing less to speculate about .

So, we have concluded:

Laser 155

12 to 14 ounce fuel tank

Electron Retracts

The drawings I'm using are good to use

Thanks everyone. 

[Mike T]

It's actually the (white) RB-45 controller I have, which has inputs/outputs for trike u/c plus brakes and nosewheel steering.  No differential timing, no gear door inputs/outputs.

[Ariel]

Thanks for the Reply Mike. I think the RB-45 will do trick. I emailed Electron to ask what they recommend so we will  see what they say and think about the cost benefit.