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Old Dec 20, 2011, 06:25 AM
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Letchworth, Great Britain (UK)
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27" wingspan f16

I've got a couple of Steve Shumate's foamy pusher-prop jets (F14 and F15) and for a while have been thinking about building a similar-size EDF-powered model. Since I've had a bit of experience doing fibreglass moulding, my idea gradually evolved to a fibreglass monocoque fuselage with a small number of liteply formers.

A question on this site http://www.rcgroups.com/forums/showt...&highlight=f16 got me a lovely set of sections produced by PPLJR from, I believe, an original manufacturer's drawing. A free CAD program, Bentley View, enabled me to print out the sections at an appropriate scale.

Further questions got me confirmation that the actual scale intake duct area was just right for a Wemotec mini fan, and suggestions for motors that would give me more power on 3S than I currently get with the same fans installed in my Learjet.

Since Wemotec offer a 280mm long exhaust tube for the mini fan, I'm planning to clone it in fibreglass and use it as the structural spine for mounting and aligning the formers for the rear part of the model. But for the moment I'm concentrating on building a solid mould from which to form a fibreglass mould for top and bottom fuselage skins.

I've printed out the long- and cross-sections, glued them onto 3mm liteply, cut them out neatly, and then assembled the cross-sections on the long-section at their appropriate locations. Now I'm glueing 2.5mm soft balsa strips between the sections to form a skin, which will be sanded down using the liteply sections as templates.

Attached are a couple of photos of progress to date. First one is some of the cross-sections being glued on, and second one is after they're all on and I've started filling between them. I can see there's going to be a lot of work filling and sanding before I've got an acceptable finished surface for moulding, but I think I'm up to it

Constructive criticism will be welcome. I'm a slow builder, but I'll update from time to time.
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Last edited by abenn; Dec 29, 2011 at 01:39 PM. Reason: Misleading title; 40" is the length of the fuselage.
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Old Dec 20, 2011, 09:40 AM
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United States, TX, Grand Prairie
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Quote:
Originally Posted by abenn View Post
I've got a couple of Steve Shumate's foamy pusher-prop jets (F14 and F15) and for a while have been thinking about building a similar-size EDF-powered model. Since I've had a bit of experience doing fibreglass moulding, my idea gradually evolved to a fibreglass monocoque fuselage with a small number of liteply formers.

A question on this site http://www.rcgroups.com/forums/showt...&highlight=f16 got me a lovely set of sections produced by PPLJR from, I believe, an original manufacturer's drawing. A free CAD program, Bentley View, enabled me to print out the sections at an appropriate scale.

Further questions got me confirmation that the actual scale intake duct area was just right for a Wemotec mini fan, and suggestions for motors that would give me more power on 3S than I currently get with the same fans installed in my Learjet.

Since Wemotec offer a 280mm long exhaust tube for the mini fan, I'm planning to clone it in fibreglass and use it as the structural spine for mounting and aligning the formers for the rear part of the model. But for the moment I'm concentrating on building a solid mould from which to form a fibreglass mould for top and bottom fuselage skins.

I've printed out the long- and cross-sections, glued them onto 3mm liteply, cut them out neatly, and then assembled the cross-sections on the long-section at their appropriate locations. Now I'm glueing 2.5mm soft balsa strips between the sections to form a skin, which will be sanded down using the liteply sections as templates.

Attached are a couple of photos of progress to date. First one is some of the cross-sections being glued on, and second one is after they're all on and I've started filling between them. I can see there's going to be a lot of work filling and sanding before I've got an acceptable finished surface for moulding, but I think I'm up to it

Constructive criticism will be welcome. I'm a slow builder, but I'll update from time to time.
VERY nice work,

do you mind linking a PDF of the formers?

I would love to make an 84" F16 EDF with a 5 inch fan
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Old Dec 20, 2011, 01:18 PM
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Letchworth, Great Britain (UK)
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Sorry, duplicate post.
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Old Dec 20, 2011, 01:19 PM
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Letchworth, Great Britain (UK)
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Thanks erh7771. The camera does lie, for it looks much rougher in the pictures than it does "in the flesh"

rick.benjamin did a set of .pdf formers in post #13 of my first link. But check the former that's 212.5 inches (actual) from the front datum, for its lower half seems to be incorrect (too large -- it stuck out like a sore thumb among its neighbours; you might be able to see it in the picture, it's the fifth rib from the start of the intake duct. Not rick's fault, for the error seems to be also on the original CAD file.). I've actually now cut out its bottom half, and planked straight between the 200 and 225 formers.
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Old Dec 20, 2011, 03:40 PM
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Disregard.
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Last edited by Lancer512; Dec 20, 2011 at 03:47 PM.
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Old Dec 27, 2011, 05:23 PM
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looking forward to seeing progress. subbed.
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Old Dec 28, 2011, 02:01 PM
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Lincolnshire, UK
Joined Oct 2009
522 Posts
3s on a 40" composite F16? Could be a bit asthmatic in performance. If you are using the Wemo Minifan (70mm) then I can assure you that with a HET 2w-25 running on 6s packs you'll have a good amount of thrust, say 1.6Kg or more depending on your ducting. I use this with 6s 3000mah 40c packs and a Turnigy 85A ESC and have installed this lot in the HET F16 kit. Now that's only a 26" span jet and it goes like stink but you're gonna be lugging around 2-3 times the airframe weight (more if you plan to have retracts) so what you should end up with is a jet with enough power to climb out safely and proceed at enough pace to give a satisfying and positive control feeling without being a real handful.

Just my $0.02

Si
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Old Dec 28, 2011, 04:45 PM
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I'de agree. I think I'de at least be looking at 5S. most know from experience how lame 64mm foamies can be on 3S and don't even come alive till you increase the cell count to 4.

Rich
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Old Dec 29, 2011, 02:37 AM
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Si and Rich, I have the option of 6S since I use them in my helis and some of my other fixed-wing models. But I've got a HET 4400kv motor (can't remember the number offhand) which is just about right for rpm on 3S, and I'm hoping will give me 700 watts or so. I'll get a better idea of where I'm heading weight-wise once I start moulding some of the fibreglass bits -- which is still some way off. No retracts though, it'll be launched off a dolly, I think, and will belly land.
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Old Dec 29, 2011, 05:43 AM
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Lincolnshire, UK
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700 watts isn't much on a big bird like what you're proposing. What batts do you have? Sounds like you may have the HET 1w-30 motor which is powerful but sucks amps a lot so you'll need lots of mAh in your batts - like 5000. You can go to 6s easy with a pair of 3s batts and I'm only proposing that you change the motor out for a 2w-25. GiantCod in the UK sell them for around 45. You'll need a fair bit of grunt to get off the ground with a dolly unless the surface is glass-smooth and very long.

Your build looks like it could be really good and I only want to help make sure you have the power system to make it work.
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Old Dec 29, 2011, 05:52 AM
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Just a thought, I had a foamy F16 by FMS with a span of about 28 inches and a flying weight of about 1000g. Power was from a 500-600watt 70mm fan unit running a 4s 2200 LiPo. The performance was okay, but nothing exciting. A real beginner-jet.

Hopefully this will provide some perspective.
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Old Dec 29, 2011, 01:39 PM
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27" wingspan f16

Thanks for your comments Si. It's the 1W-30 motor I've got. I'm planning for one or two 3S 3900mAh 25C packs -- probably it may have to be 2P to get the amps and duration.

Perhaps I've confused things by calling it a 40" model -- that's its length, so wingspan is about 27". I'll see if I can change the title.

I have no idea what the weight is going to be. Though I've had some experience with fibreglass, this is the first composite fuselage I've attempted. I'm hoping I can get it not much heavier than my Depron F14 and F15 pusher prop models.
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Old Dec 29, 2011, 04:27 PM
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Lincolnshire, UK
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Now that changes things! You are probably good to go with the motor you propose provided that the batts can deliver the current without the voltage sagging and dropping the rpm. 2 batts in parallel would give you the grunt but beware the weight. The size you are now proposing is about the same as the het f16 which flies fine on the 2w-20 and 4s 3-4000 batts. I've got no experience of the 1w-30 myself but beware that it is reported to suck amps and because of the low voltage and high current is less efficient than a higher voltage motor with similar output. Keep us posted.

Si

Ps, consider catapult launching: works for me!
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Old Jan 03, 2012, 02:37 AM
Aka: Tom Jenkins
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Palm Beach County, Fl.
Joined Aug 2008
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That 1W30 is a 1400 watt 4s motor, I think its like 4300Kv or close. Mine was the shiz on 4s but did do short flights with a fat jet. Needs a 120 amp esc for 4s. Will work on a good high C' 3s battery if the rest of the jet is light. 3s go with the 6905 het fan.
Don't go higher than 4s on the 1W30 !
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Old Jan 03, 2012, 06:44 AM
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I'm planning on 3S, ApexAero. I expect the amps to be somewhere around 70+, and plan to size my ESC accordingly -- Hobbywing Platinum 100A looks good to me. The motor's kv is 4400 according the spec I have.
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