MalcolmX

produce enough thrust for a 84'' long Vulcan bomber made from balsa, or even a smaller 63'' long Vulcan

https://shop.traplet.com/product.aspx?c=2840

i'm sorry if this is a stupid question, because my guess is no, but i need to know before i start building.

thanks

Ken Jack

Hi,Mal ,I think you have made an error in your question as you probably mean 84 inches long instead of 84 feet long.Also you need to inform us what DF units you intend to use. hope i can help you,regards ,Ken Jack

MalcolmX

sorry, i've just corrected that first post.

i was thinking of fitting Electric ducted fans, to either an 84'' version or a smaller 63'' version, but it looks like they wont produce nearly enough thrust, because i've been looking online for ages and i can only see EDF being used in much smaller aircraft and never once in anything big..... the size of EDF to use, i'm not sure; dont know enough about it, that's why i'm posting here.

i think the Vulcan will weigh between 12 and 20 lbs, but it looks like i'll have to use standard Electric motors, like this one linked below
http://www.youtube.com/watch?v=xs_lt...eature=related

gunradd

My Feedback: (9)

Well I have seen a 52 pound flyeagle F14 fly on electric so its more then enough for your plane.

MalcolmX

I've just spoken to an RC Shop and it will not fly with twin electric ducted fans, it's far too heavy, normal motors or turbines only.

he said, even the most powerful 100 mm ducted fans might not work, the only way it'll fly is if i built as a lightweight glider, but definitely not as a balsa and plywood model.

gunradd

My Feedback: (9)

I have a 18 pound yellow F16 that does 160mph on electric and thats with only one fan. So your project is very doable in electric. You are not looking at the right fans. It looks from the pics that you would not have alot of room for a bigger fan but the TJ100 would be a good fit it looks like or maybee twin stumax fans wich I saw in a big jet legend F15 and it went over 160 mph and its a huge plane that was only ment for turbine.

MalcolmX

http://www.espritmodel.com/index.asp...D&ProdID=11510

OK, you're totally right, the guy i spoke to didn't know enough about EDF, now this fan or similar will be excellent, two will be perfect.... the important thing is, it produces over 12lbs of thrust for each fan, this is a hell of a lot; compared to the ones that i've seen.

but this means due to their size, that i'll have to build the larger Vulcan bomber, or there wont be enough room, it'll look far better on a larger scale anyway

OK so it's doable, but i now have to make my mind up; because these fans are quite expensive.

whatever the case, i can still build her and make my mind up about the engines later on, i'll have to build a large access panel around her bomb bay, because my guess is; she'll need a ducted fan on either side of her bomb bay, but i wont know for sure till i redraw the plans to a larger scale, at 85'' long; she'll be massive.

this is going to be quite interesting.

MalcolmX

also, i'll need to make sure that the intake and exhaust area is smooth and large enough, with no sharp edges; to maximise airflow ?

because i've read about this already, this also points to a larger model.

i've scaled her up by an extra foot and it's not worth the bother redrawing the plans, so i may as well make her 2 foot longer; but any larger than this and she'll be too big to fit inside my car !!

the plans are arriving soon

Ken Jack

Hi Mal ,Go for it as i have seen very large models powered by ducted fans similar in size as your vulcan.Ihave a 108 inch Horton 229 which is powered by 2 Hobby King 4.5 inch ducted fans .Regards Ken Jack

MalcolmX

i have to wait a week for the plans, but in the meantime i have to find electric servo assisted retracts, i saw them the other day, because i dont want to use compressed air ! i'm after airliner style retracts..but nothing too fancy or expensive

i want EDFs because they sound far more realistic than normal props, plus twin props dont look right on the Vulcan.

i dont plan to fly her this year, so i'm in no mad rush, because i have to ``train first`` on a cheap Parkzone foamie, plus she'll be too expensive to finish this year; especially buying the EDFs !

i think i'll make her 84'' long, but the really massive ones ( about 3 of them) are 9ft long,even so; she'll still behuge.

the way i see it is, 63'' long is too small, i want her to feel and fly heavy; justlike she looks at the AirShows herein the U.K, TOTALLY AWESOME.

MalcolmX

i've found retracts, either the 787 dreamliner or the EDF DC 10, the DC10 ( 4 wheel bogie) retracts are larger at about 4.25 inches long, but these might still be too small for the Vulcan, if so; i'll fit retracts from a P51 mustang or something similar, i'm not that bothered, because it's the aircraft whilst flying that must look realistic.

she'll need a large access panel on the top to allow me to maintain the EDFs, the bomb bay isn't large enough, because the engines will be on either side of this.

this centre section of the fueselage has to be clear space, so i cant attach/join the removable wings from one side right across to the other, she'll have to have a reinforced ``belly pan``, with two vertival sides that meet the roots of the wings, this'll have to be very strong.

the plans are only any good for the basic dimensions, they're no good for the internal layout, the fueselage centre has to be totally different on mine, this is going to be a real challenge.

MalcolmX

http://www.hobbycity.com/hobbycity/s...idProduct=4242

this EDF is dead cheap too, miles more so than the others, two of these will be great for the Vulcan, combined thrust maybe about 18lbs

thanks

gunradd

My Feedback: (9)

just dont use to much power with those rotors. Bottom line you get what ya pay for.

grbaker

My Feedback: (29)

Like this one?

Merlyn Graves Avro Vulcan Bomber powered by
4 of JMP's Dynamax fans and OS 91's

Ken Jack

Hi ,Mal . You need to do some modifcations to the HK 4.5 inch fan and if you go to Hobby King forum under electric ducted fans you will see how i modified them.If you need more info on mods ,and also motors and mods to them .Regards Ken Jack

MalcolmX

thanks everyone.

with regars to that 4.5'' EDF, i'll do far more research when i'm close to buying and i'll reference that thread as well, because at the moment i dont know exactly how much room i'll have etc.

i wont be buying the EDFs till the summer or even later, because it's the last items that i'll be fitting, i just need to leave loads of room for them

that photo is of the 9ft version, there are about 2 others at that dimension, mine will be about 2ft shorter, that vulcan looks massive in that photo, way too big for me.

MalcolmX

http://www.edfmodel.com/309-airliner-xidc29308.html

please take a look at these DC 10 rear retracts, they're about 4.25 '' long; from the outside of one wheel to the other, now are these large enough for a 7ft Vulcan? and will they sell them to me? ( because i wont know till i get the plans, in about a week's time)

the DC10 is 69'' long, so it's 2 ft shorter than mine, damn it; even so it might still be ok, the alternative is to machine the parts myself, but only if i can design it cheaply.


but these 787 retracts look too small

http://www.ejf.com/images/wrLG1b.jpg

these retracts are going to be a pain, do i go for realism or not !!!!

MalcolmX

plans arrived today, she's big !

MalcolmX

Which produces more power, 4 x 55 mm EDFs or 2x 70 mm EDFs, because i'm not sure which route to take, she'll weigh about 10lbs?

but if she has twin 70mm EDFs, the exhaust tube dia will have to taper down from 70mm to 55 mm, over a distance of about 12'' ( to keep her in scale)...................but no taper required for a 55mm

i think i'll build her as per the plans, 63'' long

gunradd

My Feedback: (9)

you want the exhaust to taper down some to accelerate the air. For the most part about 80% reduction is good.

MalcolmX

oh great thanks, it looks like 70 mm then

MalcolmX

i spoke to someone recently, the Vulcan bomber has to be twin Lander 70 mm, the laser cut wood is arriving this week; so i'll start making her as soon as possible.

i've downloaded jet sound effects, by God it's as loud as hell, i've alsomanaged to get a recording of the infamous ``Vulcan Howl``, now she'll have two spare jet intakes, so i might fit a speaker into each intake, beside the EDF's................. but this will depend upon how heavy she gets.

i'll be saving weight due to no retracts, so this might be ok,not sure yet.

http://www.youtube.com/watch?v=CW06W...eature=related

THIS AUDIO IS GREAT, no background noise, kids screaming or wind sound, so i can edit this audio onto another one.

MalcolmX

whilst waiting for the laser cut ribs etc for the vulcan to arrive, i'm presently building an ``art tech jet tiger`` style of aircraft, she's very similar to the vulcan.

she has a 38'' wingspan and will have a 700 W Lander EDF, she should be very fast, i'llfinish her as a stealth type fighter, dark grey or similar.

watt_the!

it depends on what rpm you have..but for the record, a larger diam fan puts out more thrust than a smaller one for any given power...but it isnt a noticable difference (need to measure as opposed to "watching".)

to answer your question though, 4 x55 mm fans, assuming hub is same or similar size to the 70mm fans will make more thrust/absorb more power.

calc the swept area and multip[ly by 4. do the same for the 70mm fan.

this also assumes the same number of blades.

as an example, a single 90mm fan will absorb more power and develop more thrust than 2 50mm fans..just...partly due to the relatively larger hub size (in proportion), but mostly due to small diam being less efficient than a larger one...again assuming same number of blades.

i would go for as many blades and as larger diam fans as i could get my hands on if i were you. speed will be sacrificed in exchange for thrust.

also, go for a fan that will absorb lots of power at relatively low rpm..that'll give you more efficiency, easier balancing, and more choice of motors.

but again that is a compromise.

MalcolmX

I am now building a single 68mm EDF Delta wing fighter, similar to the ART TECH Jet Tiger.

the Vulcan bomber wastoo complicated for a first build, i took on too large a project and simply got fed up with it...i kept making mistakes, twisted frames, crooked fueselage etc, i managed to correct the faults; but i finally lost heart a couple of days ago, i bit off more than i could chew.

but this one i'm building now is much easier to manage, far smaller and far simpler, i should have built this smaller modelfirst... gained experience and then built the Vulcan.

i will upload photos of her soon.