Working on plans of 70" sport aerobatic job ... ULTRAWATT
First of - please bear with me and I know this is WATTflyer and not FUELflyer .. but I really love Wattflyer forum and hope you can share with me this adventure. The model is being set up for either E or Fuel ... so if anyone wants to build - you should have no problems whatever power you wish to put up front !
Online are copies of Colin Ushers plans which closely resemble classic UK models : Wot4, Acro-Wot etc.
There's a whole range to suit flying ability.
One of the best which follows on nicely from the hugely successful and agile WOT4 is the Acro-Wot .... see attached.
It literally combines sleek looks and ability of the WOT4, Edge etc. into a good sunday sport machine.
Similar concept was put together by Colin to produce the Killer-Watt ... a 58" model that will just about pull the stops out on most peoples ability with a 45 glow up front !
He then developed the MEGA-WATT which is 70" span based on a good 60 Glow.
I have a RCGF 15cc and also a 4850 650kv Aero motor sitting around doing nothing ... loads of foam ... loads of pine board ... alloy tubes etc. and a 2.4m x 1.2m sheet of WBP 4mm Ply..... and 8mm Marine ply.
So I converted the Megawatt PDF's to JPG ... and started work on them.... to create what I call "ULTRAWATT" ........
First was to modify so that the fuselage can take the power of a mega e-motor or the 15cc... this means PLYWOOD instead of balsa .. it also means finding ways to compensate to get weight back down again ...
Fuselage modifications :
a) Balsa sides amended to 4mm ply with lightening holes made between formers.
b) The Ply sides are the straight vertical side full length incl. wing seat.
c) Top curved decking is ply formers with depron folded over.
d) Bottom sheet is either laminated sheets of thin balsa or depron.
e) Tail feathers .. Fin, Rudder, Stabs, Elevators are to be laminated 3mm balsa - 3 sheets to make 9mm depth. This imparts great strength and allows easy hingeing into the central balsa layer.
f) Formers will be ply 4mm
The wing came in for the most work ... as I wanted larger shorter span ailerons so I could then fit flaps. This is work still in hand ... but basically the ailerons are 1/3rd span and flaps 1/4 ... The rear spar that on original plan that is angled back is now at angle that provides strength for the hinge line of ailerons and flaps. The size of which should allow extreme control and manoeuvres.
The wing tips were made more lined up with C/L and not swept and this made tip rib perpendicular with the others.
It is planned to fit alloy tubes into the wing halves set at slight cosmetic dihedral and allow the splitting of wing into two ...
The front dowels and rear bolts will need extra to assist with keeping such a wing together during extreme flight .. this being a large model.
Ribs will be a mix of depron 6mm and balsa, with main structural at centre / wing seat and tubes of ply. The ply mainly to add the required strength to carry the wing joint and fitting loads.
The cowl - I am going to try and secure a cowl from another model - preferably a Midget Mustang style .. with the cheek bulges. This will then help to blend in any fuel motors cylinder head etc.
I hope the airframe will have immense strength but little weight penalty ... and be capable of some entertaining flight.
The final finish I intend to revert to traditional methods with one exception ... no Dope. I will secure some ultra light silk from local dress-makers and the PVA this on as covering ... with final cosmetics via airbrush etc.
This is of course a longer term project than many of my others ... with the intention to have a model that I can show of at meetings ... to have something a little different from the EDGE, CAP, EXTRA etc. offerings so often seen.
If anyone has suggestions - then fire away ... even if I don't use them - don't be upset - all ideas are well worth it and filed away for later projects etc.
I hope someone else can have a go at this ... I reckon she'll be a real show stopper ...
If anyone wants the jpg files so they can hack at them - let me know ...
I tried uploading the wing plan as of now - but attachments keeps crapping out on it !!
NOTE : Plans are being worked on continuously - so even above may get changes before finished !
ULTRAWATT so far templates / halfwing
General idea of what I'm doing ... and templates ..
Wing - is only a half section and in jpg as attachments refuse to upload the full wing plan pdf !
OK ... I'm looking for HK based suggestions on E-Power for such a beast ....
Original Megawatt of 70" was with a 60 2str Glow ... which I have feeling may be a good size but for real performance - a larger may be called for.
My idea with the Gasoline is 15cc as minimum ... but lets look at E-power .. what to go for ?
4850 500kv + 6S ? Maybe bigger ? Or a 5S package ?
I'm looking for advice now as real large models + E-Power is not something I have experience with . give me a Wet Fuel model OK ... give me a small model and high watts OK .. but this is another realm.
Please keep to HK as I am limited on where to buy ..
Further work ...
I'm looking at ways to simplify and strengthen in one go !! Yes I know - not an easy task.
The wing is in original form - the standard top and bottom main spar affair with webbing.
So I have looked at how to get a simpler form and also gain strength .... the Egg-Box spar system.
I've attached a pdf of the spar and ribs to suit at full size ...
Wing also to be in two halves ... saves all that space when transporting ! Instead of plywood braces - I'm thinking of going for alloy tubes ...
Plywood rib at center and outer end of tubes. Oversize holes drilled ... there to be two tubes .. one on front of main spar and second at front of rear spars.
Join the wings with rod through the tubes and prop up tips a suitable cosmetic amount for removing that droopy look straight wings have ...
The tubes will now be at slight angle to wing-span C/L ...
With part ribs slotted to fit the tubes ... now glue the part ribs in place to the existing ribs, locking tubes at correct angle and location. Effectively closing up the oversize holes.
Now the question I have ... each wing half will have a front dowel and a rear bolt for fixing to fuselage. Are such enough to hold the wing together and in place in flight ? Comments please ?
I'm surprised at the lack of response from the general wattflyer readers. :oops:
You've probably seen my threads on this before, but here goes.
This thread lists a wide variety of gas/glow engines, and their power output compared to an electric motor power system. FYI, a 60 sized glow engine is very roughly equal to a 1200 watt electric motor.
Model airplane Power Systems
Thread on 70 size glow engine conversion to electric
Hacker 6S2P A123 powered Models
Hangar 9 Kantana Model
Hanger 9 Twist 40 Model
AEAJR's Site on Electric Power
BEC Linear Current Rating
And, these are heavier, higher powered electric conversions running 2000 watts plus.
Great Planes Giant Big Stick Electric Conversion (Over 300 flights so far)
Redwing MXSR Model (Over 80 flights so far)
When you get to this size model, and the power levels involved, IMHO it is wise to use an external switching type BEC, a number of them are available. And, for models costing over perhaps $1000 USA, it's wise to have dual receiver power for the receiver and servos. I've been using A123's (Or LiFe's) for backup power, and have drawings on how to do it. If needed, I can provide drawings. All it takes is a couple of 10 Amp diodes.
Second, you really don't want an accidental start of a motor of this size. If your transmitter has the capability, be certain to program in a throttle kill switch in your transmitter. For me, and my DX8 Spektrum unit, the gear switch is programmed as the kill switch.
Methinks you'll like those larger models with electric power. Last Sunday, I put on six flights on my two giant scale models. That includes 15 minute charge cycles on my 12S2P A123 battery packs. Not impressive, until I add that during this entire time, another club member spent the entire afternoon trying to get his gasoline 30 cc engine to start. And, after finally getting it started, it quit in mid flight, resulting in an off field landing.
As for motor quality from HK, I've not used them, with my models running with $$$$ Hacker motors, and one Hyperion motor. That Hyperion 1000 watt motor is nice! Again, when getting to this size model, IMHO it's not wise to cheapen up on the power system. One red flag on a cheap electric motor, is one that rates their motors at over perhaps 120 watts per ounce of motor weight. So, if you've got a motor rated at 1200 Watts, and it weighs 8 ounces, actually running it at 1200 watts might fry it!
Take the Hacker A50-12s motor. I've got three of them. Flawless. They rate it at a "Peak" 1700 watts, for maybe 10 seconds or so. This motor weighs in at about 12 ounces, and running it at the rated current of 70 Amps, it's putting out about 1200 watts. That's 100 watts per ounce of motor weight, a decent figure. Mine are only slightly warm after a hard flight. The motors are turning a 15X10 APC-E prop, pulling about 65 Amps out of a 6S2P A123 battery pack. They will haul an 8 pound model straight up, out of sight.
Hi Denny ...
Yes - I'm surprised at lack of response ... maybe they're afraid of me or big models ?
I knew you were into big models and was hoping for leads in from you.
The only problem is the only place to get Hackers in Latvia closed and funny enough it was where I found out about Hackers Far East ventures !
U-RC have the Hiperion range based on the biggies they sell ... guy who started U-RC in Riga is into big gasoline models and particularly those that cover E and IC in same frame.
I've been ordering up servos .. 40gr jobs ... looking at Rx and ignition packs as well as possibilities to double up LiPo's for E power ... I'm really sitting on the fence on this one ...
With regard to Rx power - that will be separate battery pack anyway regardless of whether IC or E ... I can supply higher power from a pack than a uBEC if needed ... so I'll go that route.
But my main point of the thread - to give a build thread that takes it from first concept - the plan stage and through all the thoughts, ideas, good and bad ... to the build and finally flight.
There must be loads out there who think about a bigger model but are afraid to have a go. I hope that what I do here can help people see that it can actually be as simple or even easier to do than a small model. No shoe-horning gear in ... plenty of room for gear ...
Just noticed this thread now. As for the bolts, I'd go to two bolts total.My hurri build uses no dowels, but the middle former is composed of essentially three former thicknesses, two balsa and two thinner plywood parts. This middle section extends past the shape of the wing, and seats into a slot in the fuse. I added a stringer piece at the bottom of the slot so the wing has no play in the slot. In the rear I am using two bolts. The mounting area is at an angle sloping down towards the rear of the plane, so as the bolts tighten then wing will be forced ever so slightly forward, making a tight fit. The design is very strong and in my view far stronger than dowels, for the former extension is very thick and doesn't actually need to support the weight of the wing as a dowel would. I would go with two dowels in your case. Of course it depends on how strong the wing halves are alone if you are making them separate. Two bolts total should be fine, and so should two dowels, but going to four dowels total may work better.
I cannot see how I could fit more than two dowels ... but anyway.
My question was to try and prompt ideas of how to join the wings more securely so the dowels and bolts were not only way of securing wing halves together.
I think they should be good enough for the job ... I may consider a way to fit a cover plate that extends similar to my ASK21 glider ... It basically locks the two halves together and then bolts go down through one end of it.
As I read your plans, and I might be missing something, this is to be a two piece wing with removable dowels at the leading edge. Removing these dowels will allow you to separate the two wing panels and remove both dihedral braces. I've got some thoughts on this arrangement if my interpretation is correct. If this is incorrect, please correct me.....
No the plans have FIXED dowels. Imagine centre section of wing is the joint of two panels. There would be a dowel in each leading edge an inch or so along from centre line.
Similarly a bolt in each panel at rear either side of centre line.
The wing panels would have alloy tubes in each wing with a suitable alloy rod insert to mate the two panels.
back to removeable dowels ... mmmm never thought of them ! But only thought I would have is the holes wearing and getting sloppy ..
If brass sleeves were used where the dowels slide in, wear would not occur
OK Nigel....I realize the "plan" is just a guideline but it does appear, if built exactly by the plan, that front dihedral brace will permanently lock the wings together. Not a problem if the dowels do not intrude into the front dihedral brace...I still might be missing something here....lol
Anyway, if you'd like a look, I'll post a .jpg of the removable dowel system I came up with when I was thinking you had the dowels removable....
Here was my idea "if the dowels were to be removable"...the alignment block built into the wing would help with insertion. As an afterthought, it might be best to establish a continuous hole using solid foam through that bay.
Bushings, brass sleeves, as piper says, or CF sleeves should address any wear problem.
The wing will be locked together through both dihedral braces....
lol...you asked for ideas...you got one, you didn't say they had to be good ones....:)
It's actually a b***** good idea ...
Yes - I did ask any ideas ... and wasn't against the idea .. just never occurred to me !
One thing that I would add to it is implementing a piece of slingshot band near where the dihedral brace is and give one end of dowel a taper. This would allow a snug fit of dowel, no play and no wear on the area. Pink band would work best, it doesn't dry up like the typical yellowish band, or the band from fitness stores.
The band ... I did consider a large rubber band like gliders use - but problem is on the gliders - usually there is a fuselage inbetween the wing halves for the band to stretch across. Had the idea on a few models in past ... and had a wire 'hook' in my box for pulling it through etc.
But here the wing halves butt to each other so no space between for stretching the band.
The removeable dowels though ... this has actually morphed into another version ... not throwing out the idea ... just adding a further one to it :
If the dowels are fixed .. then a removeable PLATE can be used to slip over the dowels BEFORE insertion into the fuselage bulkhead.
Just cut back the LE in that area to allow a plywood or alloy plate to slip in there over the dowels. If the plate or dowels wear over time - a new plate can be easily made ...
OK - another idea ... On my Skymaster biplane - I have perpendicular short dowels sticking down from top wing into the corner L joints of the cabanes. This auto-locates the wing exactly before fitting the rubber bands. OK - it's a one oiece wing ... but the principle could be used on this UW wing ...
A ply plate across the fuselage above the main spar .. a vertical dowel in each wing centre section engages a slot in the ply plate as wing mates.
Or - we could go for 4 bolts ... have the two fixed dowels up front ... then two bolts behind LE and the existing two bolts at rear .. both sets with fashion plates across the joint.
One old trick - I saw one guy do .. he was lazy and hated having to do 2 bolts ... so he modified it to a single bolt. He made a plate to go under the single bolt. That bolt was centre of plate. Further out - the plate had bolts permanently set through where the original bolts should be. So he mated the plate and bolts through their original holes ... the central bolt then went down and through to a single captive nut ... Screwed up the single bolt which tightened the whole up.
I'm sure the wing will be good enough with just dowels, two bolts and the braces .. maybe I'm just worrying unnecessarily about the aerobatic stresses on such a big wing.
With four bolts, would dowels be necessary at all? Just seems like the dowels would be sitting there for nothing. As for the band, I meant to cut a small portion out of the band that sits in or neat the dihedral brace, to make a grommet or sleeve. The dowels would then be tapered and pushed into this rubber sleeve, which would effectively grip the dowel and hold it in place. To take the wings apart, the dowels would just need to be popped out of the rubber sleeves.
The dowels would provide the lateral resistance ..
My purpose is to lock the wing halves together as well as provide good holding of wing in the fuselage saddle.
Ok - sorry - I didn't realise from previous post the method. So what you mean is similar to a bushing that is used for rods etc. on cars .. tight fit that expands to let dowel in - but tightens up once in.
Would need to be ultra accurate I think ... with the imagined forces I expect on a 71" wing doing extreme aerobatics ... mmmmmmmmm
All ideas are now milling around in the old grey matter ... it all comes down to when I start building - what is easiest to accommodate and works ..
Nothing to add on the construction, you know what you are doing.
Only suggestion is to check www.DharmaTrading.com for the silk. They carry several weights and the quality is good.
Progress photos please.
Hi "Abuelo" .. welcome on board ... don't worry about suggesting anything ... none of us know all of the answers and any suggestions are more than welcome.
With regard to the 'silk' ............
Some may question why use such in this day and age of iron-on film and Tex .. simple really.
The old way of Silk / Nylon and dope provided an incredible durable strong covering. I had a Tiger Moth back in the 80's that went through 'wars' in rough fields, bracken, even thorns on some of the flight sites. But the nylon / dope covering never tore or marked.
The Ultrawatt is going to have a lot of foam fashion pieces to create the shape - to compensate weight for use of plywood on main frame. The foam will require a covering that adheres and provides that puncture, ding strength seen on that Tiggy. I could use Tex iron-on .... but that brings in heat aspect. Tex requires more heat than film.
The supply of 'silk' will be down to a local shop that supplies dressmakers ! In the past - I've used the lining silk that some use on fancy party dresses .. very light, close weave, near see-through. It will not have much shrink ability - so will need to be stretched over and pasted down with care. Latvia is not that good on model supplies - but is excellent on Dressmakers materials !!
Watered down PVA will be the medium to paste it on ...
What I will have to be careful about - is not to add tooo much weight by use of the PVA. I do not want to fill the weave in fact. I want just enough to seal it and give foundation for airbrush colour scheme.
The weave will give it a character not often seen.
While on this subject ... many years ago - I read an article by a scale modeller in UK who actually sewed his 'silk' on to a model same as they used to do in WW1 .. he literally created a bag to insert the wing into and then stitched through. The stitches literally scale replication of the original. That's far more than I ever would do ...
I think I have too much time on hands before building this baby !!
I woke up this morning with removable dowels on mind !! No wise cracks please !! :rolleyes::rolleyes::rolleyes::rolleyes::D
Now - thinking.. maybe what if ... I make the dowels go all way back to rear spars .. so in fact they pass through BOTH braces and egg box spars.
One of the areas that concerned me with having the ply flat braces - was the splitting up of the wing ribs to allow them into wing. Creating box like affair for them. Alloy tubes got around that by ribs still being full one piece but drilled to suit.
I need to get home and start building - stop this mind game !!
Ok .. here's another idea ...
Back to alloy tubes and rod joiners ...
Put wings together and drill through to place a pin through tube and rod locking them together ........... see attached.
Another way is the spring clip idea - a groove dremeled into the rod .. it extends into wing further than tube .. the groove is hard at end of tube .. a spring clip is used to lock the tube .. the R clip type.
These clips are available in various sizes in Lawnmower shops .. Marina chandlers etc.
Both pin or R clip are out in a wing bay .. with a tape flap to cover over ... I would not put near centre as I do not want to weaken the tube or rod.
In fact ... with careful design and fitting .. a canopy Spring catch could do the pin .. set into a servo well and operated by wire hook.
This looks like a great project. Would a 60 size electric motor like a G60 w/ 100 amp esc and 6S 40C lipo deliver enough watts to power this beast? AUW? Figure 150-200 watts per # ?
Had to laugh : " The supply of 'silk' will be down to a local shop that supplies dressmakers ! In the past - I've used the lining silk that some use on fancy party dresses .. very light, close weave, near see-through."
Are the ladies of Latvia missing their lining? - LOL
Hi Hawk ...
The G60 would I think be on the light side for it ... the original Xtra Wot is classed for 120 glow 4str ... so even the 15cc Gasoline job I'm planning on fitting may be on the lower mark. Depending on build and how she looks as she goes together - I am even considering getting a 26 or 30cc engine instead for her. I have two other possibilities that are ideal for the 15 ...
For a G60 - I would suggest the 58" version .. the Killerwatt ... which is classed for 50 - 60 2str size glow.
You could take my plans modified for the Ultrawatt and with Adobe just print at 80% scale .. or use attached original Usher plans ..
Keep watching this space ... who knows what will come next !! :D
|All times are GMT +1. The time now is 08:45 PM.|
Powered by: vBulletin
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ