My next project. Magic 20, will be built with mini servos and light weight wood, power will be a piped Cox Conquest, covered in Monokote, should be able to keep the weight to around 2lb

Cheers

Ghost,

I look forward to your build!

2 lbs sounds like a really light M20. If you can do it, she will fly really nicely on the Cox 15. I think the design was supposed to come around 48-56 oz (3-3.5 lbs) but admittedly MK designs, although beautiful, are a tad heavy.

With a wing area of a little over 3 sq ft, at 48 oz she'd have a loading of 16 oz/sq ft. At 32 oz, she'd be down to 10.7 oz/sq ft! That's on par with foamy loadings.

As a possibly useful side note, I recently covered a 40" span model (~26 oz AUW) with MK and some lighter stuff as well. The 12 oz airframe gained about 2.5 oz from the covering, trim and painted canopy. The finished airframe weighs 14.5 oz and the radio and electric motor gear weighs 10-12 oz additional depending on battery used.

You might also find my rearranged M20 plans useful. I tried to unclutter them a bit to aid in scratch building. You can download the 5 page PDF from here:

http://www.4shared.com/file/77215541...s_Reduced.html

Build on!

David.

David,
Thanks for the offer, I have the plans and I can get them coppied and scaned (allready done) locally. With lighting holes on the ribs, cutouts in the fuse slab sides and thinner timber on the turtle deck, the use of mini servos (digital) that I use on my smaller models (Weight 18g @ 2.9Kg toqure) I should be able to get the weight down. Just a matter of selecting the correct timber to start with. I have built a few MK models over the years and have found that the timber that they supplied was on the heavy side.

Cheers

Ghost,

I hope the re-organized plans prove useful. They should make building and aligning the structures a little easier by having individual sheets to build on and use for templates.

18g/2.9 kg-cm (0.6oz/40 oz-in) servo's sound perfect for the M20. I'm thinking Hitec HS-65's or equivalent. JR has some nice servo's in this class but I know you lads have other brands down under. I haven't flown them yet but I've also picked up some promising inexpensive high speed digitals (CS-110) with similar specs (same wieght/47 oz-in) - perhaps a tad better than HS-65's. These are Hobbico but they are also branded by Tower for a few $ less. Futaba's S3115's also seem nice although they need to be run at 4.8V.

I used 3/32" balsa for fuse sides on my 40" build with half length 1/64" obeechi doublers. I also drilled out the fuse sides. Formers were made with 1/16" ply. 1/32" balsa sandwiched with 1/64" ply might be stronger and lighter. The majority of the balsa was in the tri stock, the fuse top and front. The wing and stab are full foam core (not hollowed out) sheeted with 1/32" contest balsa. The final weight of the completed unfinished fuse and wing was 6.5 and 6.0 oz, respectively. This did include a little hardware however. The covering added another 2 oz for a finished AUW of 14.5 oz. I then doubled that with the radio gear, linkages, motor, ESC and battery. This last varies from 3.7 to 6.7 oz depending on flight duration desired.

A built up M20 50" wing could probably be built to 5-6 oz weight. Rainedave just finished his UFO 43" built up wing and it came in at 4.3 oz (he builds pretty light). He's using only 7 ribs per panel. I would use the same number on the M20 skipping a rib starting from the end of the gear mount rib - it works out nicely.

What's the weight of your piped Cox 15? Will you be using fixed, retract or no gear (otherwise know as UC down under)?

Hope she's coming along.

David.

David,

Thanks for the info, The servos are Hextronic D-MG16's, been using them for just on 2 years now and never had any problems. Still use JR (have since the 70's) radio gear in other larger models. Been using DSX9 (9303 on 2.4) for the last 8 months.

I will be using selected balsa (light weight) in the build, just getting every thing ready at the moment. Like to have every thihg before I start as it does not hold up the build as I have to order every thing or drive to 2 hrs to get to a hobby shop. I looked at doing it electric as I have several electric models as well but could do it lighter with glow. I also have 6 engines NIB as well as 2 others that have little use, left over from my racing days.

Still thinking about landing gear as you can save a lot of weight with out it, have several small models without it. The Cox weights in at 230g with pipe, prop, spinner and tank.

Cheers

I'm glad to hear that you've had a good experience with the Hextronic's. I just put 4 of them in my Pico, albeit the analog HXT900's. It seems several people have good comments about them. At that price I admit I am a little concerned.

It sounds like you should put those 15's to good use. 8 oz for an engine setup with pipe sounds pretty good. If you build the finished airframe to 18 oz., add the power setup to bring it up to 26 oz, that would leave you with 6 oz for radio and linkages. Mind you, even at 40 oz the model would be light on the wing and have plenty of power.

I'm probably over computing this thing but it strikes me as though 50" span might be a tad large for a .15 even if piped. What if you reduced it to 43" span or 86% scale? I could do that easily if you're not an Illustrator guy.

David.

I have though about reducing the size to a 40" span 80%. I can do that on my computer or could get the plans printed at 80% by the plan service we have in town and then build it from there. Just something else to think about now. The orignal is for a 20 sized did not say anything about high speed motors.

We have been using the Hextronic servos D-MG16's because of the full metal gear train in them. The mini servos have a weak servo train(plastic gear) and can be stripped with bumping of the flight surface. The other thing is the high toqure and hold power from a small servo even if they are cheep. Orignally got them for combat aircraft to keep costs down for some of the junior members and was very impressed with them I started using them in other models. I even have them in a Satio 72 powered Ultimate and they work great.

Cheers

Went to the print shop today, Printer out of order untill Monday. Printed the plans at home on my A3 printer and stuck them together. Done 80% print and it looks good. No landing gear will be fitted as these little models don't realy need them. Motor fits well, will just have to work out the pipe setup. Will get the plans reprinted on Monday.

Cheers

Before you decide on no landing gear, think again. I built two models of the same plane, one with fixed and one with retracts, about the same size as your Magic (42" span). They weighed the same - 28 oz ready to fly. Being able to put it down on the pavement is really a nice feature.

OTOH, if you're flying from grass, then you're probably right.

Plans and construction article will be in the Sept issue of Flying Models.

Andy

Ghost,

I built my latest 40" model without gear as my intention was to fly it in my local grass schoolyard. Not having had that experience before, I keep looking at the field, reflect back on the speed of these mini pattern planes and think it would be nice to have the option to take it to my regular runway. But that's not a good reason to put retracts in it - it's a matter of finding the right field. With my previous 40" model (unfinished), a Deception, I went the full 9 yards, trike gear, a ST 23 and 7 servos. The Picorare was to be a simple and fast build and so it was.

Although Andy's design (with a built up wing) is nicely suited to retracts at this scale, I personally feel that the 48" span (and above of course) 20-32 class of models are better suited to them. The Magic 20 at 50" span would be cool with gear and a 25 size engine but seeing that you've favoured the 40" span 80% version - good call - I would build it to fly without gear and on to grass. You will have no trouble building that model to 25-30 oz AUW.

Did the Cox C15's come with and without carb or did they use a Perry?

David.

David, you could get them with venturi or carby(Perry). David I only fly off grass so its not a problem. You could always make up a dolly to fly the model off, would still need grass to land on. This is one of my other models that I use to hone my flying close in skills as its very often no more than 50' from me and only about 3' from the ground most of the time.

Cheers

With the crap weather today(really, really windy) I broke out some wood and started. The antihed of the stab seams a lot compared to the Birdy planes which have a total of 10deg's the magic has 19deg anyone done something different. I think I may reduce this to 15deg or maybe even 10deg. will have to look at it. I used 3/16" for the stab and will use CA hinges just for the ease of fitment. Looking at the wing I will proberly drop W4,6,8,&10 as the space between looks OK with out them.
Third photo is size difference between the plan for the Magic 20 and the 80% one. Printed that out to check antihed.


Cheers

Went with 15deg as 15.2 is 80% of 19deg for the magic 20.

Cheers

Nicely done Ghost. Excellent lighting in your shop too - makes for great photos!

Amazing how that 80% drops the size of the model. The Magic is notorious (at least to me) for having a serious anhedral in it's stab. I think the location of it wrt to thrust line was the reasoning behind it. It seems like a good idea to reduce it somewhat. Of course, technically, the 80% scaling would only reduce the total distance (to 68mm), not the angle but blending the two ideas is a clever approach.

Something else to think about might be to also raise the wing root chord CL to an equidistant location from the thrust line as the effective root chord of your new 15 degree stab. This trend was generally favored in later classics during the 80's particularly by Japanese designs (e.g., Aurora, Atlanta, Beetle, Cosmos, etc.).

Yup! Omitting ribs 4, 6, 8 & 10 bring her down to a 6 rib panel. Of course, rib #4 would be needed with retract gear. The GP .10 size gear would fit nicely in the 40" model for those flying off pavement. If you figure out the rib airfoil and size digitally, sharing them with us would be much appreciated. The first scratch builders always do all the hard work!

Are you thinking of a solid canopy or cut one from styrene? A solid single fuse top from F5 forward seems like the way to go for an E-powered model.

David.

P.S. Interesting canard plans in the BG, what's the model?

David, Looking at the stab on the table at the full angle (68mm) just looked wrong. The 15deg angle looks a lot better.

Used to do this with Birdy designs in the mid 80's, something else for me to look at.

Will be re doing it in Profili 2 that I have on the computer, will then turn it into a PDF file and post.

Change that to F6 would be better. A motor for it would be the Turnigy 3536-1300 turning 9-6 prop on 2200 mah 3cell pack. We use this setup in all our smaller models and you get a good 8-10min flight per bat charge. Looked at it for electric but decided on glow as I have all these motors collecting dust and I have enough electric to keep me going.

The complete stab is now finished and rough sanded and weighs 9grams.

Cheers

Excellent!

F6 does sound better yet for an e-power setup. Another nice option would be to keep the top NBU solid as per plans, maintain the removeable bottom glow hatch for access and build the fuse top from F8 (wing TE) to the canopy front at the FW (or F2) to be removable. Plug-in wing panels would also allow one to build the fuse bottom closed and with a continuous line.

What happened to the excellent lighting in your shop!?

David.

Night time and I did not have my work lights on.

I would use the top of the model for the removable part as then there is no problem with ground landing with out landing gear.

Forgot to add the wing ribs. Will do better ones later maybe, good enough to start.

Cheers

Done nothing yesterday as I got a full days flying in. First time in over 2 months, been really windy here.

Looking at my timber supply, I am short of ply, Will have to make more. I have plenty of 6mm but no 3mm. I have a lot of 1mm 5ply that I got many years ago. Just cut and layer to make what I need. May look at 2mm ply fot F4, will see how it feels when done.

Will use 2mm balsa for the sides, it will be a light model. With the reduction in size you can use 3" x 36" sheet for each side, no joins anywhere. With the turtledeck joined to the top of the fuse, and F2,3 &4 do not extend above the fuse sides the fuse can be built upside down to keep it straight and square, the turtledeck can be built seperatly and then added to the fuse.

Looking at the rudder V1 will need some thought, just something to think about while cutting and making up the ply.

Cheers

Made the ply just have to leave it till morning. (photos)Sanding the sheets and laying them cross grained and weighing them down.

Ran the motor today, just with the muffler as it has not been runn for a while, will need to replace the bearings as it had a very runny nose.[sm=drowning.gif] O'well.

Played around a bit more with the pipe and coreflute plane.

Cheers

Ghost,

what glue do you use to laminate your ply?

Hey, your VW's on fire!

David.

David, I have used all types of glue over the years, and found normal wood glue works just as well as any epoxy. I have been using Bostik MDF Glue for a long while now and find it a freat glue, a little thicker than PVA white glues. Thats why I leave it for 24 hours.

Yea, my nephew got a little carried away.

Cheers

Hi all, done a bit more after a morning of flying. Us retired guys can fly everyday ending in Y.

The fuse is in basic form now, just waiting for the timber yard to get the hardwood for the engine mounts.
Will work on the turtledeck now.

Cheers

Cool! A Magic 20 thread that is current!

I built this one from the MK kit back in the mid-late 80's. I dug it out of the stack last week, installed a new flight pack battery and used my JR7202 radio to communicate with the original Airtronics receiver and 94831 servos. Flew it yesterday for perhaps its 9th or 10th flight.
It's fast and smooth with the old OS 25FSR. 3#~6 oz. without fuel. You'll enjoy your Magic.

Rube,

great rendition of the M20! I like the authentic trim scheme and those MK wheels are really cool. I have a set along with the required SS type retracts waiting for a 20 size MK design. It's a matter of time to see which one will be first (Cosmos?). You might be interested in the thread below:

http://www.rcuniverse.com/forum/m_8963192/tm.htm

We're working on preserving some of these smaller classics for posterity. There is some effort also in re-working the M20 to allow a RE 25 to have a pipe concealed in the fuse top as with it's bigger version. Essentially modifying the Magic design to have Skymaster innards. I see from your pictures that with a straight header, a SE engine would have a pipe ride above the wing - not so cool. Another interesting option would be to turn the Magic into an electric. It's big front scoop would lend itself well to this.

Say, would you mind posting some pictures with details of the nose and fuse area ahead of the wing LE in the conservation thread? It would be a great help and reference for future builds of these classics. I'll thank you in advance.

Hey Ghost, how's your Magic coming along?

David.

P.S. Used to live down your ways for a few years - loved it. I miss those Sunday morning brunches at the various eateries in and around Narragansett. I attended GSO/URI for several years. Hey! do you happen to know if the Narragansett restaurant Spain is still around? The food was excellent! Rick (Free Bird) on this forum is helping us take care of the canopy aspect of these classics. He's down in CT. Maybe we could organize a RI summer 2010 MK 20 size fly in! I can't wait to have a couple of these pups on my work bench...

Rube,

What MA are you spinning now? I bet if you put an APC 9x5 on her you'll see a 10% increase in performance. Would a 10x4 turn without hitting the ground? That would be interesting to compare on the verticals.

David.