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Old Jul 15, 2009, 10:23 AM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
717 Posts
Build Log
Dodgson Maestro MK III - plus mods (build re-started)

I recently acquired a Dodgson MK III kit on eBay. I wasn't expecting to be successful when I bid and tried to sell it here a few weeks ago, unsuccessfully.

I also have the desire for a larger electric glider than I am currently flying so the decision has been made to build the kit with three major modifications.

1. Extended wing span and hence area.
2. Flaps and ailerons instead of the original flaperons and spoilers
3. Electric conversion

The Maestro is a 132inch sailplane with built up wings and tail plus a fiberglass fuselage. In the MK III version it has rudder, elevator, spoilers and flaperons. The flaperons are driven via a mechanical mixer and the spoilers by pull strings.

My kit appears to have been manufactured in 1977 based on a newspaper fragment used in kit packaging.

This is my first serious build since 1974 when I built one of these. Everything since has been ARF or pre-built.
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Old Jul 15, 2009, 10:41 AM
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I built one of these back in 1979. It was fun kit to build and flew well, although I felt it was heavy. I learned some building techneques from the kit which I still use today. As a matter of fact, the wings are still out in my garage. Do you have specific questions on the kit, it was 30 years ago; but, I will do my best to help.

Or, are you simply anouncing your going to build the kit!
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Old Jul 15, 2009, 11:42 AM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
717 Posts
Quote:
Originally Posted by Mode One
I built one of these back in 1979. It was fun kit to build and flew well, although I felt it was heavy. I learned some building techneques from the kit which I still use today. As a matter of fact, the wings are still out in my garage. Do you have specific questions on the kit, it was 30 years ago; but, I will do my best to help.

Or, are you simply anouncing your going to build the kit!
Thanks for the offer, any help appreciated. This is my second Maestro build but like you it was a long time ago that I did the first.

I don't remember mine being heavy and it certainly flew well. We will see what adding a motor and battery does. I am going to build it so that a mimimum of balancing ballast is needed. I also plan to put ballast tubes in the wings.

I have started the build but it will be a few days before I add photos and build steps.
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Old Jul 15, 2009, 05:12 PM
Stranger in a land
Haole's Avatar
Hawaii
Joined Dec 2007
571 Posts
Wow, that's a nice oldie find. Looks like a fun build and your modifications will help greatly. Now if only you could change the airfoil to something other than a flat-bottomed...but not to detract.

Good luck and have fun! That's the important part

Carl
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Old Jul 15, 2009, 10:13 PM
Mmmm...balsa dust!
vintagemxr's Avatar
Casa Grande, AZ
Joined Jan 2005
176 Posts
Nice find. I built a Maestro in 1977. I guess I'm a bit of a purist and hate to see classic kits mod'ed too much but to each his own.

One of the best days I ever had flying R/C was with the Maestro on a small slope near Acton, CA. My buddy Keith and I snuck out for a quick flying session on Thanksgiving morning with of course promises to our wives to be home in plenty of time for Turkey Day feasting. Out at the hill we waited a while for some wind and finally tossed the plane off and spent some time handing the TX back and forth gaining altitude and playing with flapperon settings.

I finally decided we'd best call it day and began burning off some altitude by just putting the nose down. The Maestro went faster and faster and I fed in more down trim and it went faster. Remember, you younger guys, this was in the days when nearly everyone was flying floaters and going fast with a 132" span plane seemed a bit crazy. One of the mistakes I made learning to fly the Maestro was to fly it too slow.

Anyway, pretty soon the glider is hauling butt up and down the slope like some kind of ridge racer. Keith and I kept handing the TX back and forth, laughing, and flying until we became concerned about the RX battery. I finally slowed the plane down and got it on the ground. Then we looked at our watches...... Serious trouble on the home front. 30+ years later though we still talk about and laugh about that day flying the Maestro on the slope and the pain we endured when we got home and found everyone already half way finished with their big Thanksgiving Day meal.

Part of my point in telling the story is that I'm not sure if you're going electric that stretching the span is necessary. With the flaps or flapperon set up you can let the plane fly fast, which it does very well, and still be able to slow it up for landing and such.

Regardless, have fun building the kit! I'm slightly envious.

Doug
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Old Jul 15, 2009, 11:09 PM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
717 Posts
I hear what you say about modifying old kits and I did contemplate building exactly to the original (for about 10 seconds) then I remembered by beefs with the original, an example of which I flew thermal and slope for 6 years as my only model. In the seventies nothing could touch the Maestro for versatility IMHO.

The original flaperon mixer plus linkages was sloppy and the spoilers were a pain to rig and keep functional. Using flaps and ailerons with wing mounted servos solves those problems. I am increasing the span partly to offset the extra weight of the electric setup but mostly because I like big span gliders. This is in fact a helluva lot cheaper than any 4 meter moldy.

You can still buy plans and fuselages for Maestros these days so I don't regard the kit as unobtanium.

There was another comment about flat bottom airfoils. They sure do simplify building a built up wing. In my experience things like span, weight, wing loading along with the airfoil camber have far more influence at the sort of Reynolds numbers we potter around at when thermalling. I am no aerodynamicist and I am sure I will be taken to task by those who are but I think except at the extremes of flying and flying skills airfoil is not that big a deal. Put another way, most of us are such lousy pilots that no airfoil is going to make much difference.
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Old Jul 16, 2009, 01:43 PM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
717 Posts
Here we go.

Step 1 is to draw out a new wing layout. I am using the original ribs and changing the spacing to 3.5 inches between ribs (or 3.6 inches between rib centers allowing for the 3/32 ribs). This will move the span from 132 inches to 154 inches.

My work bench is a 80" x 30" hollow core door on trestles with a surface of 1/4" foam board from Jo_Ann. (Jo-Ann, for those who haven't found it already, is an amazing resource for all sorts of materials). The foam boards are 20" x 30" so 4 fit perfectly.

The wing panels are about 75". I am going to build each panel as a single peice and hope that that won't my my life miserable with transport problems.

Major tools are: 48" and 72" graduated straight edges, an 8' aluminum 2" x 1/8" that I use for the really long drawn lines and 30" T-square.

The plan is to build as light as possible.

For glues I will use aliphatic resin for most of the wood, epoxy to join the fuselage halves, attach the tail feathers and motor mount, and silicone sealant to glue plywood trays into the fuselage.

Step 2

Weigh out the wing sheeting and distribute. The 3 x 36 x 3/32 sheets weigh from 14 to 27 grams. I have distributed them heaviest to the root, lightest to the tip. The ones from the kit all seem good but I need to buy a few extras due to the increased span.

Off to the hobby store. I need more 3/32 sheeting, more spruce for spars and some 1/4 balsa for webbing. I am discarding the original webbing wood again due to the increase in spacing and it is pre-cut like a comb.
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Old Jul 16, 2009, 03:47 PM
yyz
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USA, CA, Paso Robles
Joined Dec 2004
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Right on! Finally.... Someone really "building" a plane

This is going to be a great build thread. I had forgotten how complete the Dodgson Designs kits were. If Bob would have included velum drawings and multi-language instructions, he could have taken on Graupner

Visually, I think the fuselage can "support" the wing extensions and, like you, I really enjoy the bigger gliders. I'd keep the airfoil the same. That's part of the feel of that glider and it's pretty E387-esque w/ a beefier back end.

I built one last year and really thought the spar integrated into the sheeting was pretty clever. Makes it a challenge to strenghten up but that's a proven wing that will warn (bend hard) before breaking. The smaller wing joiners will give you some belt and suspenders in that regard too.

Are you going to have spoilers or go w/ the crow/butterfly setup?

Here's to the Maestro Mk IV w/ Whiskers!

Mike
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Old Jul 16, 2009, 04:40 PM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
717 Posts
Speaking of complete

This is the parts pack for the Maestro

I split it in two as I don't need most of it. The EK logictrol towhook is a blast from the past.

I may replace the elevator bellcrank as I don't trust ancient plastics.

I will not be using spoiler, just flaps and ailerons and the flaps will be 0 or 90 degrees, just brakes.

I am planning on doing Z hinges so there are no gaps and I can play with fancier flap options if I want to.
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Old Jul 16, 2009, 04:43 PM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
717 Posts
Quote:
Originally Posted by yyz

Here's to the Maestro Mk IV w/ Whiskers!

Mike
Actually I was going to call it Mk III.16 E but that's a bit pedestrian.
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Old Jul 16, 2009, 06:10 PM
yyz
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USA, CA, Paso Robles
Joined Dec 2004
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Naaaaaaaa... All of the upgrades you're doing deserve a full Roman numeral bump in revision number


Quote:
Originally Posted by VintageFan
Actually I was going to call it Mk III.16 E but that's a bit pedestrian.
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Old Jul 16, 2009, 06:36 PM
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Since the design is no longer being manufactured, what you do with revisions is totally your call.
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Old Jul 17, 2009, 01:54 AM
Mmmm...balsa dust!
vintagemxr's Avatar
Casa Grande, AZ
Joined Jan 2005
176 Posts
Quote:
Originally Posted by VintageFan
I hear what you say about modifying old kits and I did contemplate building exactly to the original (for about 10 seconds) then I remembered by beefs with the original, an example of which I flew thermal and slope for 6 years as my only model. In the seventies nothing could touch the Maestro for versatility IMHO.

The original flaperon mixer plus linkages was sloppy and the spoilers were a pain to rig and keep functional. Using flaps and ailerons with wing mounted servos solves those problems. I am increasing the span partly to offset the extra weight of the electric setup but mostly because I like big span gliders. This is in fact a helluva lot cheaper than any 4 meter moldy.

You can still buy plans and fuselages for Maestros these days so I don't regard the kit as unobtanium.

There was another comment about flat bottom airfoils. They sure do simplify building a built up wing. In my experience things like span, weight, wing loading along with the airfoil camber have far more influence at the sort of Reynolds numbers we potter around at when thermalling. I am no aerodynamicist and I am sure I will be taken to task by those who are but I think except at the extremes of flying and flying skills airfoil is not that big a deal. Put another way, most of us are such lousy pilots that no airfoil is going to make much difference.

Oh yeah...the spoilers with the threads, the sliding loop metal arm-thingies for the flaperons. That kind of stuff definitely deserves and upgrade to modern electronics, no doubt about it.

Agree about the airfoils comments too. By the time a wood model gets built, sanded, covered, etc. the airfoil certainly has drifted a bit from whatever the original design shape was. And even if a builder gets the airfoil dead on any gaps in the bits and pieces, or misalignment of the tail surfaces, etc. can undo all the benefits of snazzier airfoil.

Anyway, I'm looking forward to watching your build here.

Doug
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Old Jul 17, 2009, 02:40 PM
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King Salmon, Alaska
Joined Jul 2003
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I'll be watching the build as well because I have a Maestro Mk III in the kit stack. If the electrification and wing extensions work, I may just follow your lead when (if) I ever start in on it.

Don
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Old Jul 17, 2009, 03:46 PM
yyz
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USA, CA, Paso Robles
Joined Dec 2004
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Canopy

Vintage Fan,

If you're thinking ahead about tinting the canopy, this is a good article:

http://www.myhelicopters.com/canopy.htm

The technique described works but be careful w/ the thin Maestro canopy and the water temperature. You can make yourself an empty plastic taquito without much effort.

Mike
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