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Jan 13, 2014, 10:39 AM
Tinkerer in Training
RGinCanada's Avatar
Build Log

DHC-1 Chipmunk: Pettigrew/Bradley design from Manzano Laser Works


I bought the Pettigrew plans for the Chipmunk, and then saw the Manzano Laser Works DHC-1 Chipmunk -- 74" Wingspan thread by buzzltyr.

After a little hounding, pleading, and begging, I got my hands on one of the pre-production kits from Charlie at Manzano Laser Works. The box contains three large sheets of drawings, and many sheets of laser cut wood, in various weights of ply and balsa.

The plans are clear, well annotated, and extremely detailed, the parts are nicely marked, and the instruction manual is more than thorough enough to give the builder the confidence to tackle a plane this large.

(Well, 74" is large for a guy used to parkflyers!)

Update: I'll keep a running tally here of the items I purchased to complete the kit

Hardware and Miscellaneous List

Building Materials
  • (2) 1/8" x 1/8" x 36" balsa (washout strips)
  • (4) 1/8" x 3/16" x 36" balsa (spar caps)
  • (3) 1/16" x 1/8" x 36" balsa (rib caps)
  • (6) 3/16" x 3/16" x 36" balsa (fuselage stringers)
  • (1) 3/4" x 2 x 36" balsa (goof up repair and leading edge transition)
  • (1) 3/32" x 24" music wire
  • (2) 1/8" x 24" music wire
  • (1) 12" x 1/8" brass tube
Electronics
  • (1) Turnigy Aerodrive SK3 - 3542-800kv Brushless Outrunner
  • (1) Turnigy AE-65A ESC
  • (4) Mini size servos JR MC35*
  • (2) Standard servos JR
  • (1 pkg) (10 pieces) 45CM Servo Lead Extension
    *Hitec HS81 or HS82MG called for
Hardware
  • 1 pkg (2 pieces) Dubro 3-1/4" treaded wheels (mains)
  • 1 pkg (2 pieces) Dubro 1-3/4" treaded wheels (tailwheel)
  • 1 pkg (2 pieces) Alloy Oleo Strut 130mm Straight Mains
  • 1 pkg CA type hinges
  • 1 pkg 3/32" Robart pin hinges
  • 1 pkg Du-bro E/Z links
  • 1 pkg 2-56 x 48" flexible Sullivan "Gold-n-rod"
  • 4 2-56 x 12" control rods (threaded one end)
Last edited by RGinCanada; Feb 04, 2014 at 11:24 AM. Reason: Altered title per suggestion...
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Jan 13, 2014, 11:10 AM
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portablevcb's Avatar
RG,

You might want to change the thread title to Pettigrew/Bradley Chipmunk.

The original design is Ivan's. Paul Bradley did a rework to make it easy to build. I am hoping it comes out near the weight of Ivan's original.

I am in the sheeting stage on mine so will have some additional pictures to add at some point.

charlie
Jan 14, 2014, 08:12 AM
Obviously I'm a "Minus Member"
buzzltyr's Avatar
I am thrilled that someone has taken on the build of this model. Mine sits in the same state as I last posted in my thread. I have, unfortunately, built nothing in the last 18 months. I really have not done much flying either. I know that I let Charlie and Paul down, and I am truly sorry for my failure to complete the model on a timely basis. I do feel incredibly guilty for not completing the kit and meeting my obligations to Charlie, especially.

Mark
Jan 14, 2014, 08:45 AM
Tinkerer in Training
RGinCanada's Avatar
Quote:
Originally Posted by portablevcb
RG,

You might want to change the thread title to Pettigrew/Bradley Chipmunk.

The original design is Ivan's. Paul Bradley did a rework to make it easy to build. I am hoping it comes out near the weight of Ivan's original.

I am in the sheeting stage on mine so will have some additional pictures to add at some point.

charlie
Thread title change... check! I am really looking forward to seeing those pics!

Quote:
Originally Posted by buzzltyr
I am thrilled that someone has taken on the build of this model. Mine sits in the same state as I last posted in my thread. I have, unfortunately, built nothing in the last 18 months.
It took me nearly three months from opening the box to getting the first parts glued! Staying employed and putting my kids through school always gets most of my attention. For the next month or two, I've set aside an hour a day to work on this project, hoping to maiden it on our field opening day this spring.

Before I get into the actual build, you should know I make plenty of mistakes, and occasionally learn from them. Feel free to point out any
Jan 14, 2014, 09:21 AM
Tinkerer in Training
RGinCanada's Avatar
From the Assembly Guide intro:
Quote:
Originally Posted by deHavilland DHC-1 Chipmunk Assembly Guide
The Manzano de Havilland DHC-1 Chipmunk is based on a design developed by Ivan Pettigrew.The structural design has been updated to take advantage of laser cut parts and to help reduce the build time
...
Materials used in this model include balsa, liteply, plywood,brass tubing,and piano wire. A formed plastic canopy is also used. Most of the wood and the formed canopy is supplied with the kit.The builder supplies 3/16” and 1/8” square balsa strip stock, piano wire, brass tubing, and the hardware needed to complete the model.
...
The completed model should have a flying weight in the 5 to 6 pound range.To provide a reasonable power level for handling wind and takeoffs from rough terrain, a power loading of at least 70 watts per pound is suggested. That translates to a motor/ prop/ battery selection that can deliver at least 420 watts.The battery area of the model can accommodate up to four cell lipo packs in the size range suitable for this model.
A few notes on this:
Being a pre-production kit, there was no canopy included. I'm partial to the Canadian version bubble canopy, so I may try fabricate one when the time comes...

Structurally, there is very little else left out of the kit. maybe a dozen pieces of strip balsa are required. I'll try to keep track of that as I go.

As far as power systems go, I'm considering a 4S system with an 80A ESC, using the following Turnigy Aerodrive motor:

Kv (rpm/v) 840
Weight (g) 174
Max Current (A) 50
Resistance (mh) 25
Max Voltage (V) 15
Power(W) 750
Shaft A (mm) 5
Length B (mm) 49
Diameter C (mm) 37
Can Length D (mm) 28
Total Length E (mm) 70

This should provide a reasonable margin of power, and allow me to play with an assortment of props. Any comments or suggestions here would be appreciated, as this is not my forte.

For reference information and inspiration, my wife bought me "The de Havilland Canada DHC-1 Chipmunk:The Poor Man’s Spitfire" for Christmas.. The book is fantastic.
Jan 14, 2014, 10:13 AM
Registered User
portablevcb's Avatar
Mark,

No problem mate. We all have issues like that. It only took me four years to get a Gee Bee E flying and after over a year I still haven't finished detail stuff (like fake motor and struts).

charlie
Jan 14, 2014, 10:15 AM
Registered User
LesUyeda's Avatar
I bashed a Goldberg Chipmunk into this, once upon a time.

Les
Jan 14, 2014, 10:19 AM
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portablevcb's Avatar
So, a bit of explanation about this model.

Those who are familiar with Ivan's designs probably won't recognize anything here. Paul Bradley took Ivan's design and changed it to a "tab and slot" style construction. He even pre cut ALL the sheeting for the plane. So, like RG said, what you need to provide to finish is limited to things like a bunch of 3/16" sq sticks.

Paul also did a splendid job of writing a >20 page instruction manual. Not a small feat and we thank him for this. The whole thing makes this into a kit that we would recommend for a novice or even beginner builder. I am considering turning this one into a full kit, but, will wait and see how it flies.

The real test is to see what it weighs when finished. I will be happy if it comes in under 5lb and REALLY happy if it comes in under 4lb.

And, yes, functioning slotted flaps are there as well as the steerable tail wheel.

So, I will post some pics in a bit.

charlie
Jan 14, 2014, 01:08 PM
Übung macht den Meister..
Deuce's Avatar


James
Jan 14, 2014, 01:21 PM
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portablevcb's Avatar
So, the kit starts out with 19 sheets of 6x36 balsa and 6 full sheets of ply.

Here is the start. Wings first.

My building board is only 36" wide so one wing at a time and it just barely fits

The second photo is a closer shot of how Paul did the spar and ribs. The spar is built up. The balsa vertical part acts more like a shear web and positions the ribs.

Washout is built in with a balsa strip positioned correctly under the ribs.

Last photo is the ailerons and flaps.

The only thing I needed the plans for on this was to position the washout strip and to make sure the wing was square. Everything else is tab and slot.

charlie

PS sorry for the focus issues.
Jan 14, 2014, 01:27 PM
Registered User
portablevcb's Avatar
Will get a pic of the finished wings later. Yes, these are D box type wings.

Two spar 'caps' are added top and bottom. Paul spec'd 1/8x1/4 hard balsa but I used bass instead. Then the wing is sheeted from LE to spar and cap strips applied to each rib. Yes, the sheeting is precut and is near perfect. Then add the finish LE piece and shape the LE profile.

LG blocks are added underneath and Paul even provided ply keepers for the LG wire that sit flush with the wing skin. Now if I can only bend the LG correctly we'll be all set

charlie
Jan 15, 2014, 06:55 AM
Tinkerer in Training
RGinCanada's Avatar

Stab and Elevators


I started with the stab and elevators, both because that was what the instructions suggested, and it seemed less intimidating.

Each of the pieces included an ingenious tab so that the assembly could sit on the building board and everything would line up perfectly. Unfortunately, they are fragile, and while doing my best impression of Mr D. B. Gumby "O nooo, I've broken it!" Most of them snapped off.

No matter, everything went together well. Attached are photos showing the ingenious tabs, a closeup detailing the construction, and a view of the result.

And some Monty Python if you missed the reference:

Gumby Flower Arranging (0 min 36 sec)
Jan 15, 2014, 09:07 AM
Registered User
portablevcb's Avatar
This is one place where following the instructions precisely will help in the long run.

Those upper and bottom sheet parts on the stab should not both be glued on at this point. It may make installing the stab more difficult. You'll have to wiggle it a bit to fit the stab over the rudder link that is installed during fuselage construction.

I've found a couple of places in Paul's instructions that seemed a bit out of sequence until I got to a future step.

I did build the tail feathers next. Those little tabs did pop off fairly easily. Not unusual for those kinds of things on any model I have built. I just tack glued them back in place. It does mean a little more care in sanding once they are done.

charlie
Jan 15, 2014, 10:06 AM
Tinkerer in Training
RGinCanada's Avatar
Quote:
Originally Posted by portablevcb
This is one place where following the instructions precisely will help in the long run....
Damn. I could have sworn I was following the instructions to a 'T'. At worst case I'll form the final bend in the linkage in situ, I guess.

Thinking ahead...

Can anyone point me to a tutorial on forming a bubble canopy? I'm assuming it will need to be vacuum formed because of the undercut in the cross section. My searches have shown up many threads and videos, but none close enough to what I need...
Jan 15, 2014, 11:16 AM
Registered User
portablevcb's Avatar
I'd use the soda bottle method. Make the form. Put it inside a large soda bottle and heat until is shrinks up.

But, does depend on if you can find a big enough bottle.


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