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Old Jun 02, 2012, 07:38 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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Build Log
30" Dumas Mr. Mulligan

I searched for a Dumas Mr. Mulligan build log and couldn't find anything recent that was using brushless motors. Recently I finished an 80" DC-6B with the works scratch built and I am tired of thinking. I wanted to build something simple, small and light that I could fly almost anywhere.

I have a little Park 250 motor and a 10 amp light BEC. I am thinking this is sufficient for up to 10 ounces. I am thinking a 500mah 2s battery would be about right.

I am thinking of making it 5 channel with 4 tiny servos (3gram), aileron, elevator, rudder, throttle, flaps.

So, here goes:





Comes with some really nice decals:
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Old Jun 03, 2012, 11:24 AM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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This model assembles easily and the laser cutting is spot on. One thing I do before construction is photo copy all the laser sheets so if I make a really bad landing I can build new parts. I also scan the decal sheet so I can make waterslide replicas for any restoration needed if a bad landing occurs.

For this fuse I left out the bottom former just after the landing gear mount point so I can build a large hatch for battery and servo access. I am thinking of using spider line (Kevlar thread) for the controls (pull-pull) because they are much lighter than any push-rods.

I also cut the 1/16" square stringers from paulownia wood so they would be much stronger than the balsa and less prone to handling damage and hanger rash.

I skinned the firewall balsa piece with 1/32" lite ply to make a strong base for my motor mount.

I am really not sure about the motor. I am doubting whether the park 250 with 2S is going to do it or if I need a 300 size motor with 2S. The 300 motor is twice the weight of the 250 though (1.2 ounces vs. ,6 ounces). Still debating. MR. Mulligan was a racer and so it has rather small wings and less wing area that a typical high wing and because of the giant radial engine it had it looks draggy to me as a model.

I am thinking the converted model with battery ready to fly will be 10 ounces or so.



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Old Jun 03, 2012, 03:59 PM
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Gulf Breeze, FL
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Originally Posted by payne9999 View Post
I also cut the 1/16" square stringers from paulownia wood ....
Would you expound a little on where you get the wood and how you cut it, please?

Gene K
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Old Jun 03, 2012, 04:34 PM
Balsa&Tissue
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United States, OR, Beaverton
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Originally Posted by speedy01 View Post
Would you expound a little on where you get the wood and how you cut it, please?

Gene K
Gene,

Yes, It is grown in Georgia and is available on the net in small quantities for hobbyists and wood workers. I cut it with a table saw but even a miniature hobby table saw like one from Harbor freight could easily cut it for strip-wood.

Sailplane and hydro modelers have been using it for some applications because of it's strength to weight ratio. I was using some basswood and very select light engleman spruce for strengthening some areas before I found paulownia.

It is soft and carvable like balsa, approximately 4X stronger and only about 20% heavier. I use it for specific purposes. I use light balsa for everything except the stringers and I might use it to reinforce areas or make a special strut for a landing gear area etc. It reminds me of very select hard balsa but stronger.

http://en.wikipedia.org/wiki/Paulownia

http://www.worldpaulownia.com/html/p...warehouse.html
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Old Jun 03, 2012, 04:50 PM
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Gulf Breeze, FL
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Originally Posted by payne9999 View Post
I cut it with a table saw but even a miniature hobby table saw like one from Harbor freight could easily cut it for strip-wood.
Thanks for the links (I had already visited those and several other sites after I read your first post). None of the other posts I read (cursory) addressed how it was cut into small 1/16" strips..and I still can't visualize using a table saw! What don't I understand about that process?

Your build is really clean, and I'm looking forward to following it throught to maiden.

Gene
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Old Jun 03, 2012, 05:07 PM
Balsa&Tissue
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Originally Posted by speedy01 View Post
Thanks for the links (I had already visited those and several other sites after I read your first post). None of the other posts I read (cursory) addressed how it was cut into small 1/16" strips..and I still can't visualize using a table saw! What don't I understand about that process?

Your build is really clean, and I'm looking forward to following it throught to maiden.

Gene
Gene,

It is pretty easy. I use a very thin kerf saw blade not a big thick general woodworking saw and it takes some special care to get the fence at .062". However, I make some test cuts on scrap to get it just so. Then I slice off a slab of 1/16". The slabs are usually about 2-1/2" wide. Then I lower the saw blade to about 1/8" and just cut it into 1/16 X 1/16 strips. I use some special push blocks to keep my fingers away from the blade. It isn't so difficult. If the wood was much softer I would use a balsa stripper but the saw works great and I can strip up a bunch of wood for say an entire short kit like the Tritle DC-6 in about two hours.

Dave
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Old Jun 03, 2012, 05:25 PM
Balsa&Tissue
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Here is a picture of the saw set up to slice off a slab of 1/16" sheet. The blade is set to about 2-1/2" high, just 1/16 or so higher than the wood is thick.



Here is a picture of the strip-wood being cut. The saw blade has been lowered to make it safer:



I got the cowl built and primed. This model is really a joy to work on. The cowl is 18 individual pieces glued together! The vac formed pieces are going together quite well.

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Old Jun 03, 2012, 06:50 PM
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Dave, I think I'd recommend you wait on a motor choice until you have a better idea of the weight.
Having read all of your build threads, I have to think that you will be able to build this at a much lighter weight than your projected 10 ounces. A 10 gram motor, two 3.7 gram servos (or 3 if you want ailerons), and an 8-10 gram ESC will put you in the ballpark of an ounce for the electronics, minus receiver and battery. A 2 cell 350mAh battery will be plenty for a 10g motor. I can't believe a 30" rubber model airframe, covered, is going to weigh much more than 6-7 ounces, if that. I think you will be happily surprised at the weight when you are done. I can only compare it to the Mountain Models Little Bogie, which has a 36" wingspan, and has an AUW of about 4-5 oz using the kind of equipment I'm referencing. Food for thought, in any event.

Happy building!

Mark
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Old Jun 03, 2012, 06:54 PM
Balsa&Tissue
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Originally Posted by buzzltyr View Post
Dave, I think I'd recommend you wait on a motor choice until you have a better idea of the weight.
Having read all of your build threads, I have to think that you will be able to build this at a much lighter weight than your projected 10 ounces. A 10 gram motor, two 3.7 gram servos (or 3 if you want ailerons), and an 8-10 gram ESC will put you in the ballpark of an ounce for the electronics, minus receiver and battery. A 2 cell 350mAh battery will be plenty for a 10g motor. I can't believe a 30" rubber model airframe, covered, is going to weigh much more than 6-7 ounces, if that. I think you will be happily surprised at the weight when you are done. I can only compare it to the Mountain Models Little Bogie, which has a 36" wingspan, and has an AUW of about 4-5 oz using the kind of equipment I'm referencing. Food for thought, in any event.

Happy building!

Mark
Mark,

Thanks, I am really out of my normal zone here. Don't have much experience in the micro category. However, I wanted to stay with conventional servos and receiver/ESC because those Speky receiver bricks that go in all their foam micros are so unreliable. I have had several that had intermittent servos etc.

Dave
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Old Jun 03, 2012, 07:03 PM
Balsa&Tissue
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Here is how I like to put together those tricky little wheel pants:



I like to use some blue tape near the seam to allow me to put down a nice neat strip of good old green Squadron putty:

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Old Jun 04, 2012, 03:59 PM
Balsa&Tissue
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Made some progress....The tail group is framed. Added some very light balsa blocks for the hinge locations:

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Old Jun 04, 2012, 09:48 PM
Balsa&Tissue
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United States, OR, Beaverton
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I am debating on the covering. I like tissue on a small model but a white film might look better. I have Doculam but I have never found a paint or prep combination that has much adhesion or durability. I was thinking of Parklite but these frames are real light and would likely warp. I was also considering SoLite.

Anybody have some advice on the covering choices?

Dave
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Old Jun 05, 2012, 04:17 AM
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Minneapolis, Minnesota
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Beautiful build! I couldn't determine what sort of power plant it was designed for, though. Was it a rubber powered FF?

Jay
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Old Jun 05, 2012, 06:20 AM
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United States, MA, Sutton
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I picked up one of these to convert but it sits waiting to be built. I have converted the smaller P-6 and Ryan Mail Transport using UM gear. They both flew great. I must add that there is a lot more pride and enjoyment in seeing your built off plans conversion flying.

I also have some 3gram servos and a Turnigy 250 motor set aside for my build. I think I'll watch your progress and see if I can learn something. This might spur me on to finally building it.
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Old Jun 05, 2012, 07:15 AM
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USA, MA, Longmeadow
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Quote:
Originally Posted by payne9999 View Post
I am debating on the covering. I like tissue on a small model but a white film might look better. I have Doculam but I have never found a paint or prep combination that has much adhesion or durability. I was thinking of Parklite but these frames are real light and would likely warp. I was also considering SoLite.

Anybody have some advice on the covering choices?

Dave
Dave, I pretty much have used only Solite on all my smaller models, and Solarfilm on the larger ones (although not the size of your larger DC-6). Even with Solite you can warp lightweight structures. One issue with Solite is that the white is not terribly opaque. You can see your structure through it. I would think Solite would be much lighter than Doculam and paint. Peck Polymers has some other very lightweight film (.5 micron film) but I don't know if that's paintable, and I have no sense of it's durability.

I haven't used tissue in over a decade, so I can't really comment on the weight of tissue vs. film.

If it were me, I'd use Solite and be careful shrinking it (I only use my covering iron, turned up enough to just shrink the covering, and check frequently for warps).

I doubt that helps you much!

Mark
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