Groeps-bouwverslagen en ervaringen: Medicine Man 60"

@Thor, thanks. I also referred to the RealKits site as well as the RCSD article for weights and wing loading. But given the technical prowess (CNC) and look of your superb build, I was curious to see what other numbers to aim for. You made weight reducing holes in your rudder if I remember correctly. HAve others? No flutter?
@Arjan, yes, the word document, google translated. No problems there. Just in the forum comments, which I am sure, are just that, comments. I see you glassed the dihedral so I'm going to do that too.
My main issue is using 3mm flat stock, and 4x4mm. I don't have access to spruce here, but plenty of 6x19mm balsa. I don't know how robust the final structure will be and I want it to be vintage, retro. I think I'll know as work progresses if glassing fuselage, control surfaces, etc., will be a good idea or unnecessary. And if to add D-box to all balsa wing spar.
I'm pretty much following your methods, as well as US Imperial to metric, though I use carbon paper, lots of it.
If you had to build MM again, which areas would you pay attention to in terms of reinforcing. You referred to another US-builder in your first posts and he didn't seem to have luck with maiden and after.
More as we proceed. Thanks again. Best

 

Hello Vik,

Here are the weights so far:
- Wing uncovered 124 grams, covered 166 grams
- Fuselage with nose and canopy uncovered 70 grams
- Tail assembly covered 42 grams

Tomorrow I'll be working on building in the servos, receiver and control rod.

 

Hi Harry,
Hey, thanks for the rib-cutting template idea. Good stuff!
Vik

 

@Thor,
Thank you so much for the input. It will help me with my build. Good luck and do post pictures.
Best,
Vik

 

Progress so far

Both fuselage sides done, as well as horizontal stabilator, elevator, vertical tail, rudder. Nose cone awaits to tow line release mechanism from HobbyKing (very very slow)
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Tonight it's a bottle of Bols and ribs, ribs, ribs!

 

Klaar maar zwaar

Mijn MM is klaar. Wat ik nog niet helemaal snap is het hoge gewicht van 502 gram vliegklaar (met 3 cel NiZn voor in de neus, servos direct onder het luik, ontvanger onder de servo's). Ik moest zo'n 40 gram balast in de neus plaatsen om het zwaartepunt op 62 mm te krijgen. Het lijkt erop dat de staart redelijk zwaar is omdat ik 5mm ipv 4mm balsa gebruikt heb. Verder kan ik het (nog) niet verklaren.

 

Congrats Thor. Hmmm... so despite battery as far up front you still needed to ballast for CG? Did you use soft (light) or hard (heavy) 5mm balsa? 502 grams seems heavy, and you did say you made lightening holes in rudder right? Or did Google Translate give me wrong information? What covering are you using? I do remember removing all covering from tail boom once just to maintain CG. Wasn't pretty but it flew. Sandpaper the tailboom is another option but to tell the truth, from my years of experience flying (okay all ARF, RTF, PnP models), just maiden it on an early morning. Your workmanship is excellent and uncovering and readjusting is not an option now. Good luck. BTW, where did you place your towline hook?

 

I did make holes in the rudder but also used 5mm balsa instead of 4mm. Also the controlrod might be something to look at the next build. The wing is as far as I can judge within expextations.

It is however exactly what you say ... I'll give it a shot and will see what happens.
Today it is windy (thunderstorms) so maybe tomorrow.

 

Fuselage ready @ 40-grams

Fuselage complete at 40-grams. This week it's the wing. The spar will have to be vertical balsa web shears, carbon fiber capped, fiberglass sides, wrapped with aramid fiber. All because there's no spruce here.
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@Thor, what control rods did you use? I'm going with all cable pull-pull configuration.
Are you going to build another Medicine Man? Now that's perseverance.
Best

 

Nose plug

Nose plug is 10-grams before final shaping. Am still waiting for the tow-line release mechanism from HK.
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The HK mechanism: https://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=13365
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Vertical Tail Unite @ 10 gms

Vertical tail unit has come to 10-grams without covering, hinges, control horns.
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Ballast weights & balance

@Thor,
Have you maiden-ed your beauty yet? If you are still unsure about the weights you can do what I did when I moved from NiCad to Lipo and had ballast issues balancing CG. I used all-threaded rod and spacer/stand-off nuts, inserted it in the nose. Was not pretty, but it flew.
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All my 1.5 mm balsa stock is extremely hard so I'm going to have to do the ribs with 3mm stock. Trying to save weight everywhere, including the removal of case of the 72Mhz receiver. (BTW, on the Bubble Dancer forum I learned that 72Mhz is illegal in the Netherlands). Managed to save 5 grams by removing the Rx case.
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Best
Vikram

 

Pre-shrinking the tissue covering

Yeah, I know, the colors/colours may not be to your taste but they're last season's kite paper. Undoubtedly, high visibility.
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Horizontal Stabilator

The Horizontal stabilator and elevator comes in at 20-grams before reinforcing gussets and covering. Had to add bamboo leading edge to compensate for the 3-mm balsa stock used.
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Also cut stencils for the AC3PT aircraft number. AC3PT: Aircraft 3 Primary Trainer, this being my third glider build from scratch.
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Hello Vik,

No maiden yet. The weather has been very poor in the last days/weeks. I do not remember any season with so little flying days as this year. I use the cheapest control rods from HK. I do not recommend them. The sleaves are brittle and break when you look at them. Luckily I had 4 sets, 1 set was broken as it arrived, the second one while installing and 2 survived and are used.

I will build a second fuselage for the MM using 4mm balsa for the tail to see if I can save weight. The wing is okay as far as I know.

Currently I am busy building three architectural models for my wife's business (she is an architect by trade) so the 2nd fuselage has to wait a bit.

 

Monsoon Rains

It's a heavy monsoon this year, raining heavily day and night. My flying season is October onwards. Yup, I hear you on HK. Though I do buy stuff from them, I do not use anything that is critical. I am still waiting for the tow-line release mechanism to complete the MM fuselage. For such a light airframe as the MM, pull-pull control configuration is best I think.
Good luck on your new fuselage build. Have you considered installing electric motor and folding prop to move CG forward without use of ballast? I'm modifying the Gentle Lady power pod for the MM. I'll post the results and design if successful. That'll be ideal for your sturdier (but heavier) fuselage.
Best
Vikram

 

Vikram, just wondering:
Why are you waiting on a tow release hook?
An open simpel bend hook will do just fine, while a controlled hook is only a hazard?
(Or am I missing something)
other thing I was wondering: you and Thor seem to me to obsessed by weightsaving: the margins you guys seem to worry about are of no consequence at all.
Relax and fly this thing!

 

Aero-Towing Line Release Mechanism

@ Peter Den, the ventral hook for hi-start and winch launch is installed. The towline release mechanism in the nose is for aero-towing. Tug pilots require a release mechanism for safety, redundancy in case the tug's tow release fails.
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WRT weight savings, that's an ingrained trait as I am in the Himalayas where the lakes are slopes are 10,000 to 18,000 feet ASL. For improved penetration it's easy to add ballast. At the opposite end, it's difficult for me to lose weight while maintaining CG limits. I'm using two-ply kite tissue paper for covering. But as I want to fly this during the monsoon season, the required waterproofing will add a lot of weight so I'm trying to save on the airframe. Yes, I know, I'm getting anal about it. In fact, I was thinking of purchasing a new weighing scale with milligram resolution!
Best
Vikram

 

If anyone else needs tow line release mechanism, here's the hobbyking buddy code:
http://www.hobbyking.com/buddy.asp?code=05815190-14C8-4652-8CDC-A6F4685C2CCC

BTW: What does "handenbindertje" mean? Google Translator fails on that word.

 

Sorry, you are right, missed out on that.

Handenbindertje, Dutch expression literally: something that ties your hands together, but meaning something that keeps you busy/occupied all the time. (like a little child migth)

Still I would not advise to save weight to this extend and the paper covering, but he, it’s your call.
Anyway it’s a darling little plane, flies great too; keep up the good work!