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May 10, 2013, 10:59 PM
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Wormboy's Avatar
Build Log

Mission to Mars (Ivans Martin Mars)


Hi All,

Well I though I better kick off my Mars build thread now that I actually have something tangible to show rather than just lots of head scratching and thinking.

First things first, a couple of links to other Mars build threads on RCgroups to remind myself and others of the goal
Rudderman's Mars,
Falconhob's Mars
and Neons' Mars

and a link to the Great Big Thread of Everything Ivan

Hi I'm Mat and my family thinks I have a problem, I am addicted to planes
This will be about my 12th build, but only my third in Balsa. Most of my experience to-date has been with depron. Many of my builds have been seaplanes and I just couldn't go past the Mars when I saw Perry's efforts a couple of years back. It's been on the to-do list for a long time but I've only just now managed to scrounge up the courage to start on a build of this size. It will be almost double the size of my next biggest build.

The progress so far.
I started with the power system as I am more comfortable with a soldering iron than with wood. I've chosen a system I know will perform, as it uses the same components as my Puddletwin.

4xTurnigy SK3 2830 - 920kv.
4x MA 9x7 3blade
4x Turnigy AE-25A ESC
2x 2500mah 3s lipos in parallel for a total of 5000mah

I know that each of the 4 power trains will pull about 100W with the 9x7x3, but with the capacity to pull 150W turning a different prop. Thatís about 400W, with the capacity to boost up to 600W if needed. That should be plenty going on the experience of others, and should give me a nice low and efficient amp draw for a relatively long flight and cool motors. I love the idea of the 4 blade varios that others have used but I couldn't justify the extra cost on a scale detail that you would only see when the plane is on static display. Maybe I'll change my tune later.

Despite trepidation, I started on the wood. The tailplanes are almost there and while I was waiting on the glue to dry I went ahead with the tip floats.

As seems to be tradition with the Mars builds, I've had to make a couple of extra floats as the first ones failed miserably. First time I cut out my formers with the grain in the wrong direction making them collapse under the tension of the sides, making it look more than a rope ladder than a mini fuselage. The second time I had a glue-related issue. On to Mk3 and 4 now and looking much better.

Speaking of glue... I have used CA on previous builds but this time I wanted to try a wood glue for its inherent flex. To combat the water that the Mars will see I went for Titebond III, a water proof wood glue.
The glue works very nicely when there is no tension in the joins, such as on the tailplanes, or when you can pin or clam effectively. However, once there is tension on the bond, such as in the tip floats, it is worse than useless as you can't maintain more than 1 wet joint at a time. I spent an hour trying to glue the formers of one tip float with titebond and failed miserably. I tried the same task with CA and completed it in 5 mins. Needless to say I am back to the CA, it's just not worth the grief..

This is likely to be a relatively slow build, but I do have a goal of the end of November. In Perth we have a biannual float fly event south of the city and I would love to take it down there for a spin. With the last event just gone, I have almost 6 months to to complete the effort. We'll see if I'm being too optimistic.

Wish me luck,
Mat.

Back to the build bench...
Last edited by Wormboy; Aug 13, 2013 at 03:10 AM.
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May 10, 2013, 11:36 PM
Electric baptism 1975
DavidN's Avatar
Bon Courage it's a big bugger.
May 11, 2013, 12:07 AM
96RC/3178W
MattZC's Avatar
Great to see another one going. I am one of the ones with the varios' (couldn't stay away, they are too cool .)

I also wanted to mention my setup and the problems that I have recently resolved. I have a bit smaller SK3's in my thread, I think they are the 1340 Kvs. I pair those with dlux 55 amp ESCs, and the entire system is currently powered with 2 2cell 5,000mAh packs in parallel giving me 10,000mAh total.

I was having trouble with a drop in voltage resulting in the ESCs going into their low voltage cut off when testing with smaller batteries. Even today doing my testing I unknowingly ran all 10,000mAh out down to 6% charge. It went by real quick when testing sounds and diagnosing vibrations at full throttle.

If you have any problems with the motor set up, I'll be happy to lend some advice to the best of my abilities.


Good luck!
Matt
May 11, 2013, 03:54 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Best of luck with this build, we'll be watching from the other side of the world,

Mike
May 11, 2013, 03:59 AM
Registered User
Trevorh's Avatar
I'm subscribed too. Should be an interesting project Mat.

On the subject of using Titebond and holding things in place: I am sensitive to cyano so only use the odourless variety. This is a little thicker and slower than standard CA and, if you apply Titebond in the usual way and then add a spot of cyano every inch or two, the cyano will tack the part in place while the Titebond dries. Some refer to this as using 'cyano pins'.

Apart from economising on the expensive CA, this results in a joint which has the flexibility and sandability of Titebond. I find it especially useful when planking, where I tend to use the Titebond along the length of the strip and a spot of cyano on each former.

Good luck with the build, and have fun!

Trevor
May 11, 2013, 06:02 AM
low and slow
SASflyer's Avatar
Hi Mat!

Great project!
I have built a Mars, and it is still my favourite flying boat. You have probably watched the video.
I still take her out as often as I can. Winter has finally given up here in Norway, the last ice melted 2 weeks ago on the lake I fly from..

Thought I was going to suggest a few things..

First: make the tail removable! Otherwise you will never get out the door in one piece! Falconhob has a nice solution I used as well: https://www.rcgroups.com/forums/show...=696752&page=8

Get proper programmable speed controllers. I used some Hobbywing ones, but the Turnigy Plush series seems to be identical: http://www.hobbyking.com/hobbyking/s...ontroller.html
Get the programming card for them. You need to be able to sync them properly as well to get even power. Set the inboard motors to hard cutoff at high voltage, and the outboard to soft cut and low voltage. That way you will lose an inboard motor first as warning of low voltage. You can still complete the circuit on 3 motors.. And taxi back..

Arvid
May 11, 2013, 09:19 AM
Cut it twice, still too short
dglo's Avatar
Hi Mat, I'll be watching, and trying to learn along the way since I'm building Ivans PBY. It's the 4 motor / differential throttle thing that I haven't worked out yet. The PBY is big, but the Mars is a monster, I admire the gumption, and good luck on the build.

Doug
May 11, 2013, 09:54 AM
Summit Model Aeronautics
Steve85's Avatar
You can't have too many multi's!

Steve
May 11, 2013, 07:12 PM
Registered User
LukeZ's Avatar
Hi Mat, nice to see another Aussie tackling an Ivan build. There's only one other recorded that I know about, but Ivan suspects there are others sneaking about. However you can probably be rather certain this is the first Ivan's Mars on your continent.

I've added your thread to the sticky-list. Best of luck as you go!


Luke
May 11, 2013, 09:46 PM
Owner - Flying Models
Good luck Mat, can't wait to see its progress.
May 12, 2013, 12:46 AM
Registered User
Wormboy's Avatar
Thanks everyone for the well wishes!

See this is why we do build threads. We're still on the first page and I've already got 2 good ideas. Cyano pins and having only one ESC set to hard LVC as a battery fail safe. Awesome!

Luke, Thanks for adding me to the sticky. I do know of another Australian Ivan build, Trumps Solent He actually lives about 15mins down the road from me but we've never met. We're planning to fly our seaplanes at the same lake when they are both done.

Arvid, Yes, I have seen your low and slow video. It is a permanent link in my favourites bar I consider it my seminal inspirational video.

Trevor, thanks for the cyano pins, strip planking the tip floats is next so I'll be giving it a go.

quick build update: the tip floats are half way there, just need to add the mounting plates and strip plank the tops. They were a little interesting, harder to make straight than a box full of springs. The product is OK and I'll move forward with the ones I have and reassess if they are good enough when I come back to mounting them on the wings.

Cheers,
Mat
May 12, 2013, 01:47 AM
AMA 670207
Rudderman98's Avatar
Sub'd!
May 12, 2013, 03:19 AM
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Quote:
Originally Posted by Rudderman98
Sub'd!
Welcome aboard. I wondered when you'd turn up
May 12, 2013, 03:23 AM
AMA 670207
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Quote:
Originally Posted by Wormboy
Welcome aboard. I wondered when you'd turn up
Just lurking in the shadows.
May 12, 2013, 01:17 PM
Registered User
Here's a great Mars build from several years back. If desired you can skip forward to page 27 to get past the build proper and teething pains to see flight videos.
https://www.rcgroups.com/forums/show...ght=martin+mar


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