Martin Mars XPB2M-1R Scratchbuild - 1943-123 inch Wingspan

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Neons
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

Post by Neons »

I decided that the timing to do my wiring for the motors and ESC's, and aileron servos is now. What better time than with the open spaces. I used #14silicon wires. This stuff has some weight to it. When I pick up the wing at the spar the wing tilts forward with the wires. At least it is forward the CG. I cut and spliced all the joints then shrink wrapped them. The 3 wire connectors are all in. I bought all raw 3 wire length. I cut them to fit with some slack.

Then I have the #202 tool for installing the plugs and pins on them. The male Futaba plug that is at the wing joints fits snug in a slot I made in the plywood rib face. It will be glued in place sticking out 3/8". When I slip the outer wings in place I just plug the female in. The outer wings will have a small mating slot with room for a wire looping in it when the wing pushes together. I have the balsa sheeting glued on tonight and setting up.
Attachments
Same wiring as the Emily has.
Same wiring as the Emily has.
Note the wires are long on this plane. Voltage spikes can damage the Esc's . Add capacitors.
Note the wires are long on this plane. Voltage spikes can damage the Esc's . Add capacitors.
Last edited by Neons on Sun Apr 08, 2012 1:52 am, edited 1 time in total.
Bob Pacheco
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

Post by Neons »

Bob
Are you going with your plan and mounting the esc's with the motors?
It's just everything I have read says extend the wires from the esc's to the motors and mount the escs as close to the battery as possible?
david

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You are right. I believe I will have space for some capacitors. It is not on my immediate to-do list at the moment. I have 10 feet of #14 wire in this layout so far with +/- wires. If I go with 3 wires per motor of maybe #14 and maybe over 25 feet long which would most likely compound the weight in there now. I think capacitors are better and to have each ESC behind the motor getting air in the cowlings.
Here is the article
http://www.rcgroups.com/forums/showthread.php?t=952523
I just have not ordered any yet.
Last edited by Neons on Thu Apr 12, 2012 9:12 am, edited 1 time in total.
Bob Pacheco
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

Post by Neons »

Info Added:
Long power leads can destroy Esc's over time from spikes.
I believe a set of these on each motor will do the trick. Mount near the Esc's in the battery leads.
HK listing.
http://www.hobbyking.com/hobbyking/stor ... duct=17100
Here is the story on spikes effecting Esc's over time.
http://www.rcgroups.com/forums/showthread.php?t=952523

ADDED NOTE:
Here is a picture of a real good wiring system. It allows 2 motor control on the water for steering and a backup motor failure system for a low battery.
This is a very welll thought out system.
Attachments
Tie this unit in each power lead before the Esc's.
Tie this unit in each power lead before the Esc's.
Concerned about damage due to long wire leads to the Esc's can be corrected by adding capacitors parallel
Concerned about damage due to long wire leads to the Esc's can be corrected by adding capacitors parallel
Here is a good alternate wiring system for split  motor controls
Here is a good alternate wiring system for split motor controls
Last edited by Neons on Thu Apr 12, 2012 9:20 am, edited 1 time in total.
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

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Nacelles Glued- Wing Mounting
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Here is what is going on. . I sheeted the mid section wing and made adjustments to the ribs for 1/8" (3mm) Depron foam in the middle. I guess my order for 1/4" (6mm) foam has failed. Change of plans for covering now. It is ready now.

After the sheeting I was able to mount the 4 nacelles. I cut 8 ply circles for the nacelles. The one shown gives me plenty of access with the routed opening to mount the ESC,s and my capacitors. The next ply covers this one and will each have an air slot for air flow through the nacelles. Of course there has to be a hole in the bottom for air exit. Secured with small screws around the circle. It will have cowling mounting blocks also.

Next I got the wing all lined up and made a nice fitting saddle. Then I made 2 -1/4" dowels through plywood in the leading edge of the the wing into the fuselage. I faired it all in with balsa seen in the picture. Now I am on the turtleback and wing screws today. I hope to fair it in also and have the nylon screws in place. Then I am of to the stores to find my coling molds. They could be a cup, mug, plastic seal tupperware, or something like a cowl that can be used as a fiberglass mold. The diametor on my nacelles is 1/2" larger than the plan for more space.

I weighed the plane today. First I weighed myself. Then with the plane. 7lbs. up to here. I am satisfied so far. I think epoxy finish will be 1.5lbs. Battery 1lb. Motors and Esc's, sevos. 1lb. I think I have leeway here.
Attachments
4-9-12 Nacelle and Wing Mounting (2).jpg
4-9-12 Nacelle and Wing Mounting (1).jpg
Last edited by Neons on Thu Apr 12, 2012 9:12 am, edited 1 time in total.
Bob Pacheco
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

Post by Neons »

Arvid,
I finally found your thread posting of the Martin Mars JRM water tanker. I viewed the video of your beautiful Mars JRM flight today. Just perfect. I enjoyed your flight and very informative postings. You are a very advanced accomplished builder and pilot. I like the way you wired your plane. The 4 motor wiring is simple for me. I wish I saw it last year. It is OK though. I had to figure out how to do my wiring for myself. It did work fine for me also. I will keep your schematic in mind also.

For anyone that has not seen them, here they are.
Slow and serene lake flight.
http://www.rcgroups.com/forums/showpost ... count=1524

Another flight video of the plane.
http://www.rcgroups.com/forums/showpost ... count=1217
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

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Got the turtleback and wing mounting done. It came out great. Now I looked around Walmart for some cowling shapes. I found these food savers with snap lid. Correct size and a good shape for cowlings. There was some cup size glass Pyrex ovenware there. It would make good fiberglass molds. I found the plastic near perfect and I do not have to make fiberglass parts. These are tough and will paint up very well. The ridge may be cut out if I can't utilize it into cooling vents.

The motors are Hextronic DT-750's. Also known as Blue Wonders. They have good mid range torque. I ordered 4 Master Airscrew 10x6x3blade props. 2 pusher and 2 tractors. If there is a good flyboy out there that can advise me how I should run 2 props of the opposite direction please chime in.
Attachments
Test fit is good. Notice the turtleback bolt area all faired in.
Test fit is good. Notice the turtleback bolt area all faired in.
The cup size food storage are 3 1/2". Hole saw the bottoms out. They have a ridge for the cover. I have plans for that.
The cup size food storage are 3 1/2". Hole saw the bottoms out. They have a ridge for the cover. I have plans for that.
All setup for a test fit. Test props
All setup for a test fit. Test props
The cup size food storage are 3 1/2". Hole saw the bottoms out. They have a ridge for the cover. I have plans for that.
The cup size food storage are 3 1/2". Hole saw the bottoms out. They have a ridge for the cover. I have plans for that.
Mounting screws and blocks are in. They get sheeted over after some formers get glued in.
Mounting screws and blocks are in. They get sheeted over after some formers get glued in.
Bob Pacheco
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

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Wing Sheeting
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Tonight I got the top of the wing covered. Tomorrow the bottom and start the outside plugin wing covering. Moving along again. I have less than 2 months here so far. It could be possible I may almost be done by May.
Attachments
4-12-12 Wing Sheeting (0).jpg
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

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Wing Sheeting Done
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After a few days on the sheeting of the wings I am relieved now that all the components on the Mars is 98% done. Smaller items to do after the plane is primed. I got my new cowlings to fit perfect and they look great. I have to mount the motors and cowl screws soon. I am going to assemble the plane maybe tomorrow for an outdoor shoot out in my yard. Watch for the prefinish pictures. This is now getting into the final work stage for painting now. I first have the epoxy/cloth to do. Depron is very prone to rash. 4 days short of 2 months up to here in the build
Attachments
4-12-12 Wing Sheeting (2).jpg
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

Post by Neons »

Unfinished - All Assembled
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Got the pictures. Not too sunny today. Nice day though. The plane parts are just stuck on. The plane with the cowlings, motors, props, and a large 1lb batterry is just over 10 lbs now. It will climb more with the finish coats, servos, short wires, and reciever. I like the closeness of the CG with 1 battery so far I am satisfied so far. This what I can do in 2 months.
Attachments
4-15-2012 Plane Assembly Overall (5).jpg
4-15-2012 Plane Assembly Overall (3).jpg
4-15-2012 Plane Assembly Overall (2).jpg
4-15-2012 Plane Assembly Overall (1).jpg
4-15-2012 Plane Assembly Overall (0).jpg
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Re: Martin Mars XPB2M-1R Scratchbuild - 1943

Post by Neons »

Firewall Setup
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Today I did some work on the plane after working on a couple other flight repairs and painting. The dual firewalls and the motor mounts all were secured. I used 6 screws to hold the outer firewall in place. Then I installed wood blocks for 3 cowling screws. There is plenty of room behind that firewall. After it is glassed there is an intake air scoop on top of the nacelle that will help get more air flow inside also.

I ordered 4 new ESC,s as I only have 3 here and a matching fourth cannot be replaced as they are not in stock. The " Blue Wonder" Hextronic DT-750's motor shafts have to be changed to solid 4mm shafts and with 4 collets. I do not trust these props with small nuts holding them tightly. Not so good with 2 motors going the opposite direction with the thread. They could fly off. I was able to sand the plane and do some Lite Spackling today. I will be glassing the bottom first.
Attachments
4-18-2012 Firewall Assembly.jpg
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