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

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

Post by Neons » Sun Feb 19, 2012 1:42 am

Hello,
I started a new Build Log for my new plane the Martin Mars XPBM - ! and 2 version
I have 3 days into the build and have the slab side framing done now. I have the V formers and turtle back to do next. I will post updates here as I go along with notable parts in progress. For the most part it is in the RC Groups - Waterplanes forum. All the pictures, drawings and info is there alongwith subscribers comments.
http://www.rcgroups.com/forums/showthre ... st20789781
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The complete Photo Build log is in Photobucket Here als:
http://s1190.photobucket.com/user/neons ... t=6&page=1

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Martin XPB2M-1 Mars 1943- Scratchbuild

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I have started the new build of the early version of the Martin Mars that had the twin rudder. I have the fuselage framing started. I am basing the model on Ivan Pettigrews plans.
You can contact Ivan by emailing him. Here is his email address:
ivanp@dowco.com

Scale 1/20
Wingspan: 120 Inches
Length: 72 Inches
AUW: 13 pounds. as I estimate.
Wing Area: 1515 sq. in.
Wing Loading: 15.7 oz/sq. ft.
Airfoil: Eppler 197 with NACA with washout built in on outboard wing sections.
Power: Hex DT-750 brushless. MAS 10x7 with opposite rotations Nanotech 4s 5000Mah 14.8v Lipolys

The model will not be true scale as there are modifications on the plans that are not exact. I am going to divert from the plans some to use a mix of Depron foam and wood with some carbon fiber also I am first going to upload some pictures and drawings and maybe some notes of this version Mars.
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First off. There is another thread building the same plane in the JRM format by Rudderman a few years back. It is a very good build log if you follow Ivan's plans closely. As I mentioned I will follow some what closely. My plane will probably be slightly heavier. I am deiviating with different building materials here.
http://www.rcgroups.com/forums/showt...ght=ivan+plans

New Update: Mars XPB2M-1R Original Footage Found 1-2013
http://www.youtube.com/watch?feature=pl ... 22F9O3A0EM
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Update:
My Mars has been Maidened and took Part in the 5th Annual Nicolaci Floatfly Event Sept 6-7, 2013
Go to Page #7 to see the 2 videos posted.
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The framing was started with some fresh cut clear hard pine wood. I cut strips from 1/4inch thick pieces in 3 sizes. 1/4x1/4, 1/4x3/16, and 1/4x1/8th inches. Most framing was laid out with 1/4 square along the bottom longerons. The rest is mostly 1/4x 3/16inch. I used 1/8th inch balsa reaching above the waterline. Progress went along good for the 2 days here.
**Neons** Bob
Attachments
9-6-2013 Martin Mars Pics (6).jpg
9-6-2013 Martin Mars Pics (3).jpg
$-25-12 Picture Build Collage.jpg
XPB2M-1 Mars08.jpg
XPB2M-1 Mars-test.jpg
XPBM Mars- Cub.jpg
Full size Piper Cub on the wing.
XPBMMartinMars.jpg
Martin Mars Early 01.jpg
Mars Early2 view drawing.jpg
Mars- blue.jpg
XPB2M-1 Side View Drawing 01.jpg
2-15 Mars Hull side Frames (1).jpg
irst 3 pics - Day 01
2-15 Mars Hull side Frames (2).jpg
2-15 Mars Hull side Frames (3).jpg
2-17 Mars Hull  Framing (1).jpg
Next 3 pics - Day 02
2-17 Mars Hull  Framing (2).jpg
2-17 Mars Hull  Framing (3).jpg
2-17 Mars Hull  Framing (4).jpg
Last edited by Neons on Sat May 23, 2015 9:27 pm, edited 13 times in total.
Bob Pacheco

tomapowa

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by tomapowa » Sun Feb 19, 2012 11:32 pm

Very nice Bob!... I wish I had 1/2 your enthusiasm and energy... and time! :D

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Neons
Posts: 462
Joined: Tue Nov 22, 2011 10:28 pm

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by Neons » Tue Feb 21, 2012 12:50 am

Thanks Tom. It takes time to do these. Here are some more pics of todays work.

V hull formers , Water Rudder, Modified tail sector
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Here is what I did in the last couple days. I curved the nose section by making fine slits in the sticks and pinching in the sides to give it some round shape . The plans were showing flat. The photos look round. I laid all the V formers in place. I used a 1/4 x1/4" square for the keel. Tied it down in the nose and bent in the curve and CA'd in place. I put in a support gusset behind the plywood nose bulkhead. Next I installed gussets all along the chine corners inside. There just was not enough glue contact in that sharp angle. Here is a weak point I strengthened. Another point of stress that I wanted strengthened was the area under the wing trailing edges on the fuselage. I have seen many planes break right at that area in a crash including mine. These were all gusseted also.

The next thing I wanted is a water rudder that would conform to the original profile lines. I made the mount and cutout a rudder from the existing hull taper on the bottom. Using brass tube and a shaped copper end I soldered and then inserted that tube end into the hollow rudder. The outer housing was fitted into the hull and then a new former was installed with another gusset. The curved outer balsa hull shape was glued in place also. The bottom of the hull and rudder will have a thin plywood flared in place. All I have to do is solder a copper servo arm on the rudder post when ready.

The rear picture shows the rudder dropped in. There were additional formers installed in the tail section. I changed the keel angle to a slow curve rather than the straight run on the plans.as the real photos show. The stern post was widened to accept a tail gunner station. It will also help the elevator seating too.

Next I am looking at getting the elevator and rudder cables in place. The side sheating will go on first so I will also get better gluing access also. Then the bottom sheeting can be done.
Attachments
2-20 Mars Rear Hull Bot.01.jpg
2-20 Mars Rear Hull Bot.02.jpg
2-20 Mars Rudder prts 01.jpg
2-20 Mars Rudder prts 02.jpg
2-20 Mars Rudder prts 03.jpg
Bob Pacheco

tomapowa

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by tomapowa » Wed Feb 22, 2012 5:35 pm

Wow Bob... progress to the n'th degree!... Great to see such a unique and large scale model being built from scratch... mega kudos to ya! 8-)

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Neons
Posts: 462
Joined: Tue Nov 22, 2011 10:28 pm

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by Neons » Wed Feb 22, 2012 5:55 pm

Tom Thanks,
Just the way I build. I put in time like you do going to work. I flew 3 planes today. It was windy and I stopped after 5 flights. I just did not want to push my luck and create more work here. I enjoyed my new Hobby King - Tek-Sumo combat wing. Real fun flying that one in the wind.

Back to work on the Mars now. The upper formers on the turtle back and cable routes are in. I want to start sheeting the side of the hull now. I may have the hull almost all covered very soon.
Seeya,
Bob Pacheco

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Neons
Posts: 462
Joined: Tue Nov 22, 2011 10:28 pm

Re: Martin Mars XPBM-2 Scratchbuild - 1943- Hull Sheeting

Post by Neons » Mon Feb 27, 2012 11:30 am

Hull Sheeting

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Here is some work I have done so far today. I may go do a little more later. I use 3mm Depron foam skin. I use Elmer's Ultimate polyurethane glue. It does not matter what type glue you use but CA is not for this work. Poly glue is light and very strong. It cures overnight. It can be used without water spray but cures slower. The working time is slow. It allows adjusting the sheet. I also use a big syringe used for baking and to inject the meat with juices as you cook. I ground the needle flat and loaded it with glue. It is perfect for this job. It allows very controlled placement of a glue bead. I like this a lot. It can reach way into the plane and get the glue right where you want it. Look closely at the pictures and you will see the glue gun syringe. Probably can be found in kitchen supply stores.

This Depron foam is the best stuff I have worked with. It scores high in workability. The down side is it is not ding resistant. It will need spackling and 0.75oz glass cloth and a skim of epoxy. Even then I have to be careful. It is very light weight also.

I cut the foan to fit and put it in place like 1 -2 -3. That easy. Did a couple pieces and take a short break . Come back clean up any foam action from the glue and prep another section. About 1.5 hours I pull the pins. When I started the tail section bottom it has a 1/2 round former. This was a little different approach. I cut the sheet to almost fit. I got the edge to be glued straight and a good fit. Then I hot melt glued just the edge. When nice and solid I ran a masking tape along the seam. Then I used the glue gun and gave it beads of glue on all the contact edges. Taped it over the formers and pulled it dowm. Grab a stick and clamps and secure it. Let it dry before doing the other side.

After getting the last sheets on the sides I will be doing the bottom next. I shot a picture inside the hull to show how the sheeting is flat and a smal bead of Poly-U Glue foam action. It bonded very well
Attachments
2-23 Mars Hull Sheeting (0).jpg
Fitting and cutting a panel.
2-23 Mars Hull Sheeting (1).jpg
2-23 Mars Hull Sheeting (2).jpg
2-23 Mars Hull Sheeting (4).jpg
2-23 Mars Hull Sheeting (7).jpg
both sides layed up.
2-23 Mars hull Interior.jpg
You can see the light foaming on the longeron on the left side. Good bonding power and still light weight glue.
Last edited by Neons on Sat May 16, 2015 2:55 pm, edited 2 times in total.
Bob Pacheco

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Neons
Posts: 462
Joined: Tue Nov 22, 2011 10:28 pm

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by Neons » Mon Feb 27, 2012 11:43 am

Hull Bottom

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I did the half round under the tail section of the hull. Then I finished closing in the curves on the hull yesterday. I had to do it in 3 pieces each side due too the compound curves.The closing plank on the side would be a butt joint all around. I did not like relying on edge glue to support a closing plank. I put in battens to give more strength due to the extra bonding area. Look at the picture and you will see the pieces behind the foam edge. Glued it in and taped it up.

Today I did all the bottom sheeting. It called for 1/32 inch plywood and I did not have enough. I had 5mm Depron sheets that were firm.. I put the bottom glued in place in 6 pieces. . Before gluing, the bottom on each former near the keel has to be notched to allow water to pass (limber holes)without trapping it. The bow had to be pinned, taped, and clamped the get the curves. I secured the pink foam nose and tail blocks in place. I set it aside now to dry overnight.. I have some sanding to shape and nose and tail blocks next. Right now the plane weighs in at 1lb 13oz. (83Kg). Not bad.
Attachments
2-23 Mars Hull Sheeting (8).jpg
2-24 Mars Hull Sheeting (9).jpg
2-25 Mars Bot Sheet.jpg
Bob Pacheco

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Neons
Posts: 462
Joined: Tue Nov 22, 2011 10:28 pm

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by Neons » Thu Mar 01, 2012 12:40 am

Nose, Battery, and Access Hatch work.

The work in the past few days needed some thought as where I want my battery. A tray was installed and the hatch was framed. The nose and open cockpit is installed now. I will frame the cockpit windows and finish the hatch cover next. The cockpit floor will be shallow and not much details. The battery is below. I will put another sub floor under the wing also. So much room here.

I have the wing saddle frame to make then cover the turtleback and then I will think about epoxy skinning the fuselage. Sanding and priming soon.
Attachments
2-29-12 Nose Work (0).jpg
Formers in place
2-29-12 Nose Work (1).jpg
Battery tray in. The cross member in the middle is being cut out. A U shaped former will take its place. Lots of room
2-29-12 Nose Work (2).jpg
The hatch frame is made and nose sheeted. Wood use is preferred ahead of the wing leading edge into the hatch for strength.
2-29-12 Nose Work (5).jpg
The frame in the middle of the hatch was removed and it is easy access now.
2-29-12 Nose Work (6).jpg
The cables are in and the rudder is connected. Ready for Depron covering. A pink foam tail block is in place and will be shaped later
Bob Pacheco

tomapowa

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by tomapowa » Fri Mar 02, 2012 12:24 pm

WOW!... great progress Bob! Love the foam fuselage holders too! :D
How much "battery" do you anticipate is needed? Was that a 4S pack I saw?

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Neons
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Joined: Tue Nov 22, 2011 10:28 pm

Re: Martin Mars XPBM-2 Scratchbuild - 1943

Post by Neons » Fri Mar 02, 2012 1:28 pm

I am working with a 5000Mah 4S 14.8V battery. Weighs 1lb. I have accomadations for 2 if needed. one will fly the plane well if it balances good. The original plan had Nimhs in the bottom of the V hull. They probably were heavy also. I am building my way as the plan was over 8 years old with can motors. Brushless was in its infancy and Lipo batterys just started coming around then. The plan is designed to be very lightly built but it has many flaws in strength. If you see the video, it is a floater. You will see these are the later tail conversions from 1943 on. They later were called JRM"s.

Both of these planes in the videos use obsolete can motors and nicad systems.
Rudderman's plane.
http://gvillette.rchomepage.com/marsduo.wmv

Havsgard's plane
This is a nice video. Low and Slow.
http://www.youtube.com/watch?feature=pl ... sgM6-AmDhg
Last edited by Neons on Sun Mar 11, 2012 1:56 pm, edited 1 time in total.
Bob Pacheco

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