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Very Hot Topic (More than 25 Replies) Marcoux Bromberg (Read 10118 times)
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Re: Marcoux Bromberg
Reply #15 - Jan 5th, 2019 at 8:14am
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I'm back on the Marcoux Bromberg racer and have started from scratch since I started this with the wrong attitude and a more simplistic approach. I was intending to just make it a "good to look at" model without a great deal of detail in an effort to make my commitment but as I got in to the details I decided to move away for a while. I'm now approaching this with a more sincere motive and far greater detail. So to that end all the documentation and paperwork have been recycled and all balsa committed to the project has been reclaimed and as mentioned before, the wood is in the wing of my Interstate Cadet. The documentation for this project has been enlarged to a 1/12 scale (1" = 1'). Since there is not a great deal of design documentation available, I will use some more common design methods for the wing ribs and will stick very close to the available information on the drawings and the model will be representative of the last modification to the airplane in 1938. This is the version purchased by Rudy Profant and modified further by him. His modifications did not add any great difference in the plane but he did change the color from a cream color finish to the current yellow fuselage and black wings. So with all the being said, I have completely cleared my building area, cleared the drawing board, vacuumed the floor (made my wife happy), added some storage area for all the new toys I managed to accumulate and sanded my mag board to remove all the bumps and stray glue bits of glue and dope. So, this is the new beginning and I will stay on course to the end. There will be a lot of design work  but with no more outside distractions, should be a fun build.
Mike
  

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"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #14 - May 20th, 2018 at 6:10am
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Greetings all - The rudder and horiz stab were built using the typical stick and tissue method then the 1/32 sheeting was applied as Tom mentioned. His caution is well placed as the reactivation of the glue is permanent and tight, as I have heard say "bark on tree tight" and no going back. The wing has been completely rethought and I took it apart and used the material in my Interstate Cadet wing. The reason was that I was intending to use two spars spaced at the sheeting width I didn't allow for the reduction in rib length as it neared the tip and completely changed the airfoil and I was using a leading edge that was too thick and too tall, too much carving. The new wing will use ribs sliced along the chord line and built in two pieces allowing the rib to be flat on the building surface to add the portion of the leading and trailing edge and two spars, then take that assembly up and add the bottom of the airfoil and the lower spars. The chord line exits slightly below the trailing edge so no need to add any more material there. That and I have a very small building area and the wing was taking up too much room on my drawing board. I'll finish the Cadet and get to the Marcoux Bromberg very soon as it is quite important to me.
Mike
  

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #13 - May 19th, 2018 at 5:31pm
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I believe the tabs are so the wing can be built flat on the table till it's ready to add dihedral. 

As far as the heat treatment on the sheet balsa you'll need to add glue to the bottom of the sheet marking out the areas that will touch the L.E. and T.E. and the ribs and apply glue to that area only allowing it to dry completely.  The heat from the iron will polymerize the glue on both surfaces and lock them together.  Just make sure you have everything aligned correctly before applying heat.  You'll have to experiment on getting the heat hot enough without too hot!

Make the sheeting a bit oversized.  And trim it at the L.E. and T.E. after the heat is applied and the sheet is attached.
Tom
  

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Re: Marcoux Bromberg
Reply #12 - May 19th, 2018 at 5:19pm
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NB:
I really learned a lot from your build.  I also learned a lot from Sky9's suggestions on sheeting.  This is an area that will be tried (& tested) on my future modeling project.  From what I can see, it appears you're building the wing without any spars, only the leading and trailing edges will hold the ribs in place, with the sheeting forming "an enclosure."  I wondered about the small tabs along the trailing edge of the ribs.  Did you have to compensate for the size of the ribs? That's new to me.  Great job!  Gary (Skye)
  
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Re: Marcoux Bromberg
Reply #11 - Apr 18th, 2018 at 10:52am
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Been working in the background on this model while doing two others in parallel. Wing started, all ribs cut and leading edge cut and glued together. It's big but when I started to shim up smaller parts it seemed better to do some sculpting to size after all is in place.
Mike
  

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Ribs_In_Perspective.jpg

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #10 - Apr 11th, 2018 at 11:23am
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Got some better prep work done on the rudder and horizontal stabilizer. Will continue to do the fill type finish work as I go so now off to the wing.
Mike
  

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Rudder_and_Horizontal_Stabilizer_1.jpg
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"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #9 - Apr 9th, 2018 at 11:40am
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Tom - The stacked method seems like the most reliable method and thank you for the link, always like to see other sites and possibilities. Help like this saves mountains of time and thanks again for the link - bookmarked for future reading. I'll post pictures as I go, maybe save someone else some time. I used the hot iron/glue method for the rudder and horizontal stabilizer and will also use it for the wing. I'm using a small travel iron I found at a second hand store. Checked with the remaining hobby shop in my area and he cannot get monokote irons any more due to his small volume. To temperature, I use the iron setting some where near the wool setting and assume if it turns the wood brown, probably too hot.
Mike
« Last Edit: Apr 9th, 2018 at 2:07pm by New Builder »  

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #8 - Apr 9th, 2018 at 11:26am
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NB...
There are several ways to make wing ribs.  With this wing I'd suggest two ways. 
1. the stack method.  With the center of the wing having constant chord before the taper to the tip I'd stack blanks of balsa the length of the ribs and height of the ribs.  Then sandwich the blanks between two rib shaped former/templates made from hard wood/ply/plastic that can be screwed or pinned together together.

2. the second stack method would be for the ribs from the wing center ribs to the tip using similar templates as above stacking blanks (equal number for all ribs needed, don't forget both wing panels).

Here's a link with pictures: Click Here

As for skinning the wing with thin balsa, an old rc trick was to apply alphatic glue (white or carpenter's yellow glue) to the ribs and on the inside of the  skin where the ribs would contact by measuring and marking the place of the ribs.  After the glue has dried an iron can be used to heat the skin and ribs.  Place the skin on the rib framework aligning the glue joints.  Then apply heat from the iron on the skin heating the glue which will bond together the ribs and skin.  You'll have to experiment with how much heat, doesn't take much.  If you have a Monokote iron the temp should be around 200 degrees.  Just iron over the joint areas.  This will weld the skin to the wing structure.    Works really well.
Tom
  

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And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Re: Marcoux Bromberg
Reply #7 - Apr 9th, 2018 at 8:15am
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Some progress since I last posted. The rudder is complete and the horizontal stabilizer with elevators is also nearly complete. The wings soon but have been going back and forth with the idea of the Dave Rees sliced rib method so as not to have to create every rib for the wing. after trying some vain attempts, decided to go ahead and create each rib. Went to the print shop and reduced the main rib to the proper length and now am ready to go for it. The wing has a semi-symmetrical airfoil so will employ a tab at the trailing edge to help with alignment and trim it off later. Only need a couple of spars to hold alignment and then sheet the entire wing since the airplane is all metal should go fast. Planning and trying methods is the slow part.
Mike
  

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Rudder_and_Horizontal_Stab_2.jpg
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Wing_and_Airfoil_Closeup_001.jpg

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #6 - Mar 17th, 2018 at 1:54pm
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More progress. rudder 3/4 complete, horizontal stab about 1/2 complete.
Mike
  

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Rudder_Near_Done.jpg

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #5 - Mar 17th, 2018 at 12:38pm
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Creating airfoils for the horizontal stab and the rudder. This is my favorite method, create a 1/16th frame, laminate 1/16th to both sides, sand to shape, cover with 1/32nd, add the top and bottom, sand again and finished. Will fill and finish all the parts as sub assemblies then assemble. Lots to do between now and then. Seems I need to look into the macro setting on my camera as it is on but doesn't look like it.
Mike
  

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"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #4 - Mar 17th, 2018 at 8:04am
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Some history is in order here. Can't be out done by the WWI guys. The Marcoux Bromberg started life in 1933 and was financed by Mrs. Edith Clark and W. H. Marcoux. The plane was fabricated in an abandoned casket factory in Santa Monica, Calif. and was designed for the MacRobertson Race. At the completion of the build it was test flown in 1934 by Jim Grainger and lacking experience with high performance aircraft, landed too fast, over braked and nosed over damaging the tail, crushing the cockpit and killing Grainger. Earl Ortman was later hired to fly the plane. He took the plane to the Vancouver to Agua Caliente, Mexico race and set a record 5 hours, 27 minutes and 48 seconds that stood unchallenged for 2 years. A larger engine was installed for the 1935 Bendix race and on a test flight the cowl pulled forward into the prop and hasty repairs were made and the plane departed for Cleveland but made it to Kansas City with further damage and was declared to be not air worthy for the race. The plane was repaired, flown back to Calif. and was retired due to labor liens. In 1936 title was transferred exclusively to Hal Marcoux who then hired Douglas Aircraft engineer Jack Bromberg. They made extensive repairs and changes and renamed the plane the Marcoux Bromberg Special. The plane was entered in the Thompson Race in 1936 and placed second with an average speed of 248 MPH. The plane was reworked several times over the ensuing years and was flown in the MGM movie "Test Pilot". In 1938 the plane was raced in the Golden Gate Classic winning with a course record of 266 MPH and won several other races. A new more powerful engine was installed and the plane departed for Calif. and landed in Kansas City and with ice on the brakes and no flaps, nosed over. The plane was rebuilt in Kansas City and took part in the 1939 Thompson Race. During the race, the engine quit 3 times but managed to complete the race in 3rd place with an average of 254 MPH. The plane was retired after the race and this is where history seems to end. The history or more importantly, lack of history, would place the plane in the New England Air Museum. Actually the plane was purchased by Rudy Profant and was in his care for 20 years. He made some modifications and changed the color to that described in his letter to me, then made its way to the New England Air Museum. So ends the capsulized history of this airplane and now it's my turn to add to the history.
Mike
  

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"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #3 - Mar 16th, 2018 at 1:45pm
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More pics of the build.
  

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Rudder.jpg

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #2 - Mar 16th, 2018 at 1:17pm
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Hi Tom - I'm using built up structures like a rubber power plane and sheeting the entire plane since it is an all metal plane. My original plan was for functional controls but decided to build one like a rubber model for a "proof of concept" and you are right, it will make a good rubber power plane further on down the line.
Mike
  

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Re: Marcoux Bromberg
Reply #1 - Mar 16th, 2018 at 1:11pm
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Looks great.  I look forward to seeing this build.  You're talking solid???  If so, what are you building it out of material wise.  Basswood, balsa, or something else. 

I'll be watching with interest.
Tom

P.S. this might make a great rubber powered plane!
  

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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