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Old Jun 06, 2012, 06:19 PM
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United States, IN, Indianapolis
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Build Log
Embraer ERJ-145 build

This will be a build log of an ERJ-145. I decided to build one if my Brasilia was mildly successful. I have yet to fly the emb-120 but I was fairly happy with the way it turned out and I learned a lot from building it. After the EMB-120, I knew I would have to build an ERJ-145 as it is the plane I fly for a living.

I am super excited to complete this build and hopefully add an ERJ to my hanger. I am late to start posting this, just have been really busy lately, but I started this project in late February.










Working hard.... or hardly working?
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Old Jun 06, 2012, 06:31 PM
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I started by adapting a 3 view to the size of a 70mm fan unit. I wanted the aircraft to have plenty of power in case it gained a little more weight than planned (as most builds tend to do). 64mm can sometimes seem anemic and I wanted a bigger model.




After laying out the 3 views and blowing them up on blockposter.com, I set about cutting out the profile of the fuselage onto dollar tree foam. I left the paper on, as paper-less seems to be a bit more brittle and harder to make clean cuts.



I then glued all three poster sections together and then layed across one larger carbon fiber tube and a square dowel the length of the fuselage. I then tacked the dowels down with hot glue so they would stay in place and tight. Then I applied gorilla glue to the dowels and foam joints.



I then drew out and measured as to what the fuselage diameter should be. The ERJ fuselage is sort of egg shape kind of like a dc-9. Thicker around the top than bottom. It isn't much though. I tried to then eye-ball that and adjust my drawing accordingly. When the fuselage diameter pinches down at the nose, it gives the nose sort of an oval shape in diameter. I tried to incorporate that as best as I could.
I then created bulkheads in the templates I had drawn. Then I glued the bulkheads down the fuselage length. Crossmembers were glued and a overhead profile was cut for the tail.

Completed profile with bulkheads:
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Old Jun 06, 2012, 06:37 PM
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Looking great! Are you going to do it in AA Eagle?

Ethan
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Old Jun 06, 2012, 06:38 PM
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Yes, so far that is the plan.
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Old Jun 06, 2012, 06:48 PM
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After the bulkheads were fitted and glued into place I decided to start finishing out the tail. Used wooden Popsicle sticks to stiffen the vertical stab. Then created two carbon fiber rods for two pieces of dollar tree foam to lay on. They will become the base of the horizontal stab. A dollar tree foam block was glued the length of the vertical stabilizer on both sides to create the airfoil shape of the tail when I wrap it with depron.





Now I glued on the two pieces for a horizontal stab. So far this setup seems to be strong.






Then I embedded a control rod on either side of the vertical stab to actuate the elevators. This way I can place a single park size servo in the middle of the fuselage on CG.


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Old Jun 06, 2012, 06:57 PM
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A few days later I started skinning the tail. Used 1mm depron. The stuff is like paper. Super light weight. Layed it over/ fold over, and used hot glue. Used a utility knife to trim the edges.






After that I sanded them down. Surprisingly the poor quality paper attached to the dollar tree foam somewhat sands off, so I created nice clean edges all around.
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Old Jun 06, 2012, 07:05 PM
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Next I installed the tail control surfaces. The only problem that I regret is the the elevator "horns" on the end don't go all the way to the leading edge on the real aircraft. The 3 views are wrong and I failed to catch it. But too late, not a huge deal, and should give me some extra elevator authority.

I did the same fold over technique of the dollar tree foam control surfaces. I layed the dollar tree foam over the depron and traced the profile. Then I trimmed a cm or two off the trailing edges of the DT foam so that way the depron can be pinched together to form a nice aerodynamic trailing edge.

I used pin hinges. The ones on the tail are "Great planes" hinges that I had bought off the bargain rack at an LHS.




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Old Jun 06, 2012, 07:19 PM
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Some construction problems I forsee will be dealing with CG. The real aircraft is nose heavy with passengers, especially with light baggage load <500lbs. A heavy load of 50 people can result in a noticeable heavier pull on the yoke to get the aircraft nose off the ground on takeoff. The RC version however will be tail heavy and I will have to work hard to keep things balanced. I plan to keep the ESC's mid-wing, the servos, rudder and elevator servos midwing, and the batteries up front. Still unsure on battery size but thinking of two 2650 or larger 4 cell batteries. Going to do two parallel power systems and a separate NiMH receiver batt. This way the aircraft has some redundancy and I might have a fighting chance at getting it home in one piece.
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Old Jun 06, 2012, 07:26 PM
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Now came the decision on what 70mm system I should go with. I looked at AEO fan combos, detrum, and changesun. I decided to go with the change-sun 10 blade fans with Turnigy 2855~2800kv motors. I bought two detrum 60 amp ESC's from hobbypartz during one of their coupon code sales. I have been very happy with the quality of dynam/detrum products. I have two dynam models and have had zero problems with them.

After a few weeks of waiting on HK, I received and put together my fans. The motors didn't come with any mounting screws. Luckily Menards Hardware had 3mm screws that fit perfect and I bought their last 3 bags worth.
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Old Jun 06, 2012, 08:12 PM
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AMAZING ERJ-145 build JD! Very impressive work Sir

You know I'm subbing to this thread!
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Old Jun 06, 2012, 09:06 PM
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I figured the next step should be building the nacelles. At first I tried making rings out of dollar tree foam but it was brittle and hard to make a thin ring. I was going to place the rings around the fan housing and then cover over with depron. I was frustrated with how they were turning out.

I asked my grandfather for help and he convinced me to use dow sheet foam and make larger rings. We cut four thick rings out of Dow blue and pink foam and glued them together. Their diameter was slightly larger than the intake lip of the 70mm fan housing. Then I spent a few hours a week or so later and carved them into the shape of the AE3007 nacelles. I also cut the inside so that the tabs on either side of the fan housing allowed it to slide in. This way in-case one fan would fail, I could easily remove for maintenance. I used cheap plastic utility knifes to carve the foam.

I then sanded everything down. Pics below are carved, not yet sanded.


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Old Jun 06, 2012, 09:44 PM
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Whoa, one of my favorite aircraft......definitely subbed for this one
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Old Jun 07, 2012, 07:35 AM
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While we were cutting out the nacelle rings, I told my grandfather my plan of using light weight foam spars and doing a flat bottom, fold over wing. He disagreed and thought a solid foam wing would be better. I figured why not try it. So we measured the wing out on dow foam, cut it with a band saw, and then traced the cord lines on it to guide me while shaping the wing. While it is not scale, we used a North American airfoil that is similar to the p-51. My grandfather has used this airfoil on a lot of his scratch balsa builds and claims it is very high lift.

The actual ERJ wing camber is pretty weird anyway so this would keep things a bit more simple. Plus it should behave well and be docile. Whereas the real ERJ wing is a mess with vortilorons, vortex generators, horns, etc that engineers had to install because flutter and low speed handling on the wing is terrible.

So after a week later after cutting out the shape of the wing, I set about carving it. It took 2 days of 3-4 hour sessions and a few sanding sessions. Several utility knife blades and lots of work. The wing is a bit thicker than the real thing but is very strong.





If the wing doesn't work out I will just go about building the original plan of flat bottom, fold over, with a few ribs and spars.
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Old Jun 07, 2012, 08:22 AM
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Quote:
Originally Posted by jdlilfan View Post
While we were cutting out the nacelle rings, I told my grandfather my plan of using light weight foam spars and doing a flat bottom, fold over wing. He disagreed and thought a solid foam wing would be better. I figured why not try it. So we measured the wing out on dow foam, cut it with a band saw, and then traced the cord lines on it to guide me while shaping the wing. While it is not scale, we used a North American airfoil that is similar to the p-51. My grandfather has used this airfoil on a lot of his scratch balsa builds and claims it is very high lift.

The actual ERJ wing camber is pretty weird anyway so this would keep things a bit more simple. Plus it should behave well and be docile. Whereas the real ERJ wing is a mess with vortilorons, vortex generators, horns, etc that engineers had to install because flutter and low speed handling on the wing is terrible.

So after a week later after cutting out the shape of the wing, I set about carving it. It took 2 days of 3-4 hour sessions and a few sanding sessions. Several utility knife blades and lots of work. The wing is a bit thicker than the real thing but is very strong.





If the wing doesn't work out I will just go about building the original plan of flat bottom, fold over, with a few ribs and spars.
Very nice set of 145 wings you've fashioned there JD!
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Old Jun 07, 2012, 08:40 AM
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Very nice work.
You know I'm subbed.
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