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Very Hot Topic (More than 25 Replies) Diels F7F Build - My First Twin (Read 61077 times)
MKelly
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Re: Diels F7F Build - My First Twin
Reply #40 - Jul 29th, 2017 at 7:43pm
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Tom,  I thought about that quite a bit.  However, this tail is like a peanut scale wing - 11" span with a fairly thick airfoil.  I figured if a peanut wing doesn't need a rear spar this tail could probably get away without one as well.

Time will tell how foolish I am... Worst comes to worst it'll be quick to build another one.

Cheers,

Mike
  
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Re: Diels F7F Build - My First Twin
Reply #39 - Jul 29th, 2017 at 6:48pm
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You might want to consider that rear spar to help avoid warps.  Just a thought!
Tom
  

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MKelly
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Re: Diels F7F Build - My First Twin
Reply #38 - Jul 29th, 2017 at 5:42pm
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The infill is mostly cosmetic - I like solid cowlings.  The nose on this airplane is long enough that any cartwheeling will involve nose, tail and wingtips.  I doubt the nacelles are likely to hit.  I've used 5lb/cuft balsa to try to keep the weight down, and most of the infill gets sanded off.

Got the other side of the ribs on the stab today, and after that was dry I blocked it up on the magnet board, sanded in the lower spar notches and installed the lower spar.  The plans show a rear spar and separate elevators, but I intend to make the stab screw-adjustable so I left the rear spar out.

Mike
  

( 161 KB | 81 Downloads )
0729_Stab_Ribs_-_Bottom_Side.JPG
( 179 KB | 69 Downloads )
0729_Stab_With_Lower_Spars.JPG
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LivingroomFlight
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Re: Diels F7F Build - My First Twin
Reply #37 - Jul 29th, 2017 at 3:05pm
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The nacelles are looking great. Is the filling also for the CG or only strength? Very interesting build  Smiley
  
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MKelly
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Re: Diels F7F Build - My First Twin
Reply #36 - Jul 29th, 2017 at 11:05am
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LWM,

The L-square with equal thickness supports really helps a lot - you can put enough pressure on the square to hold the part steady without having the part roll like it would if you were using just a ruler.

Mike
  
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LASTWOODSMAN
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Re: Diels F7F Build - My First Twin
Reply #35 - Jul 29th, 2017 at 8:38am
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Thanks Mike - I always have trouble holding a thin balsa part down with a straight edge metal rule, and cutting with an exacto knife - the part always moves on me ... I need much lighter cut passes like you ...   Smiley  and a fresh blade (duh) - I only have a box of 100 new Hobbico #11 blades sitting here ...  Lips Sealed
LWM
  

OH, I HAVE SLIPPED THE SURLY BONDS OF EARTH ... UP, UP THE LONG DELIRIOUS BURNING BLUE ... SUNWARD I'VE CLIMBED AND JOINED THE TUMBLING MIRTH OF SUN-SPLIT CLOUDS ...
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MKelly
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Re: Diels F7F Build - My First Twin
Reply #34 - Jul 28th, 2017 at 9:13pm
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Thanks guys - it's looking good, and pretty light so far (under 6 grams for the sanded nacelle).

LWM,

I cut the stab ribs from the parts sheets just outside the line using an xacto knife.  After match-sanding, I sand in the L.E notch using a homemade notch sander (220-grit sandpaper glued to the edge of a scrap of 1/16" sheet).  Then, with the ribs still tacked together, I line up a small L-square on the cut line (supporting the back of the square with parts sheets or scrap balsa matching the thickness of the rib stack), then cut along the edge of the square with the xacto making several light passes and taking care to hold the blade vertical.

Takes longer to write it than to do it - see picture.

Hope this helps,

Mike
  

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Re: Diels F7F Build - My First Twin
Reply #33 - Jul 28th, 2017 at 5:29pm
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Nice job on the nacelles.  Like I said before...very inspiring work here and makes one want to build a Tigercat !!!
  

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LASTWOODSMAN
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Re: Diels F7F Build - My First Twin
Reply #32 - Jul 28th, 2017 at 5:26pm
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Mike - Wow - that Nacelle sanded down beautifully!   Smiley  I have a question about your ribs you cut out into airfoil shape, and are cutting them in half lenghtwise, one larger half for the top of the stab, and the other smaller half for the bottom of the stab.  How do you hold the ribs, and how do you make that cut on that line, and make that cut perpendicular ?
LWM
  

OH, I HAVE SLIPPED THE SURLY BONDS OF EARTH ... UP, UP THE LONG DELIRIOUS BURNING BLUE ... SUNWARD I'VE CLIMBED AND JOINED THE TUMBLING MIRTH OF SUN-SPLIT CLOUDS ...
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MKelly
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Re: Diels F7F Build - My First Twin
Reply #31 - Jul 28th, 2017 at 4:36pm
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Thanks, Tom.

With the nacelles assembled, I started laying out the stab.  To match-sand the stab ribs, I used glue-stick to tack each rib pair together, held them in place on one of my sanding bars, and sanded the edges using a right-angle sanding block.  For this model the ribs get cut so that one half is assembled on the board, then the remainder gets glued to the other side of the assembled stab.  Gives a nice symmetrical airfoil.

While the stab frame dried I got to work sanding the infill.  One down, one to go...

Mike
  

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0728_Match-Sanding_Stab_Ribs.JPG
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0728_One_Down_One_To_go.JPG
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0728_One_Down_One_To_Go_Front.JPG
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0728_Sanding_down_the_infill.JPG
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Re: Diels F7F Build - My First Twin
Reply #30 - Jul 27th, 2017 at 8:14pm
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The nacelles are looking very good!  Well Done Smiley
This is a very tempting build.  I know there will be an F7F in my future sometime.  Keep up the great work!
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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MKelly
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Re: Diels F7F Build - My First Twin
Reply #29 - Jul 27th, 2017 at 8:08pm
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LWM, we'll see about the filler once they've been sanded - that'll be the proof of the work...

I got the rest of the infill done today.  The top side of the two formers under the wing was a bit floppy due to grain direction, so I glued some medium 1/16x1/32 strips across them to protect them during sanding and other handling.  I'm sure they'd be fine per plan once the nacelles are on the wings.

I also added some 1/16" square crosspieces to the aft former, as I intend to open that up to allow more room for the motors (and maybe blast tubes).

Cut the parts for the stab this evening - will work on that between sanding sessions.

Cheers,

Mike
  

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0727_Nacelles_with_Former_Reinforcement.JPG
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Re: Diels F7F Build - My First Twin
Reply #28 - Jul 26th, 2017 at 9:18pm
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Very good discussion and great pics and tips on infill planking there fellas.  I also razor saw cut on a slight angle with the blade, and all four sides of each trapezoidal plank do have a slight beveled edge.  I like the idea of one flat edge though ... I will try that on the next nose ... one gets really efficient with a sanding block to take off that last little bit.
     Great word, "Trapezoid" - a convex quadrilateral with at least one pair of parallel sides.  I really like math ...  Smiley Smiley
     Mike - your infill planking looks so clean, like you don't even need ANY filler ...!!   Shocked
LWM
  

OH, I HAVE SLIPPED THE SURLY BONDS OF EARTH ... UP, UP THE LONG DELIRIOUS BURNING BLUE ... SUNWARD I'VE CLIMBED AND JOINED THE TUMBLING MIRTH OF SUN-SPLIT CLOUDS ...
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MKelly
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Re: Diels F7F Build - My First Twin
Reply #27 - Jul 26th, 2017 at 8:55pm
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Tom,

I had read that somewhere in the last year.  For this build I've been angling the blade when cutting the sides so that I get a trapezoidal block for the infill pieces.  When necessary I used a sanding block to take off that last little bit necessary to squeak it in between the stringers.

For the forward blocks I also sanded a slight angle into the front and rear faces so that they would butt tight up against the formers despite being angled in towards the front of the cowl.

Hoping that all this finagling will result in minimal gaps when everything has been sanded out.

Cheers,

Mike
  

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Re: Diels F7F Build - My First Twin
Reply #26 - Jul 26th, 2017 at 7:00pm
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One other thing Tom Arnold pointed out on one of his builds, can't remember if it was on SFA or HPA on filling the balsa in on models was to sand an angle on one of the long edges of the planking so that the balsa slides down into the space a bit easier.  Works really well and just sand off the rest down to the stringers and formers.
Tom
  

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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