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Author Topic: Build: Farman F.400 16 inch  (Read 1161 times)
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rrfalcon
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« on: June 09, 2021, 02:26:37 PM »

I've decided to get back into building models after a brief layoff of 40 years or so. As a starter, I'm building a Farman F.400 with a 16-inch wingspan using a plan that's a modern reproduction of the old Comet dime-scale plans. I can't read the name of the plan artist, since it's cut off, but it looks like maybe Mike Marrisa. I think he did a "Bogus Series" of Comet look-alike plans, and this is one of them.

So, here are the first pictures, of the plan pinned out on the table, and the first side glued up.
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Build: Farman F.400 16 inch
Build: Farman F.400 16 inch
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Bredehoft
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« Reply #1 on: June 09, 2021, 02:55:08 PM »

Almost certainly the late Mike Nassise from Massachusetts.

--george
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rrfalcon
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« Reply #2 on: June 10, 2021, 03:05:28 PM »

Thanks for having the right name!
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strat-o
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« Reply #3 on: June 10, 2021, 05:03:07 PM »

I'm literally laughing at the irony.  The irony is you are new here so you may not know that for the last seven months there has been a very popular cookup of the forum members building Mike Nassise designs:    https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=25679.0

Of course it is not too late to enter yourself!
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rrfalcon
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« Reply #4 on: June 11, 2021, 02:10:36 PM »

You're right - I wasn't aware of that! I've been on for a few months, but have spent most of that time uploading various magazine issues and looking at the threads that were active about the time I joined. I'll check out that cook-up thread.  Thanks!
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rrfalcon
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« Reply #5 on: June 13, 2021, 02:20:53 PM »

Both fuselage sides are assembled. I still need to trim away the glue residue from the joints, and improve my photography!
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Re: Build: Farman F.400 16 inch
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rrfalcon
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« Reply #6 on: June 17, 2021, 12:55:44 PM »

Continuing on - the fuselage framing is in progress. I've re-done the nose former three times, and finally got something I could live with. Most of the fuselage bottom sticks are in, although the one at the nose is a bit short. I'll have to slot in a small filler piece, but since it's all glued up to the nose former I don't think there will be any strength issues. I'm not very good yet at getting the cross-pieces both lined up with the verticals on the fuselage side *and* level with the longerons. I'll have to think about that a bit.
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rrfalcon
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« Reply #7 on: June 26, 2021, 03:44:59 PM »

The fuselage is done, along with the vertical fin/rudder. I've started on the wing, with the wingtips, spar, and trailing edge pinned down and glued.  Next will be to cut out the wing ribs, trim to proper shape, and glue on to the spar and TE. I'm still experimenting with the best way to transfer the shapes from paper to wood. Outlining in a fine-point Sharpie still results in a very coarse line with a lot of bleeding along the grain, so I want something better for the next project.
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Re: Build: Farman F.400 16 inch
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OZPAF
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« Reply #8 on: June 27, 2021, 03:11:15 AM »

Quote
I'm still experimenting with the best way to transfer the shapes from paper to wood.
I have found that gluing copies of the ribs onto the balsa with glue stick gives a good outline to cut and sand to.

I cut close to the outline and sand to final shape.

Soaking the ribs in thinners will enable the paper to be removed easily.

It's looking neat - the rust will soon disappear Smiley

Have fun.

John

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rrfalcon
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« Reply #9 on: July 03, 2021, 12:46:21 PM »

The basic wing structure is complete.  I still need to trim the leading edge and sand things down, then set the proper dihedral.
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Re: Build: Farman F.400 16 inch
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rrfalcon
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« Reply #10 on: July 09, 2021, 11:59:13 AM »

The structure is done, weight of what's shown is 3.05 grams. I haven't yet done the landing gear, and the rubber and prop are obviously not in place. Now it's time to set the dihedral and figure out covering.
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rrfalcon
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« Reply #11 on: July 25, 2021, 04:14:43 PM »

It's time (maybe past time) for another update. After I mostly finished the structure, I decided to try using printed tissue for the covering. That meant that I needed to go figure out how to clean up the plan PDF so that it showed just the markings I wanted on the tissue. So, after a week or two of searching for info, trying stuff, and learning, I figured it out (mostly). I printed the patterns first on plain bond paper so that I could make sure the size and orientation were correct, then after trimming the tissue to fit the paper it was off for another trip through the printer.  Success! The tissue made it through without tearing or wrinkling, and after I peeled it off the bond paper substrate it was ready for application. It does curl up where the spray adhesive held it to the bond paper, but that doesn't seem to affect how it goes on to the structure.

I started with the fin, and immediately discovered that the ink wasn't going to survive the 50/50 water/isopropyl alcohol mix I was using to shrink the tissue. I'll have to re-do that bit. I'm thinking about trying an alternate method of covering in plain silver and then cutting the letter from blue tissue and using spray adhesive to put it on the fin.

On the fuselage sides, I tried spraying the back side of the tissue (Peck Polymers silver), and that worked better. If I kept the spray down to just dampening the tissue, it didn't cause the printer ink to run. It didn't tighten up as much as I would have liked, but I think it will be enough. For the sprayer, I'm using a perfume atomizer. That gives a very fine mist, and is easy to re-fill. I used the same technique for the wings.

I had printed alignment marks on the tissue at the edge of where the structure should go to help me get everything in the right place. Unfortunately, I put the marks too close, so some of them ended up on the tissue that's staying with the model. I'll know better next time!
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Re: Build: Farman F.400 16 inch
Re: Build: Farman F.400 16 inch
Re: Build: Farman F.400 16 inch
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rrfalcon
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« Reply #12 on: August 03, 2021, 02:27:44 PM »

Finished the wing covering with a little bit of run on the left wing markings, and the wing bowed up a bit on both sides as the tissue dried. I also got the blue tissue on the fuselage. Next for the fuse will be the windshield and landing gear.  I need to build a jig to help with aligning the gear. The fin is re-covered in silver only, and I'll cut out the 'F' marking from blue tissue and glue it on.
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Re: Build: Farman F.400 16 inch
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rrfalcon
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« Reply #13 on: August 18, 2021, 01:10:34 PM »

And construction is finished! Now to figure out how to trim it and what amount of rubber will work best.  Right now, it's very lightly powered - one loop of 1/16 square, so I'll probably bump that up as I get more familiar with the plane. Weight with the Peck Polymer 6" prop and one loop of rubber is about 10.5 grams - 9.5 on the main wheels, and 1 gram on the tailskid.
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Re: Build: Farman F.400 16 inch
Re: Build: Farman F.400 16 inch
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OZPAF
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« Reply #14 on: August 19, 2021, 03:00:33 AM »

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Weight with the Peck Polymer 6" prop and one loop of rubber is about 10.5 grams - 9.5 on the main wheels, and 1 gram on the tailskid.


That sounds good to me. You'll have a floater at that weight. My ELF - same span was 14 without rubber and flies well on 3/32.

Are you using the full size way of estimating the Cg position - just a little curious re the tail skid weight?

happy flying
John
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rrfalcon
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« Reply #15 on: August 19, 2021, 01:31:11 PM »

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Weight with the Peck Polymer 6" prop and one loop of rubber is about 10.5 grams - 9.5 on the main wheels, and 1 gram on the tailskid.


That sounds good to me. You'll have a floater at that weight. My ELF - same span was 14 without rubber and flies well on 3/32.

Are you using the full size way of estimating the Cg position - just a little curious re the tail skid weight?

happy flying
John

The model is too large to fit on my scale, and I didn't want to bother with making a holder and re-zeroing the scale, so I just measured the weight with the main gear on the scale, and then with the tailskid on it. The tabletop the other end was on isn't level with the bed of the scale, so the weight will be slightly off but I don't think it's enough to matter. No CG was shown on the plans, so I'm balancing it at the main spar for starters. That shows it a little bit nose-heavy, but preliminary glide tests indicate that it's pretty close to where it should be. It's not diving into the ground, although it may be descending a little faster that it should. If I throw it too hard or a little too nose-up, it will climb and stall.
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OZPAF
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« Reply #16 on: August 19, 2021, 08:37:58 PM »

 Smiley Thanks.

Good luck. Have you looked at Don Deloach/McCombs CG estimation for flying scale models ? It worked well on the Elf.

John
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rrfalcon
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« Reply #17 on: August 22, 2021, 02:46:06 PM »

Smiley Thanks.

Good luck. Have you looked at Don Deloach/McCombs CG estimation for flying scale models ? It worked well on the Elf.

John
No, I hadn't heard of that estimation method.  Do you have a link to it?

Thanks,
Roger
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OZPAF
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« Reply #18 on: August 23, 2021, 09:18:01 PM »

Apologise for the delay - here is a link

https://www.stickandtissue.com/forum/cgi-bin/yabb2/YaBB.pl?num=1394915928

It is basically

C.G. (%) = 16 + [TVo x 36]            
            
TVo = stab area/wing area x tail moment arm/wing average            
chord            
            
tail moment arm (length from wing LE to stab LE)         
               


If you have the ability to change the tail (preferably) or the wing incidence settings, then I have found it is best to establish the CG and then adjust for the glide by changing the tail setting(or wing) rather than moving the CG. The CG from the DeLoach/McComb approach gives enough stability.

good luck

John
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rrfalcon
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« Reply #19 on: August 24, 2021, 10:43:07 AM »

Apologise for the delay - here is a link

https://www.stickandtissue.com/forum/cgi-bin/yabb2/YaBB.pl?num=1394915928

It is basically

C.G. (%) = 16 + [TVo x 36]            
            
TVo = stab area/wing area x tail moment arm/wing average            
chord            
            
tail moment arm (length from wing LE to stab LE)         
               


If you have the ability to change the tail (preferably) or the wing incidence settings, then I have found it is best to establish the CG and then adjust for the glide by changing the tail setting(or wing) rather than moving the CG. The CG from the DeLoach/McComb approach gives enough stability.

good luck

John

Thanks much! Further testing shows a consistent tight right turn and dive, so some adjustment is definitely needed. This should get me started.

Roger
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« Reply #20 on: August 25, 2021, 08:11:19 AM »

ozpaf - Thanks for the refences to the calculation of Tail volume and CofG position. I have a question regarding TVol when applied to biplanes.  When the upper and lower wings are staggered and perhaps have different chords, how do I calculate where the 'wing leading edge' is, and what is the 'average wing chord'?

rrfalcon. I'm hope you will forgive me for posting a question about TVol on your build thread.

Regards,

Steve
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Richard Hewitt
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« Reply #21 on: August 26, 2021, 12:42:45 AM »

The tail moment arm is actually the distance from the centre of area of the tail, to the CG. Thus, a tailplane's effectiveness is improved by moving the CG forward, as this increases the moment arm. (It also means that the nose-down pitching moment caused by the wing downwash is reduced, as the centre-of-rotation of that torque remains fixed relative to the wing position, i.e. it DOESN'T move with the CG - so the requirement for a tailplane is reduced).

Like Steve-de24, I apologize for butting in on your build thread.

Richard
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steve-de24
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« Reply #22 on: August 26, 2021, 05:31:57 AM »

A google search came up with this web page which answers my question regarding TVol and biplane layouts.

https://www.rc-airplanes-simplified.com/scale-model-rc-airplane.html

Can I suggest that if anyone wishes to comment on the calculation and/or application of TVol  then they open up a new thread on the subject rather than we continue to hijack rrfalcon's Farman build thread.

Regards,

Steve
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OZPAF
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« Reply #23 on: September 02, 2021, 08:32:52 PM »

Steve -I missed your request, but your find seems quite useful and practical. I don't believe I could have found a more practical answer.

To avoid confusion though I would like to add that the formula I presented is an empirical approach based on the analysis of many top models by a top practicing modeller who was also an aeronautical engineer , and then altered slightly by another experienced modeller. It doesn't hold for all classes of models - but works well for rubber scale. Anyway this explains why the tail moment arm is measured the way it is.

Anyway Roger i hope the trimming of your Farman is coming on well.

Happy flying.

John
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