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Dec 30, 2008, 10:23 PM
Student of Ivan
mountainman2442's Avatar
Jeff,

You're really moving along! Nice work.

I like the props you'll be using, they look quite scale. I think you'll be happy going with the leading edge cuff. Ivan seems to add it to most of his planes and it's really not that noticeable but certainly helpful when we come in a bit too slow...

I had planned on posting the 600 files but will wait until I add the missing center ribs which should be an easy edit. But like you said, they are easy to hand cut...

John
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Dec 31, 2008, 08:05 AM
Registered User
paulbw's Avatar
Hi Jeff,
Still following your excellent progress - I was interested to see the comment about the Otter's planned tail surfaces too - I'll be building similar components on the Sealand very shortly! Was it the horizontal or vertical surfaces that were being referred to? Your rib capping must have added a lot of stiffness to the fin for little weight gain.
Paul W.
Dec 31, 2008, 08:44 AM
Two left thumbs
Very neat and tidy construction. That I-beam spar looks as if it'll allow this bird to pull about ten Gs! Aerobatic Otters?

In looking at my Ivan's plans (Lancaster and Albatross) I see no evidence of the mentioned leading edge cuff. What am I not seeing?

The one with his name spelled the old-fashioned way - Geoff
Jan 11, 2009, 10:37 AM
If it flies, I crash it!
dlazarus6660's Avatar

Updates?


Geoff,

You are an incredibly neat builder!

Where are you now on the build?

Daniel
Jan 16, 2009, 07:52 PM
Go FASST or go home...
Ben_E's Avatar
Lovley build!

I have two Twotters one is the VMAR kit, the other one is a foamkit slightly larger. On my VMAR Otter I use the same motors with the same props too. Worked out very well. I later have changed the props to Master airscrew 9x7 and performance incrased a lot. Pulling 15 more amps all together but can now climb 45 degrees slowly without problems. It pulls 35A all together on WOT.

Ben_E
Jan 22, 2009, 08:21 AM
Student of Ivan
mountainman2442's Avatar
Jeff,

Anymore progress lately?

If anyone's interested, here's the cut files for the Twin Otter 600. I still have yet to start building her but should commence this week. No guarantees about the accuracy of the drawings but they should be close. They are provided in CorelDraw and Autocad file formats but since I no longer have a program to view .dxf files, I'm not sure how well they will work in that file type.

John
Last edited by mountainman2442; Dec 05, 2009 at 04:30 PM. Reason: Changed cut files to Version 5
Jan 22, 2009, 06:54 PM
Registered User
Quote:
Originally Posted by paulbw
Hi Jeff,
Was it the horizontal or vertical surfaces that were being referred to? Your rib capping must have added a lot of stiffness to the fin for little weight gain.
Paul W.
Paul, I will be capping both the horizontal and veritcal stabs, but the pics in question were of the vertical stab.

Quote:
Originally Posted by paulbw
Lovley build!

I have two Twotters one is the VMAR kit, the other one is a foamkit slightly larger. On my VMAR Otter I use the same motors with the same props too. Worked out very well. I later have changed the props to Master airscrew 9x7 and performance incrased a lot. Pulling 15 more amps all together but can now climb 45 degrees slowly without problems. It pulls 35A all together on WOT.

Ben_E.
Thanks for the suggestion Ben, I also have the MA 9x7 3 blade props. I thought they might be too beefy for an electric motor, but I'll give them a try.

Quote:
Originally Posted by Geoffinpdx
In looking at my Ivan's plans (Lancaster and Albatross) I see no evidence of the mentioned leading edge cuff. What am I not seeing?
Geoff (with the archaic spelling ),

The Lanc and Albatross might noe have the cuff, but you will see it on the Twotter soon as I finish the wing. Basically the leading edge droops on the outboard wing section kind of like a Nexstar trainer to reduce tip stall tendency.
Jan 22, 2009, 06:57 PM
Registered User
The next step is sheeting the leading edge of wings. I can't beleive how much torsional strength this added. I think I will strip my SA CAP 232 and d-tube the wings like this.

I also added the curved sheeting to the inboard trailing edge where the flaps meet the wing.

My process for sheeting the LE was to lay the wing on flat surface making sure it was flat and weighted down. I cut and fit the bottom LE sheeting, then glued in place with thin CA. Keeping the wing flat and straight I cut and fit the top sheeting. To glue it, I ran a bead of thick CA all along the spar and ribs. Without using activator I positioned the sheet and held it down by hand until the glue set.
Jan 22, 2009, 07:01 PM
Registered User
After D-tubing the LE, I had a big "Head scratch, red-face, then curse" moment when I started thinking about wing rib capping. Inboard of the NACA break the TE of the wing ribs are supposed to be capped top and bottom. Outboard of the break, the TE of the wing.

However, when fitting my wing-ribs I neglected to offset the bottom of the rib from the building surface. As a result all my TE ribs are flush with the bottom of the spar and I've got a 1/8" gap from the top of the rib to the top of the spar.

I dont think this is a major issue, but it means I'll need to cap the top of the rib with 1/8" sheet, and the covering on the bottom of wing might not look as nice. Alternaively, I might just sand/cut into the bottom of the ribs to make room for a 1/16" cap strip. What do you guys think?
Jan 22, 2009, 07:22 PM
Registered User
gerg's Avatar
Just have to pipe in and say great build!!

I too have a set of these plans, which I was going to start soon. But thank you sooo much for the cad files. Now I'm going to have to start it sooner than planned.

I have about 1.5 years as a mechanic on twins, and I think they're probably one of my favorite airplanes of all time. Although, i'll have to modify the plans a bit to do the short nose version.

Cheers
Greg
Jan 22, 2009, 07:35 PM
It actually Flies!
Float Flyer's Avatar
Hi Jeff,

I first have to say, great build, great aircraft and great quality construction!!

I think your plan to just cap the top with 1/8th is a good idea and sand the bottom of the overall wing as best as possible to get a clean covering job, is the best bet.

Sanding each rib down a 1/16th evenly will be very difficult and I know if I did it, I would never get all the ribs true.

I think the other benefit is that you get a tougher top to the wing with the laminated 1/8th material which will only add strength to the ribs.

BTW, I am only suggesting this because I have accomplished the same mistake in my own building!!

What is your total wing loading that you think you will acheive at completion?

FF

Quote:
Originally Posted by JeffElecRC
After D-tubing the LE, I had a big "Head scratch, red-face, then curse" moment when I started thinking about wing rib capping. Inboard of the NACA break the TE of the wing ribs are supposed to be capped top and bottom. Outboard of the break, the TE of the wing.

However, when fitting my wing-ribs I neglected to offset the bottom of the rib from the building surface. As a result all my TE ribs are flush with the bottom of the spar and I've got a 1/8" gap from the top of the rib to the top of the spar.

I dont think this is a major issue, but it means I'll need to cap the top of the rib with 1/8" sheet, and the covering on the bottom of wing might not look as nice. Alternaively, I might just sand/cut into the bottom of the ribs to make room for a 1/16" cap strip. What do you guys think?
Last edited by Float Flyer; Jan 22, 2009 at 10:29 PM.
Jan 22, 2009, 11:25 PM
Formerly "vonJaerschky"
Wolpertinger's Avatar
Quote:
Originally Posted by JeffElecRC
I dont think this is a major issue, but it means I'll need to cap the top of the rib with 1/8" sheet, and the covering on the bottom of wing might not look as nice. Alternatively, I might just sand/cut into the bottom of the ribs to make room for a 1/16" cap strip. What do you guys think?
That kind of stuff keeps me awake at night, I just hate making goofs. In all reality, it is likely not a big deal at all and the easy fix of 1/8" capstrips on the top only will work fine. One of the benefits of a rib with capstrips on the top and bottom is that it adds stiffness to the rib, as it forms an "I-Beam" cross section. Without the strip on the bottom, there's no I-Beam.

If it were me, I would probably use a razor saw and make a 1/16" vertical cut at the front and rear of the capstrip position on the bottom of the rib. Then use a knife blade (tough to get the handle in there for a 90 degree cut) with some sort of guide to make sure I cut straight, and slice off enough of the rib to fit in a 1/16" capstrip. But that's just me, and I always seem to pick the hard way
Jan 23, 2009, 12:24 AM
Registered User
LukeZ's Avatar
Yeah, that does sound like the hard way Frank! Having made this same sort of mistake myself I can testify to the difficulty of getting a precise amount off the bottom (or top) of a wing rib after it's been installed. Nearly impossible, but if anyone could do it, Frank would be the one!

But I'd also agree that leaving it be on the bottom certainly won't hurt anything.


Luke
Jan 23, 2009, 04:10 AM
Student of Ivan
mountainman2442's Avatar
Don't have any pictures handy but I ran into something like this on my Beverley where in order to obtain a better profile on several hand cut ribs, I cut another rib then sliced just about 1/2" off the top and glued this new top rib section onto the side of the existing rib. Once the covering is in place, you'll never know the difference...Of course, this was without using capstrips but the same principal applies.

John
Jan 23, 2009, 06:55 AM
Registered User
paulbw's Avatar
Hi Jeff,
If I understand correctly, you can still apply cap strips top and bottom out as far as the cuff? Then as John says, can you fit a small doubler to one side of the ribs that remain, in effect creating a 'c' beam? If the rib has a straight/flat underside then even just a piece of 1/8" square section should do the job for you and result in a worthwhile increase in strength
Paul W.


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