ALOFT: AH-100 Build (new title)

[G-man]

Don,
I made no provision for beveling , either front or back.
Seems that the sloppiness in my fitting work let me get away with it.
There is some give or play with wires-in-the-holes in front, and threaded fasteners in the back.
// Dave

PS: Found these pics. Perhaps there is enough flex in the molded fuselage to accommodate the dihedral angles.

 

[G-man]

Honorable wife's phone has the level feature.
OLYMPIC-II: dihedral: 5 degrees, polyhedral 9 degrees
RISER-100: dihedral: 6 degrees, polyhedral 8 degrees

Now, take a look at the two 100-inch wings on the 96-inch bench.
It looks to me like the polyhedral break on the OLY is farther out from the center line than on the RISER.
Hmmmm... another factor for designers to consider.
I wonder how we figure out where it should be.
What are the considerations?

 

[Sandman]

Dave

I see your point, the little bit of flex in the wing trailing edge mounting area of the fuselage, works to your advantage.
I noticed in the Riser photo, your shear webs appear to be between the upper and lower spars, as opposed to glued to the front of the spars,
is this a stronger arrangement.

Don

 

[G-man]

I noticed in the Riser photo, your shear webs appear to be between the upper and lower spars,
as opposed to glued to the front of the spars, is this a stronger arrangement?

I think it's stronger. It might depend on whether you favor adhesives or joinery for strength.

The most common failure mode for two-sticks wood spars is the top stick fails in compression.
Shear webs installed BETWEEN the two spruce sticks makes the spar into an I-Beam.
Shear webs glued TO THE SIDE of the two spruce sticks makes an incomplete box.
I like the I-Beam, even though more careful fitting is needed.
Make sure the web grain goes up and down. The job of the shear web is to keep the spruce sticks apart.

My wife has a Norm Hall spinning wheel.

The Hands of the Artist

The Hands of the Artist

www.lostvalleys.com

When we went to pick up the wheel and met Norm, he told us that the joinery
is such that if every drop of glue failed, the wheel would still hold together and still work.
That knowledge influences my shear web installation preferences.

 

[Wayne]

Feel free to pipe in, but for me, if you make the wing breaks to make more of a cleaner ARC, you may get some "rocking" if you are not smooth on the rudder. (Think Hobie Hawk)

Since the main goal for this plane is catching some lift, the Oly layout should have the advantage. The flatter and longer center section would work a little better if the airfoils and all else were the same. At least that is my thinking. The Riser probably responded to rudder a tiny bit better.

Was discussing the Oly wing flutter with a local expert on balsa models yesterday. He had been following this forum posting and brought in a number of wings to show me and discuss. On the subject of flutter, he points out that you commented on using original old formula monokote to avoid flutter. Basically the Oly II wing depends on the film for torsional reinforcement to a higher degree. Old Monokote was an excellent film, but they changed it in the 90's or so and it was never as nice again. I think full weight Ultracoat is pretty similar. It is hard to find the heavy coverings anymore. (Some of our 1.7 mill lam films on the bottom would probably do the trick.)

I suggested that perhaps the rather horrible entry on the Oly airfoil was also part of the equation. Perhaps there is a bubble that is created under the wing when the nose is pushed down. It would be an interesting test to build one with a better airfoil, but probably not many people care about the results. LOL

It was suggested to drop the turbulators in exchange for some diagonals. I don't think the AG35 foil will benefit from turbulators, probably just the opposite. The diagonals would fight the twist concerns much better and hopefully end up with a better performing model due to the better airfoil shape. This and adding a few more ribs to reduce the ribs spacing a bit should work out well. The diagonals will only be in front of the spar and they will not touch the covering.

Would this be OK? Sorry no great CAD rendering on this one. It will be a manual process to add them.

 

[Wayne]

Also - Would you guys be against using carbon strips for the spar caps? The tolerances and fit would be better than Spruce. I've gone back and forth on this.. Wood probably looks better but is a little more trouble to deal with.

Lightening holes in the ribs? They are cute, but really don't do much else, weight savings is very little.

Thinking this is getting pretty close. What do you think? Diagonals are not shown, final wood sizes not yet selected. Diagonals will go from spar caps to leading edge comb, every other bay reversed.

There are 3 ribs under the sheeting per side. End ribs have no holes.

Here is a little closer look. There is a comb just behind the leading edge. This gives us more rib alignment and a laminated leading edge.

Spar caps are moved behind the high section of the airfoil to avoid messing up the airfoil in the critical areas.

Love it? Hate it?

 

[G-man]

Since the main goal for this plane is catching some lift, the Oly layout should have the advantage. The flatter and longer center section would work a little better if the airfoils and all else were the same. At least that is my thinking. The Riser probably responded to rudder a tiny bit better.

This all makes sense to me. Thanks or explaining it.

On the subject of flutter, he points out that you commented on using original old formula monokote to avoid flutter. Basically the Oly II wing depends on the film for torsional reinforcement to a higher degree. Old Monokote was an excellent film, but they changed it in the 90's or so and it was never as nice again.

This fits with what I have observed.

I think full weight Ultracoat is pretty similar.

Similar to the old Monokote, or the new?
How about we try the covering film that Aloft is stocking now?
I wonder how my fluttery OLY-2 Number 4 wing would work If I re-covered it with the Aloft film.

It was suggested to drop the turbulators in exchange for some diagonals. I don't think the AG35 foil will benefit from turbulators, probably just the opposite.

Works for me.

The diagonals would fight the twist concerns much better and hopefully end up with a better performing model due to the better airfoil shape. This and adding a few more ribs to reduce the ribs spacing a bit should work out well. The diagonals will only be in front of the spar and they will not touch the covering. Would this be OK?

Man-o-man this sounds great to me.
I want to be in the first round of builder/testers for the new Aloft-100 wing.

 

[G-man]

Also - Would you guys be against using carbon strips for the spar caps?

Fine by me. Precise it is a plus.

Lightening holes in the ribs? They are cute, but really don't do much else, weight savings is very little.

Agreed. Lightening holes not needed.

Thinking this is getting pretty close. What do you think?
Diagonals are not shown, final wood sizes not yet selected. Diagonals will go from spar caps to leading edge comb, every other bay reversed.

It IS close.
I AM STOKED.
Can hardly wait.

 

[Sandman]

Wayne, the wing design looks like the a giant leap forward.
I'm amazed at how quickly you addressed all the issues, and conceived, a better wing design.
On a side issue, I've read that covering materials should be cut span wise (on the bias)? to reduce sagging between the ribs.
Does anyone know if it makes a difference.

Don

 

[Wayne]

Similar to the old Monokote, or the new?
How about we try the covering film that Aloft is stocking now?
I wonder how my fluttery OLY-2 Number 4 wing would work If I re-covered it with the Aloft film.

I'm no expert, but I recall Ultracote being pretty nice stuff. No idea if that is still the case.

The 'Flying Film' we stock is a lighter weight material, I think it would not be a good choice for a model that REALLY needs the film strength to avoid flutter. It is great for well structured models.

I need to step out of the office, so may not be an update on this for a day. I'll add in the correct dimensions for all wood and go with some carbon spar caps. Also add in the wing joiner tubes. Then I think we can kick it over to Rafael for all of the detailed work to make it actually a functional design. He is a bit buried in other CAD projects, so probably be after the holidays before we can cat some wood and print some plastic.

Thanks all! I love doing design work like this. This is just a simple one for now. I'd like to do up a little nicer design sort of inspired by another of Mr Garwood's creations using a Blezjyk fuselage. Think this one will get a more complex wing, and maybe a 2 meter span.

 

[G-man]

That sure was a fun project.
Many thanks to Wayne for sourcing that fuselage.

Curved lines are pleasing to the eye

Search results for query: sensoar

forum.alofthobbies.com

 

[G-man]

> Here is a little closer look. There is a comb just behind the leading edge. This gives us more rib alignment and a laminated leading edge.

Here the comb acts as a precision spacer. Would notches in the LE stock do as well?
Wayne, You mentioned earlier you favor notches in the TE stock.
Is lamination better than thicker LE stock, or stronger material LE stock?
Worth the trouble both in manufacturing the parts and in construction?

> Spar caps are moved behind the high section of the airfoil to avoid messing up the airfoil in the critical areas.

Agreed. I like that idea.

 

[Wayne]

A local builder talked me out of the original layout I had for the leading edge where the ribs get notched for the insertion of the balsa leading edge material. He commented that it just acted like a wedge and blew up ribs in hard landings. He strongly urged me to stay with a simple traditional leading edge, and then added a laminated leading edge would be even better. There was also some discussion about less impact on the wing when balsa stocks warp before building.

Notching leading or trailing edge stock is a tricky operation for us. We do this for the BOW kits where we process both the shape, and then the grooves on 2 different faces. This is a slow process with our current tools. For now I think I will leave it to the customer if they would like to notch the trailing edge. With the Comb on the leading edge, I do not think any notching will be needed as it basically already will be notched with the Comb. It's a little hard to see:

 

[Wayne]

Did a little work on the wing joiners. So we have some limiting issues here. In fact the main joiner may need to move in front of the spar caps. Currently as drawn the joiner is a 6mm carbon rod as that is all the more that will fit inside the wing without hitting the sheeting with this rib spacing.

The rear pins will probably only pick up 2 ribs. And both joiners will end up being a 3D printed assembly very similar to what we did in out Trix design. Notching into the ribs and the cap strips.

Honestly not even sure we need the rear pins since this is a bolt on wing.

Hmm, this is a work in progress.. A few different ideas floating around as I write this up.

 

[G-man]

> Notching leading or trailing edge stock is a tricky operation for us.
> For now I think I will leave it to the customer if they would like to notch the trailing edge.

That works for me. The builder can cut notches with a Zona saw or a hacksaw blade.
Especially if you leave enough extra material on both ends of the ribs.

 

[Wayne]

OK- a little more work and a quick meeting with Rafael and we have some refinement and a plan of attack the for 3D printed assembly. I got rid of the extra rib and standardized the rib spacing. We figure the main spar rod could be a 6mm unit, but currently planning on a 6mm, and a 3mm secondary.

The wing joiner assembly will include shear webs, both joiners, wing bolt holes and leading edge pins.

Here is a look at the cleaned up center section. Not sure where I will locate the rear pin just yet. I don't want it super far back into the trailing edge.

 

[G-man]

> Not sure where I will locate the rear pin just yet.
The rear anti-rotation pin must clear the mounting bolts.
My bolt hole centers are 7 15/16 inch, 203 mm from the LE.
OLY wing and RISER wing are interchangeable on their respective fuselages.

 

[G-man]

Still looking for additional wing mount ideas.
I have a RISER-78 with four bolts wing mount.
I didn't do it again because too much fiddling in the field.

 

[Wayne]

Yeah, I'm not a fan of 4 bolts. I have a few planes like that and you just spend too much time turning screws.

The rear joiner will be near the rear bolts. Rear bolts will be far enough back to pickup the fiberglass in the fuselage.

 

[Sandman]

Wayne
I can't wait to see the wing joiner assembly.
The comb laminated to a leading edge, should create a strong, lightweight balsa leading edge.
Would it be possible to 3D print a trailing edge "hold down devise" that covered the top of the trailing edges for an inch or 2 that bolts to the fuselage.
The soft wood of the trailing edge would need the 1/16 plywood stiffeners like the ones that come with the Riser kit.
Just trying to think outside of the box.
Dave's bolts/pins combo is hard to beat,