Alpenbrise 157 (4M)

[Doc James Hammond]

ALPENBRISE, 4 meters of lightning fast loveliness coming soon to an alp near you!

Wonderful CAD work done by Aeroic test pilot Jonathan Wells.

 

[Konrad]

Love the lines! Is this aimed at any FAI class? I like that it isn't a "V" tail.

 

[Doc James Hammond]

Love the lines! Is this aimed at any FAI class? I like that it isn't a "V" tail.

Not really aimed at anything FAI, Konrad - its just an alpine soarer.

But...if I were to be honest I'd say this is my take on the lovely old classic MPX Alpina model.

But it's got a few tricks up its sleeve which should let it shine on the slope or up on the side of a mountain.

BTW if you are tired of V-Tails too, you will like another new one coming later the year: Redshift X - YES a red-hot new Redshift with an X tail!

Cheers,

Doc.

 

[Konrad]

Not really aimed at anything FAI, Konrad - its just an alpine soarer.

But...if I were to be honest I'd say this is my take on the lovely old classic MPX Alpina model.

But it's got a few tricks up its sleeve which should let it shine on the slope or up on the side of a mountain.

BTW if you are tired of V-Tails too, you will like another new one coming later the year: Redshift X - YES a red-hot new Redshift with an X tail!

Cheers,

Doc.

You tease! Maybe call it an X-Men. I'd think with the loss of quality control with the V tail it might be best to make a clean break.

Yes, I do see the MPX lines, I like the tail a bit better on your Alpine soarer.

 

[Wayne]

Looks a lot like a big Strombird mixed with some Alpina. I think the Alpina was sort of based on an ASW-17 early on, and then the changed the tail shape..? Anyhow, I like the design a lot, but a little concerned about the small diameter tail, will need some carbon in the layup back there for sure.

 

[Konrad]

Good point about the diameter of the tail boom. I wonder why so many "new" designs have such a narrow booms? I'd think that a larger diameter would offer much more geometric strength for any give mass. With the narrow boom it looks like a LOT of carbon would be needed! I know with my landing style these pencil thin booms are a poor design. That is while they may offer less drag (skin drag), they have a huge weight penalty, this is negating any parasitic drag benefit with induced drag penalties.

And then there is the practical issue with boom flex and whip. I know with the RCRCM SunBird 60" the tail boom is the Achilles heal of the design.

 

[Wayne]

Yeah, I think we all like the look, but to make it stiff and able to take some rough landings I suspect we end up with a heavier boom that is more likely to have some high frequency rebound concerns.

I'd say this would be a good design to use a small foam insert in the boom layup to build a stronger, yet light tail section. Kind of like a stringer in a boat. (I know there is a name for this, but my brain is farting right now.)

 

[Konrad]

Yes, we like the look!

I know nothing about boats, but is the term you are looking for sheer web? Something to keep the load bearing members apart. I’ve been known to fill tail booms with 30x expanding polyurethane for this very purpose, as a fix. This is done to keep the boom from kinking.

But from a design perspective I’d like to see a larger diameter tube. As I recall the stiffness of a tube goes up by the square of the diameter. So a boom that has twice the diameter will be 4 time as stiff assuming the cross section of the material is kept the same.

 

[jvaliensi]

The front section looks big. I think it makes the tail look small. About 30-35mm diameter behind the wing should be big enough.
But the six servo wing is more interesting. Less control surface distortion and opens up trim posibilities.

 

[Doc James Hammond]

Looks a lot like a big Strombird mixed with some Alpina. I think the Alpina was sort of based on an ASW-17 early on, and then the changed the tail shape..? Anyhow, I like the design a lot, but a little concerned about the small diameter tail, will need some carbon in the layup back there for sure.

Thanks, Wayne - yes the boom will be nicely reinforced - same with the new Firechicken (!)

Cheers,

Doc.

 

[Doc James Hammond]

Good point about the diameter of the tail boom. I wonder why so many "new" designs have such a narrow booms? I'd think that a larger diameter would offer much more geometric strength for any give mass. With the narrow boom it looks like a LOT of carbon would be needed! I know with my landing style these pencil thin booms are a poor design. That is while they may offer less drag (skin drag), they have a huge weight penalty, this is negating any parasitic drag benefit with induced drag penalties.

And then there is the practical issue with boom flex and whip. I know with the RCRCM SunBird 60" the tail boom is the Achilles heal of the design.

Actually chaps - please do remember that this is a very big fuselage - its 25~30% again as long as a typical F3f plane.

The boom diameter behind the wing is over 70 mm and behind near the tail its closer to 40mm.

Its that way because I like it - and I'll make sure you guys can fly it with no undue worries.

Cheers,

Doc.

 

[Doc James Hammond]

Yes, we like the look!

I know nothing about boats, but is the term you are looking for sheer web? Something to keep the load bearing members apart. I’ve been known to fill tail booms with 30x expanding polyurethane for this very purpose, as a fix. This is done to keep the boom from kinking.

But from a design perspective I’d like to see a larger diameter tube. As I recall the stiffness of a tube goes up by the square of the diameter. So a boom that has twice the diameter will be 4 time as stiff assuming the cross section of the material is kept the same.

Please again - do remember this is a big plane, guys - much larger than most of you fly right now.

Having foam sheer webs in the fuse is actually a really good idea though, in the same way as the sine wave spar AND wing sheer ribs do such great things for high A/R wings.

The way I do it is the same that I have used all along:

1. Decided the envelope or the work of the model.
2. Do the sums an select the sections that will be best for the work.
3. Try to make it look sweet but without sacrificing the original design parameters and the things needed to meet them.

I have now been doing this for a fair while, and I think that especially with the new factory in the picture, it can be made very light and strong with really good induced and sympathetic vibration damping.

Remember too that once the moulds are made we can then mess about with the internal construction to our hearts content - and as you know, or I hope you know, I DO LISTEN to people.

More comments please, lads! I need all the help I can get.
Cheers,

Doc.

 

[Jonathan Wells]

Get it done James.....

 

[Konrad]

... Having foam sheer webs in the fuse is actually a really good idea though, in the same way as the sine wave spar AND wing sheer ribs do such great things for high A/R wings.

....

Remember too that once the moulds are made we can then mess about with the internal construction to our hearts content - and as you know, or I hope you know, I DO LISTEN to people.

More comments please, lads! I need all the help I can get.
Cheers,

Doc.

Yep, think of that long narrow tail boom as a high aspect ratio structure.
While I have had good success with the expanding foam, I have to admit it was a mess. Read the process wasn't under control. I'm not sure I would want to using it in a production environment. I hope with a little development work a process could be found that results in consistent results. If doing this make sure a tunnel is made to allow the servo wires, control snakes or rods to pass through the foam.

All the best,
Konrad

 

[Wayne]

I was not talking about expanding foam. That is for houses.

 

[Doc James Hammond]

I was not talking about expanding foam. That is for houses.

And packing crates.

Nope I was thinking pre-cut /shaped glass faced hard structural foam in strategic places.

Cheers,

Doc.

 

[Konrad]

I used expanding foam to apply a uniform load so as to NOT have stress riser anywhere along the boom. I did this with a lot of race car structures. But you are the designer.

 

[Doc James Hammond]

I used expanding foam to apply a uniform load so as to NOT have stress riser anywhere along the boom. I did this with a lot of race car structures. But you are the designer.

I think it's great, Konrad, but as you have observed its a little bit hard to control - especially in a production environment.

Its also pretty hard to clean up if you do get it wrong (I am very good at getting it wrong...)

Cheers,

Doc.

 

[Konrad]

Yep, Thats why you make the big bucks. Please understand I'm not telling you or anybody how to design or make the models. I'm just say what concerns "me" as both as a customer and at one time a production engineer. If it was easy I'd be doing it. But from my vantage point it is better you are taking this on than I.

All the best,
Konrad

 

[Doc James Hammond]

Yep, Thats why you make the big bucks. Please understand I'm not telling you or anybody how to design or make the models. I'm just say what concerns "me" as both as a customer and at one time a production engineer. If it was easy I'd be doing it. But from my vantage point it is better you are taking this on than I.

All the best,
Konrad

And...this type of constructive comment is EXACTLY what I need - especially from someone who knows what he's talking about.

Carry on the good work Konrad - your comments are both very welcome and highly valued.

Cheers,

Doc.