GrantR
Well-Known Member
I want to learn about aircraft design. Such as how to determine appropriate tail surface sizes, fuselage lengths, how to pick the right size material like do I want a 2 inch round or 3 inch round leading edge spar. How do determine the stress loads and how to configure the wing and fuselage geometry to equally distribute the stress loads to avoid highly concentrated areas of stress.
I am mostly interested in light plane design like the ultralights. I currently own a Kolb Mk III. I am also interest in wood aircraft design.
I do not have an engineering background so an advanced aircraft engineering book would probably be well over my head!
I want to buy some good books that go into detail covering all of the important aspects of building experimental aircraft. My overall goal is to learn as this is a very interesting area to me. I am a radio controlled aircraft engineer! LOL I enjoy building r/c airplanes from scratch however stress and load factors are not that critical on 1 to 20 pound airplanes.
I do have intentions of building a part 103 fixed wing motor glider in the future.
I do have questions concerning wing attachment bolts
This is a post I made concerning vertical wing attachment bolts at the root of the wing spars on the sweet pea biplane from Hart Aero.
Alan / Doug: since there are no wing struts on the Sweet Pea biplane
how are the wings rigidly attached to the fuse? I noticed the wing pins
appear to run through the spars vertically.
A lot of reading I have done suggests this creates a concentrated
stress point which is likely to develop stress cracks and possibly fail
since the top and bottom of the round spar bear almost all of the
flight loads. What I have read suggest that holes should be drilled
only horizontal in wing spar and no more than 30o from the horizontal
center line. From the video it appears that the ends of the wing spars
are attached to the fuselage via vertical pins.
I guess this is sort of like a cantilever wing but the tube spars with
vertical pins have be a bit worried.
Hart Aero Answer:
>Vertical bolts in most of the span of the spars is never a good
> idea. You are correct about the load factor and crack probability
> AND VERY correct about only horizontal and +/-30 degrees throughout
> the span of a tubular spar.
>
> However, this doesn't apply at the end of the spar, anywhere near
> as critical as the middle of the spar where the majority of the
> bending loads take place such as at a lift strut or brace wire
> connection.
>
> The inboard spar attach points experience compression or tension
> loads due to the nature of cable/strut bracing
>
> There are other factors like the wings experience an evenly
> distributed load, force trianglulation and distribution, etc.
>
> I can assure you that even with the vertical pins at the wing
> attach points that it's strength is far beyond any anticipated
loads.
>
> The Sweet Pea biplane uses typical biplane cable bracing/cabanes
> for positive and negative loads and because of this is self
> supporting. (a big box kite really)
>
> I hope this answers your questions.
>
> Sincerely,
> Doug Hart
> Hart Aero
>
More questions from me.
Thanks Doug for clarifying that. I think I was looking at it from a
different prospective. If this was a monoplane configured without
struts with the vertical bolts holding the ends of the wing spars
this would not be a good way to secure the wing as it would impose a
significant bending load around the bolt holes. Right?
With the Biplane the two wings are locked together therefore the
vertical pins do not see bending loads since the upper and lower
wings are rigidly attached to each other and move in unison.
Is this correct?
Another thing my Kolb has a vertical bolt which connects the wing spar to the strut bracket. I am guessing this is ok since Kolb has been a successful design. The 6 inch wing spar tube does have an internal steel bracing in the area as well.
Thanks,
Grant
I am mostly interested in light plane design like the ultralights. I currently own a Kolb Mk III. I am also interest in wood aircraft design.
I do not have an engineering background so an advanced aircraft engineering book would probably be well over my head!
I want to buy some good books that go into detail covering all of the important aspects of building experimental aircraft. My overall goal is to learn as this is a very interesting area to me. I am a radio controlled aircraft engineer! LOL I enjoy building r/c airplanes from scratch however stress and load factors are not that critical on 1 to 20 pound airplanes.
I do have intentions of building a part 103 fixed wing motor glider in the future.
I do have questions concerning wing attachment bolts
This is a post I made concerning vertical wing attachment bolts at the root of the wing spars on the sweet pea biplane from Hart Aero.
Alan / Doug: since there are no wing struts on the Sweet Pea biplane
how are the wings rigidly attached to the fuse? I noticed the wing pins
appear to run through the spars vertically.
A lot of reading I have done suggests this creates a concentrated
stress point which is likely to develop stress cracks and possibly fail
since the top and bottom of the round spar bear almost all of the
flight loads. What I have read suggest that holes should be drilled
only horizontal in wing spar and no more than 30o from the horizontal
center line. From the video it appears that the ends of the wing spars
are attached to the fuselage via vertical pins.
I guess this is sort of like a cantilever wing but the tube spars with
vertical pins have be a bit worried.
Hart Aero Answer:
>Vertical bolts in most of the span of the spars is never a good
> idea. You are correct about the load factor and crack probability
> AND VERY correct about only horizontal and +/-30 degrees throughout
> the span of a tubular spar.
>
> However, this doesn't apply at the end of the spar, anywhere near
> as critical as the middle of the spar where the majority of the
> bending loads take place such as at a lift strut or brace wire
> connection.
>
> The inboard spar attach points experience compression or tension
> loads due to the nature of cable/strut bracing
>
> There are other factors like the wings experience an evenly
> distributed load, force trianglulation and distribution, etc.
>
> I can assure you that even with the vertical pins at the wing
> attach points that it's strength is far beyond any anticipated
loads.
>
> The Sweet Pea biplane uses typical biplane cable bracing/cabanes
> for positive and negative loads and because of this is self
> supporting. (a big box kite really)
>
> I hope this answers your questions.
>
> Sincerely,
> Doug Hart
> Hart Aero
>
More questions from me.
Thanks Doug for clarifying that. I think I was looking at it from a
different prospective. If this was a monoplane configured without
struts with the vertical bolts holding the ends of the wing spars
this would not be a good way to secure the wing as it would impose a
significant bending load around the bolt holes. Right?
With the Biplane the two wings are locked together therefore the
vertical pins do not see bending loads since the upper and lower
wings are rigidly attached to each other and move in unison.
Is this correct?
Another thing my Kolb has a vertical bolt which connects the wing spar to the strut bracket. I am guessing this is ok since Kolb has been a successful design. The 6 inch wing spar tube does have an internal steel bracing in the area as well.
Thanks,
Grant
