Calculation question: for a wide cockpit is it correct to consider the wingspan only the sum of the wings lenght?

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wsimpso1

Super Moderator
Staff member
Patience and a big head can co-exist, Bill.

Was hoping to see both you and Beth at Oshkosh this year.

BJC
I am sorry we missed you at OSH. How are you holding up?

wsimpso1

Super Moderator
Staff member
Yes, he puts a lot of work in his post. I'm sure I'm at the bottom of his class but I'm trying.
You sir have built and flown a bunch of airplanes. I am still building my first. That makes you the experienced builder here…

I just try to help folks understand how the book learning stuff works. While cranking along on my bird…

WonderousMountain

Well-Known Member
I would go ahead & include it, in rule books you are allowed to count the carry over as a section of equal chord to 25% span. If the wing section is constant then our number is simple. The SnS Guppy (unsupported) comes out to 129ft to the second, as a biplane the carryover is doubled. Be aware that fuse generally doesn't go through a wind tunnel testing regime.

BJC

Well-Known Member
Supporting Member
I am sorry we missed you at OSH. How are you holding up?
It has been difficult. Wife and I drove a van full of our granddaughter’s stuff to the University of Tennessee - Chattanooga where she is starting her junior year. Girls sure have lots of stuff that they think is indispensable. She and her mother drove up yesterday with a car load.

Our daughter has decided to go back to work - teacher - next Friday. Just got one of the necessary documents from the bureaucracy late Friday. We have lots of things to take care of on Monday through Friday. Staying busy is better than sitting.

BJC

Pops

Well-Known Member
Supporting Member
You sir have built and flown a bunch of airplanes. I am still building my first. That makes you the experienced builder here…

I just try to help folks understand how the book learning stuff works. While cranking along on my bird…
Just like the old man said. " I was born a learning, not knowing . " I need all the help I can get and you are a good teacher.
When you are finished with your airplane it will mean more to you than anything you could have bought. Part of you is in it.
Thank you for all the work you do trying to make us understand . I don't miss a class.

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b7gwap

Well-Known Member
I am planning on snowboarding in the Cottonwood Canyons again sometime... Could make for an entertaining rest day...
Stop by any time, we have a great craft scene, we could invite Hot Wings and any other Utah HBA lurkers too.

Well-Known Member
Supporting Member
I’m southern Utah, but I’ll be up there at some point skiing!

Norman​

In average the seaplanes that I choose have the desired characteristics of my project. I still have no minimal idea about my final flight characteristics only a vague estimation. I know about the WIG x aircraft and all these things. What I'm trying to do is to build a thing wich I can register as a boat, so It don't need to have lift = a seaplane. Here's the IMO definition for a WIG.

WIG craft is a multimodal craft which, in its main operational mode, flies by using ground effect above the water or some other surface, without constant contact with such a surface and supported in the air, mainly, by an aerodynamic lift generated on a wing (wings), hull, or their parts, which are intended to utilize the ground effect action.

WIG craft are categorized according to the following types:

• type A: a craft which is certified for operation only in ground effect. Within prescribed operational limitations, the structure and/or the equipment of such a craft should exclude any technical possibility to exceed the flight altitude over the maximum vertical extent of ground effect;
• type B: a craft which is certified for main operation in ground effect and to temporarily increase its altitude outside ground effect to a limited height, but not exceeding 150 m above the surface, in case of emergency and for overcoming obstacles; and
• type C: a craft which is certified for the same operation as type B; and also for limited operation at altitude exceeding 150 m above the surface, in case of emergency and for overcoming obstacles.

I know about some cases here in UK and mainly in other EU countries of WIGs sucessfully registered as a boat. I'm trying to avoid as plage a registration of an experimental aircraft here in UK due to the bureocracy, cost and time.

So I'm pursuing the "Type C" IMO WIG Craft. This means that I have to build short wings, but sufficient to take off and sustain flight at least up to 150m.

dog

Well-Known Member
what sea state do you expect to be able to operate in?:takeoff and landings and now that
I think about it running in ground effect over
big long waves in a small wig might be strange

TFF

Well-Known Member
Your categories are only legislative limitations. We are talking about physical limitations; you can call it blue or green, it doesn’t matter.

It’s all about weight. You have to get way more nitty gritty with your answers. If you use a hull, how much is is stripped out? It’s definitely too heavy stock, because the whole thing needs ready to fly needs to be about the same weight as an empty hull on a trailer. My quick guess numbers, it seems you need about half the weight that you do or you need to takeoff at a high rate like 100 mph just for WIG. Way faster if you want 150m. While it would actually be cool to see something like that streak across the water, my imagination says you want a 50-60 mph craft.

Norman​

In average the seaplanes that I choose have the desired characteristics of my project. I still have no minimal idea about my final flight characteristics only a vague estimation. I know about the WIG x aircraft and all these things. What I'm trying to do is to build a thing wich I can register as a boat, so It don't need to have lift = a seaplane. Here's the IMO definition for a WIG.

WIG craft is a multimodal craft which, in its main operational mode, flies by using ground effect above the water or some other surface, without constant contact with such a surface and supported in the air, mainly, by an aerodynamic lift generated on a wing (wings), hull, or their parts, which are intended to utilize the ground effect action.

WIG craft are categorized according to the following types:

• type A: a craft which is certified for operation only in ground effect. Within prescribed operational limitations, the structure and/or the equipment of such a craft should exclude any technical possibility to exceed the flight altitude over the maximum vertical extent of ground effect;
• type B: a craft which is certified for main operation in ground effect and to temporarily increase its altitude outside ground effect to a limited height, but not exceeding 150 m above the surface, in case of emergency and for overcoming obstacles; and
• type C: a craft which is certified for the same operation as type B; and also for limited operation at altitude exceeding 150 m above the surface, in case of emergency and for overcoming obstacles.

I know about some cases here in UK and mainly in other EU countries of WIGs sucessfully registered as a boat. I'm trying to avoid as plage a registration of an experimental aircraft here in UK due to the bureocracy, cost and time.

So I'm pursuing the "Type C" IMO WIG Craft. This means that I have to build short wings, but sufficient to take off and sustain flight at least up to 150m.
Legal definitions are nice but complying with physical reality is nicer. The physical reality is that you're designing an airplane with a limited service ceiling and if you don't comply with the stability requirements of an airplane it'll be dangerous. WIG and aviation have different roll and pitch problems. Ground effect causes the aerodynamic center of the wing to be farther aft, thus the apparently ridiculously large horizontal stabilizer of WIGs. When you leave GE in such a craft the AC moves forward which could lead to instability in pitch so you need to make sure it's stable out of GE. Pitch stability is simply a matter of the static margin for either condition. Just make sure that the center of gravity is forward of the neutral point out of GE and you'll be fine but meeting that requirement will mean that you need a large down load on the tail while in GE, which is not the way WIGs usually work.

Then there's the roll stability problem: Avoid the type of WIG with forward swept wings with anhedral. This type of wing works great in GE but is totally inappropriate out of GE because without the enhanced lift gradient of chord dominated ground effect it makes the plane nearly impossible to hold upright. Anhedral good at 1.3 x MAC chord length above the water but bad at altitude.

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Riggerrob

Well-Known Member
Once you climb out of ground effect, forward-swept wings need substantially more dihedral than straight wings. Note how the Cessna 210 wing is slightly swept forward (measured at the quarter chord) and it has a bit of dihedral. Stability and control engineers wanted to add even more dihedral, but Cessna's salesmen nixed that idea. Salesmen won that debate, so 210 only got as much dihedral as Cessna's smaller singles ... almost zero dihedral.

At the extreme far edge of the envelope, military transports with high-mounted, aft-swept wings need anhedral (negative dihedral) for roll stability. Since both the high-wing and sweep improve roll stability, they got too much roll stability. That extreme excess roll stability caused Dutch Roll, so Airbus, Antonov, Embraer, Lockheed, etc. drooped the wings to limit Dutch Roll.

Protech Racing

Well-Known Member
If you want actual lift calcs , use 50% of the center area from 1 ft of either side of the fuse.

wsimpso1

Super Moderator
Staff member
It has been difficult. Wife and I drove a van full of our granddaughter’s stuff to the University of Tennessee - Chattanooga where she is starting her junior year. Girls sure have lots of stuff that they think is indispensable. She and her mother drove up yesterday with a car load.

Our daughter has decided to go back to work - teacher - next Friday. Just got one of the necessary documents from the bureaucracy late Friday. We have lots of things to take care of on Monday through Friday. Staying busy is better than sitting.

BJC
We understand he was your flying buddy too. Our condolences. Good that your granddaughter and daughter have fallback plans. Hang in there.

BJC

Well-Known Member
Supporting Member
We understand he was your flying buddy too. Our condolences. Good that your granddaughter and daughter have fallback plans. Hang in there.
Thank you, Bill.

I appreciate your comments as well as those that others have expressed in private comversations.

Things are suddenly very different for all of us. HBA is a pleasant distraction.

BJC

dog​

The operation will be limited to 0.7 wave height (for takeoff and landing). For cruise up to 1.5 m Wave height.

TFF​

I already bought a hull, Its a Fletcher 13Ft. Stripped all the unecessary appendices and now I have a shell with more or less 70Kg. I'm still working in the drawings but my goal is 750Kg MTOW. I'll use a water cooled car engine around 140 Hp (Didnt buy it yet) and I estimate around 160 Kg for engine + oil + coolant system. In my ideal world I will be taking off at 50 -60 Mph, just this I need low loads in my wings.

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Norman​

Thanks for the tuition mate! Good points!

I would like just a clarification about 2 things u said:

"Just make sure that the center of gravity is forward of the neutral point out of GE and you'll be fine but meeting that requirement will mean that you need a large down load on the tail while in GE"

I have no Idea about my final CG, neither I have knowledge and experience in calculating this. The main load will be me (110kg) just in front of the wings and the engine (above the middle of the wings), the tail (I believe) will be less than these 2 loads. Its a shame that I dont have a sketch to show you yet but I would like to ask you more detailed explanation about this phrase.

"Avoid the type of WIG with forward swept wings with anhedral. This type of wing works great in GE but is totally inappropriate out of GE because without the enhanced lift gradient of chord dominated ground effect it makes the plane nearly impossible to hold upright. Anhedral good at 1.3 x MAC chord length above the water but bad at altitude."

No diedral nor anhedral. I'll build with 0 angle. My only doubt is about the shape of the wings... Reverse delta or retangular... I'd like to build a reverse delta cause I'll save a bit of span and It's noticeably beautiful but trying to figure this kind of engineering is a nightmare, so probably will be a retangular one.

wsimpso1

Super Moderator
Staff member
"Just make sure that the center of gravity is forward of the neutral point out of GE and you'll be fine but meeting that requirement will mean that you need a large down load on the tail while in GE"

I have no Idea about my final CG, neither I have knowledge and experience in calculating this. The main load will be me (110kg) just in front of the wings and the engine (above the middle of the wings), the tail (I believe) will be less than these 2 loads. Its a shame that I dont have a sketch to show you yet but I would like to ask you more detailed explanation about this phrase.

You have a steep learning curve ahead of you. The simplest most straightforward coverage of calculating CG is in pilot training manuals, with examples. below is a summary of finding the longitudenal CG of a set of weights:
• Establish a longitudenal datum;
• Find the weight and location of the CG of all items in your study and list them - note that if weights are ahead of and behind the datum, those ahead have opposite sign of those behind;
• Find the moment of each weight by multiplying the weight by the longitudenal position of the weights - maintain signs - all weights will be positive, but some positions and thus moments will be negative.;
• Find the total weight by summing the weights;
• Find the total moment by summing the moments;
• Find the CG by dividing the sum of moments by the sum of weights.
This is most easily done in a spreadsheet like Excel or LibraOffice Calc . I prefer to list all of the components expected in a project, and keep updating the sheet as the design evolves, continuing to update as you obtain and/or build the pieces. This is an excellent tool for weight control and knowing how you are doing on balancing the airplane.

Neutral point calculation for in flight uses many of these same skills but will require the more involved thinking of computing lift and moment differentials. That topic has been discussed in many other threads, but I would get weight and balance calcs straight in your head and applied in a maintainable form (Excel is your friend) first, then get into stability and control.

I actually do this in longitudenal and vertical axes. If your project has any significant asymmetries, you may even want to do this with lateral axis as well.

"Avoid the type of WIG with forward swept wings with anhedral. This type of wing works great in GE but is totally inappropriate out of GE because without the enhanced lift gradient of chord dominated ground effect it makes the plane nearly impossible to hold upright. Anhedral good at 1.3 x MAC chord length above the water but bad at altitude."

No diedral nor anhedral. I'll build with 0 angle. My only doubt is about the shape of the wings... Reverse delta or retangular... I'd like to build a reverse delta cause I'll save a bit of span and It's noticeably beautiful but trying to figure this kind of engineering is a nightmare, so probably will be a retangular one.
This is stability and control... Let's walk before we run.

Billski

Arnaldojrbr

Active Member
wsimpso1

Brilliant buddy! As soon as I finish my pre-project drawings I will list all relevant weights and try to spread it in a spreadsheet. I'm still fighting with the shape & metal structure and I believe this will take lots more than I thought in the beginning.