Stretched Long-EZ

[RSD]

Looking at building a Long-EZ, and am considering putting an additional 18 inches in the fuselage behind the rear seat to create a baggage compartment for soft bags.  Not being an aerodynamics guy I'm wondering should the wings etc stay right at the back or would this change necessitate moving them forwards a little?

The other question is how much does a bare fuselage weigh?  I'm wondering whether there might be a sufficient enough weight benefit to build the fuselage out of carbon fibre instead?

[macleodm3]

1 hour ago, RSD said:

Looking at building a Long-EZ, and am considering putting an additional 18 inches in the fuselage behind the rear seat to create a baggage compartment for soft bags. 

Unfortunately this can't be done...  there are lots of little changes you can make to an EZ, but changing the canard/pilot/wing/engine balance will prevent the airplane from flying properly.

Thankfully there is already alot of baggage room in a Long-EZ...  the parts of the wing that are closest to the fuselage (the strakes) are hollow and open to the inside of the plane for baggage.  Also, its very easy to add baggage pods under the wings (there are kits for this).  Two people can camp out of a Long-EZ.

1 hour ago, RSD said:

The other question is how much does a bare fuselage weigh?  I'm wondering whether there might be a sufficient enough weight benefit to build the fuselage out of carbon fibre instead?

Most completed EZ's weigh around 950 lbs.  Don't know what the fuselage weighs with no other parts.

The airplane is an engineered system that uses three different weaves of fiberglass that the engineer chose as the best material.  Changing these primary materials to a different product would have many undesirable consequences (and it may or may not weigh less) .  The lightest, strongest, and fastest EZ's ever built kept is simple and followed the plans.  There was a canard kitplane that used some carbon fiber... the Berkut.  The design included carbon fiber from the ground up (but I think it was still mostly fiberglass).

[RSD]

1 hour ago, macleodm3 said:

Unfortunately this can't be done...  there are lots of little changes you can make to an EZ, but changing the canard/pilot/wing/engine balance will prevent the airplane from flying properly.

Wouldn't for instance the E-Racer have changed this balance?

[Jon Matcho]

11 hours ago, RSD said:

Not being an aerodynamics guy...

Hello RSD, it's excellent you are self-aware in your limitations.

11 hours ago, RSD said:

...I'm wondering should the wings etc stay right at the back or would this change necessitate moving them forwards a little?

No modification should change a design's center-of-gravity or aerodynamics.  

What you're asking is, "Can I modify the Long-EZ design into an entirely new aircraft and fly it?"  Andrew's to-the-point response ("this can't be done") is where you need to be.  The concern is that you and/or someone else will sustain serious injuries, potentially death.

Choose a flight-tested design and lock-in to its geometry and aerodynamics.  Do not mess with the design.  If you do then you are no longer building that model -- you would be building an "RSD Flyer" and are totally on your own.

8 hours ago, RSD said:

Wouldn't for instance the E-Racer have changed this balance?

Yes, they have, and also put in sufficient design considerations, testing, and had a number of test pilots and builder/guinea pigs prove the design change is airworthy.  If that's the design you want to build, then choose that design and build-to-plans.

11 hours ago, RSD said:

I'm wondering whether there might be a sufficient enough weight benefit to build the fuselage out of carbon fibre instead?

10 hours ago, macleodm3 said:

There was a canard kitplane that used some carbon fiber... the Berkut.

This is a very common first question/observation (myself included).  In the decades Rutan aircraft and fiberglass has been around, this question comes up.  Andrew pointed out the Berkut, which was a kit designed and built by someone that built MANY Long-EZs.  The changes were structural, with little (if any) changes to CoG and aerodynamics.  There are many issues to address with doing things in carbon fiber, and you're not really saving that much for a whole bunch more cost and complexity than it's ultimately worth.  That may sound like it's an option, but it should definitely be ruled out for a new builder.

Build a few pieces per plans, and then build those same pieces in carbon fiber and you'll have a hint of what we're talking about.

Best thing you can do is continue to ask questions!  Please feel free and welcome to do so. 🙂

[Marc Zeitlin]

17 hours ago, RSD said:

Looking at building a Long-EZ, and am considering putting an additional 18 inches in the fuselage behind the rear seat to create a baggage compartment for soft bags.  Not being an aerodynamics guy I'm wondering should the wings etc stay right at the back or would this change necessitate moving them forwards a little?

So contrary to a previous comment, the Berkut was stretched (from the LE dimensions) 12" between the wing and canard, with 6" being aft of the rear seat to give room for the retracts, and 6" forward of the rear seat to give more leg room in the back. This substantially changed some of the aerodynamics with respect to CG range for the aircraft, which has NEVER been properly characterized regarding the neutral axis and stability or with respect to deep stall susceptibility. Stretching the aircraft turns it into a new airplane and requires more skills than "that looks about right".

Is it possible? Sure. Would I recommend it? Nope.

14 hours ago, RSD said:

Wouldn't for instance the E-Racer have changed this balance?

The E-Racer kept the canard/wing relationship - there was no stretch. It moved the front seats aft, so that a 2nd person in the front seats wouldn't change the CG enough to require changing ballast. The aerodynamics were not changed (other than the wider fuselage).

17 hours ago, RSD said:

I'm wondering whether there might be a sufficient enough weight benefit to build the fuselage out of carbon fibre instead?

The short answer is no, because the weight of the fiber in one of these planes is a relatively small percentage of the total weight of the aircraft. The cost of materials, vacuum bagging, etc. is not worth it for the theoretical weight savings. I won't even get into the issues around needing to use molds if you're using carbon. There are a lot of longer answers as to why this is contraindicated in the archives here and in the COZY list as well as the canard-aviators mailing list.

[RSD]

Many thanks for all of your replies.  My take from all of this is 

• For a roomier Canard go with one that has already flown - e.g. a King E-Racer

I'm still interested in the carbon fibre aspect though as a lot of these designs are very close to or over MTOW with two adult males and full tanks - a 30 pound saving on the fuselage is still of significant benefit.  Having to make molds isn't an issue because if it is a flying success then producing them as a kit aircraft is a possibility.

Edited August 4, 2019 by RSD

[macleodm3]

1 hour ago, RSD said:

For a roomier Canard go with one that has already flown - e.g. a King E-Racer

Have you considered building a Cozy MKIV?  Its the biggest plans built canard... and the plans are excellent.  

1 hour ago, RSD said:

I'm still interested in the carbon fibre aspect though as a lot of these designs are very close to or over MTOW with two adult males and full tanks - a 30 pound saving on the fuselage is still of significant benefit.  Having to make molds isn't an issue because if it is a flying success then producing them as a kit aircraft is a possibility.

It takes a million years to build one of these things.... its fun, but a really big project.... no kidding, its ALOT of work.  How about for now build the fiberglass practice parts and see how much fun it is?  Then try some carbon fiber parts.... 

[RSD]

6 minutes ago, macleodm3 said:

Have you considered building a Cozy MKIV?  Its the biggest plans built canard... and the plans are excellent.  

It takes a million years to build one of these things.... its fun, but a really big project.... no kidding, its ALOT of work.  How about for now build the fiberglass practice parts and see how much fun it is?  Then try some carbon fiber parts.... 

I haven't figured out how to break down quotes on here into smaller chunks to reply to each part individually so you'll have to escuse me, but

The comparison I've heard is that the E-Racer is the sportscar whereas the Cozy MkIV is the SUV - there are only two of us and I want the sportscar😁

The carbon fibre aspect doesn't daunt me as much as it would some because we already make some carbon fibre components for my subsea robotics business - mainly wrapping buoyancy foam to protect the foam from dings and compression at depth but we want to make other components as well

[macleodm3]

10 hours ago, RSD said:

The comparison I've heard is that the E-Racer is the sportscar whereas the Cozy MkIV is the SUV - there are only two of us and I want the sportscar

Comparisons like that are more or less builders ribbing each other.  Another analogy is that an EZ is a touring motorcycle and the Cozy is a Porsche 911(tiny back seats), the E-Racer is a (insert 2 seat sports car of your choice here).  There is some very good actual flight testing out there that is more appropriate to use when considering which airplane to build.  Do an online search for "CAFE Aircraft Performance Report" and read about the Varieze, the Cozy, and others.

10 hours ago, RSD said:

The carbon fibre aspect doesn't daunt me as much as it would some because we already make some carbon fibre components for my subsea robotics business - mainly wrapping buoyancy foam to protect the foam from dings and compression at depth but we want to make other components as well

Yes, you can use it... its possible.  Carbon fiber is the wrong material.  Its not better or worse... its wrong.  When the instructions tell you to use 10 layers of UNI fiberglass to make a structural part, how will you know how many plies of carbon fiber to use?  You'll need to reverse engineer the entire plane... and it could end up being heavier.

[Barry]

"Not being an aerodynamics guy..."

I'm just guessing, you're not a composites engineer either. There are many reasons to stick to the plans created by one of the finest aerodynamic and composites engineers ever to walk fly this earth. Primarily, so as not to kill yourself or a friend, and two - that you might finish your project. 

Edited August 5, 2019 by Barry

[Jon Matcho]

10 minutes ago, Barry said:

I'm just guessing, you're not a composites engineer either.

RSD, not discounting Barry's entirely valid points, you do have some useful composite experience which many don't have (building a bird house once upon a time is good enough).  You need to get through the "designer phase" many tend to go through -- you're not better than Burt Rutan and the others that have thoroughly been down these roads, at least yet.

On 8/3/2019 at 11:18 PM, RSD said:

The carbon fibre aspect doesn't daunt me as much as it would some because we already make some carbon fibre components for my subsea robotics business - mainly wrapping buoyancy foam to protect the foam from dings and compression at depth but we want to make other components as well

That's a type of "moldless composite construction" which is how these planes are built.  You'll learn several other techniques and practices, and gain an understanding of how forces are transferred through the different types of fiberglass (unidirectional "uni" and bidirectional "bid").  Chapters 1, 2, and 3 of the VariEze, Long-EZ, Cozy, and maybe even the E-Racer plans (not in front of me right now) take you through these basics.

I wonder why you need to bother with carbon fibre for subsea robotics as opposed to just using a comparable fiberglass weave?  

[RSD]

1 hour ago, Barry said:

There are many reasons to stick to the plans created by one of the finest aerodynamic and composites engineers ever to walk fly this earth.

The Long Ez was designed 40 years ago by Burt with presumably the best composite materials and techniques available at the time - surely its time someone revisited it given the advances in composites since then?

[RSD]

40 minutes ago, Jon Matcho said:

RSD, not discounting Barry's entirely valid points, you do have some useful composite experience which many don't have (building a bird house once upon a time is good enough).  You need to get through the "designer phase" many tend to go through -- you're not better than Burt Rutan and the others that have thoroughly been down these roads, at least yet.

That's a type of "moldless composite construction" which is how these planes are built.  You'll learn several other techniques and practices, and gain an understanding of how forces are transferred through the different types of fiberglass (unidirectional "uni" and bidirectional "bid").  Chapters 1, 2, and 3 of the VariEze, Long-EZ, Cozy, and maybe even the E-Racer plans (not in front of me right now) take you through these basics.

I wonder why you need to bother with carbon fibre for subsea robotics as opposed to just using a comparable fiberglass weave?  

I'm certainly nowhere near Burt and am a long way from being there.

Carbon fibre is stiffer so won't flex under pressure and therefore change volume/buoyancy.  A lot of subsea things that are used to maintain or adjust buoyancy are made from carbon fibre for this reason, and the less weight the better.

[Jon Matcho]

I opened a can of worms! 🙂

6 hours ago, RSD said:

Carbon fibre is stiffer so won't flex under pressure and therefore change volume/buoyancy.

Carbon is stiffer, but it does flex.  Everything flexes to an extent, then it breaks. 

6 hours ago, RSD said:

The Long Ez was designed 40 years ago by Burt with presumably the best composite materials and techniques available at the time - surely its time someone revisited it given the advances in composites since then?

You're not the first person in the 40 years since the Long-EZ was developed to ask, "Has anyone thought to use carbon fiber?"  It certainly can be used here and there for various things, but it is far more involved than even those here are stating.

As a new builder, your best bet to finish is to stick to proven plans, line by line.  Most new/one-off designs produce abandoned projects that nobody would consider taking over.  

[RSD]

4 minutes ago, Jon Matcho said:

I opened a can of worms! 🙂

Carbon is stiffer, but it does flex.  Everything flexes to an extent, then it breaks. 

Back to airplanes... you're not the first person in the 40 years since the Long-EZ was developed to ask, "Has anyone thought to use carbon fiber?"  It certainly can be used here and there for various things, but it is far more involved than even those here are stating.

As a new builder, your best bet to finish is to stick to proven plans, line by line.  Most new/one-off designs produce abandoned projects that nobody would consider taking over.  

LOL!  Can of eels maybe?😃

I should have said that it flexes less easily than fibreglass, and stands up to pressure compression better - especially if the shape is a sphere.

I'm waiting on a set of plans to arrive then will see how it looks.

 

[Barry]

"The Long Ez was designed 40 years ago by Burt..."

Yes. I will just note that in that entire time, no one has successfully deviated much from the Rutan design. Those that have worked off of the Rutan design have been fair composite/aero engineers and often worked with Rutan to make the changes.

I have used glass and carbon and I'm building new bodywork for my formula race car now, all carbon. A composite engineer I am not. All the properties of carbon are not always good when used as a direct replacement for something designed in glass. This is the point I would make. Burt designed in glass and moldless. Taking the same design and trying to replace the glass with carbon is not something to be done by the seat of your pants. One, you'll likely never finish, two - which is probably for the best since you'll more likely than not cause yourself harm.

Put it another way, if you are not capable of designing a canard in carbon from a clean sheet of paper, your are not qualified to substantially modify a Long EZ. if you have that skill level then go for it.

[RSD]

10 hours ago, Barry said:

Those that have worked off of the Rutan design have been fair composite/aero engineers and often worked with Rutan to make the changes.

Dave Ronnenberg didn't work with Burt on the Berkut but was a good composite guy, I'm not sure whether Shirl worked with Burt for the E-Racer?

I'm starting a 14 day intensive course in carbon fibre at the local college soon, that will give me some more grounding, and probably networking opportunities with composite engineers etc.  After that I will evaluate where I think that I'm at and then make some decisions.

Something that I'm conscious of is that there are very few people these days starting to build Canard aircraft from plans.  If the homebuilt canards are to continue then somehow we need to come up with a kit solution that the average person can build in about a year like an RV.  Hopefully a solution can be worked out because the long range, speed and anti-stall features of a canard mean that there is a need for them.

[Barry]

Ronnenberg did work on the Voyager project with Dick and he had built multiple Long EZ's. But I understand Burt had nothing to do with the Berkut. 

I go back to this "Not being an aerodynamics guy". Quite a few non engineers have built a nice airplane following the plans. And some darn smart people have built and followed the plans precisely. There is a reason for this.

I have not built an airplane, likely never will as I'm just going to run out of time  

But I have studied the plans and dream.

Anyway, I hope you get to build a Long EZ to plans or modified.

[Marc Zeitlin]

5 hours ago, RSD said:

... there are very few people these days starting to build Canard aircraft from plans.  If the homebuilt canards are to continue then somehow we need to come up with a kit solution that the average person can build in about a year like an RV.  Hopefully a solution can be worked out because the long range, speed and anti-stall features of a canard mean that there is a need for them.

There are a number of folks starting down the path of different types and sizes of canard composite kit aircraft. I don't hold my breath that any will be successful from a business standpoint (and one will certainly not be from a technical standpoint), but I wish most of them luck and hope I'm wrong.

With respect to your reason for wanting canards to continue - I love my COZY MKIV, and wouldn't trade it for any other aircraft out there (except maybe a Pilatus PC-12, if someone else paid for the fuel and maintenance), but while in theory they're safer due to the stall/spin resistance, a study of the accident rate of canards vs. conventional planes over the 45 odd years that they've been in existence does not show any advantage in either fatal or non-fatal accident rates. There are other airplanes with similar performance and range as well.