Contemplating major engine modification to Velocity

[vayoodev]

Dear fellow Canardians!

 

I'm very green to the aviation world, I don't have a PPL or a plane. It was my life long dream to be a pilot (which boy doesn't) and now it seems I'm on my way. I plan to get my PPL in 3 years and build myself a plane in 5 (hopefully). I have done some research and based on agility, speed, comfort, safety (canards after all have the best stall characteristics) and endurance, I have decided on a Velocity SE-RG or XL-RG.

 

What I want to do is use two Centurion 1.7, 135 hp jet fuel engines in pusher format. I want to install these balanced on the two sides of the canard equally spaced about the centerline of the fuselage. I want to use the space where the engine presently sits for fuel tanks and avoid the Jeffco and the strakes fuel tank mess.

 

Becuase cost is a factor, can I buy plans instead of a kit for the XL-RG?

 

Now as I said, I am a novice if there ever was one, but I do have a dream. I would like to ask the experienced people on this forum to bring to bear their considerable experince and tell me if it is at all feasible (I don't want to spend the next 10 years experimenting with this either). Any posting about this would be very much appreciated.

[raiki]

A guy (nam withheld cos I don't know if he wants to be listed) tried twin pushers on a LongEZ but I am pretty sure he decided it didn't work well and changed back to a single pusher.

 

As for fuel where the engine goes, too far from the CG and that will change drastically with different fuel loads.

 

The Velocity can only be built from a kit, so that cans that idea as well.

 

Have a look at my idea for a push-pull Cozy. It would suit two centurions perfectly. http://www.canardzone.com/forum/showthread.php?t=1735

 

Only a doodle and not a lot of thought put into it but I am sure it could be worked out and built from plans (as all Cozys are).

[bferrell]

If you are serious about doing this, I would suggest that you discuss it with the factory. They had looked at building a twin Velo, but set it aside because of other committments (UAV, the Rocket Racing league, etc.), but might support the effort (at least technically) by a private party.

 

Brett

[Marc Zeitlin]

.... tell me if it is at all feasible ....

No. You've basically redesigned the whole aircraft. Unless you're an aircraft designer, the answer is that you can't do what you're proposing, and even if you were, it would mean changing about 85% of the plane.

 

And Velocity doesn't sell plans, just kits. If you approached them with this idea, they'd either laugh you out of their office (if they were jerks) or very politely tell you that it can't be done and you should do something substantially safer.

 

And although Raiki didn't ask the same question, he'd get the same answer if he did ask, for his proposed COZY modification.

[bferrell]

No.

And although Raiki didn't ask the same question, he'd get the same answer if he did ask, for his proposed COZY modification.

Marc,

 

Are you responding to the only the Cozy, or the Velocity as well (the subject states Velocity)?

 

The factory has been very clear that they are interested in developing and marketing a twin Velocity, and have done a lot of the design and modelling work to achieve it, and had in fact started the tub for a prototype when the hurricanes hit Florida. Due to that set back, and the resource strain of their UAV and RRL actives, as well as the turbo Conti engine installation, put it on the back burner, so I don't think your comments are relevant to the Velocity at all. The factory *may* not be interested, but I suspect under the right circumstances they would be supportive. The twin is mention in the Velocity newsletters here and here for those that are interested. I looked for a picture of the model, but couldn't find it, though I know I've seen it online somewhere.

 

Brett

[Marc Zeitlin]

Are you responding to the only the Cozy, or the Velocity as well (the subject states Velocity)?

Since the OP was talking about Velocity's, my response to HIM was about Velocity's, and since Raiki's post was re: COZY's, I mentioned COZY's as well.

 

The factory has been very clear that they are interested in developing and marketing a twin Velocity.... so I don't think your comments are relevant to the Velocity at all.

You miss the point. Whether or not the Velocity factory is interested in developing a twin version (and I don't doubt that they are), they will NOT be moving the engines to "either side of the canard", putting fuel where the engine was, and putting nothing in the strakes. That, I can guarantee. Those were the aspects of the design concept that I was stating would require an almost complete redesign, and that the factory would eschew.

 

... The factory *may* not be interested, but I suspect under the right circumstances they would be supportive.

Of a "twin" idea - sure. But not of this particular design concept.

[bferrell]

Since the OP was talking about Velocity's, my response to HIM was about Velocity's, and since Raiki's post was re: COZY's, I mentioned COZY's as well.

 

You miss the point. Whether or not the Velocity factory is interested in developing a twin version (and I don't doubt that they are), they will NOT be moving the engines to "either side of the canard", putting fuel where the engine was, and putting nothing in the strakes. That, I can guarantee. Those were the aspects of the design concept that I was stating would require an almost complete redesign, and that the factory would eschew.

 

Of a "twin" idea - sure. But not of this particular design concept.

OK, I didn't see the "engines on the canard" as a critical factor, more of his concept. The Velocity concept has the engines on pods either side of the fuselage, so the engine bay would still be open, which I thought was the bigger consideration.

 

Brett

[bferrell]

Also, I forgot to mention, the Velocity concept had a center rudder for single engine control. I can't recall if they did away with the winglets (ala the "firefly" or here) or not.

 

Brett

[Nathan Gifford]

...I want to do is use two Centurion 1.7, 135 hp jet fuel engines in pusher format. I want to install these balanced on the two sides of the canard equally...

Like Marc says it would be a substantial piece of work and not likely that the Velocity folks would want you to do it.

 

If you are really up for a twin, I would try to locate plans for the Defiant. The plans are not made anymore (or are they on the Terf CD short of the templates). Plans do appear on eBay, but they are rare.

 

The Defiant is typically powered by O-320 engines but it was always designed to be a twin and one that the Rutans still use as a workhorse.

 

It is a plans a/c, meaning there are very few manufactured parts like the Velocity. Also it will require a lot more hours to build than a single engine aircraft. Reports I have heard about typically suggest that a minimum of twice what a LongEZ needs.

[Jon Matcho]

What I want to do is use two Centurion 1.7, 135 hp jet fuel engines in pusher format. I want to install these balanced on the two sides of the canard [aircraft] equally spaced about the centerline of the fuselage. I want to use the space where the engine presently sits for fuel tanks and avoid the Jeffco and the strakes fuel tank mess.

Notice the omitted word, and besides "...jet fuel engines in a pusher format." was clear to me.

 

Assuming someone has the money, I don't see this to be as crazy as anyone would imagine. The issues w/where to put the fuel are with weight and balance. If there's no engine AND you can put fuel there AND you can maintain the same Cg (no idea), then the idea is not that bad (at least in my little book). Again, assuming mega $.

 

Also, assuming the RRL takes off, which I hope it does, it's only a matter of time before something like this would be considered... or at least more horsepower.

 

If you are really up for a twin, I would try to locate plans for the Defiant. The plans are not made anymore (or are they on the Terf CD short of the templates). Plans do appear on eBay, but they are rare.

Join the Yahoo! DEFIANT mailing list and ask for plans. Someone will offer to make you copies for $800. This is how they do it over there, and it's accepted. If anyone has a set of these (or actual Defiant plans) that they want to lend me, I'll digitize and make available for free.

[bferrell]

Like Marc says it would be a substantial piece of work and not likely that the Velocity folks would want you to do it.

 

If you are really up for a twin, I would try to locate plans for the Defiant. The plans are not made anymore (or are they on the Terf CD short of the templates). Plans do appear on eBay, but they are rare.

 

 

Why is it that people keep saying crap like this?! How annoying. What data do you have for that position? Why would you assume Velocity wouldn't want this? I'm telling you, I have talked with them personally, and they want a twin built! And, recall, the Swings got involved with the company when they built the first retract systems for the Velocity, so why would they consider it a bad deal to have someone else help with development?? If you are serious about this, you should call Duane and talk to him, based on their own comments, I would be very surprised if they didn't assist you in pursuing this.

 

Brett

[CFernandez]

Hey, Brett!

 

I saw your engine running on your website, how sweet it is.

 

As to the posts about Velocity wanting or not wanting a twin, is about putting engines on the canard. I think it is likely that arrangement is not something Velocity wants to do (oops I said it ). I do think Velocity would do a twin just not one with the engines on the canard.

 

I'm not an engineer but the idea seems extremely difficult, having engines on the canard; cg, engine-out ops, etc.

 

Vayoodev, if cost is a factor one engine is less costly than two. Building a proven design is less costly than designing one.

 

My $.02, but don't let naa sayers stop you, this is the beauty of this thing we call EXPERIMENTAL. Experiment, learn.

[Jon Matcho]

...having engines on the canard...

The original poster did not actually mean to put jet engines on the canard wing itself -- just on the airframe in a pusher setup.

[CFernandez]

The original poster did not actually mean to put jet engines on the canard wing itself -- just on the airframe in a pusher setup.

Thanks for the correction I was thinking on the canard. Now I see vayoodev wants to put engines in the "strake" area and make the original engine compartment a fuel tank.

 

It could work...

[Jon Matcho]

It could work...

Just add $$$.

[bferrell]

Thanks for the correction I was thinking on the canard. Now I see vayoodev wants to put engines in the "strake" area and make the original engine compartment a fuel tank.

 

It could work...

Hey Carlos. Agreed, putting them on the canard is a bad idea in my opinion, but the factory's concept does have them mounted on the aft strake area, with a mid rudder, so if that is acceptable to vayoodev, I think they'd be happy to work with him.

 

I'm not crazy about the idea of a twin velo/canard myself, but apparently Velocity gets a lot of requests for this from folks that just refuse to fly single engine aircraft.

 

Brett

[vayoodev]

I knew when I found this forum that it was an awsome resource. I really appreciate this feed back from every one. I haven't talked to anyone at velocity, I have been contemplating this for a while and have only spent a few hours thinking about it.

 

The CG discussion is something i knew was an issue with the concept but could be corrected by elongating the cockpit and placing the fuel between the pilot row and the passenger row thus keeping the fuel closer to the plane's CG also I was thinking of adding luggage compartment in front to offset the extra weight due to two engines in the strake area.

 

I know it is a major modification but that's what I was hoping to to get out of this forum for the time being. I'll do some more research into what it takes to get there and in the mean time if anyone has any more ideas then please keep them coming.

 

Sincerely

[Spodman]

"I want to install these balanced on the two sides of the canard equally spaced about the centerline of the fuselage." I've seen a few assumptions above and am still not sure I understand what you are contemplating. Could you do a quick sketch of what you want and post it? I think you wanted a pusher, but do you want the engines perched on the canard (small front wings), the strakes (front part of larger rear wing - which would place pusher propellors in the middle of the wing???), the rear of the wing (like both twin-eze I've seen pictures of) or on pods in the middle.

 

If you put the fuel tank between the front seats & the back the fuel will be far forward of the standard c of g position. Your rear seat pax should be patriotic Americans, coz they will have the same view of the world as Lindberg did on his way to Paris. They should also be reasonably sedantary in habits, as once they are fibreglassed in there will be no access to the door to let them out again... It is easy to think of alternative locations for the fuel tanks, just a lot harder to think of BETTER locations.

 

The Centurion makes economic sense when fitted to a certified aircraft in lieu of a certified new/overhauled engine, coz it is much cheaper to run and to overhaul (as in replace) when the time comes. Compared to a single non-certified conventional engine of the class of an O-540 you are going to have to fly it's pants off (if it flys - there is a risk here) before you could pay off two Centurions. Those suckers are expensive here, and can't be that much cheaper over there, and both need a c/s prop.

 

The manufacturers don't seem to be all that homebuilder friendly either, I gather they reserve the right to design & fit their installations, and want to do all the maintenance also. Works in Europe with their more restrictive rules but probably not that realistic in a US homebuilt.

 

I know it is only supposed to develop 135hp (from memory) but they are being fitted here to replace bigger inContinents & Lycosaurs in Arrows & C182, etc. Given all the above it may be practical to fit one (and only need one) in a completely stock Cozy, maybe in a Velo:confused:

[bferrell]

Here are the pictures I promised, they had the model at Airventure again this year, and I got my own set of pics. As I mentioned before, they've started the tub, but got distracted, but they did bring the Turbo this year, and were throwing numbers like 250Kts around, so that was pretty cool.

 

Brett

[triple7driver]

Thanks for finding the pics Brett. Very inspirational. I am toying with a similar idea only using a long eze sized fuselage and twin rotax turbos. If Piaggio can pull this idea off with their Avanti I don't see why it can't be done on a smaller scale. I think the guy who tried it with the twin eze before went wrong because he did not have the central rudder. Fuel would be kept in the wings as always.

Cheers,

R.P.

[David Staten]

Dear fellow Canardians!

 

... I have decided on a Velocity SE-RG or XL-RG.

 

Excellent choice... Sorry I am late replying to this thread

 

What I want to do is use two Centurion 1.7, 135 hp jet fuel engines in pusher format.

 

As someone else mentioned, even though this engine makes only 135 hp (on the dynomometer, I presume), you need to understand that this powerplant is being used to replace gasoline powerplants that make over 200 hp. The key is Torque from the Diesels being able to generate equivalent THRUST despite lower HP. What this means: One engine should suffice. Diesel reliability being what it is.. should provide adequate reliability.

 

Becuase cost is a factor, can I buy plans instead of a kit for the XL-RG?

 

As others have said, Velocity is a kit-built plane. In short, NO. The factory manufactures certain parts - fuselage shell, spar's, strakes, doors. If cost is such an overwhelming factor that you cannot afford to buy the kit, then how do you propose to buy ONE Aero-Diesel engine, let alone two? Have you actually checked the prices on them? If you must have a plans built, then I would say go with a Cozy, and if you must, scale it up a few points. The Velocity XL was made to handle the larger engines that people wanted to keep putting on the Standard versions.. its not all that much bigger.. and all that extra HP does is burn more fuel.

 

Now as I said, I am a novice if there ever was one, but I do have a dream. I would like to ask the experienced people on this forum to bring to bear their considerable experince and tell me if it is at all feasible (I don't want to spend the next 10 years experimenting with this either). Any posting about this would be very much appreciated.

If you dont want to spend 10 years on it, then don't deviate from plans doing all sorts of fancy customization ESPECIALLY without a solid background in aircraft design/engineering. I'm not saying DONT do it.. but if you do, prepare to be challenged, and prepare to fix ONE problem and have two or three others pop up as a result of that fix. Deviations from other peoples proven design add time and problems.

 

Flying multi-engine aircraft adds a level of complexity above that of single engine aircraft, ESPECIALLY in emergency procedures (such as one engine out). This complexity demands proficiency, or it will come back to bite you in the worst way. Twin engine aircraft have greater fuel costs and maintenance costs as compared to single engine aircraft. Some people have characterized the cost as THREE times the cost of a single engine aircraft with equivalent seats, due to maintenance and systems complexity. That may not translate as well to homebuilts, but its a good data point to consider.

 

If you have a reliable enough powerplant, what is it about your mission that dictates the need for a twin engine aircraft?