Thoughts on the GP-5?

[spacegrrrl]

Re: Thoughts on the GP-5?

They don't last as long as Continentals and Lycomings even in the most benign usage. Count me in the "car engines don't fly" camp, and I'm a dyed-in-the-wool car engine geek. 40 years of trying and no successful racers with car engines yet. Odds are it'll never happen. The design requirements are completely different. An engine with the qualities suited to an airplane would make a horrible car powerplant and vice-versa.

The camp based on no actual data? What racers can you point to in those 40 years that proves your point. Other than the Pond the GP-5 has to be the first real serious effort on the ramp at Reno to date. The Pond failed because of airframe design as much as the powerplants. We could do a whole seperate thread into why the Pond was a failure before it was even built. Hint, "intersection drag". The engine failures were also not the fault of the powerplants, the program was the issue, again, that could be a whole 'nuther thread about where that went wrong.

The reason is there really aren't any 'car engined" racers is there is only one class so far they could make any sense. When they upped the unlimited minimum weight there was no class for a plane like the GP-5. It wasn't untill the Super Sport class that we have an opportunity to really try and build something around a "car" plant.

Do you have any direct experience to support your position about car engines in aircraft (I do) (I'd have built small block Ford or racing versions of the Chevy V-6 by the way, but it really is a toss up, its what you know). Have you ever built a car racing engine (I have). Do you know anything about car engines in racing boats (I do).

So I love that you have a strong groundless position not supported by real life experience.

Subscribe to Contact magazine, buy all the back issues when you do, be sure to read carefully, then crew on an Unlimited Light hydro or maybe an offshore boat, don't even get me started about Nascar engines or long distance speed record attempts on banked courses.

Then think about how many Merlins it took to get to where they are today, ask yourself where all the 3350 Seafuries are, ask Kevin how that totally airplane technology firewall forward worked for him this year, ask yourself how many Thunder Mustang V-12s blew up before they got it right then come back with a case as to why the first serious effort to race a car V-8 failing on the first attempt is anything other than the cost of learning how to build a seriously race hardened powerplant.

Bottom line, you race stuff and it will blow up at some point. If you are lucky, you can find out why and go even faster and harder next time. Watch kevin next year! I bet the prop stays on and he goes faster than ever! That oil system failure has taught everyone a lot!

When you build an engine it has no idea where you are going to put it. There is nothing fundementally wrong with a variation of an american V-8 engine that precludes it from working in a race plane. That is a fact.

But what this illustrates for ANY racing powerplant, the devil is in the details. If you start out trying to put a powerplant in a new application you can expect to have to learn a lot about those difficult details. This is why folks always say develop a new airframe with an existing power plant, then develop the power plant in a proven airframe. To do both is a complex challenge. I think we could say the GP-5 is doing at least as well the first attempts to get the Thunder Mustang racable so far. They ate engines in the beginning.

So unless you have hard data to support that good ole' car muscle can't make our racers awesome on the course I'd suggest you should sit back and watch (and cheer on) while folks like the GP-5 team help us to the future!

I celebrate any team that decides to think "outside the box" and try something new! I can't wait to see someone think about a three bank rotary or a current generation high performance car engine.

Spacegrrrl
Confident we'll see a "car engine" raced very successfully at Reno in my lifetime

[kiwiracefan]

Re: Thoughts on the GP-5?

They don't last as long as Continentals and Lycomings even in the most benign usage. Count me in the "car engines don't fly" camp, and I'm a dyed-in-the-wool car engine geek. 40 years of trying and no successful racers with car engines yet. Odds are it'll never happen. The design requirements are completely different. An engine with the qualities suited to an airplane would make a horrible car powerplant and vice-versa.

That is totally baseless, I know of a GP-4 here in NZ that is running a 2L Subaru motor and has done around 400 hours, at the local GA Airfield there is a scale hawker Hurricane that is powered by a 3.5L Mitsubishi V6 and it has been pretty successful by all reports.

[Race 29]

Re: Thoughts on the GP-5?

Sorry dude! I have to agree with Spacegrrrl. I've seen to many aircraft using auto engines.

Race 29

[MRussell]

Re: Thoughts on the GP-5?

I celebrate any team that decides to think "outside the box" and try something new! I can't wait to see someone think about a three bank rotary or a current generation high performance car engine.

Spacegrrrl

No you don't. You attack the Pond effort like nobody else in the world, and it was one of the best examples of outside-the-box thinking ever to land at Stead.

[spacegrrrl]

Re: Thoughts on the GP-5?

No you don't. You attack the Pond effort like nobody else in the world, and it was one of the best examples of outside-the-box thinking ever to land at Stead.

There is a difference between "out of the box" and a bad idea. The Pond Racer was without a doubt the worst "out of the box" idea to ever make it to Stead. What compounds that tragic fact is it shouldn't have been, it was well funded, we well intentioned and in theory was going to be designed by someone thought to be a real "genius" in the aircraft design world. If only some "genius" had actually made it into the airplane we all saw on the ramp this would be a different story....

I don't want to rehash all the failures of the Pond Racer project so I'll just start with two obvious ones that should have kept the aircraft from ever being built in the form it was. Dig out your well worn copy of Hoener "Fluid Drag" (you have one, right?) and you'll see that one of the biggest contributor to overall drag of an airframe is the intersection between surfaces. Now count how many there are on the Pond Racer compared to other designs. My quick count at least 17 places where a wing or tail surface intersects an engine pod or center fuselage. If for example the pond had been a DO335 style design that count would be 5 or 6.

Another total "fail" of the design was the forward swept wing. What that caused (and this is confirmed by actual CFD studies of the design) was a strong inward span wise flow that created a draggy high pressure bubble at the pilot pod. It also negated any safety having the engines away from the pilot as any fluids and fire are carried by that flow right to the pilot. We all know the tradedy that caused in the end.

I was told by a well respect aero engineer and CFD expert that likely would prefer to stay out of this conversation that no amount of HP could have gotten the Pond to go much faster than low 400's it went and even a basic CFD study of the design should have made these flaws obvious.

The Pond racer in the end seems to have been designed with the rigor and deep thinking normally associated with grade school boys doodling on the back of their notebooks. All it really lacked was machine guns to use to blow up the zephlin it was probably drawn next to.

When I first saw the Pond I was a big fan of the concept, design a racer that used non-aviation components to preserve the dwindling stock of warbird parts. Then I took a moment to really think about what I was looking at and the flaws in thinking just gushed out (kind of like the huge amounts of fuel it was always leaking!). Finally getting someone I consider an expert to comfirm what I had seen made it clear the Pond Racer was poorly conceived and had Pond hired another designer Reno might have a half dozen Ponds on the ramp now.

In the end you can't dispute the science. Pond sadly payed a lot of money to someone that chose to ignore that and we saw the results. We had a cool looking airplane that could never go fast and was a real hazard to the pilots that raced it because of a simple design flaw that negated the safety the unusual configuration chosen was intended to provide (get all the engine systems and fuel safely away from the pilot).

Now if only someone like Bruce Boland had been paid to build a DO335 inspired airplane (or even a Tsunami II with the engines geared together as was done in the late Italian Schneider Cup racers) with the same powerplants Reno might be very different today.

One other point I want to make. My issues are with the design of this engineering calamity. The team members that did their best to get this racer on the course and competitve were another story. Their efforts were incredible given the mess they were handed! A complicated dual fuel powerplant and fuel system. Avionics and wiring gremlins. Unproven automotive based powerplants. New propellor systems. And by the end of the program very real financial constraints. One by one they tackled those challenges and made great progress on every front.

So to anyone reading this that might have been involved with the racer directly (outside of designing it) I saw the huge effort you made and that is the sort of thing that makes Reno the special event that it is.

We also have to acknowledge Bob Pond's brave experiement to make a huge contribution to unlimited racing. If it had worked out we would likely have a clearer and more solid future for unlimited racing that would no longer rely on the scarce warbird resources we depend on today. If only some other aero engineer had been given the "at bat" chance to make that happen....


Spacegrrrl

[FlyKidChris]

Re: Thoughts on the GP-5?

I was told by a well respect aero engineer and CFD expert that likely would prefer to stay out of this conversation that no amount of HP could have gotten the Pond to go much faster than low 400's it went and even a basic CFD study of the design should have made these flaws obvious.
Spacegrrrl

I, along with two friends, spoke with Rick Brickert less than an hour before his last flight. He told the three of us that the airplane had been over 500 just weeks before Reno, but blew both engines in the process.

Do I have that on tape? No. Do I have any proof that it really went that fast? No. Just Brickert's word.

Like you, Spacegrrrl, I believe that with more developmental effort, auto based engines could be successful in an air racing application. We're all well aware of the years of destroyed Merlins, but the "never-say-die" attitude prevailed and Strega's speeds today were unimaginable (at least to me) not so long ago.

I'm glad you have some experience in race boat applications, I suspect that there could be better "transfer" from boat applications than from car applications.

Given a wallet like Bob Ponds, what would you try for an unlimited air racer?

[stuntflyr]

Re: Thoughts on the GP-5?

The airplane went 401, timed around the old course with a two lap average, on less than 800hp. That was it's first time out.

[spacegrrrl]

Re: Thoughts on the GP-5?

I, along with two friends, spoke with Rick Brickert less than an hour before his last flight. He told the three of us that the airplane had been over 500 just weeks before Reno, but blew both engines in the process.

Do I have that on tape? No. Do I have any proof that it really went that fast? No. Just Brickert's word.

Like you, Spacegrrrl, I believe that with more developmental effort, auto based engines could be successful in an air racing application. We're all well aware of the years of destroyed Merlins, but the "never-say-die" attitude prevailed and Strega's speeds today were unimaginable (at least to me) not so long ago.

I'm glad you have some experience in race boat applications, I suspect that there could be better "transfer" from boat applications than from car applications.

Given a wallet like Bob Ponds, what would you try for an unlimited air racer?

I was likely one of the last non-crew member to talk to Rick before the accident. What he said totally confirmed what I learned earlier. There just wasn't "any more" in the Pond Racer speed wise. The brief testing with "adult beverage derived fuels" showed more HP didn't really matter. The last showing was therefore going to be the end of the program. It was one last show for the fans then permament home in a museum hangar. I gave him the photo I'd taken of him and the crew earlier and he gave me a Red Knight pin as a "thank you". We exchanged phone numbers and I promised I'd catch up with him after Reno to send him that year's photos. Thirty minutes later was the end of that story.

I have no idea what Rick shared with you (and I'm sure he was very willing to talk about the plane, he was a great guy to the fans), but I'll stick by the CFD expert and what Rick told me personally at the end of the Pond's career that day in his pit. I can definitely confirm what you said about blowing up the engines the week before. He didn't hessitate to say to me he knew the racer could never be competitve and they were there really just there for the "show" one last time before the plane was retired.

One thing to be fair to the designer of the Pond, everyone that flew it said it was a very well behaved airplane to fly. The handling characterstics were never a concern and the view from the cockpit was supposed to be incredible. Engine out was also considered very managable. I know for a fact that not all ground up race planes have had such kind pilot reviews.

What I think can be pretty easily established it that other designs would go faster with the same HP. An easy way to show that is the NXT has done close to the best the Pond ever did on basically the same course with what is in theory 1/3 the HP.

An interesting thing to think about. When you look at aircraft speed, drag reduction will make greater gains in almost every case when compared to trying to increase HP. Speed increases from drag reduction look linear. Speed increases from HP alone are scary looking curving functions that soon have slopes that can't be accomodated.

Look at Stega carefully and you can see all the clever things they have done to make sure every ounce of the Merlin go gets turned into pure fast! So no matter what you do you need to maximize the aerodynamic advantages of your choosen configuration. The Pond Racer started out with both hands tied behind its back.

So if I had a shot (and the first think I'd do if someone offered me the chance is try to find them someone else better qualified! ) I'd have to start thinking about how the minimum weight changes things. I don't remember the Pond Racer ramp weight but I think it was under the current minimum.

If aircraft engines are still "allowed" in the solution:

I'd likely look into how available R-2800s are because that is an easy path. I think we could see developments of the R-2800 that could make the warbird engine of choice. I'd also look at Allisons and Griffons (really just because of availability, they may be just as scarce now). I think I already know that I think about Griffons (too heavy and no one has sorted the blower problems, not to mention limited prop choices) My guess is in the end there really aren't any remaining abundent war bird based engine choices today. Someone once told me that you can actually build a completely new Merlin today with new reproduction parts. It would interesting to know if that's really true and just what it would cost.

If I had to go with non-warbird tech:

I think I'd be looking at tandem (or three) big block V-8s. Hard to fault cubic inches! Tractor pull guys have been ganging engines for some time. I'd see what I oculd learn from them about that. Maybe some variation of alluminum big block hemi. I'd lean more towards what could be proven more reliable than light because you have a pretty big weight budget (I think, again, I haven't really run the numbers)

Plan on turbos for boost. You'd have the advantage to be able to design the airframe to properly accomdate them. Maybe plan on alcohol. I think you'd need to do the fuel consuption calcs before you could commit to that. I think boil off looks like the cooling solution of choice. Again, design the airframe to accomdate a boil off system but maybe start with radiators to make it one challenge at a time.

For airframe configuration the "crazy talk" plan would be the mother of all ME-163 flying wings but once the drugs wore off something pretty conventional. There is a lot to be said about push-me pull-u like the DO335. But you have to measure risks to decide if the pusher drive shaft is worth the risk. No matter what I think you'd end up with a driveshaft/gearbox but a long shaft for a pusher prop might be a risk not worth taking. There certainly are examples where high HP in airplanes with drive shafts have worked so I'd learn all I could about that.

I'd also consider managing the program in stages. For example.

1. First stage, under wing radiators, low boost, show up year one to finish with eveything in one piece. Do as well as you can but this all about data collection during racing conditions. Serious tear down and inspection of the powerplants after the race. Maybe consider testing one of the engines to destruction on a dyno right out of the plane to see what you can learn about how she'll let go if she does.

2. Move to boil off, start upping the boost. Serious showing in gold. Finish with all pieces working. Again, this is really still a research stage.

3. Go for #1 in gold, start looking at speed records. Especially the seaplane record.

There are some other things you could look at to get something together quicker. For example, the Foland Gnat or other small jet might be a great donor for airframe components. Although with modern compostites, maybe just build exactly what you want is a better plan from the start.

I've also wondered about leveraging some of the propellor tech we see in commercial turboprops. Also, I'd be talking to Paul Lipp about props as well. I am convinced his prop designs may have real benefits at the speeds the unlimiteds fly.

That's all off the cuff speculation. What I can say for certain is that what I really know is that I really don't know what I'd end up doing if asked to build something like that, but I do know I'd find the right folks to get the answers I'd need and that would include some serious CFD studies of any design before a single component was constructed.

One final thing, I'd go into it with eyes wide open understanding that no matter how good a team you pull together, no matter how clever the engineering,no matter how well its built, crewed and flown. It could all go horribly wrong in an instant! All the air racers in the unlimited class today are building from costly lessons (both in dollars and lives) that were learned when the basic airframes were developed.

The Mustangs and Bearcats of today got to as good as they were with basically unlimted supplies of engineers, dollars, materials and sadly in many cases test pilots. They were built in the thousands and refined over years of extreme use.

To build something that could challenge aircraft building on such a base is a huge and in many ways a crazy dangerous undertaking. I think Skip Holmes made a lot of sense when he said he'd never race a plane he owned because he didn't want to hessitate for a second to get out of it if he felt he had to.

After reading this again and again, I think I'd finally decide if you really want a "new" unlimited racer do something like the Matt jackson project. Hybrid mash ups of proven pieces is maybe the best way to get a new racer that could dominate the gold. Or build a new Tsunami.

The real excitement I think may end up being Super Sport. If I was going to focus on going fast and trying someting "out of the box" these days I think I'd pick that class.

Three rotor rotary turbo engine in a flying wing......


Spacegrrrl
(wow, sorry, thats a lot to read! )

[MRussell]

Re: Thoughts on the GP-5?

Spacegrrrl, thanks to the book you wrote here today, I rest my case about you attacking the Rutans at every opportunity. Now I suggest putting it behind you and growing up. So yeah, good luck with that.

[spacegrrrl]

Re: Thoughts on the GP-5?

The airplane went 401, timed around the old course with a two lap average, on less than 800hp. That was it's first time out.

So how many HP do you think it needed to be competitive today? If you do some basic calcs I think you'd see there was no way the powerplants were going to ever be able to provide the output they needed to do that.

These are really crude calcs but assuming 1600HP (remember that has to be maintained for 10 laps) you would see 500 MPH (assuming that there weren't other aerodynamic factors that make the drag behaviors act in an unexpected manner, which I maintain in the Pond racer there were).

So I suppose that if someone had managed to get those powerplants to make 800HP+ each for all the racing at Reno required to win gold the Pond could have worked. Looking into the realities of the engine a lot of folks like say when raced in cars the motor made 1000HP. If you look in more detail, maybe momentarily and not on gasoline but reliable sustained output levels on gasoline were closer to 550HP on a good day. And that assumes alot of things working optimally like the intercoolers, induction flows and being operated at the optimal RPM. Not sure how close to sorted they ever got things like that on the Pond. Those HP figures are also based on a fresh zero time engine. The Pond Racer engines weren't close to that most of the time.

If you believe the Wikipedia article about the Pond they were making 600HP a side when it was all working, so if that's the case then you'd need 2400 HP to get to that magical far side of 500 MPH.

But the point is a different design would do better with the same HP.

So lets look at the NXT. If you could get 1600HP in an airframe that slick assuming Jon makes 600HP today (seems high to me) the next would do 582 MPH. NXT FTW!! Of course, its too light and no idea how to shoehorn 1600 HP into a NXT (where is that Rosewell alien space tech when you really need it??!!). And at the speed there is probalbly all sorts of propellor secret sauce required.

Remember, crude rule of thumb is cube the HP to double the MPH.

Spacegrrrl

[spacegrrrl]

Re: Thoughts on the GP-5?

Spacegrrrl, thanks to the book you wrote here today, I rest my case about you attacking the Rutans at every opportunity. Now I suggest putting it behind you and growing up. So yeah, good luck with that.

How about instead of atacking me personally you make a case to refute a single thing I've said. Otherwise give up your life as a Rutan fanboy and get a life.

Spacegrrrl

[gorace71]

Re: Thoughts on the GP-5?

I always love a good automotive vrs aircraft engine war. This one was somewhat mild, thanks.

Burt Rutan designed a motorglider for a one class design contest sponsored by the Soaring Society of America. It was suppose to be for a self launching cross country machine that would be suitable for homebuilders. He won, mostly on his reputation at the time. I am sure he regrets that design, especially since he apparently did not know how gliders go cross country. It was a complete failure, especially as a glider.

Don't get me wrong, I have the greatest respect for Burt, but sometimes even the best get things wrong!.

I am concerned about the future of the Reno Races. It appears to me that with the loss of several unlimited ships and the disaster that is Super Sports this year, the sport is going to be further down each year. The Unlimited, except for the first three or four ships, is turing into an Airshow. The hope is in the GP-5 type of approach, I hope they keep going and don't give up after this year. May inovation live!

Bruce Patton

[spacegrrrl]

Re: Thoughts on the GP-5?

Spacegrrrl, thanks to the book you wrote here today, I rest my case about you attacking the Rutans at every opportunity. Now I suggest putting it behind you and growing up. So yeah, good luck with that.

And to be totally accurate, I don't have issues with Rutan(s). I maintain that as an aircraft designer Burt Rutan has been over hyped and hardly as successful as has been claimed by his many over zealous fans. And in many cases he has been a pretty horrible failure given his reputation.

He seems to be a man that would design a rubber ball with two flat sides and 9 spikey points just because he can, and that tendency often results in a product that doesn't work as well as the proven simple approach.

He has however brought amazing advancements to the aircraft industry in terms of materials and fabrication techniques. Why that can't be enough for his fans I'll never know.

I'll stand by that postition until someone can show me where I'm wrong,

Spacegrrrl.

[FlyKidChris]

Re: Thoughts on the GP-5?

I enjoyed "the book" though I'm left wondering about what Brickert said to us (about going 500 m.p.h.).

I've thought about it more than a few times and came to the conclusion that a "twinned" configuration had some merit (think P/F-82 Twin Mustang) for an unlimited racer primarily due to propellor efficiency, known or existing parts or components and the problems with pusher drive systems (as mentioned by SpaceGrrrl).

But I'm not an engineer, so I may have overlooked a lot.

Nonetheless, I enjoyed SpaceGrrrl's reply (I did ask, after all) and I didn't consider it to be an attack on the Rutans. I'm a big fan of Burt's designs - I'd love to have a Long EZ.

The Beech Starship wasn't a commercial success - but in saying that, I don't blame Burt Rutan.

I also think there are great opportunities for speed gains in the Super Sport class.

[spacegrrrl]

Re: Thoughts on the GP-5?

I enjoyed "the book" though I'm left wondering about what Brickert said to us (about going 500 m.p.h.).

I've thought about it more than a few times and came to the conclusion that a "twinned" configuration had some merit (think P/F-82 Twin Mustang) for an unlimited racer primarily due to propellor efficiency, known or existing parts or components and the problems with pusher drive systems (as mentioned by SpaceGrrrl).

But I'm not an engineer, so I may have overlooked a lot.

Nonetheless, I enjoyed SpaceGrrrl's reply (I did ask, after all) and I didn't consider it to be an attack on the Rutans. I'm a big fan of Burt's designs - I'd love to have a Long EZ.

The Beech Starship wasn't a commercial success - but in saying that, I don't blame Burt Rutan.

I also think there are great opportunities for speed gains in the Super Sport class.

Beechcraft definitely made it impossible for Burt to make the Starship a success. I definitely don't hold that against him.

Think about how you could "desconstruct" the pond, particularly given the strength you can achieve with modern composites.

You don't need a full lenght pilot pod and full length engine booms. Its not clear you need a horizontal across the rear booms either, think Transavia Airtruk (of course you might not save much eliminating that). Look for every one of those intersections of surfaces and think about how you could eliminate them. Can the engines be blended into the wing for example?

I'm sure a twin could be made to go very fast. I think you just have to realize you start with some disadvantages. Even minor things I expect could add drag, stuff like you now have two induction paths if the engines are in the traditional pair out on the wings config. Is that a big deal? No idea, but every little thing adds up.

I would be fun to figure out how slick you could make a twin. Putting the pilot in one of the booms in a twin boom design like the F-82 might be the key (so will the CAF let us have their F-82 so we can race it and find out how well that could work? )

Spacegrrrl