Doc James Hammond
Very Strong User
Its beginning to look a lot like Christmas...hahaha - samples are here!
Aloft Forums
Welcome to Aloft Forums. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!
Glider News from Aloft
- Thread starter Wayne
- Start date
Doc James Hammond
Very Strong User
Oh - the two Firebirds?
Very Christmassy in Namibia - they are "Desert Camo", and "From Russia with love" Colour schemes.
The Schwing Forza's are "Lean Green Racing Machine" and "Yellow Peril" - just for reference!
hohoho
Doc.
Very Christmassy in Namibia - they are "Desert Camo", and "From Russia with love" Colour schemes.
The Schwing Forza's are "Lean Green Racing Machine" and "Yellow Peril" - just for reference!
hohoho
Doc.
Konrad
Very Strong User
Doc. in image 5574 I notice that the wings have tips of vastly different sizes. The butterscotch/red camo one has a very large tip. And the green camo one looks to be much smaller than the butterscotch/red camo. What is the reasoning for the different size wing tips.
I ask as I've cutdown the aileron on my "Mibo Dart III" to try to control the early stall we often see when the aileron hinge line goes all the way to the tip. As this is a simple mod (No changes to the mold needed) I'd like to understand why the various wing tip lengths.
In IMG 5570 I'm noticing a lot of dihedral in the one piece wings (60"?). I saw this earlier and thought is might be an artifact of the lens. But it looks to a design feature. Normally I don't like a lot of dihedral in my full house sport ships. And if this is the wing to the Firebird I'm really curious, as I really don't like my rudders to be coupled to the roll axis in my racers.
Enquiring minds want to know,
Konrad
I ask as I've cutdown the aileron on my "Mibo Dart III" to try to control the early stall we often see when the aileron hinge line goes all the way to the tip. As this is a simple mod (No changes to the mold needed) I'd like to understand why the various wing tip lengths.
In IMG 5570 I'm noticing a lot of dihedral in the one piece wings (60"?). I saw this earlier and thought is might be an artifact of the lens. But it looks to a design feature. Normally I don't like a lot of dihedral in my full house sport ships. And if this is the wing to the Firebird I'm really curious, as I really don't like my rudders to be coupled to the roll axis in my racers.
Enquiring minds want to know,
Konrad
Last edited:
Doc J
Very Strong User
Doc J
Very Strong User
Konrad
Very Strong User
What?
If a ship is not responding the way I like I have no problem changing things. The dihedral is a classic example. If I get too much roll coupling from the rudder I've been known to hack at the wing to change the dihedral.
In the case of trying out a new dihedral that dramatically differs from the established norms. I'd hack away on a known good example to change the dihedral, and take the weight penalty for this one test article.
One might make the argument that there are no good examples to work with, that have a planform anywhere near what you have in your Firebird.
If this is what is driving the need to make a new set of molds I have to ask why make a production master plug. And why don't the components of this plug (master or prototype) fit the new test configuration (added dihedral).
My comment was that looking at your photos it looked like there might have been an error made in the CAD/CAM process as the dihedral looks to be about twice that of what we see in comparable models. Having done some CAD/CAM work myself I can tell you this is easy to do.
BTW: I've seem some of the first production ships. They have some real nice work both in the manufacture and with the design elements.
But as you have said subsequent production runs will have some changes. Looking forward the feed back from the flight testing.
All the best.
Konrad
If a ship is not responding the way I like I have no problem changing things. The dihedral is a classic example. If I get too much roll coupling from the rudder I've been known to hack at the wing to change the dihedral.
In the case of trying out a new dihedral that dramatically differs from the established norms. I'd hack away on a known good example to change the dihedral, and take the weight penalty for this one test article.
One might make the argument that there are no good examples to work with, that have a planform anywhere near what you have in your Firebird.
If this is what is driving the need to make a new set of molds I have to ask why make a production master plug. And why don't the components of this plug (master or prototype) fit the new test configuration (added dihedral).
My comment was that looking at your photos it looked like there might have been an error made in the CAD/CAM process as the dihedral looks to be about twice that of what we see in comparable models. Having done some CAD/CAM work myself I can tell you this is easy to do.
BTW: I've seem some of the first production ships. They have some real nice work both in the manufacture and with the design elements.
But as you have said subsequent production runs will have some changes. Looking forward the feed back from the flight testing.
All the best.
Konrad
Doc J
Very Strong User
Actually what I meant was the "If it was me" part, Konrad because I don't think you would have the chance to change anything on one of your designs; the reason being that I don't think we will ever see one of your designs.
But honestly I'd like to. For someone who is as voluble as you are on the subject, I think it would be really interesting.
You have given me a lot of design advice, indicating a lot of experience, added to that, you have indicated that you could do an "Engineered solution" - if you had enough data, and you have also indicated familiarity with Catia. Surely these are all the requirements? So, could we see one of your designs?
I'm tired of bing the only person here - even a back of the envelope sketch would be great as this is honestly where most of mine start.
Look forward to your thoughts,
Cheers,
Doc.
Konrad
Very Strong User
Hum?
I made my millions in design work with turbines.
I have said; I did try my hand at bringing a few toy models to market. Staying with toys, here is a photo of a design I was part of. We called it a D.U.M.P. (Denver Unlimited Mustang Prototype) we may have had a marketing issue. This was an AMA 424 quarter midget class 0.15 cid racer. In the market place it was a failure. That is only about 100 of these were sold. OK, the rules where changed to allow AMA 424 to grow into the 0.40 cid class we know today as QM-40. This DUMP was obsoleted by the stroke of the pen.
I designed and built set of F3F pylon engines. This engine won the AMA 89 NATS. Ok, this had more to do with the strategy of the team than my input. The design concept that was different in at the time it used the of long stoke crankshaft and long connecting rod, as it allowed for larger intakes ports. With the loss of the ring, piston acceleration wasn't as much of a concern as it was in the past. This engine was based on the Picco and OPS engines. Most of its design work was done on a flow bench. This engine ran in the 30K rpm band. I think there is a photo in the Model Aviation magazine coverage of the 89 NATS where the chairman on the R/C Pylon committee is giving me credit for the engine work. (I later learned that the actual engine was an earlier lower power prototype. I wasn't on the field of battle).
Doc, having owned a few of your products I can say as a consumer that the integration of the sub systems is often lacking. I'd have thought that these fit issues could effectively have been addressed in the CAD/CAM programs. That is what I'm saying, and to your credit you have agreed with most of my findings.
All the best,
Konrad
I made my millions in design work with turbines.
I have said; I did try my hand at bringing a few toy models to market. Staying with toys, here is a photo of a design I was part of. We called it a D.U.M.P. (Denver Unlimited Mustang Prototype) we may have had a marketing issue. This was an AMA 424 quarter midget class 0.15 cid racer. In the market place it was a failure. That is only about 100 of these were sold. OK, the rules where changed to allow AMA 424 to grow into the 0.40 cid class we know today as QM-40. This DUMP was obsoleted by the stroke of the pen.
I designed and built set of F3F pylon engines. This engine won the AMA 89 NATS. Ok, this had more to do with the strategy of the team than my input. The design concept that was different in at the time it used the of long stoke crankshaft and long connecting rod, as it allowed for larger intakes ports. With the loss of the ring, piston acceleration wasn't as much of a concern as it was in the past. This engine was based on the Picco and OPS engines. Most of its design work was done on a flow bench. This engine ran in the 30K rpm band. I think there is a photo in the Model Aviation magazine coverage of the 89 NATS where the chairman on the R/C Pylon committee is giving me credit for the engine work. (I later learned that the actual engine was an earlier lower power prototype. I wasn't on the field of battle).
Doc, having owned a few of your products I can say as a consumer that the integration of the sub systems is often lacking. I'd have thought that these fit issues could effectively have been addressed in the CAD/CAM programs. That is what I'm saying, and to your credit you have agreed with most of my findings.
All the best,
Konrad
Last edited:
Konrad
Very Strong User
My voluble write ups are actually a credit to you as you are coming out with a lot of new products. I don't recall offering to give you any "engineered solutions" to any of your products. I have no reason to think that your engineering work is lacking. I do give you "market feedback" as I am part of that marketplace. And I comment (often by asking) on what "I" think would help me and maybe others understand your products to their full potential. In my Redshift thread I thought we were playing a light hearted game to see if I can find the major design criteria in your design of the Redshift.
A quote from you "I'm tired of bing the only person here".
What? While the Aloft forum site might not be as active as we would like you are not the only participant in this forum.
All the best,
Konrad
P.S.
Is this the read you have an issue with my term "engineered solutions". I don't see where I'm second guessing your engineering prowess?
forum.alofthobbies.com
I can only give a high level recommendation (SWAG) as to what lay up schedule to use. "I" don't have enough information to make an engineered recommendation. If you can generate a lay up schedule, ether based on experience or actual engineering data, please let him know. I'm sure it would be much much better than my recommendations.
A quote from you "I'm tired of bing the only person here".
What? While the Aloft forum site might not be as active as we would like you are not the only participant in this forum.
All the best,
Konrad
P.S.
Is this the read you have an issue with my term "engineered solutions". I don't see where I'm second guessing your engineering prowess?
4 meter scratch build - Glass schedule / reinforcement questions
Over this next winter/summer i want to get a big 4 meter build going for the 2021 sunset event. While i have made a couple bagged fiberglass wings they have all been fairly short, 50 ish inches or so and i haven't really needed to worry too much reinforcement. This build is going to be two 80...
forum.alofthobbies.com
I can only give a high level recommendation (SWAG) as to what lay up schedule to use. "I" don't have enough information to make an engineered recommendation. If you can generate a lay up schedule, ether based on experience or actual engineering data, please let him know. I'm sure it would be much much better than my recommendations.
Last edited:
Doc J
Very Strong User
My voluble write ups are actually a credit to you as you are coming out with a lot of new products. I don't recall offering to give you any "engineered solutions" to any of your products. I have no reason to think that your engineering work is lacking. I do give you "market feedback" as I am part of that marketplace. And I comment (often by asking) on what "I" think would help me and maybe others understand your products to their full potential. In my Redshift thread I thought we were playing a light hearted game to see if I can find the major design criteria in your design of the Redshift.
A quote from you "I'm tired of bing the only person here".
What? While the Aloft forum site might not be as active as we would like you are not the only participant in this forum.
All the best,
Konrad
P.S.
Is this the read you have an issue with my term "engineered solutions". I don't see where I'm second guessing your engineering prowess?
4 meter scratch build - Glass schedule / reinforcement questions
Over this next winter/summer i want to get a big 4 meter build going for the 2021 sunset event. While i have made a couple bagged fiberglass wings they have all been fairly short, 50 ish inches or so and i haven't really needed to worry too much reinforcement. This build is going to be two 80...
I can only give a high level recommendation (SWAG) as to what lay up schedule to use. "I" don't have enough information to make an engineered recommendation. If you can generate a lay up schedule, ether based on experience or actual engineering data, please let him know. I'm sure it would be much much better than my recommendations.
Rant time...
I think I am the only "Published" designer here, Konrad, and like you I have worked on engines.
I grew up in real aeromodelling from self-designed chuck gliders at age 7, through the mid '70's when we flew what is now F2c control line competitively - and did very well I might add. During those years, actually decades, we HAD to design our own models - or else you were not allowed to fly, and we HAD to make our own engines because there were simply no competitive engines available. You either leaned how to design and build your own models and engines better than the next guys or you'd always be relegated to the non competitive ranks.
Personally this "upbringing" means that I always did, I always have, and I always will actually put my stuff out there, in the flesh, for all to see and hopefully use for fun
So my ideas are not just ideas - they evolve into real objects that can be seen, touched, and in this case, flown. As you have seen, I even attempt, from time to time to reveal or explain the thinking processes that I have used (I dare not say Logic) to arrive at these things, and this I think is another thing that sets me apart from other (normally completely anonymous) designers. Even if people request my wing sections - shapes often held by many designers as "top secret" - are public domain. I don't ask for people to name their models after me, or for that matter charge them money - both of which seem to be prevalent now - I give them to anyone who asks because I want to help to develop our hobby.
Perhaps I am too open, and too accessible, because wanting to help it seems, in the world of model gliders just puts a target on your back, and sometimes its really hard to deal with when the attackers either don't actually have any experience, don't know half as much as you do, or even more common - don't actually know what they are talking about.
These armchair designers are the people who blindly believe the stuff that comes out of computers predicting the performance of models.
Since there is actually no good formulae or information on ultra slow, super low Reynolds numbers to put in to the computers, then how can we expect good stuff to come out?
There ARE no model glider formulas or equations, or for that matter much helpful info to put into a computer at all. Its not the CAD programmes or their performance analysis add ons that make the errors - its just simply not possible for the programmes to do their work - sometimes to the extent of being very, very wrong. These blind believers are the people I normally don't respond to at all, because if they cannot see the glaring mistakes in their basic thinking then there will be little that I can do to point them out.
Rant over.
So when someone says to me "I'd have done this" - or that...My immediate thought is, well dude, you will never get the chance, because you will never put yourself in the position to do so.
Thats why I want to see YOUR ideas on the design of a model glider. I'm lonely.
Cheers,
Doc.
Konrad
Very Strong User
Doc. I don't design low Reynolds number toy glider. I buy toy gliders. But as a customer I want to be able to fit servos where the designer indicates they should be placed. I'd also like the parts (assemblies) to fit each other (servo covers fit and wings seat properly on the fuselage). These requests have nothing to do with CFD code. Rather these are basic CAD functions.
When I do my build threads you do see how I interpret what the OEM supplies us and how try to improve on the design to meet my needs. No, I didn't write a full engineering justification as to why I narrowed the V-tail inclusive angle for my Mefisto build. But I did say why I changed the V-tail inclusive angle. I also report that the my Mefisto has the strongest responding V tail rudder response, second only to the DJ Aerotech Chrysalis F3-RES.
There is alway a competitive design. This is the design we need to surpass if we want out latest ideas to be embraced by others.
As to the code for Low Reynolds numbers you might be surprised what is used for the LPT blades.
As to ultra ultra low Reynolds number airfoils I have seen the code and windtunel data from Jef Raskin's work. This data is now about 15 years old.
Doc, you need to take a step back. I am NOT one of your attackers! (Other than the Camo stuff) I never said anything derogatory about your flow work. I also agree that the product of digital code needs to be tested/validated in the analog world. I've never discounted the empirical approach. I just said that there are fields where I would not want to revert back to the empirical approach used when I was in school. The computer code is a tool that has opened up a lot that we as designers didn't have access to in the old days. I know few in the ultra high end glider community credit your work. But please know I'm not one who has belittled your work on wings. As I have said time and time again; I'm not an aerodynamicist. So I have no real back ground to discount your findings.
I have worn the hats of a manufacturing engineer, performance engineer, system integration engineer and flight test engineer. So I do know a bit about form fit and function. And when I see something that I don't understand why something was done the way it was done I ask why.
All the best,
Konrad
When I do my build threads you do see how I interpret what the OEM supplies us and how try to improve on the design to meet my needs. No, I didn't write a full engineering justification as to why I narrowed the V-tail inclusive angle for my Mefisto build. But I did say why I changed the V-tail inclusive angle. I also report that the my Mefisto has the strongest responding V tail rudder response, second only to the DJ Aerotech Chrysalis F3-RES.
There is alway a competitive design. This is the design we need to surpass if we want out latest ideas to be embraced by others.
As to the code for Low Reynolds numbers you might be surprised what is used for the LPT blades.
As to ultra ultra low Reynolds number airfoils I have seen the code and windtunel data from Jef Raskin's work. This data is now about 15 years old.
Doc, you need to take a step back. I am NOT one of your attackers! (Other than the Camo stuff) I never said anything derogatory about your flow work. I also agree that the product of digital code needs to be tested/validated in the analog world. I've never discounted the empirical approach. I just said that there are fields where I would not want to revert back to the empirical approach used when I was in school. The computer code is a tool that has opened up a lot that we as designers didn't have access to in the old days. I know few in the ultra high end glider community credit your work. But please know I'm not one who has belittled your work on wings. As I have said time and time again; I'm not an aerodynamicist. So I have no real back ground to discount your findings.
I have worn the hats of a manufacturing engineer, performance engineer, system integration engineer and flight test engineer. So I do know a bit about form fit and function. And when I see something that I don't understand why something was done the way it was done I ask why.
All the best,
Konrad
Doc J
Very Strong User
Konrad - I never thought that you were attacking me. Sorry for that impression.
It was a "general" rant that I had had coming for a while - you only set me off with a mistimed comment.
I'm sure there is stuff done on low speed aerodynamics, because I have done an awful lot of it myself - but as far as I know its either unavailable, or not in any kind of code that could be used in any commercially available simulation programme. In this I was not referring to you - although you did indicate that you actually believed a lot of that stuff - or maybe I took that the wrong way. The point I am making is that many people refer again and again to the results of computer simulations - especially for our small aerofoil sections.
To me, with my experience this is like saying the earth is flat.
Its very likely that I could now simulate what we all did when we were kids: Hold our hands out of the family car window at 40 when Dad was driving us to the shops, and then see what happened lift and drag wise when we changed the angles. Of course I'd need the "Hand out of car window" Rev1 programme with all the good data already input and integrated. Problem is - just like our toy plane applications, the Hand out of car window Rev 1 programme does not exist, so people use the only stuff that does exist, in the sure and certain knowledge (if they are smart) that it is very unlikely to apply or to give good results.
These people are whom you refer to as "The ultra high end glider community"
I certainly would not be listened to - though, surprisingly I do find that a lot of the real (Not the fashionable) designers do talk to me and we do have some really good discussions. But, I'm an innovator and therefore a pariah by default. When you look back through history you'll find this repeated ad infinitum. In fact almost any innovation had been met with at best skepticism, always resistance, and at worst war and death. Coincidentally the fact is that a lot of the outcasts and pariahs who made these breakthroughs and inventions went to my school.
Lets face it, lets be really honest, lets put our cards on the table what do we REALLY know? We know the whatever we do to vary the thickness, curves, cambers etc etc, on any of our aerofoils that the boundary layer will nevertheless depart, break free, disappear at about 45 to 65% of the chord length. So, logically unless we go to much larger chords - which we can't, or go much higher speeds - which we constantly strive to, but struggle to achieve, then much of the information put out by the computer simulation must be pure garbage and the difference between in aerofoil and another is at best theoretical, and in may cases pure wishful thinking.
You can only do what you can do by using experience - maybe get some info on the simulators, but only a little and with no guarantee of accuracy.
ONLY by actual testing can you get true and reliable data.
Using computer code to make part A fit well in part B etc is a wonderful tool that is frankly startling in it's beauty, especially to an old style mechanical engineer who still has a slide rule, such as this old phart. And that not only in the way it can model things that previously - even with detailed general assembly drawings - required a great deal of skill for the beholder to actually understand, but also to identify possible mistakes and problems that in the pst world only have revealed themselves on a final assembly. For mechanical design and modelling they are absolutely fantastic because the data that they feed off is available and accurate.
I love to draw! But, alas the computer does not love my drawings and I still need to use CAD in order to produce the kind of fit and finish that I believe people should expect in the products that they buy. How could I integrate these two non compatible methods? Then in a blinding flash of the obvious I adopted a "go between" - something that was analogue but also digital and could talk to nee and with a little coaxing to the computer too. A cunning stunt that allowed hand drawing and computer CAD programme to meet - with of course the help of someone far more competent than I at CAD design. Now my designs can be reproduced EXACTLY - well as exactly as I can draw them.
So now I'm happy in one way with "using" computers in empirical design. But, and its a big BUT - I have to say although I mostly keep silent, I also cringe inwardly when someone makes casual comments on a particular computer simulated curve "oh it looks like there is a bit of separation near the mid chord section probably due to the camber curve distribution..." or something similar.
Really?
Cheers and sorry for anything that looks aimed. Its not but honestly I'd love it if a few more guys really would make their own designs and lets have some nice constructive chats about them.
Doc.
Yaaaahhhh!...
Konrad
Very Strong User
Doc, that's a very good point about commercially available or open sourced code.
As I don't know what programs you are referring to I don't recall ever indicating that I have any level of confidence in them.
Fit issues between the drawings and the real world are still major issues even for billion dollar corporation. For example the first six 747-8 had to have the wings and fuselage hand fitted, This is because there was poor integration between the vellum drawing of the well proven fuselage and the new computer drawn wings.
Then there was the issue with the side of fuselage joint on the 787-8 that didn't show itself until actual stress testing. I don't know what constraints there were in the programing. But the real world testing found the structural deficiency in this area of the airframe.
Burt Rutan made very good use of the open road wind tunnel in his early designs.
And yes new ideas often are slow to being picked up. In science we look to repeatable results. In racing we look to tangible results. I'm thinking of the quantum shift in F1 aerodynamics when the Williams team introduced ground effect. Or when wings first were seen on Indy cars.
Now Spencer Lisenby gives a lot of credit to his aerodynamicist for his quantum leaps in speed that now reach over 800kph. I don't know what code was used but the proof is in the end results.
All the best,
Konrad
As I don't know what programs you are referring to I don't recall ever indicating that I have any level of confidence in them.
Fit issues between the drawings and the real world are still major issues even for billion dollar corporation. For example the first six 747-8 had to have the wings and fuselage hand fitted, This is because there was poor integration between the vellum drawing of the well proven fuselage and the new computer drawn wings.
Then there was the issue with the side of fuselage joint on the 787-8 that didn't show itself until actual stress testing. I don't know what constraints there were in the programing. But the real world testing found the structural deficiency in this area of the airframe.
Burt Rutan made very good use of the open road wind tunnel in his early designs.
And yes new ideas often are slow to being picked up. In science we look to repeatable results. In racing we look to tangible results. I'm thinking of the quantum shift in F1 aerodynamics when the Williams team introduced ground effect. Or when wings first were seen on Indy cars.
Now Spencer Lisenby gives a lot of credit to his aerodynamicist for his quantum leaps in speed that now reach over 800kph. I don't know what code was used but the proof is in the end results.
All the best,
Konrad
Doc J
Very Strong User
Hi Konrad,
I think that Spencer Lizenby has a very good designer in Steve Seim. Steve will be coming to the ISR - we have a lot in common in the directions for glider design. I am, however, not at all sure that the credit given for the aerofoil is correct placed. But that my own opinion only.
Cheers,
Doc.
I think that Spencer Lizenby has a very good designer in Steve Seim. Steve will be coming to the ISR - we have a lot in common in the directions for glider design. I am, however, not at all sure that the credit given for the aerofoil is correct placed. But that my own opinion only.
Cheers,
Doc.
