How to draw up plans?
09-27-2003, 06:39 AM
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How to draw up plans?
I was thinking of trying to make a model of the Ligeti Stratos and was wondering how to draw up some plans. This would be a first scratch build attempt.
09-27-2003, 06:41 AM
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RE: How to draw up plans?
I saw a model of this plane in the November 2003 Model Aviation
magazine, and thought it was a cool looking plane. Don't know if
anyone else has seen it.
I was thinking a 35 inch wingspan (about 1/6 scale) for the first attempt. If that flies well then maybe up it to a 70 in wingspan (about 1/3 scale).
Here is a pic:
magazine, and thought it was a cool looking plane. Don't know if
anyone else has seen it.
I was thinking a 35 inch wingspan (about 1/6 scale) for the first attempt. If that flies well then maybe up it to a 70 in wingspan (about 1/3 scale).
Here is a pic:
09-27-2003, 12:09 PM
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RE: How to draw up plans?
You're taking on a world of hurt all at once. My advice is to start small. First you need to learn to CAD if that's what you want to do. Pencil and paper the old fashioned way may be better for this unless you want to learn to do the whole thing at once. Second you need to know a little about how to draw and what details you need. If you can imagine how it should look in the end then what you need to actually lay it out can be minimal. If you don't really understand structures and how the bits go together then you had better spend more time detailling out each part. As for load bearing structure this is a very different sort of design and will require some thought as to how the spars should be layed out and, more importantly, joined at the center to ensure that the load is graduated and passed through adequitley. Swept designs are always complicated in that way.
If you want to go the CAD route I'd start with some CAD learning. Do a few simple boxy drawings and learn the tools. Then import an image scan of the Stratos and trace around it using your new skills. Use the basic tracing to learn more about drawing in CAD by designing a simple profile fuselaged test glider. This will teach you CAD and also give you something to act as a "wind tunnel" for learning where the balance point should be located on this design. From there go for a mid sized model of about 4 foot span and simple construction for a 25 or so engine. From there you should be able to reach for the stars with whatever size you wish.
If you want to go the CAD route I'd start with some CAD learning. Do a few simple boxy drawings and learn the tools. Then import an image scan of the Stratos and trace around it using your new skills. Use the basic tracing to learn more about drawing in CAD by designing a simple profile fuselaged test glider. This will teach you CAD and also give you something to act as a "wind tunnel" for learning where the balance point should be located on this design. From there go for a mid sized model of about 4 foot span and simple construction for a 25 or so engine. From there you should be able to reach for the stars with whatever size you wish.
09-27-2003, 01:23 PM
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RE: How to draw up plans?
I was thinking I would go with pencil and paper as I know nothing about CAD.
How do I determine rib spacing?
I was thinking in the end I would sheet it with 1/32" or 1/16" balsa? would this be okay or would fiberglass be better?
How do I ensure that the load is graduated and passed through adequitley? Is this trial and error?
The upper wing will have airlerons and elevator... should I mix them in the radio or split them and use 4 servos?
This will probally be a project that will be all winter and most if not all of next summer.
I also and trying to design an electric solar powerd plane that will take some time next summer. was thinking that foam would be perfect for this
How do I determine rib spacing?
I was thinking in the end I would sheet it with 1/32" or 1/16" balsa? would this be okay or would fiberglass be better?
How do I ensure that the load is graduated and passed through adequitley? Is this trial and error?
The upper wing will have airlerons and elevator... should I mix them in the radio or split them and use 4 servos?
This will probally be a project that will be all winter and most if not all of next summer.
I also and trying to design an electric solar powerd plane that will take some time next summer. was thinking that foam would be perfect for this
09-27-2003, 01:36 PM
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RE: How to draw up plans?
Pencil and paper is still good... 
If you have a scanner you could scan in sketches of what you are planning and then offer them up to us to rip them to shr..... er.... offer some constructive criticism
[sm=lol.gif]
Sheeting can often add a lot of weight if you don't know how to use it effectively. D tube on the leading edges is good as it adds a lot of torsional rigidity but overall sheeting can often lead to a flying brick if you're not careful A lot will depend on the area and your ability to choose wood. On the whole I can seriously recomend using lots of "air" in your construction. Rib spacing for fabric, tissue or plastic covering works out fine and very nicely at 2 inch spacing for the most part. There's other types that use more or less but you can't go wrong with 2 to 2 1/2 inch spacing on the whole.
At this point I'd avoid fiberglass and epoxy except for local strengthening. If not used right it can get heavy in a hurry. On the other hand I can see that a carved foam plug covered with a couple of layers of epoxy and fiberglass and then chewing and melting out the foam would be perfect for the egg shaped fuselage of the Stratos. Or a box inside with foam slabbed over, carved to shape and then a single lighter layer of epoxy and cloth for the outside shape. That may be the easiest and lightest compromise method for this. A clear canopy would be nice but it would add it's own problems. It may be better to just use a painted on one for the time. Unless you're thinking of a one piece model then the canopy would be ideal as an access hatch to the box insides.
Options, you've got LOTS of options. What size engine and model are you thinking of building this up to?
If you have a scanner you could scan in sketches of what you are planning and then offer them up to us to rip them to shr..... er.... offer some constructive criticism
[sm=lol.gif]
Sheeting can often add a lot of weight if you don't know how to use it effectively. D tube on the leading edges is good as it adds a lot of torsional rigidity but overall sheeting can often lead to a flying brick if you're not careful A lot will depend on the area and your ability to choose wood. On the whole I can seriously recomend using lots of "air" in your construction. Rib spacing for fabric, tissue or plastic covering works out fine and very nicely at 2 inch spacing for the most part. There's other types that use more or less but you can't go wrong with 2 to 2 1/2 inch spacing on the whole.
At this point I'd avoid fiberglass and epoxy except for local strengthening. If not used right it can get heavy in a hurry. On the other hand I can see that a carved foam plug covered with a couple of layers of epoxy and fiberglass and then chewing and melting out the foam would be perfect for the egg shaped fuselage of the Stratos. Or a box inside with foam slabbed over, carved to shape and then a single lighter layer of epoxy and cloth for the outside shape. That may be the easiest and lightest compromise method for this. A clear canopy would be nice but it would add it's own problems. It may be better to just use a painted on one for the time. Unless you're thinking of a one piece model then the canopy would be ideal as an access hatch to the box insides.
Options, you've got LOTS of options. What size engine and model are you thinking of building this up to?
09-27-2003, 07:03 PM
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RE: How to draw up plans?
As Bruce is trying to explain, this question perhaps deserves a whole forum. There is just too much to explain and otherwise chat about for one setting. You are quite a ways from developing a plan at this point. You cannot build an exact scale model, as those weights, powerplant, formulae, do not work for models on a proportionate basis. You can't just build a 1/4 scale model, and use 1/4 the power, and 1/4 the weight, 1/4 the area for control surfaces, and....
To make a plan, you need a working prototype first. Rough out an exterior on paper, then try to build it with the knowledge you have. As you get going, it will become obvious what works and what don't. What you have to move around to make room for controls, and what may have to be widened to make fit. You most often cannot use scaled airfoils, as they tend to get too thin, and thus flexible, and flapping when flying. Go obtain a model builder's handbook which includes a chapter on locating the CG properly, what power for what weight, what rear moment for what wingspan, etc. Then you try and build a prototype A/C using these parameters. You correct the original design, and build yet another prototype. You are going to find that some of the ribbing and spar system to increase rigidity you came up with is too complicated to build. Then, you may be ready for making up plans. About this time too, you finished the night school courses to learn CAD.
Forget the exotic building materials for now. You first need a prototype, and it is much easier to sand simple balsa to shape than fiberglass. You still haven't figured out if it balance out and fly. I am sure it will fly better than expected, and that you will be able to show the readers with a few decades of experience under their belt just how things are done today.
Wm.
To make a plan, you need a working prototype first. Rough out an exterior on paper, then try to build it with the knowledge you have. As you get going, it will become obvious what works and what don't. What you have to move around to make room for controls, and what may have to be widened to make fit. You most often cannot use scaled airfoils, as they tend to get too thin, and thus flexible, and flapping when flying. Go obtain a model builder's handbook which includes a chapter on locating the CG properly, what power for what weight, what rear moment for what wingspan, etc. Then you try and build a prototype A/C using these parameters. You correct the original design, and build yet another prototype. You are going to find that some of the ribbing and spar system to increase rigidity you came up with is too complicated to build. Then, you may be ready for making up plans. About this time too, you finished the night school courses to learn CAD.
Forget the exotic building materials for now. You first need a prototype, and it is much easier to sand simple balsa to shape than fiberglass. You still haven't figured out if it balance out and fly. I am sure it will fly better than expected, and that you will be able to show the readers with a few decades of experience under their belt just how things are done today.
Wm.
09-27-2003, 07:30 PM
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RE: How to draw up plans?
Thanks. So what you are saying is to make rough guesses and see what happens? I had planed on trying multiple wings and such to see what worked best. That is pretty much what you are saying to do right? I didn't think this would work right the first time. But if you never try how can you learn.
09-27-2003, 09:36 PM
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RE: How to draw up plans?
I did some plans for a large scale model back as a courtesy back in 1997. The fellow had the general shape, but it took seven prototypes to make one which would balance out correctly, fly and do as intended. We changed the position of wing ribs three times, mostly because available retracting landing which fit the wing thickness did not fit properly, or would position the extended gear such that the model nosed over too often.
A few of the inovative ideas like slots and tabs for locating parts perpenducular to one another did not work out on the first try. Often times a revision to one part affected another, and it wasn't updated either. Some of the slots were inverted, and some of the tabs did not take into account the thickness of the wood. I think it was prototype number three which eventially balanced out correctly, and it was number four which actually flew. It got faster to just cut wood with a razor blade one part at a time, then think about how next part is to fit correctly, and do the plans engineering later.
For your design, you are going to need several prototypes also, as looks to many of us that it may be into new ground. One flying A/C and a host of abilities does not mean the fellow standing next to you can repeat it all again. You have to have a basis of experience of knowledge base behind you in order to proceed, including dumming down such that the other fellow can do it also. I would consider working on something similar in design or appearances which has flown in model form, and then figure out good points and bad from this design to which can be applied to your personal designed prototype. Lean on another design, not one in thin air or you will fall over.
Wm.
A few of the inovative ideas like slots and tabs for locating parts perpenducular to one another did not work out on the first try. Often times a revision to one part affected another, and it wasn't updated either. Some of the slots were inverted, and some of the tabs did not take into account the thickness of the wood. I think it was prototype number three which eventially balanced out correctly, and it was number four which actually flew. It got faster to just cut wood with a razor blade one part at a time, then think about how next part is to fit correctly, and do the plans engineering later.
For your design, you are going to need several prototypes also, as looks to many of us that it may be into new ground. One flying A/C and a host of abilities does not mean the fellow standing next to you can repeat it all again. You have to have a basis of experience of knowledge base behind you in order to proceed, including dumming down such that the other fellow can do it also. I would consider working on something similar in design or appearances which has flown in model form, and then figure out good points and bad from this design to which can be applied to your personal designed prototype. Lean on another design, not one in thin air or you will fall over.
Wm.
