GyroRon
07-03-2004, 06:00 PM
Today I went to our PRA chapter 13 monthly meeting and took one of our Airport Rats Rick Keenen to the meeting with me. We drove down to Aiken - nearly a 2 hour drive - since the weather today was nearly or was IFR and that means no flying in the Pacer today!
After the meeting we went over to another Airport I like to visit Trenton airport. Here we hung out and BSed for a few hours and the highlight of the trip is they let us all - Ray Pierce and John Magnum also came over from the meeting to hang out at Trenton today - Take the Hovercraft the Trenton guys built for a ride or flight or whatever you call it. Anyway this is the problem....
So after all the fun we decided to drive home. From Aiken till nearly Rock Hill all I did was Argue with Rick over that Hovercraft..... He thinks a few things I disagree with him over and we fought the whole way back over it. He thinks the following things, you guys tell me what you think
1. He believes that the hovercraft at full power on the lift engine was " hovering " only 2 inches off the surface. He considers the bottom of the skirt to be the bottom of the craft. Now saying that he feels that if the lift engine made a lot more power the whole craft including the bottom of the Skirt would " hover " higher off the ground. ------ I disagree because IMHO it don't matter how much air that lift motor pushes the craft will rise to a certain point and that is it, any more power or air pumped under the thing and the excess wil just blow out and the craft will remain at the same height. He believes that if the lift motor had alot more power that at full power the bottom of the skirt could be 3 or 4 or 5 or more inches off the ground instead of the 2 inches off the ground it hovers at now...
2. He believes that in general a hovercraft if sitting on WATER in hover mode will by the force of the air being blown down to " lift " the craft will cause the water underneath the craft to sink or be blown out. He feels that for every action there is a equal and opposite reaction and his logic is if you blow enough air down to lift a 500-700 pound hovercraft, then that force blown down has to " push" on the water. And since water isn't a solid like concrete the air blown or pushed down on it will cause a 1-3 inch lower water level just under the craft. He compares it to blowing on a straw into his coffee cup. Or compares it to a helicopter hovering over the water etc.... -------- I disagree because the hovercraft operates on the principals of low pressure and high volume of air being trapped under the craft causing it to form a cushion of air allowing it to " hover " a few inches off the surface your on. There is not enough pressure under the craft to displace that much water IMHO.
3 He believes that all hovercraft " ride " lower and slower on water than land since they "sink" into the water anywhere from a few inches on a lightweight model like the little single place at Trenton to a much deeper level of sink on big military units such as a L-Cat the Marines use to deploy troops and Tanks and so on. ---- I think this is just the way they look because of all the water spray from the edges of the skirt....
4. Also going along with numbers 2 and 3, he believes if a hovercraft just sat in one spot over a very dry soft sandy beach it would just sit there and sink and sink and sink till it either hit a hard surface like Rock or dug it's way to China.... --- I disagree to a point. Yes if it sat there it would blow out sand around the edges but the middle area would not blow away and sooner or later the hovercraft would effectively highside on the mound in the middle.
5. On that hovercraft at Trenton he believes it will nose over in the water since the skirt is only 2 inches off the surface on the ground when hovering, and in water the craft will " sink" into the water it displaces as it is blowing down on the water which will cause the skirt to no longer be above the surface but now at or below the surface and the faster you go forwards the more the skirt will go under water till a point where the nose of the machine will dig in and the craft will sink or whatever. ---- I disagree because I think every idea he is using for his beliefs is wrong for starters, but also because the bottom of the skirt is not the end all bottom of the craft. The Bottom of the craft is at least a foot higher than the bottom of the skirt and that is the part you want out of the water. That is the part that would be a problem if it dug into the water. Saying that I think the only problems the Trenton Hovercraft would have on water is if they try to drive it down a very steep boat ramp into the water and the nose goes under flooding the lift engine and causing it to quit running, But even then if the rest of the ship floats like it was designed to, there should be no big problems.
Me and Rick fought over this stuff steady for well over a hour and a half. Tell me guys if I am right or is Rick right? someone is going to be eating crow tonight!
After the meeting we went over to another Airport I like to visit Trenton airport. Here we hung out and BSed for a few hours and the highlight of the trip is they let us all - Ray Pierce and John Magnum also came over from the meeting to hang out at Trenton today - Take the Hovercraft the Trenton guys built for a ride or flight or whatever you call it. Anyway this is the problem....
So after all the fun we decided to drive home. From Aiken till nearly Rock Hill all I did was Argue with Rick over that Hovercraft..... He thinks a few things I disagree with him over and we fought the whole way back over it. He thinks the following things, you guys tell me what you think
1. He believes that the hovercraft at full power on the lift engine was " hovering " only 2 inches off the surface. He considers the bottom of the skirt to be the bottom of the craft. Now saying that he feels that if the lift engine made a lot more power the whole craft including the bottom of the Skirt would " hover " higher off the ground. ------ I disagree because IMHO it don't matter how much air that lift motor pushes the craft will rise to a certain point and that is it, any more power or air pumped under the thing and the excess wil just blow out and the craft will remain at the same height. He believes that if the lift motor had alot more power that at full power the bottom of the skirt could be 3 or 4 or 5 or more inches off the ground instead of the 2 inches off the ground it hovers at now...
2. He believes that in general a hovercraft if sitting on WATER in hover mode will by the force of the air being blown down to " lift " the craft will cause the water underneath the craft to sink or be blown out. He feels that for every action there is a equal and opposite reaction and his logic is if you blow enough air down to lift a 500-700 pound hovercraft, then that force blown down has to " push" on the water. And since water isn't a solid like concrete the air blown or pushed down on it will cause a 1-3 inch lower water level just under the craft. He compares it to blowing on a straw into his coffee cup. Or compares it to a helicopter hovering over the water etc.... -------- I disagree because the hovercraft operates on the principals of low pressure and high volume of air being trapped under the craft causing it to form a cushion of air allowing it to " hover " a few inches off the surface your on. There is not enough pressure under the craft to displace that much water IMHO.
3 He believes that all hovercraft " ride " lower and slower on water than land since they "sink" into the water anywhere from a few inches on a lightweight model like the little single place at Trenton to a much deeper level of sink on big military units such as a L-Cat the Marines use to deploy troops and Tanks and so on. ---- I think this is just the way they look because of all the water spray from the edges of the skirt....
4. Also going along with numbers 2 and 3, he believes if a hovercraft just sat in one spot over a very dry soft sandy beach it would just sit there and sink and sink and sink till it either hit a hard surface like Rock or dug it's way to China.... --- I disagree to a point. Yes if it sat there it would blow out sand around the edges but the middle area would not blow away and sooner or later the hovercraft would effectively highside on the mound in the middle.
5. On that hovercraft at Trenton he believes it will nose over in the water since the skirt is only 2 inches off the surface on the ground when hovering, and in water the craft will " sink" into the water it displaces as it is blowing down on the water which will cause the skirt to no longer be above the surface but now at or below the surface and the faster you go forwards the more the skirt will go under water till a point where the nose of the machine will dig in and the craft will sink or whatever. ---- I disagree because I think every idea he is using for his beliefs is wrong for starters, but also because the bottom of the skirt is not the end all bottom of the craft. The Bottom of the craft is at least a foot higher than the bottom of the skirt and that is the part you want out of the water. That is the part that would be a problem if it dug into the water. Saying that I think the only problems the Trenton Hovercraft would have on water is if they try to drive it down a very steep boat ramp into the water and the nose goes under flooding the lift engine and causing it to quit running, But even then if the rest of the ship floats like it was designed to, there should be no big problems.
Me and Rick fought over this stuff steady for well over a hour and a half. Tell me guys if I am right or is Rick right? someone is going to be eating crow tonight!