Skipjack 1/72

[crazygary]

Great looking electronics setup, Mark!!

Really clean and efficient looking!! Sweet!!

[greenman407]

Thanks Guys. I am really happy that I was wrong about a porpoising problem that I thought I might have. If you dont get the center of balance right, your boat will porpoise up and down at high speed. If you are not looking to go fast, you dont have a thing to worry about. In my Albacore build, I had such a problem:http://forum.sub-driver.com/showthread.php?824-Albacore As I was building this boat, Dave told me right where to locate the Subdriver, front to rear. It would seem that it was dead on as I was hauling Butt yesterday with it and there was absolutely no tendancy at all to porpoise.http://forum.sub-driver.com/showthre...core-continued
Right now if you take a string and cradle the hull with everything in place and ready for the water, it balances about an 1&1/4" in front of the hull mid-seam. Which is behind the sail.
Also I am pleased that I dont have a depth keeping problem like I had with the Albacore. You see, the Albacore now has two motors and two gearboxes and two propellors. Apparently there was just too much vibration to dial out and it was affecting the ADF too much, which was giving the highly sensative X-tail controls with their electronic mixer, too much jitter. What I ended up doing was moving the ADF up into the front battery compartment to try to escape those vibrations. When that didnt prove to be enough, I mounted the ADF to a thick piece of sheet plastic and then wrapped the plastic sheet in bubble wrap. The plastic ADF mounting board sits on top of the NIMH pack with a barrier of bubble wrap in between, effectively isolating those vibrations. You can see the X-tail stern here in these pictures. Now, the Albacore flies like the wind, like a thoroughbred straining at the starting gate, awaiting the bell. Another thing I like about it is the way it leans and banks into the turns. Very controlled and magical. Ill push the Scamper and see how she does and where that big sail will cause it to lose control.
The Xtail gives extreme manueverability. Itll go straight up while spinning on its axis, howling its way to shallower waters and then dive straight down like a Banshee, until you lose your nerve and haul back on the stick like a fighter pilot trying to get an ME 109 off his back. Great fun! Of course you need deep clear water to do this. At any rate, part of the Skipjacks, or should I say the Scampers success in this is that its not an X-tail. Therefore, since its control surfaces are not 1/4 of the Albacores, its not so sensitive to jittering of the stern planes. Even so I want to keep them under control so that it doesnt develop into a problem. Like using the first hole on the servo horn closest to the mounting screw or no more than the second hole. Setting the ADF on the least sensitive setting.

[greenman407]

Hey! I thought this thread was about the Scamper?
Im heading back to Clearwater on Friday for some more testing. Until then....................

[Albion]

We all hate the water you have , you know that dont you :)

[Slats]

What Albion said Mark.....

[greenman407]

LOL! Well, its not all a bed of roses to be sure. The three pictures a few frames up were taken at Blue springs which is about 3 to 4 hours from my home. Also, when you go there you have to go on a day when the local kids are in school, otherwise youll have 200 kids diving and splashing. Another good place is about 2 hrs. from my home, Oscar Scherer state park. Crystal clear water but water has sulfur in it which interferes with your radio. The Sombra reciever is manageble there. All other receivers that I know of wont work. Its shallow though. Pretty much periscope depth or just a tad more. Same problem with kids. gotta go when there in school. So, thats why I mainly go to my regular old pond. Not the greatest but keep her near the surface.

[greenman407]

Again on Monday, we found ourselves back at the pond. Into the water she went to test the adjustments that we had made to the adjustments. I wanted to test at what point this things sail would affect its turning performance. So, I started at about 1/3 throttle and made a hard turn. It banked steeply but remained visible and in control. I then bumped her up a notch and tried it again. This time she again banked hard.............but then headed sharply for the bottom. It was only about 4 ft. deep there and it clouted the bottom. Well, without pulling her out for inspection, she appeared to be OK so on we went. Not too long after that she blew her own ballast. I thought that it might be a radio glitch so I vented the tank and took her back down. It then did it again, not like a gas blow but one like the SAS pump. I pulled her out for inspection and found quite a bit of water in the rear dry section. Heres what I think happened. When the sub went to the bottom, I think that the snorkle valve became unseated due to being inverted. It then took on water thru the induction line. Also, I think that when you blow the gas ballast, I think it pushes water back thru the other line and into the pump and perhaps beyond.
As far as the SAS pump coming on, I think that since the SAS pump is mounted low in the cylinder, I think that water got on the board perhaps causing the pump to come on. I will take steps to isolate things and make sure we dont have any other leaks.
As far as speed is concerned, yes its very fast, but, keep in mind, I dont have any periscopes on the sail yet. Im going to wait and put them on after the paint job. I think that multiple projections coming from the sail put a healthy drag on things. We will see.

[greenman407]

When the submarine banks up to 90 degrees, the rudders become stern planes, forcing her to dive rapidly. You can stop the dive and turn it into a surface by going the other way on the rudder. Or..."All Back Emergency". Also, I have a one way check valve I can put in the SAS output hose at the top connection on the Ballast tank. That should stop water being pushed into the pump output and more.
I also notice that at anything past what I call slow speed, it seems to take a lot of stern plane to get it to go under. But, once its under you need to pull back on the stick to keep it from going too deep and keep it near periscope depth. The faster you go the more this thing wants to go deep. So you need to adjust it up to keep her in sight. She is by no means hands free, especially If you want to be moving along. I spooked three ducks yesterday. They were heading across to the other side and my timing was perfect. I caught them about 15 ft out from shore. No periscope to give it away but they sure knew something was there. They shreiked and took to flight while the Scamper was about 8" under them. If it had been a Gator, it would have had one of them.

[alad61]

Man I would happily drive a couple of hours to have water like that!

i agree it is defiantly not a hands free boat. But when you get used to how it runs it is a fun boat to drive. It's funny that yours on the surface needs extra rear planes to dive where mine is the opposite? Just curious at what EPA is your throttle set. It is good to hear that you are getting some dive time with it. As for a sail top full of masts, they may well cause a bit of drag but none the I have noticed with my lot. The littler radar dish does tend to catch a bubble which sits under motion but a little creative maneuvering cleans it most of the time. In hind site I'd remove most of the masts if for nothing other than just a more streamlined look.

[greenman407]

Alec, EPA is like everything else , its set for MAXIMUM....................dude.

[greenman407]

Maybe Monday again. Today I got involved with the Seaview at the pond trying to sort things out.

[greenman407]

Ran her again today to test out some changes to her trim and to figure out where the water is coming from. I completely plugged off the SAS and ran on Propel. No Leaks. Therefore ,I believe that the water is coming in thru the SAS hose that leads from the ballast tank to the pump when I hit and engage the Propel. The propel ,forcing the water out of the ballast tank also forces water back into the SAS system. Ive got a nifty little check valve thatll stop that.

[He Who Shall Not Be Named]

It's the pump discharge line? If so, is the leak at the nipple(s) or the LPB? Find out. Are you using the motor-bulkhead manifold. If so, is that the source of water getting into the system?

M

[greenman407]

At this point im not sure yet. I believe that the gas was pushing water into the pump and beyond, so a check valve will stop that. Im still looking , in between other projects.

[He Who Shall Not Be Named]

If water is getting by the pump into the SD, then you have a bad pump (maybe a pin-hole in one or all of the diaphragms).

M