Skipjack 1/72

[Slats]

Here you go mate. Hope it helps. Over all length of mine measures 527mm with the ballast bulkheads measuring 10mm thick.

Thanks so that is Bat Compartment =160mm = 6.3"
Ballast tank = 143mm = 5.63"
Motor compartment = 165mm =6.5"
Looks like you using a standard 7.2v Car stick type battery in there Alec - with room spare.- I like it. So sick of LIPOS and those pesky restrictions certain club here places on them!

I'm toying doing the Skipjack or an original Permit (no towed array fairing), the Skipjack SD would be ideal for both boats. But I'll ask to see if David could make one up of the same OAL but taking the Bat compartment down to 6" even, the Ballast tank to 5.5" and the back end the 9" making the 20.5" that these are overall.

Alec is your SD valve in the ballast tank?

Thanks
John

[greenman407]

Yeah, I cant be of much help yet, I havent ordered the Sub Driver yet.

[alad61]

Your welcome John. The ballast tank valve is set up as it is in all David's SD's. He uses the same rear ballast bulkhead as per a normal one so if you wanted you could retro fit a gas system too. As for the battery I prefer the nmhi type and even on a 7.2 @ 4200 mha with 100%on the throttle stick epa, the boat goes like a rocket. I've found 75% on the forward and reverse end points is ample and still gives a good scale speed. Not to mention it is easier to drive.

[greenman407]

OH NO, we gotta have warp speed if shes going to catch the Albacore, and shes gonna need it,........ and then some. I was thinking about swapping out the supplied motor with a after market 20 turn quad, but they are rated for 7.2 volts. Probably wouldnt hurt anything because it wouldnt be at full throttle constantly.

[greenman407]

Im sorry, Ive got a 52 year old body and a twelve year old heart.

[Slats]

Your welcome John. The ballast tank valve is set up as it is in all David's SD's. He uses the same rear ballast bulkhead as per a normal one so if you wanted you could retro fit a gas system too. As for the battery I prefer the nmhi type and even on a 7.2 @ 4200 mha with 100%on the throttle stick epa, the boat goes like a rocket. I've found 75% on the forward and reverse end points is ample and still gives a good scale speed. Not to mention it is easier to drive.

Thanks Alec,
I don't mean to be mixing up terminology. There is a ballast tank VENT valve - that is in all of David's SDs, appropriately in the ballast tank. What I am referring to is not the ballast tank vent valve BUT the secondary SAS valve that draws in air from the dry section of the SD should you be beyond snorkel depth and keeps water out of the SD dry spaces. This valve, which looks like a small copper bottle can be mounted in the ballast tank or dry spaces. So is where is this mounted in your SD?

I'm yet to go SAS myself yet but will as IMHO I think this is is state of the art.

Cheers

John

[Slats]

OH NO, we gotta have warp speed if shes going to catch the Albacore, and shes gonna need it,........ and then some. I was thinking about swapping out the supplied motor with a after market 20 turn quad, but they are rated for 7.2 volts. Probably wouldnt hurt anything because it wouldnt be at full throttle constantly.

Mark your nuts - suffice to say I like you!
get over here for the Australian Subregatta and beer and steaks are on me!

I find the motors David puts in the SDs are more than adequate. I find 7.2v provides heaps of grunt.
Our subs just a couple of feet down tend to bite the water far better than a skimming target. Combination of a full displacement hull, and probably a tad denser composition of water / less air cf the top 3 inches that skimmers run in. The biggest advantage of LIPOs is higher density of energy gram for gram much higher than NimH, but in Nanny State Australia, we have a much easier time running the NiMH stick batteries.

J

[alad61]

Ohh sorry about that John, I do tend to be a bit literal at times... The sas bypass valve sits beside the motor at the starboard rear quarter, facing forward, with a radial notch cut out of the equipment tray to keep it inplace and upright. I will put up a picture of the motor bulk head and equipment tray outside the cylinder. Probably won't be tonight as I have a rehearsal for the play my wife and I are in.

[Slats]

Ohh sorry about that John, I do tend to be a bit literal at times... The sas bypass valve sits beside the motor at the starboard rear quarter, facing forward, with a radial notch cut out of the equipment tray to keep it inplace and upright. I will put up a picture of the motor bulk head and equipment tray outside the cylinder. Probably won't be tonight as I have a rehearsal for the play my wife and I are in.

Thanks mate.
good luck with play.

Thought so re the SAS valve. Do you think that it would be a less cluttered setup with the valve sitting up right in the ballast tank? My view is that its neater in there and given I'm not running Gas, it could easily sit where the gas bottle once was.

J

[alad61]

John In my opinion, such as my limited knowledge and experience goes, would be a lot of effort and little or no gain. I guess you could place it in the battery dry space but running all the tuning?? Also with the small breather on the top of the valve cylinder being placed in water such as a flooded ballast tank could well, if I'm not mistaken be a disaster. Iight be wrong so best check with HWSNBN...

[Slats]

[
John In my opinion, such as my limited knowledge and experience goes, would be a lot of effort and little or no gain. I guess you could place it in the battery dry space but running all the tuning?? Also with the small breather on the top of the valve cylinder being placed in water such as a flooded ballast tank could well, if I'm not mistaken be a disaster. Iight be wrong so best check with HWSNBN...

Actually Alec, that SAS secondary valve can be placed anywhere - ballast tank is not a bad spot for it. See this diagram from David's SAS article:



and note this development photo from David



Seeing your motor room there I think it would be less cluttered - one less thing in there.

Cheers

J

[Slats]

Alec a bit of tip re the push rods in your photo:

Yes you do need to create a bend in them to take a clear path through the WT seals, but I find a sharper bend (couple of small 90 degree sections) tend to create a smoother route and are less prone to binding. That said if it works well - it works well.

Looks like you have a fair amount of cable bunching in there Alec too. What RX are you running?
I have found that some of the Futaba 36MHZ jobs we use tend to not take too kindly to having the a lot of cable in close quarters. Have you found any jittering servos with the setup or interference?

Cheers

John

[alad61]

Thanks for the tip on the push rods I just assumed that to much of angle would work against the push of the servo. But in this case, more ass than class I reckon, the servos placement meant that the rods only needed to be tweeked to do the job. Yep the sas bypass valve could work in the ballast tank alright. It is food for thought though... As for the receiver & cables. I use a JR 7 channel synthesised type which I run in all my subs. I don't seem to get to much chatter or interference and they work well with the adf2. I am always conscious of cable interference even on the cables for the PCs and my home theatre setup. If anything I reckon having the antenna wire so close to the motor even though they're suppressed. One thing I'm considering is in the future to take off the outer case of the Rx and use heat shrink to cover it.

[Slats]

Thanks for the tip on the push rods I just assumed that to much of angle would work against the push of the servo. But in this case, more ass than class I reckon, the servos placement meant that the rods only needed to be tweeked to do the job. Yep the sas bypass valve could work in the ballast tank alright. It is food for thought though... As for the receiver & cables. I use a JR 7 channel synthesised type which I run in all my subs. I don't seem to get to much chatter or interference and they work well with the adf2. I am always conscious of cable interference even on the cables for the PCs and my home theatre setup. If anything I reckon having the antenna wire so close to the motor even though they're suppressed. One thing I'm considering is in the future to take off the outer case of the Rx and use heat shrink to cover it.

Glad its working Alec - and if it ain't broke - no need to fix it. - Just suggestions. With push rods if I do put a couple of near 90 degree bends in - its near the servo clevis and I then try and gun as straight a line possible down to the WT seals.

Your right about the Rx size - only bugga we have running 36 mHZ. I run 40Mhz and use the Shulze one's - a tad smaller and practically interference free.

J

[greenman407]

Nice, Im glad to see that there are two O-rings on the endcap. Thatll help keep leaks down.