Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[SlimRick]

Hi folks,

Thought I'd start a new thread showing a few bits that I'm doing to my recently acquired Perkasa.  Here's as she arrived:

[SlimRick]

And a few after removing the model rockets (fully elevating and functional!), refixing a few things and a quick touch up.:







A quick polish of the props:



Recycled LED's from old PC's:

[Shipmate60]

She is looking good now, well done!!!

Bob

[Perkasaman2]

What a transformation. you'll have a lot of fun with her - she looks the part now.

[jonny shoreboy]

Nice job mate, she looks the business now! I like the lights too!

[SlimRick]

Been on a shopping spree this week.  I've just received a P94 from Action, ordered 2 MMB 900 motors from Mark, and picked up a Spektrum 5xe from Ebay.  I have 2 12v 7ah batteries from work which I'll use....should be interesting 

[marmoi]

You have done a superb restoration. I hate to see good models go to waste.

Those nice sharp rockets must have been a liability when fired from the boat!

Mark

[Perkasaman2]

Hi Slimrick, It's VERY important to place these big batteries (same as mine) on the centre line and in the right locations in your hull - I had to experiment a lot to get the planing/weight balance just right - if you want some precise location measurements  from the transom (stern) comeback.    I have the 49 grp hull but the measurements should be still ok for your identical plywood hull. I'm very interested to see how your boat performs - speed/duration, with these monster motors. You may have to change to plastic props (rather than the scale brass jobs) to really take advantage and maximise efficiency to avoid wasting battery power. Some upgrade high speed Hanna or ballrace propshafts might be a good idea if the new bigger motor/mount combo won't fit/align with  existing motor mounts/shaft alignment arrangements. My 2 graupner 700BB Turbo engines/mounts are bolted direct onto the bottom of my hull on a resined rigid alum plate to get the drive/thrust axis as horizontal/efficient as possible. Shortish/steep angled shafts are inefficient and waste energy - tending to push the stern at  a more upward angle/trajectory and therefore indirectly generating forward thrust - wastes power/energy. Low motors/long shafts/minimal prop clearance - 1/4 " (or allow a little extra for fitting bigger props/experimenting later) will get prop thrust as horizontal as possible. 
I've tried to share my own thoughts/experience. Comeback for more detail if you need it. 

[SlimRick]

I'd really appreciate some details from yours Perkasaman - any chance you could post a couple of pics of the internal fit too?

[Perkasaman2]

[Perkasaman2]

Hi Slimrick finally got the 6 pics loaded. Pic 1 indicates exactly where I'm measuring from. You will notice that my grp hull is relatively open/accessible with few frames and no central keel structure, however my installation was limited by a frame/bulkhead at 515 mm (from stern) and my alu engine baseplate position was limited by/was butted to it. The forward battery tray was built/extended forward from this bulkhead. The rear battery (pic 2) sits upright between the motors 362mm (rear edge) from stern - initially, narrower twin 6v batts were tried (poor performance) hence the 2 strips glued on baseplate (pic3) to centre narrower batt. Luckily, I installed the propshafts at 5" parallel and had plenty of clearance between the motors for larger 12v 7Ah (weight: 2.6 kgs each and W65 x H95 x L150 mm   ) and glued a rear retaining stip to restrain it. The front battery is located on the tray on it's side (easier) 820 mm (rear edge of battery) measured from stern. I found that the front battery had to be placed 70mm further forward on the tray and glued positioning strips front/rear to locate (pics 4&5). This more forward position stopped the hull from wallowing with a too high bow/buried stern and got her planing/looking right and moving a lot quicker. Bad weight placement produces this bow high attitude/buried stern setup - gives a planing look, displaces vast amounts of water - but much less speed/little, if any planing, irregardless of how much engine power you have/waste. Placing the front battery further forward reduces drag at speed since the more forward weight is born by the pressure built up under the front section of hull ( a pivot/balance point) and the reduction in weight to the rear reduces the tendency to bury the stern while rising to the plane. I always inted to fit stern trimtab as the original.
I used twin X45 props with 13" (330mm - stuffing tube) shafts. The graupner 700 Turbo + Huco coupling is 5" (127mm) combined length. The elongated prop slots through the hull are at 11" (280mm)centres and 5" apart measured as in pic 6
I always intended to fit  stern trimtab/plate, similar to the original. The rudders were offset to accomodate/position cooling pickups later.

Your hull/deck access is constructed differently (?) as mentioned earlier and seperate engine bases or an alternative mounting system may be easier. My final arrangement, after a lot of alterations/scars  met my installation criterior and managed to get these huge batteries in the hull - planing and with some endurance. I've tried to give useful detail/measurement. Using large, much lighter 12v nicad type batts could avoid the need/hassle for centreline placement, my grp hull can carry the big gels with style - but be flexible  You have great motors and getting the prop axis as horizontal as possible through lower mount/longer shafts etc is well worth it. Please comeback if I can help further. 
     

[Perkasaman2]

Hi again, I've read in another section that you've decided on nicad 12v 4600 Mah    

[SlimRick]

Brilliant pictures, thanks Perkasaman.  I'm undecided which battery set up to go for yet - will give it a try on both and see which suits it better.  It already has a tray fitted for a Lead Acid battery in roughly the same position as yours.
On a side note - I found the makers name and date inside the superstructure, built buy a guy called David Sargeant in 1993.  Anyone else sign and date their models?  Seems like a nice idea.

[Perkasaman2]

Hi Slimrick, my Perkasa was built almost 10yrs ago and was unfinished although I got her tweaked/optimised for good planing/endurance. (I usually took a couple of spare batts to swop poolside for longer sessions.) She finally ended up on a large shelf in my garage due to pressure of work/earning a living. I enjoyed the challenge - at that time large gel batts were the only realistic electric power option for our large hulls.
I'm also tempted to try/compare twin 12v 4600 Mah, but only in parallel config, since my engines will destruct at 24v  . Nicads do have a much lower/limited (300ish) charge cycle lifespan and higher discharge/lower output, on paper, but they're a hell of a lot lighter. Planing/endurance trials on twin/single MMB 900's on 45X/50X/55X props tried on both batt types in series and parallel would be very interesting.  An agreed benchmark course/performance profile at continuous running - say, alternating 5 min periods of high then low speed - timed, using a decent size pool?  My twin 700's are high revving on the 45X props but I might try 50X and see if  this can reduce the current drain/extend endurance - less frantic/wear n tear.
I wanted scale features/authenticity above the waterline (topside) like yours, but was willing to sacrifice/abandon this goal underneath for efficient/good performance. I had intended the largish space between my motors to enable a third engine, but happily, this was'nt needed. My props could have been 'handed' and external propshafts brackets designed/installed without restricting/obstructing the water flow past the props - perhaps improvements for the future, although I don't recall vibration/cooling issues on this installation at the time. When Precedent went bust I bought a duplicate 49 grp kit and put it on top of the wardrobe - it's still there, happily, Anglia Models took over production and all versions are currently available. They are a great starter model - impressive on the water.
 

[SlimRick]

Had a bath test last night on both 12v, and on 24v.  12v it felt like it was stretching my muscles trying to hold it still.  24v it emptied the water out of the bath and left some rather pretty patterns where the props gouged the bath tub...oops.

[Perkasaman2]

Hi Slimrick, you're lucky it did'nt cross the bathroom ceiling as well.  
My first 'trials' (10 yrs ago) caused a 'plague of mosquitos'   - (SWMBO reminded me of that  'little problem' - another Tom /Jerry episode  .)
I had lugged and sited a huge scrap 'victorian style' cast iron bath at the back of our house which is very sheltered.  My test tank duly festered/transformed into  a perfect skeeter breeding facility during that very hot summer - back door regularly left open. We were under siege for weeks by the 'Bzzzzzt'  bug***s.  
I had already terrified/lowered the house values of my close neighbours with my 'unearthly' howling banshee abc irvine 40 - mounted in the 'F' boat - named, without affection, by my family.    
Looking forward to the lakeside test report on your twin 'griffin MMB900's'. Checkout the exhaust soundtrack on You Tube - type 'rolls royce griffin engine' - imagine this  'doubled'. 

[Perkasaman2]

Don't worry Slimrick, I know the Perkasa did'nt have 'griffins' but my intended Vosper RTTL certainly did and those twin MMB's are on my optin shortlist for a 1:18 scale with soundtrack. Not sure if a 'triple gas turbine' chorus is available. Your current trials will provide very useful data for my project.

[SlimRick]

Well....it floats 



Video to follow once I've found the right cable.

[SlimRick]

[Perkasaman2]

She looks scale 'right' - front  hull clear of the water and the stern is'nt buried.   Your scale props are nice but restrictive - your high torque MMB's will easily drive a pair of higher performance 45X props (not sure about economy on 50X's) and give much greater thrust for hopefully the same or even less amps. Looking forward to the video. Were you on twin gels 12v 14Ah parallel or 24v 7Ah series or other batt type? Enjoy a bit of sailing after all your effort.