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Author Topic: Perkasa 49in Renovation.  (Read 25303 times)

gregk9

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Perkasa 49in Renovation.
« on: November 23, 2010, 07:07:35 PM »

Following on from yminitial request for some helpful hints in the beginners section, I am beginning the renovation of a 49 inch Perkasa torpedo boat. the original Kit as a Precedent one, fitted with an "i/c" engine at some stage, which has been removed and the following owner had tried to convert the single prop to electric drive, but not having sufficient speed on the water, the craft has been sold on and now I own the craft and am about to start a refit to include twin elkectric drive motors with independent propeller shafts, but will include the original centre rudder board, thuis giving 3 rudders and 2 props.
I will be fitting [following Perkasaman's suggestions] twin graupner speed 700BB turbo motors and runnign 12v batteries in a twin battery pack setup for added capacity on the water.
I am proposing to add a working radar, replace the original torpedo carriers from the over thick dimensioned wooden items supplied in the kit. Add operational navigation lights, improve the open wheelhouse detailling and seats, improve [or replace] the original front mounted bofors gun and to add a rotational servo to the mount. Same goes for ths missing stern gun mount, this will be constructed and made to rotate also. All the original railings have been removed for replacement later.
This i think is enough info for now, but any help with detailling pictures or pictures of your own craft would be greatly appreciated as this refit progresses. :D
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Steve. G.
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #1 on: November 23, 2010, 08:59:10 PM »

Pictures of the "before" craft.
I firstly lifted odd the superstructure and then took to the "washing dep't", namely the bath! Sprayed the main deck and the superstructure with ordinary car "traffic film remover" which rapidly dissolves the grime and old grime from the i/c engine deposits, then washed off with warm water. I prefer to use this type of film remover as its biodegradable in water, its cheap to buy, does not harm any paintwork or glue and leaves the surface clean and clear of any residue as it even removes polish and silicones .





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Steve. G.
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Perkasaman2

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Re: Perkasa 49in Renovation.
« Reply #2 on: November 23, 2010, 09:35:09 PM »

Hi greg, I found this site and it contains some good info sources and pics.

http://sites.google.com/site/kdperkasa/Home
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #3 on: November 23, 2010, 10:37:13 PM »

Thanks for the link, it is appreciated.
I have now removed all the main deck fittings, hatches,bollards, rail posts,vent heads etc, so I can resand the deck properly and get a smoother finish and loose all the open wooden grain that is still visible through the paint.
I have removed the original centre propeller shaft, with careful and prolonged use of my dremel with a small router bit, I carefully cut away the fibreglass matting and filler that bonded it to the hull floor, both inside and on the outside, to allow me to remove the shaft completely. At the same time I also removed the stern water pickup pipe, thats was installed forward of the centre rudder bar. being as Im going to use motors with cooling fans already fitted inside the motors, i dont really ned a water pickup, so have removed it to reduce drag in the water.
I have filled the resultant hole in the hull by these 2 items with some P40 glass filler. One reasonably dry [but not too dry] I gacve it a good sanding with a flat block to remove the excess filler before it sets rock solid, as its easier to sand like this. then ionce it was 100% set, I finished off the sanding with some finer 800 grit paper before adding some fine moddeling filler to fill the smaller gaps that remain. I will leave this overnight to dry fully before flatting off using the 800 grit paper "wet" to get a finer smoother finish.





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gregk9

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Re: Perkasa 49in Renovation.
« Reply #4 on: November 24, 2010, 05:16:20 PM »

After careful consideration, I have removed ALL the main fittings from the upper deck, cabinets,lockers,gun platforms as in my opinion they just dont look right at all. the original builder had made these items from wood, but had not bothered to sand the sawn edges, sand the wood before painting etc, so they look appauling. So I will use the items as patterns and will make new ones from plasticard.
I have now given the main deck its first coat of sanding primer, to again, fill all the wood grain, this will be sanded before a second coat applied.
I have cleaned up the wheelhouse window frames, prior to sorting out some windows to fit, but they wont go in untill the whole thing is repainted.
The centre propeller shaft hole is now fully filled and sanded smooth, but will leave the hull "as is" untill I have fitted the 2 new shafts and bonded in place, then I can fully finish off the hull before painting it all again.

Incidentally, has anyone else fitted a "transom flap" as  it appears they did have one fitted, albeit usually set at 0 degrees but adjusts to  3 degrees "down angle".  id be interesyted to hear if anyone has and how the boat performs with it fitted.

I do run a similar item on the stern of my dusseldorf firebaot [as they had them fitted too] and that works well and stops the stern sinking too deeply under higher speeds.



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TomP

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Re: Perkasa 49in Renovation.
« Reply #5 on: November 25, 2010, 12:10:47 AM »

Hi, I also have a 49" Perkasa. I have the rear transom flap fitted and I am currently installing a Pneumatic system to raise and lower it. It seems to stop the props dragging air down the back of the boat and also helps bring the front of the boat up on the plane. I have 3 Props and 2 rudders, just a word of advice as I have been there and failed, keep the boat as light as you can. I used 3x Graupner 600BB turbo motors on 7.2 Nimh battery packs and they struggled to get any speed. I have since installed 3x 850 MFA torpedo motors on 12V Nimh finally I get the scale speed but because of the high current draw (about 20Amps) my Mtroniks 40A speed controllers cut out as the voltage drops to low. Its been an never ending battle caused by myself as the boat is too heavy. Ive been told the best solution for the 49" hull is a single prop and rudder, 850 MFA motor 12V Nimh battery and a 30mm prop but its your boat do what you want and think is best, Ive had to many people giving me their expert advice which never helps. Good luck Tom 

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Perkasaman2

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Re: Perkasa 49in Renovation.
« Reply #6 on: November 25, 2010, 10:19:35 AM »

Hi tomp, The Graupner Speed 600BB Turbos would need to be run on the higher voltage of their operating range (4.8 - 14.4v) to show their potential and I can understand their poor performance on 7.2v.
The MFA 850 motor at 600g is a much heavier motor than the 220g Speed 600BB Turbo unit and have increased hull weight by 1140g, however, they have had the advantage of higher 12v running and planing was achieved. (It would be very helpful to know what size props were used with both the earlier Speed and current MFA setups.)
My twin 700BB Turbos ( 350g each) spin a pair of 45X props and use twin sla's (2.6 kgs each) running @ 12v 14amp/hr in my 49 grp Perkasa and planing performance is excellent, although the hull is heavily burdened. My 700 Turbos  have a voltage range 4.8 - 16.8  and are probably running at their most efficient (75%). although more oomph is there........... on paper. I will probably run/trial twin or quad nimh packs and should save at least 3kgs of battery weight. I will dust off the hull /do comparative trials when the weather is warmer.
I also bought the fittings packs, however I have'nt used them, largely because of their heavy weight, however, they are a huge improvement on the kit items.  
  
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #7 on: November 25, 2010, 12:33:11 PM »

we have similar problems of weight with the 102 ft vosper patrol craft , it started with a pair of 900 brushed motors , but after the escs melted on the bench have gone for a twin brushless set up ( e flight park 450 s ) through individual esc s but running from a single 12volt 7 amp gel battery , it now gets up to plane but with a better battery ( ie less weight ) should help its performance ? photos under vosper ferocity , weve since learned its not the ferocity but i cant change the title ! :-))

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gregk9

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Re: Perkasa 49in Renovation.
« Reply #8 on: November 25, 2010, 01:58:02 PM »

I have already removed the centre prop shaft and sealed the hole up, so I will fit just the 2 motors as Perkasaman suggested.
I am wary of the weight of the boat, thats why i have removed all the original wooden fittings, lockers , guns etc and replacing with far lighter plasticard items, plus can get a much cleaner/sharper edges on all the lockers with plasticard over the old wooden ones.
For example, Ive just weighed the forward 40mm bofors wooden version thats was fitted to my boat, it weighs in at 5 ounces, whereas the new one im making in plastic is a mere 1.5 ounces at present, and thats half built as yet.
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #9 on: November 25, 2010, 03:58:55 PM »

are you able to remove sections from bulkheads to save any more weight ? thats what ive done to the patrol boat , some have been drilled , while others have had large sections cut out using my dremel & a disc cutter ( bulkheads are 1/2 inches thick , & the keel is over an inch thick ! )
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #10 on: November 25, 2010, 05:04:12 PM »

Good idea ! id not thought that far yet, but yes, its worth looking at, once ive arranged where the twin motors are going to sit. there are already 2 wooden cradles set on the hull floor, either side of where the petrol engine sat, but they have never had anything in them. There is a square plinth in the stern section, nearest the rudder post which I presume was where the fuel tank sat. It has been fibreglassed in, but will coax that out too with the ever faithful dremmel [ha ha].

However, i do want to add another bulkhead in, towards the bows, as where the 40mm bofors sits, the deck is very flexible, so when I cut out the circular disc to enable me to make the gun rotate via a servo, I will add a plstic constructed bulkhead in, to hold the deck level and stop from drooping.
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #11 on: November 25, 2010, 09:41:14 PM »

when i refitted the boat , it too was a conversion from single shaft to a twin shaft , i removed the original 17" shaft  but fitted a pair of 12" m4 ones , i also placed them further back in the hull , the new motors are now below the funnels , behind them ive a full height watertight bulkhead that has our heavy 12v 7 amp gel battery , the rear compartment just houses the steering gear and rudder servo ! it may next summer get treated to a pair of lighter higher voltage battery packs in the quest for more speed !
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #12 on: November 27, 2010, 11:56:57 PM »

I have started to lighten some of the interior bulkheads, starting with the easiest one to get at, the stern bulkhead. I have left sufficient strength to hold everything together, by virtue of the 2 vertical pillars and left a horizontal bean top and bottom. I still have to sand smooth all the cut edges, so it looks a bit on the rough side as yet. the next one to attack will be the forward one, but I also need to cut a lareg doameter hole in the forward deck yet, so i can drop in the 40mm bofors with a servo mounted underneath, so that will give me better access to the bulkhead for lightening too at the same time.
I have also removed the stern exhaust covers, the original wooden ones look too large in diameter, so will make up some new plastic ones and maybe even deepen the actual ports so they look like they are actually turbine exhausts. Whilst the covers were off, I took time to run my sander across the stern to level the fibreglass off to look and feel more squarer then the original mould had left it.



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Steve. G.
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #13 on: November 28, 2010, 05:55:00 PM »

when i put the rotating & elevating gun on the one i made i fitted a sub plate below the deck with the rotating servo fitted to it , then using a long m3 bolt and tube transmitted the drive out through the deck to the gun , my method for elevation was a micro servo inside the gun body ! hence ive only got a very small hole that splashes of water could find there way into the hull ! ! most models seem far to over engineered when you look at the thickness of some of the bulkheads , id rather have a lightweight model than something that becomes too heavy to carry to the lake .
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TomP

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Re: Perkasa 49in Renovation.
« Reply #14 on: November 29, 2010, 10:32:48 PM »

Hi, yeah i wish i had tried the 12V batteries the only problem was the motors were reving so much that they were cavatating so the motors would rev but the boat wouldnt go forward thats why i decided to change them to a lower rpm but higher torque motor. I had 6 7.2V nimh battery packs on the BB turbos but reduced that to 3 12v battery packs to make the weight the same with the larger MFA motors. the props are 40mm just need to stop the speed controllers from cutting out maybe a capacitor would help?? Tom 
Hi tomp, The Graupner Speed 600BB Turbos would need to be run on the higher voltage of their operating range (4.8 - 14.4v) to show their potential and I can understand their poor performance on 7.2v.
The MFA 850 motor at 600g is a much heavier motor than the 220g Speed 600BB Turbo unit and have increased hull weight by 1140g, however, they have had the advantage of higher 12v running and planing was achieved. (It would be very helpful to know what size props were used with both the earlier Speed and current MFA setups.)
My twin 700BB Turbos ( 350g each) spin a pair of 45X props and use twin sla's (2.6 kgs each) running @ 12v 14amp/hr in my 49 grp Perkasa and planing performance is excellent, although the hull is heavily burdened. My 700 Turbos  have a voltage range 4.8 - 16.8  and are probably running at their most efficient (75%). although more oomph is there........... on paper. I will probably run/trial twin or quad nimh packs and should save at least 3kgs of battery weight. I will dust off the hull /do comparative trials when the weather is warmer.
I also bought the fittings packs, however I have'nt used them, largely because of their heavy weight, however, they are a huge improvement on the kit items.  
  



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gregk9

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Re: Perkasa 49in Renovation.
« Reply #15 on: December 01, 2010, 09:29:56 PM »

Ive now had the x45 props arrive as well as the new rudders. So Ive marked out the rudder positions and installed them, so i can fibre bond in the support blocks, as well as make up the link rods between all 3 .
ive also started work on the transom flap, this [so far]is 2 layers of 0.4mm plasticard, the third layer to be added once these 2 are dry. I can then add the hinges and linkage rods. the rods ive decided will be adjustable ones, so I can have a play with different angle settings, to get the best performance from this particular boat [hopefully]. admittidly there's only about 5 degrees to play with so its between -1 and plus 4 in my books. but we will see in time.





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Steve. G.
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #16 on: December 01, 2010, 09:48:40 PM »

your rudders look quite big , you may also need to cut the top and bottom corners off to assist in reducing the lift when the rudders are used at speed ! the twins i fitted in the patrol boat have an adjustable tie rod that links the pair together at the outer end of the tiller arms while my servo is acting on one of the inner most holes , i have however found a dual  ended ball link that may be of use to you for your rudder , its a ripmax part number F-GPMQ3930  retails at 2 .75 , this may make the linkage neater ?
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #17 on: December 01, 2010, 10:36:52 PM »

Ive matched the 2 rudders ive fiotted, with the original that was already in the hull, this being a "medium" size [according to the books], its approx 54mm deep by  34mm at its highest width point.
 but as it was going to be matched up with 45mm props, they may well be ok, but proof will only be once its in the water, as at higher speeds, I tend not to put a full rudder input in anyway with my boats, knowing how it can affect them and cause  them to lift or baulk out in the water.
thanks for noticing though, it is appreciated.

So what dimensions are your rudders then?

I have a selection of screw threaded ball/rose joints I make all my linkage shafts up with.  I cut 2mm rod to suitable lengths, and then cut sufficient screw thread on them, thus giving a nice fine adjustment to the links. these being of the "aero type", not car ones as they pop off too easily, the ones I use have a nut and bolt going right through the centre of the ball joint to secure to the servo arm, thus going "belt n braces", to prevent linkage loss due to vibration so to speak.
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #18 on: December 01, 2010, 11:44:50 PM »

i cant remember off the top of my head how big the rudders were , & the boat now lives in woking , which is around 50 miles from here , so cant check very quickly ! i know the idea of belt n braces with the rudder linkages as its no good racing across the lake if the rudder wont turn it around at the end ! im currently fitting the pushrod connectors to all of my builds , as iits a solid metal unit held onto the sevo horn with a nyloc nut , the linkage bar is retained with a grub screw , im also using balraced servos for the rudder control .  :-))
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Perkasaman2

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Re: Perkasa 49in Renovation.
« Reply #19 on: December 02, 2010, 10:45:54 AM »

Lots of progress.
It may be worth fitting small brass washers to the rudder stems where they enter the hull to allow the rudders to swivel more freely. The E boats utilised what became known as the 'Lurssen Effect'. It was discovered by their designer. The outside rudders were offset outwards a few degrees and this slightly increased speed/reduced drag. I don't think this phenomena was ever properly understood, however this effect and advantage was exploited. (The allies discovered this subtle arrangement when an E boat was captured intact and evaluated. Apologies for rambling a bit.  :-) )
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #20 on: December 02, 2010, 11:27:11 AM »

Thanks Perkasaman, will take the brass washer bit on board, I have some,somewhere, will track them down and slip them on. Same goes for the small plastic/nylon hinges I have. I've got a pack of them somewhere, but do you think you can find them when you want them? [ha ha]. I was going to use them in the "plastic sandwich" of the transom flap, thats why I havent added the "third layer" together yet, wanted to leave apart till i'd got them in, so they wont show too much once assembled together.
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triumphjon

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Re: Perkasa 49in Renovation.
« Reply #21 on: December 03, 2010, 09:06:38 PM »

sandwiching the plastic hinges sound different , im also looking into making my trim tabs work , so may try this too , i was also thinking of making my tabs from stainless steel sheet , as i normally operate in salt water ! its how to make the hinges that has me puzzled ! !
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #22 on: December 03, 2010, 11:40:04 PM »

The hinges I use came from an item I needed for the rear stern hinged door on my graupner Adolph Bermphol Lifeboat. I needed some hinges, that were  lightweigth, but alos not going to rust away when submersed in water, so came across thes little cute things, belonging to the aero moddellers brigade. They use them for the wing and tail flaps, light in weight, 2 sections of the hinge are a quite flexi plastic, with a stainless steel pin locking the two halves together, so no chance of premature rusting [ i didnt say any rusting- as appreciate you will get a slight corosion on this st/steel pin].

they are pre drilled with all the holes you see in the pic, so adapt easily to any fitment, plus you can source larger hinges if these are too small for your purpose.  price? cheap as chips mate, bought a pack of 10 for less than 3.00 inc postage.
Thats why i said ive just simply cut a slot in the 3 layers of plastic ive bonded together, these hinges will slip in to the slot, then its either glue them in or drill through and drop some plastic rod through and heat over the ends, like a rivet, so can be removed/replaced if ness later, by simply cutting the heads off the plastic rivets and the hinge slides back out again. then to attach to the stern, you could use some stainless steel bolts and nuts, rather than just risk to epoxy glue.
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Perkasaman2

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Re: Perkasa 49in Renovation.
« Reply #23 on: December 04, 2010, 12:11:07 PM »

The trim plate in use only needs a few degrees of adjustment to generates a slight 'upforce ' to dissuade the stern from digging in at speed and some sort of micro adjustment  rather than twin servo powered rams may be less complex and  more useful. Independant adjustment of (wider-spaced) supports will enable fine tuning/warping and this may also reduce 'crab running'.
This facility may help to correct any lack of symmetry in the submerged hull shape or any steering/handling bias where handed props are not being fitted and  help reduce/neutralise the torque reaction of the hull and encourage straight running at speed. This upforce from the trim shelf should also help to reduce the size of the stern wave and 'rooster tail'. Less water displaced is more efficient.
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gregk9

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Re: Perkasa 49in Renovation.
« Reply #24 on: December 04, 2010, 02:44:20 PM »

I have an old pair of robbe trim tabs, somplete with some threaded adjustable rods attached, was going to raid them off the robbe ones, and adapt to fit the perkasa transom flap. All i'll need to do is replace one of the threaded rods with longer versions, but have loads of 2mm rod and a 2mm die set, so can make these up easily.

Pics attached of the "donating" items, no, not using the bases, just the threaded rods and joints.




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