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Author Topic: pt-109 build  (Read 19683 times)

Tug-Kenny RIP

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Re: pt-109 build
« Reply #75 on: March 03, 2012, 11:27:22 am »


Yes indeed. Very clever with the Scratch building.  (right up my street).

Keep em coming.   :-))


ken

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MikeA

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Re: pt-109 build
« Reply #76 on: March 05, 2012, 02:32:03 am »

Well 2 weeks for a boat build might seem a long time to most of you but to me it felt like months!! %% So what have i been up to then?

First i got the controls done. I allways like doing the cabin fittings of any of my builds:


The dash is all mounted on a small piece of plasticard, Ive never used plasticard to this extent before in any boat and on first trial of it wasn't impressed, but now Ive seen the uses for it in the right places and its great stuff. The gauge binnacles are small slices of an cotton ear bud, usually i would go to the extent of putting in the needles and digits but they are just too small. The throttles are made from wire and they the knobs are blobs of solder. To make each one basically i cut the wire first about 3 inches, then using the soldering iron I heated and applied and small blob of solder to tin the ends I then rested the soldering iron on its stand then holding the wire, heated the end again and fed more solder onto the molten tinning i did previously gradually making the blob bigger. I let the solder cool off holding the wire up side down so that a blob would hang off the end, when turning the wire the right way round a near perfect ball was formed. I cut down the wires to approximately 4mm and pushed and glued them into a semi Circle balsa block. Worked out great and was so simple.

Next up was the exhausts.



These arnt shown on the plan but a fairly elaborate feature of the stern demonstrated by images on google. So using a ruler i scaled their dimensions off the SCREEN. It turned out that each muffler was about a 1/3 the length of the height of the transom, so measuring my own transom which is 90mm gave me a length of 30mm. What seemed like the width of each muffler was roughly 1/3 the length i made them 10mm wide. Constructed from plasticard and drinking straws they were time consuming but worth the effort if i say so myself  :-)

Numbers and markings:



The numbers had been bothering me for a while and it was something i eventually had to face. Although MANY models actually show a large white pt 109 lettering on the bow actual photographs of the real thing contradict this. Albeit my boat is semi scale and fairly inaccurate i felt that a slight lean towards reality wouldn't go amiss so they were not included, however the little numbers are. Although the photographs i have here do not show them they are dotted around the boat in various positions. I had considered all kinds of methods of doing the writing, but in the end settled for the cheapest option. It is blatantly obvious they are painted and maybe not well. I could have bought some lettering but i wanted the challenge of trying to paint them myself, which you have to bear in mind i cant paint a door without catching the walls! Its all forward progress in the art of painting :-))

The bow:



I thought it was time i showed the results of the bow. Despite it being constructed out of bits of left over scrap it turned out pretty smooth. The picture makes the paint job look like dog poo but its not as bad as it makes out honestly  :embarrassed:



I have gone as far as the plans have suggested and which i am comfortable with. Im not ignorant to the endless list of improvements and additions that could be made but for me as far as I'm concerned its finished. I got out what i wanted from this build which was to make a simple version of a PT boat, this boat in particular after watching a film. All in all its cost me about 60 quid to make i reckon. I do need an esc yet and that will shove the cost up a bit but ill have to use what Ive got till i can fund one solely for this boat. When i get it on the lake ill make a clip and you can see what happens :-))
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Norseman

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Re: pt-109 build
« Reply #77 on: March 05, 2012, 05:11:21 am »

These arnt shown on the plan but a fairly elaborate feature of the stern

You nailed that one Mike.  :-))
What build have you got planned/dreaming of next?

Dave
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MikeA

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Re: pt-109 build
« Reply #78 on: March 05, 2012, 09:03:02 am »

thanks Dave. Ive got a hole list of things i want to build. When i was gathering the materials for this build i was working but now im not my next build will some what even tighter.

I want to do some jet boat experiments and ive salvaged some rc car parts so i am seriously considering an amphibious vehicle. Simple plans doodled on the back of a fag packet :-)) its going to be a while before i build something grand.  :-)) Ill start a new thread when all that comes about. Until then i will put my funding into a esc and transport case for this boat.
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tt1

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Re: pt-109 build
« Reply #79 on: March 05, 2012, 10:39:46 am »

Well done Mike - a true scratch builder if ever there was one.

           Good luck with your next venture, regards, Tony.
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MikeA

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Re: pt-109 build
« Reply #80 on: March 05, 2012, 10:12:48 pm »

Ive been a bit hasty coming to a close on the build thread, yeah aesthetically speaking its complete but was the boat ready to go? no way! There was still lots to do! %)

positioning the battery:



It was decided at the very beginning what battery i would be using and i was well aware that it didn't fit between the bulkheads, so i dont have a clue why i left it so late to mess around with. In order to get the battery to fit a had to cut a section of the bulkhead out, it is held in position with some off cuts from the 6mm square i used to make the cross member for the servo mounting. All very simple, secure and easily removable.

The ESC and gubbins:



I suppose many people have their ideas about where to place their esc's and stuff, i like a lot of service access. On This boat and actually a few of my others Ive temporarily mounted the esc on a bulk head right under the deck and completely off the bottom to avoid splashing and submersion due to flooding. The receiver is also mounted high up on the underside of the deck near the steering servo to avoid the same problems. I just use sticky back velcro from Wilko, works great for holding batteries still and keeping stuff fixed like deck lids etc. Off course the balance needed checking so in the test tank it went:



This isnt actually the first time ive got the boat wet. The first time was after i had resin doped it to check for leaks, its was still exciting though, especially because this time the boat was working  :}

Firstly i checked the water line:



Due to the position of the ESC the ride was slightly slanted but not much, at slow speed i dont think it would have made any difference but on a plane it might have had an affect, i was hoping the slight offset of the motor from the middle would have counterbalanced the ESC, it did to some degree but needed help. A method i used for ballasting in my trawler was using fish tank gravel, If i remember rightly it was about a 1 for a kilo from wilko, not the plastic stuff either proper stone. Using a sandwhich bag sat on the port side i added pinches of gravel till the ride of the boat was level. I then emptied the sandwhich bag into a balloon tied it up and stuck it way under the deck on the port side:



The method may seem barbaric and crude but it works fine, I suppose lead wheel balancers would be better but this works and cost me nothing, well nothing as far as the budget is concerned for this build. Anyway checked the waterline again:




Im sorry the pictures are a bit fuzzy i was trying my best not to drop SWMBO's camera in the bath %%

While the boat was in the bath the temptation to have a sail was overwhelming, so i had a tootle backwards and forwards albeit very slowly. While i was at it i tried a current test. Holding the boat still and giving it some welly I tried a 10amp fuse, it popped. I then tried a 15 amp fuse, it was fine. I was actually rather surprised and was expecting the amperage to be in 25 - 30's region, goes to show what i know. So i reckon the current draw is about 12-14 amps. I put a 20 amp fuse in to give it some head room but i can go a lot higher if necessary. The esc is rated to 225 amp continuous with a 675A spike limit, although i take these numbers with a pinch of salt. Esc's only temporary till a find another one.  :-))

Anyway its ready for a maiden run now :}
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John W E

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Re: pt-109 build
« Reply #81 on: March 06, 2012, 07:48:02 pm »

Hi there Mike
Nice to see you have finished the build; it looks smart.   Do the plans show any spray rails fitted around the chines of this boat?   If not, it may be wise to fit them make them out of 1/8 square softwood to run the full length of the boat along the chine.  This will aid in deflecting water from the sides of the hull and give a better performing boat.
Keep on with the build and good luck with your next project.
aye
john
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Norseman

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Re: pt-109 build
« Reply #82 on: March 06, 2012, 08:48:39 pm »

Hi Lads

I found this site with lots of links - some to PT boats. Fascinating stuff - of course some of you might already know of it.
http://www.hnsa.org/doc/index.htm
http://www.hnsa.org/doc/index.htm#pt
http://www.hnsa.org/doc/pt/specs/index.htm

Put kettle on and break out the biscuits before viewing these full text declassified Navy documents for researchers of historic naval ships :-))

Dave
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MikeA

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Re: pt-109 build
« Reply #83 on: March 08, 2012, 12:32:56 am »

I took your advice john and fitted spray rails. No they wernt shown in the plan and it had actually crossed my mind, but since they wernt on the plan i decided not to fit them at first. Anyway they are now  :-))

Took the pt out for its maiden voyage today. Got to the lake only slightly damaged lol, just the front light and part of a torpedo broken. Wasnt suprised at all really it was really combersome and awkward to get under the pushchair but managed it :}

Anyway heres some shots:






I ran the boat till the battery was flat, brought it and opened it up. First thing i got was a faceful of either smoke or steam or something. I checked the motor temp and it was too hot to touch, i splashed it with some water and it boiled off in seconds. I let it cool it down then had another run with a second battery. It came back hot again but I didnt quite run it aslong because i didnt want to risk any damage, i packed it away broke some more bits off and came home. I fixed all the damaged bits then dropped the b***** deck house!! I was quite lucky because it hit the hard kitchen floor and the only bit that broke was a 50 cal and it just needed sticking back on. Dont understand it.

I re tested the amperage to draw to work out why it got so hot. Its still only 10-15 amps which i thought was well within the limitations of a standard 27t 540 mabuchi. The motor is second hand so i think ill get a new one and fit a cooling coil. if that doesnt cure the heat issues ill down size the prop to a 30mm

Now youve read my waffle you can watch some youtube:

http://www.youtube.com/watch?v=CEBLJ757JA8&feature=context&context=C494aab3ADvjVQa1PpcFOvRVGjVP9sCyzeGfg0zNaeqY1ZxOjJUKY=
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MikeA

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Re: pt-109 build
« Reply #84 on: March 08, 2012, 09:58:36 am »

My budget it well limited now basically im down to a handful of coppers, and hadnt planned for the set back of the motor overheating. I need some oppinions. Im thinking instead of going for a 27t 540 i thinking about using a 545:


http://www.ebay.co.uk/itm/Electric-Motor-545-RC-Remote-Control-Cars-Boats-Standard-Size-5-Pole-/230740063773?pt=UK_ToysGames_RadioControlled_JN&hash=item35b92df61d

Im fairly confident that will do it and may not even have to bother using a cooling jacket/coil, what do you all think?
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John W E

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Re: pt-109 build
« Reply #85 on: March 08, 2012, 02:21:45 pm »

Hi Mick
that motor in your Link is the same motor that I have fitted in to the Swordsman Model when I upgraded from the first motor I fitted in, from a Johnson 600 to 545. and on a 7,2 pack and on full belt you can fry eggs on the 545 after10 minutes I think you will be better off fitting a cooling coil on the motor you have.

 

aye john

 
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MikeA

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Re: pt-109 build
« Reply #86 on: March 10, 2012, 12:36:19 am »

ordered a new motor and coil today. Also worked on the speed controller, seeing as it does the job it can stay. On the maiden run it go a little warm so Ive decided to plumb it in with the cold water feed.  Few problems arose and took some thinking to work out but got there in the end. Anyway heres what Ive done:



First off i wanted to fit a watercooled heat sink which seemed the simplest solution, that was until i found out that the top of the fets are live and would short out if bridged. I just thought it was the legs that had current in them.

 

The esc comes with 4 small heat sinks that fit over the fets, theres a fence between the fets that stops you from bridging the fets and causing a short. Obviously then a flat water cooled heat sink bridging all the fets in not an option, I even considered using a thermal pad between the fets and the heatsink, until i found out the thermal pad conducts current as well as heat, No good either! {:-{ I thought about a fan, but considered that the warm air would most likely circulate inside the boat and render the fan pointless. But then for some reason i came up with an idea of combining the two! A small pc cooling fan to cool the fets and what i can only describe as a water cooled air conditioning matrix.

I first soldered brass tubing into a square U shape and made the joint water tight so avoid leaky plumbing. I then soldered wire across the brass pipe work to make the radiator. You can clearly see it on the top of the esc. I checked to see if it worked by plumbing it with some silicone pipe to the cold water tap, and to my astonishment it worked better than i had imagined. The little rad went cold in seconds and after a minute or two even formed a bit of condensation on it!!  %% The pc fan was attached underneath and a box was made to surround the fan and the radiator togeather, the fan was then tapped into the bec circuit in parallel. The motor said on it 3w at 12v which by my calculations is 250ma. The bec makes a 6v supply so the fan is running slower than intended, it still causes a draft but i dont know how much current it draws like this, possibly 125ma? I then painted it matt black as this is the best colour for absorbing the heat out of the air into the water. I know that the rad goes cold but i still have to test weather or not it makes the air cold too. Its theory based at the minute so i got my fingers crossed till the paint finishes drying.
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MikeA

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Re: pt-109 build
« Reply #87 on: March 13, 2012, 12:18:38 am »

managed to get all the new motor and watercooling stuff in, bit of a squeeze but im happy with it. got to do a test run though to see how well it works.




 :-))
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Geoff C

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Re: pt-109 build
« Reply #88 on: May 29, 2012, 06:11:55 pm »

Hi MikeA,      Very nice job indeed, I've nearly finished one from the same plan pdf but I scaled it up to 35" loa.     If I ever build another one it won't be from balsa wood,  I'll use ply next time.       I glassed the sides and bottom and planked the deck with mahogany strips.     It has a 543 motor controlled by an Mtroniks viper marine 15 with a 40mm brass 3 blade ww2 prop l/handed.      Kind regards, Geoff.      Here's a few pics.
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Mad_Mike

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Re: pt-109 build
« Reply #89 on: May 30, 2012, 01:27:51 pm »

great boat. I noticed that you went with the access hatch rather than the vent on the back. that threw me actually and wasnt sure so i stook with the plan in casen i was wrong.
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Geoff C

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Re: pt-109 build
« Reply #90 on: June 01, 2012, 03:59:06 pm »

Hi Mike,    Yes, I did a load of research into 109 and it didn't have the large E/R vent and access as shown on the plan but everything else is correct.      The next job is a plug-in mast.         I  loved the video on youtube,  she can really shift.       Best regards,  Geoff.
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