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Author Topic: Higgins PT boat, 1/32  (Read 35180 times)

andrewh

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Re: Higgins PT boat, 1/32
« Reply #50 on: October 07, 2008, 05:07:39 pm »

Non-sequitur #2  - triggered by Andre

I watched the Scots Guards trooping their colour (mid 70s?) , with their colonel at the head - he was (and still is) Gregor MacGregor of MacGregor, who was also THE MacGregor (of that ilk). 
I mentioned this in Liege to a flying friend (as you do) and got the reply:  "Yes, I know him - went to his wedding in Invararray!"
small world, not many names!

i don't usually seal any wood inside a boat - I generally incline with Glyn Guest and let things drain and dry with the hatches open.
Howsomever you lot of Andrews, andres and andys have persuaded me to dollop the inside  - so I will have a go at the inside of the deck with my U-shaped brush for brushing round corners.  Actually I will probably hold a lump of foam in my fingers and sloosh the stuff in place! 
The hatch is easily coated - but I have a little re-inforcing to do first round the edges
Thanks for the explanation - I'm a little errrrrr; errrrrr;  slow on the uptake
andrew
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #51 on: October 12, 2008, 05:37:15 am »

Hi Andrew

Sorry it has taken so long to post a photo. I used the film cases as my machine gun tubs. I also had the hull fiber glassed at a fibre glass factory.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #52 on: October 13, 2008, 01:20:48 pm »

David - Looks very nice!

What motor, prop, please?  and have you had her in the water?

Speaking of which - this happpened over the weekend:


and also this


So I reckon I'm catching you-all quite fast :D
These pics are after 3 coats of nearly neat dope - good enough to be waterproof, especially with blue-tack in the propshaft hole
Funny thing making models - or indeed anything - I put about the same time in every day  - about 20 to 30 mins, but sometimes there is a lot of progress, and sometimes you move what seems like a long way!  It must be quantum, or something

I have realised that the original and all the replicas I have seen do not have the characteristic Higgins bronze exhaust pipes - these will be added when I find a good enough side view or drawing to be able to space them properly.

Now the doping on of the tissue - this is venerable heavyweight model tissue - applied wet (damp) and applied with thinners in the time-honoured way - it went on  very well, with (near-) perfect smooth surface, and reasonable edges.  I used one peice for the deck and hull bottom (slit along the keel for 1/3rd of the way back from the bow)


and this is the hull this morning getting its 3rd coat of dope

pardon the mess - I took her into the garage to dope at about 6.15 this morning - the lovely odour should have reduced enough to bring her into the house by this evening

andrew






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amdaylight

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Re: Higgins PT boat, 1/32
« Reply #53 on: October 13, 2008, 05:19:04 pm »

Andrew

" I have realized that the original and all the replicas I have seen do not have the characteristic Higgins bronze exhaust pipes - these will be added when I find a good enough side view or drawing to be able to space them properly."

Is this what you mean?   :-))

By the way you might want to explore this site "Save the PT Boat" ( http://www.savetheptboatinc.com/ ) it is a site where a group of PT Boat Veterans here in Portland Oregon are restoring a Higgins PT Boat. I am sorry it took so long for me to put 2 and 2 together and get 4, :embarrassed: and realize that you were building a model of one of the Higgins boats and there was a great source of photos and information right here in Portland.

Andre (Andy 1959)
over yonder in Portland Oregon
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #54 on: October 14, 2008, 06:56:09 am »

Hi Andrew

She has yet to undergo sea trials. I am going to use a Johnson 540 motor (I have 10 of them) and a 35mm three blade prop. I want to use a SLA battery as my brother is in the battery business. I have one of those EL ESC's that you get off Ebay (it was cheep, cheap) it is rated at 110amps and I think the motor might just scrape under that {-) {-). What I do have a problem with is the angle of the propshaft. I can not take it out as it has all been fibreglassed in and would be too hard (for me) to put in another tube at a different angle. What I would like to do is use a belt drive from the motor to the shaft (less noise than gears). That would give me room to put the larger motor on  a proper mount. I recall someone on the forum who uses belt drives on their models but can not find the post. If anyone has any ideas of belt drives and advice it would be most appreciated.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #55 on: October 14, 2008, 01:16:12 pm »

Andre,

Thanks for the link to the PT boat site - I was a little aware of it as Umi has posted us one of her videos of that boat in action (on the Hellcat thread).  So you are up in Portland, too - its an area I have always wanted to visit - I come from the West Coast of Scotland so sea, forests and weather are all familair.

Thanks too for the pic - this is one of the pics that I was going to take the dimensions off. 
It really is a goldmine because it shows the size and location of the exhausts, and the "chocks" ahead of them, and the way the spray chine rail stops at the rear exhaust (it also doesn't run quite to the bow)

David
I think you might squeeze in under 110Amps {-)
Will a gel cell survive the current draw?  I don't know which winding of motor you have, but it could take up to 30 Amps!  This would distress a gel cell, I think.
Removal of a prop shaft is not totally impossible - even if epoxied in.  Let me know if you really want it out.  i assume that it is at too great an angle so the prop is very low and the motor very high?
belt drive is a good idea - suggest that you find a suitable belt (they are sold by the model boat traders over here - and also used by all MFA olympus drives.
I will do a sketch when time permits - but basically you epoxy an aluminium (or ply or glassfiber PCB) plate to the existing propshaft tube with a good strong fillet for support.  You need a hole for the motor bearing housing and slots for the motor fixing screws (so you can adjust the belt tension)  Probably a speed ratio of between 2:1 and 3:1 seems good with a bigger propellor to suit (Glyn Guest suggests starting at about 45mm diameter with 2:1 ratio)

Sketch and URLs follow
andrew
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andyn

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Re: Higgins PT boat, 1/32
« Reply #56 on: October 14, 2008, 08:48:57 pm »

An SLA battery will most definately not take the current draw.

I had a 12v 5ah SLA in the club Perkasa, which got way too hot for comfort (SLA batteries shouldn't even get warm)

You would probably be best off going to component shop and getting one of their Ni-Mh's, I've now got one in the perkasa that lasted plenty long enough but nearly burnt the motors out. Nice plume of smoke coming out of them after about 20 mins...
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #57 on: October 15, 2008, 01:19:03 pm »

David,

Forgive the Janet-and-john sketch, please, but this would fit a belt drive to existing boat with prop shaft



Whatever you do please add good bracing so that the motor/drive assembly can't flap around :D

andrew - just one session from the water
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #58 on: October 15, 2008, 01:50:05 pm »

Hi Andrew

Thanks for the sketch, I will go down that path. However I will have to have the motor around the other way. Sort of in line with the propshaft as apposed to over it, as I would not have any room for the battery.

Thanks again.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #59 on: October 15, 2008, 02:14:27 pm »

Great, David, but even more need for the bracing to avoid destructive flapping :D

I use a lot of foam Polyethylene and polyproplyene salvaged from computer and similar packing - usually I use it as motor mounts by just cutting a trough of the same diameter as the motor case (using a dead motor case as a cutter) then rubber-banding (or tie-wrapping) the motor down to the block of foam and hot-melt-gluing the whole assembly in place
(I may yet do this on the PT boat - with motor cooling slots or watercooled coils )

andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #60 on: October 15, 2008, 02:30:58 pm »

David

The belts I was thinking of were:
http://quantrum.co.uk/redbankmodels/olympus-belt-drive-p-1363.html
http://www.mfacomodrills.com/timing_belts_timing_pulleys/timing.html

Admittedly all these are UK based - There used to be a 2:1 Graupner unit called the Speedgear - don't know if it still exists.

My scrap box has several suitable belts and pulleys salvaged from dead printers, etc

andrew

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bigfella

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Re: Higgins PT boat, 1/32
« Reply #61 on: October 16, 2008, 12:29:55 pm »

Hi Andrew

The Olympus looks ideal. I have bought a lot of stuff from Redbank in the past so no worries there. I do have a few questions though. Is it a motor mount or do you have to mount the whole thing onto a mount and then the boat. Does the threaded shaft have to be attached to the prop shaft via an in-line universal joint. Sorry about all the questions but I have found some new enthusiasm.

Regards David

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andrewh

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Re: Higgins PT boat, 1/32
« Reply #62 on: October 16, 2008, 02:34:20 pm »

David,

From the top: 
It was designed for IC engine replacement so it has flanges for beam mounting - not easily visible in the pic
so you might need to arrange something to give support at the right angle

I have an idea about how this might be atrranged - again easier to sketch than describe

I think its an M6 thread, I seem to remember so you would need an M6 or maybe plain 6mm end for a universal joint

Have you got a pic off your boat wit the hatch off - showiiing how far the prop shaft comes, and at what angle?
andrew
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andyn

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Re: Higgins PT boat, 1/32
« Reply #63 on: October 16, 2008, 04:20:05 pm »

Would one of these suffice, or three of them for scale...

http://robotbirds.com/catalog/product_info.php?cPath=56_102&products_id=961

You may have figured by now I quite like robotbirds...

Andy 1964  :-))
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #64 on: October 16, 2008, 04:52:19 pm »

Andy,

They would look to be ideal {-), but I can see an 11x7 prop might be a challenge and where would we put the touchpaper?

3 times 150 watts is er;  a lot of watts.

I had done a little figuring, and have a 15A bell motor, so with say 10V thats 150Watts (and good efficiency) and light weight whereas the S600 might be 10A at 7V  = 70 watts with  no more than moderate effiiciency.

And I have a spare channel and can reverse it with just a changeover switch on two of the phase wires.  I have been mentally working out an electrical interlock so that I can't reverse unless the throttle is closed

And two bell motors or other cheap 15A brushlesses  would be great - altho the structure would have to be modified to get appriopriate access.

andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #65 on: October 17, 2008, 10:00:07 am »

Disaster narrowly averted!

Had a short session last night - epoxied the propshaft, rudder bearing tube into the hull and assembled the motor mount from ply parts.  Opened a new pack of epoxy - using my favourite fast epoxy  - its called 151 and comes from a pound shop for guess how much.

It has always been reliable, hardens to a rock-hard state and takes 20 to 30 minutes at room temperature to set (Much, much less if I put the component on a light bulb or mosquito-killing heater :D)

Last night the new pack (twin tube dispenser) didn't want to dispense the brown component (it seems to crystallise in the tube nozzle) but I got a fairly even amount of both bits, mixed it very well (starbucks stirrer), added a little microbaloons for gap-filling and did the job.

 3 or 4 hours later it had not started to set , or even gell, so I prepared to worry, but left it overnight, and this morning it seems to be OK. 
I will give all the bonded parts a very good heat cure as well, to be quite sure (in fact I don't like the bare propshaft stickin' out of the bottom of the hull, so I will fair it with a 1/4 balsa strake and will have to mix another batch to do this and will cook both of them in one go (fan heater aimed carefully). 
I believe that support for the prop shaft is important  - I  am quite capable of putting the boat down unwisely, and hitting an obstruction at speed would certainly try to bend the prop shaft if it was unsupported

Has anyone else faired the prop shaft, or have you left it bare?

andrew
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Martin [Admin]

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Re: Higgins PT boat, 1/32
« Reply #66 on: October 17, 2008, 11:09:08 am »


I like a support for the tail end of the prop shaft, usually a triangular fillet on a planning hull.
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andyn

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Re: Higgins PT boat, 1/32
« Reply #67 on: October 18, 2008, 03:26:33 pm »

Heres the support on my I.C Huntsman, 1/32nd brass.

None of my other boats have one, even my big Zenoah catamaran has about six inches of exposed Flexi, so i dont think it'll be too much of a problem.

Andy 1964 :-))

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andrewh

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Re: Higgins PT boat, 1/32
« Reply #68 on: October 20, 2008, 12:37:17 pm »

Thanks for the replies, I would always aim to have lots of support for the propshaft, and have given it a triangular fill-in fairing, altho I could have made up a brass stern-bracket, maybe silver soldered

Sorry about the quality of the photos - I suspect that the camera is in macro mode (but can't easily check since the screen on the back is broken)




I see that the rudder tube is rather less than vertical :((
I have screwed in a floor made from satsuma ply  and mounted the rudder servo poking through it with a rather awkward angle on the linkage


BTW the t'other box on the end of the servo lead is my servo tester  - one of the best  6 quid 50p I have ever spent


On the water this week?
andrew


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andyn

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Re: Higgins PT boat, 1/32
« Reply #69 on: October 20, 2008, 06:45:35 pm »

What are you going to power it with batteries wise, and what motor have you settled on?

Those robotbirds motors would have been ok, the Tethered Hydro guys use airscrews that are cut down and balanced ok2
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Capricorn

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Re: Higgins PT boat, 1/32
« Reply #70 on: October 21, 2008, 04:09:17 am »

It's looking great Andrew.  I will be interested to see the motor and battery set up too, I'm sure you  have it well figured.  I would have thought you'd replaced your camera by now, but I imagine you can get a pretty dandy motor and battery for the price of a camera.  You will need a new camera to take the movie though right?  Looking forward to seeing it under power.  Cap  (or Andycap as you say)   
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #71 on: October 22, 2008, 02:07:47 pm »

Thanks for the comments. 

I am on a deep economy setting now and for the foreseeble future so all the gear will be what I have, or can make
This makes Andy's question simpler to answer  :}
No new camera, too, for the same reasons!

Motor will be either a Hummingbird 15, a very soft flight motor from the dawn of time, a Speed600 Eco, or a bell motor (brushless); batteries will be initially a 6cell 2100mah buggy pack, possibly an 8-cell sanyo2000 flight pack or a load of Li-ions  (2S:3P?) reclaimed out of computer batteries.

Invidentally I notice that  at work our drills run on 35V, 1.3AH packs (hundreds of them!)  on investigation they are Li-ion, obviously 10S, 1P, and each cell is clearly able to handle reasonable amps - If I could reconfigure one as 3S;2P I reckon i would be on a winner, except that they don't belong to me :((

Motor mount tonight, possibly followed by trials :} :}
before painting I will fit the spray rails, exhausts rubbing strakes and probably the toe rails as well

Does anyone have a good way to make toe rails?
I am thinking of making two together, out of 1/16 styrene, by drilling holes for the rounded inner shape, cutting out a slot to join the holes - then slice into 2 parts for finished rails

andrew
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #72 on: October 23, 2008, 01:56:47 am »

Hi Andrew

I made my toe rails by cutting lollipop sticks in half length ways and using my dremal scalloped out the holes, after sanding them to size. It does not look perfect but it was the only way I could think of how to make them.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #73 on: October 23, 2008, 08:16:21 am »

David, thanks, thats a very workable solution.  I use lollipop sticks and stirrers a lot for strip wood and packers.

How do you get them to follow the curve of the deck edge?  That's the reason I was thinking of styrene.

Got the motor mount ready for installation this morning - it will also (initially) be screwed down.
While playing with the motor/coupling/shaft i noticed the reason that I originally "retired" the Hummingbird motor - it suffered a bent shaft in one of my "tent-peg" landings. 
So the S600 eco it will have to be - I will equip it with supression and flying leads

I also noticed that the local boat shop have sold me the wrong coupling end for the shaft I am using (which I bought at the same time) its probably usable but not good.

andrew

 
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #74 on: October 23, 2008, 08:50:00 am »

Andrew

What I did was cut the stick into three once scalloped and then glue into position following the curve. I filled the joins with CA and micro sawdust from the sanding. I know it is not completely curved but I think it looks OK after all trees are not curved {-) {-) {-). I also used these sticks for making the radar mast, they are very handy things. I am unsure of the type of motor you are using (it must be for Aircraft) It is a bit of a pain when you get home from the hobby shop itching to go and they have given you the wrong bits.

Regards
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