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Author Topic: Higgins PT boat, 1/32  (Read 35177 times)

andrewh

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Higgins PT boat, 1/32
« on: August 20, 2008, 01:15:54 pm »

AndyN, Umi and the rest of the Mayhemmers have a lot to answer for!

They helped with such wonderful information while I was building my "cartoon" scale Higgins Hellcat that I was inspired to build a more-scale model of a MTB/PT boat.

AND, while I was competing at the Footy Nationals at Aylesbury (don't ask) my young son and I saw a couple of large Perkasas (one badged as PT109  :-\) and we decided to make (together) something large and FAST.  So when we got home I dug out the candidate plans and Angus unhesitatingly selected the 78foot higgins boat by Peter Miller (model Boats free plan just after the roman invasion)

(The candidates, by the way, were Glyn Guest's PT boat, his Miami crash  boat, and his Hellcat - all, I think 1/32nd scale)

So, having read the plans and article several times and checked the balsa stocks, off we went:

Photocopied (all-in-one printer) the formers (Peter calls then F1 to F8 - he is, like me a aircraft modeller)
What are they made of? - not on plan or in description, but photos appear to be ply (other builders have used ply and 1/8 balsa)
I aimed to use satsuma ply (recovered from scrap fruit boxes) but that source has dried up at the moment
So I used 3mm ply from the local DIY store - this is thin enough to be cut with a big knife (but I did destroy my cutting mat with the force used!)
Wisdom of hindsight suggests that liteply would be a good material, or satsuma wood, or balsa ply.  I would not suggest 1/8 balsa sheet as I think it would be weak and prone to splitting with the grain during the build stresses.

The stack of formers seemed to be a bit heavy - so I added a lot more lightness with a holecutter.
The construction goes on "in the air" with the use of a slotted jig - I found that my table saw produced a slot which was a good tight fit on the former ply, and I glued the formers into the jig with a spot of balsa cement (quick drying and I could easily break or dissolve it out later!)

Keel cut out and fitted - I made the keel and formers to plan, but thought that the keel stuck out too much from the formers, so I notched the keel the make half-and-half joints with the formers and fitted it.

The deck and chine stringers are 1/4 square, but I didn't fancy making the bend at the bow (I could do it but would need the kettle, a waning moon, some ammonia and a virgin to sacrifice) so like other builders I used two laminations of 1/8 x 1/4

The stringers "land" at the bow on solid 1/4 balsa "sub-decks" - they may be visible in the bow pictures labelled S1 and S2.  When I cut them out and offered them up there was clearly something missing - of about 1/4 inch thickness.  In fact there needs to be a stem plate between them - its in the Peter's pictures asa part, butI can't see it on the plan! 
Anyway easily made and fitted, followed by the sub-decks and stringers

I will stop there for now - and anticipate the completion
1/32 nd scale - final length about 36 inches
Power:  500 or 600 type motor - direct drive, 36mm racing prop
cells;  2000MAH 6 or 7 cells buggy pack
Colour scheme:  to be determined, but not the single-colour khaki-green.  perhaps one of the Zebra/dazzle schemes?

Your feedback, please
Too much/ too little/shut up, andrew/other

andrew




   
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BreezyB

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Re: Higgins PT boat, 1/32
« Reply #1 on: August 20, 2008, 06:17:07 pm »

Yep, I'm in!!. Keep it going Andrew.
Barrie.
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tigertiger

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Re: Higgins PT boat, 1/32
« Reply #2 on: August 20, 2008, 08:22:06 pm »

Yep keep it up.

As much detail as you have the time to input is always good. There is always somebody who will use the knowledge.


Thanks for sharing.
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andyn

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Re: Higgins PT boat, 1/32
« Reply #3 on: August 20, 2008, 10:44:45 pm »

Ooo it's all kicking off now  O0

Have a look at http://www.pt-boats.net/  -  wow!!!! gotta get me one  ;D

Keep it coming

The other Andy  O0

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andrewh

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Re: Higgins PT boat, 1/32
« Reply #4 on: August 21, 2008, 02:07:05 pm »

Thanks for the responses - I take them as positive, thanks

Time is short today - I work with the US and they have woken up today

Couple of pics  - word to follow

Barrie - glad to see you are out there.  How goes the Hellcat?
BTW, when I dug out the 540 size motors I found:
A MFA power 15 (flight 540 that used to fly my EMP Silent Knight)
Speed 600 Eco
An Overlander buggy motor - fairly "hot" wind
Two salvaged 540 s from Black and decker screwdrivers (2.4 and 3.6 V labelled)
A carriage drive motor out of a Printer with ribbon cable - has about 365 poles and more torque than a politician

The S600Eco sounds like the favourite on 35mm graupner prop and 6 or 7 nicad buggy pack

andrew

andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #5 on: August 24, 2008, 07:57:10 am »

So here we are, Formers and keel finally assembled in the jig, stringers stripped from sheet
How do you strip material from sheet?
WhenI embarked on my Thames barge there was  a lot of parallel strips required to be cut from 1.5mm styrene sheet, so I made myself a little stripper which scores a line so that a strip can be snapped off.  It works also with a no.11 blade in place of the scoring operative point (or Pin as mortals call them)
Takes nearly a second to make so its quicker to make a new one than find the previous version
Pic follows when I take one!

It is now evident (see the pictures of the stringers lightly clamped in place) that I can either glue and clamp the tringers in the slots and have a very wavy boat, or allow the stringers to take a fair line and sdjush several of the formers.
Where is the error?  Dunno.  I make mistakes for england, but the formers cannot be more that 1/2 mm from the drawing (they stilll have the paper copy pasted to the front side); and they cannot be mis-spaced fore and aft enough to give errors like this.
I could investigate with a ruler and dividers but its an old plan and life is short.  (I am certan that the original did not have the problem - this would not be Peter Miller's way and he would have mentioned it)
So I am going for the fair curve, even if the stringers "miss" two of the formers by up to 3mm.
Glued (PVA) the first four 1/8 x 1/4 stringers in place, (not wetted or pre-bent) - left to dry

more later

andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #6 on: August 26, 2008, 12:58:06 pm »

Second stringer lamination added - using white glue and all the clamps possible (clothes pegs)

The side planking of the boat is 1/8 balsa applied with the grain vertical so it was out with the sanding block and sand the "sides" flat for the planking to fit on.  When I started it became clear that the bow section had a lot of twist and was too much even for the medium-soft 1/8 balsa I was using, so I covered the last 2 inches of the bow after the rest of the side -planking had dried. 

You can't have too many clamps, can you?  I buy packs of them occasionally when I see them in "pound" shops.  I needed all of them and a few bulldog clamps as well for doing the side planking.

andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #7 on: August 26, 2008, 01:12:04 pm »

Two bits of backtracking.

Before doing the side planking I filled gaps between the formers and stringers in the two places where smooth and beautiful lines required that the stringers missed the slot in the former.  These had slivers of balsa inserted and sanded smooth when dry.  I also ran a batten over the formers to see if the planking would run smooth, and built up the "shy" formers with balsa strips cyanoed in place.

There, I have confessed to you, I'm not perfect, and my boats contain "adjustments" as required

I mentioned a balsa stripper - here are a couple of pics.
Body is HARD balsa (tea cheast wood) and the fence down the edge is a bit of coffee stirrer or similar hard wood or ply
width of strip is set by measuring from the fence and inserting the no 11 blade or scoring point (pin) through the wood at that place!
Highly technical, innit.
I'm a southpaw so the "in action picture shows it being held against the left edge of a sheet  - several light cuts are better than one heavy one (BYKT)

andrew
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andyn

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Re: Higgins PT boat, 1/32
« Reply #8 on: August 26, 2008, 04:34:17 pm »

The poor mans balsa stripper {-)

Mines a plastic job from SLEC that came with a 4 foot rail and various adjustment pieces

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Capricorn

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Re: Higgins PT boat, 1/32
« Reply #9 on: August 29, 2008, 02:49:03 am »

It looks great Andrew!  I think it will fly by the time you are done with it.  As with your other boats, the lightweight will pay off I'm sure.  I like the jig you used, getting the frames straight is critical of course.

I still use the metal yardstick and blade (meter stick I suppose now), long ago I sliced a piece off my thumb doing that, nothing too bad, it grew back, no flat spot even, but have been much more careful since.  Tends to yield beveled edges but sure beats ripping them with a saw.  The yardstick method doesn't produce constant width either but usually close enough for me.

Joe
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #10 on: September 15, 2008, 12:54:41 pm »

After a slight gap in building things have got under way again :)

Andy - I had one of these strippers, but the size and length meant that I was nevver likely to have it to hand when needed - I also "created" my cheapo stripper when I needed to follow curves when building a Thames sailing barge - so the original design had two map pins to follow the curve  instead of a "fence"

Planking of the bottom started and finished  - this morning at 06.00

Planks next to the keel were straightforward (garboard strakes).  MEMO TO SELF - NEVER plank again with ANY joints like this - I should have run a balsa bearding strip along the side of the keel for the plank edge to land on. 
There is a lot of twist, quite a bit of taper in the garboard strakes, and a little taper on the next two planks away from the keel - all the rest are parallel and 3/8 wide.   Any wider than this and the twist would become difficult




The snag of non-fitting formers reared its head - normally I plank onto balsa formers and have no difficulty pinning the planks in good contact.  This hull has ply formers and it took a bit of thought to keep it all fair.
I used white glue for all but the two final closer planks - these are actually at the edge, and used PU glue for these - because it sands very well, and there was at least the possibility of some gaps needing to be filled - and PU expands as it cures.



While I was playing with the PU glue, I put a dollop in a mixing cup - added an equal quantity of water, stirred hard and fast and ladled the pink (this PU cures pink) frothy mess into the forepeak (the triangle at the pointy end) to see it it would expand and fill the space

It did, and before I cut the surplus off I will take a picture or two
So I have bonded the entire bow together, gained a little buoyancy foam and learned something all at the same time

Can't be all bad
 
Next sanding and deck!
andrew

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andrewh

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Re: Higgins PT boat, 1/32
« Reply #11 on: September 18, 2008, 10:38:56 am »

Bottom planking finished and sanded - actually one of my favourite jobs

I have not taken the sanding to the final surface, since the lower bow is later made of block balsa, and this will need considerable sanding/persuasion to fair with the bottom planking.  Holding the bottom up to the light shows a few thin areas, which I will reinforce on the inside if necessary.

I have decided to finish with dope and tissue (out of doors) not least because I love the smell, and have mumblety years experience dope and tissue covering.  It will also be a good base for a car primer spray finish.
I am not decided on the final paint scheme, but I'm seriously tempted by the Zebra stripes!  I certainly want someting other than allover grey or (far worse) allover green.  Did any Higgins ever get a north atlantic splinter scheme like a flower-class?

Bottom planked and sanded

close-up of my bow filling experiment - the PU foam is pink

bottom view

I had mental and physical trouble with the plan where the planking met the keel.  Plan sections show the bottom planks covering the keel towards the stern, but clearly fitting against the side of the keel in the bow half of the boat.  I compromised by running the garboard planks so that they fitted the sides of the keel at the bow, and carried on to the stern with a 1/4 inch gap, which I later filled with another plank glued in with PU glue.  THIS is why the prop shaft and rudder tube holes are invisible! ;D
Sharpened tubes will recut them thru the final plank

You do collect dead radio aerials don't you?  I take them apart and use the tubes (slightly sharpened) to cut holes in soft woods, etc, plastics when heated and my left palm (always)
andrew



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andrewh

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Re: Higgins PT boat, 1/32
« Reply #12 on: September 18, 2008, 10:42:14 am »

Preview of the bow block as glued (I have already removed a big clamp)

To carve this roughly to shape I will use the long blade out of a "snap-off blade" craft knife - usually I have to take it out of the knife to get the angles and access required, but they are SERIOUSLY sharp when new

andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #13 on: September 19, 2008, 10:55:14 am »

Comin' at Ya


and leaving

There is a 1/4 balsa transom cover to come before deck planking


andrew
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dreadnought72

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Re: Higgins PT boat, 1/32
« Reply #14 on: September 19, 2008, 03:29:14 pm »

This is a great write-up of a great build. More please!

The other other Andy
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #15 on: September 22, 2008, 10:36:41 am »

OYEZ;  OYEZ!
BE IT HEREBY KNOWN AND DECREED!

You don't have to be christened Andrew to post here (even if it helps)

Andy - thanks for the comment - its not a patch on your magnum opus, but it pleases me and my lad

Brilliant sunshine over the weekend so I did the bow block sanding outside - always more pleasant

The bow area needs another block or two letting in, but is then within reach of filling with Polyfilla

Made the basis of a stand - I use huge sheets of polythene foam and cut them with a breadknife (I know - it looks like it)


I may cut a slot in the entire forefoot and insert a 1/32 ply piece - cos this is where the impacts will occur



I'm pleased with this - I have punched the prop shaft and rudder tube holes through the skin
Transom doubler, Hatch outlines and deck planking next

andrew


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andyn

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Re: Higgins PT boat, 1/32
« Reply #16 on: September 22, 2008, 08:27:52 pm »

They did have these in splinter camo, see the Hellcat thread.

Another Andy  O0
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #17 on: September 23, 2008, 09:47:36 am »

Hi Andy

Looks good. I started this same boat about two years ago after acquiring the part finished hull. I have yet to complete it (I think I am a bit of a procrastinator). I am enjoying your build and wondering if you are going to scratch build the torpedoes and guns and other fittings.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #18 on: September 24, 2008, 06:53:21 am »

David,

I,  too, plan to take up procrastination, but probably later sometime,

and yes I aim to scratchbuild the guns and torpedoes - In the original plan that is what Pete Russell does and my scrap box is probably similar to his (only younger)

I made a "Cartoon" higgins hellcat and the torpedoes on that were rolled paper tubes with blue foam ends and plasticard fins

How far have you got with yours?   Pictures, please ;D

andrew
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #19 on: September 25, 2008, 11:47:10 pm »

Hi Andy

I am at the stage of painting and then assembling the fittings and guns and the like. However I have inherited a problem from the previous owner. The propshaft was put in at an angle for a 380 size motor which would not be enough power for a boat of this size. I have a 540 motor and I am concerned about  how the motor and propshaft align. There is no room for the motor to go at a better angle so will have to find a really flexable coupling. I will have to take a couple photos and post them.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #20 on: September 26, 2008, 06:47:56 am »

David

So the build is well advanced

You would seem to have several motor options - you could fit a 380 size brushless, or a beefy 380 size brushed motor like an AP27 , or you could modify the shaft to gear or belt drive (if you can get a bigger prop in there) or you could remove the offending propshaft.

If its buit as the plan the keel is balsa - I wounder if you can determine what the glue is holding the shaft?  It MAY be possible to find a tube which fits down the ourside of the prop shaft tube, sharpen the end till its serrated, chuck it in a cordless drill and attack from the outside - it will be  a lot easier that describing it and the existing shaft &tube can be cleaned up and re-used.

And of course you can re-insert it to suit your 1000W brushless outrunner ;D ;D or whatever

Hope this helps and pictures, please, especially of the hatch area

andrew
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bigfella

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Re: Higgins PT boat, 1/32
« Reply #21 on: September 26, 2008, 08:52:44 am »

Andrew

I altered my hatch (i have two) so that the front of it slides under the front cabin. The rear of the front hatch will be attached with magnets. The second hatch just drops in once the front is in place and it too will be secured with magnets. I will have to take a couple of pics over the weakend.

Regards David
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #22 on: September 26, 2008, 10:08:58 am »

David
TIA
andrew
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andrewh

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Re: Higgins PT boat, 1/32
« Reply #23 on: September 26, 2008, 01:16:06 pm »

CONFESSION TIME >:(

While fitting bow blocks to tidy up the bow area I peered down the run of the planking, held it up to the light and ran fngers along it (as you do).

Many of the planks are no longer glued to their neighbours, and are free therefore to twist and to run away from the sanding block!
Not a disaster, but a palpable setback!
I planked with a new bottle of PVA glue from a trade counter - it is enormously concentrated, thick and seems to dry hard and brittle.  I had added as much water as I could get into the bottle, but the glue was still too viscous.  I normally use PVA well diluted so that the water penetrates wood fibres.  So I have probably caused this failure by using the glue without diluting it enough. 
I am certain that there is nothing wrong with the glue - indeed the quality is just too good for my need with porous woods.

So, how do I recover from here?
There isn't an overall problem - because I will be covering the whole hull with at least tissue and dope, which will bond the whole enchilada together.
However I would like to re-bond the planks before finishing the sanding.  Hence the method has to allow me to sand afterwards.

My favourite plan at the moment is to dollop the same pva (better diluted) onto the inside of the hull, and squooge it with a squoogee into the gaps between the planks - they can move enough to allow this to happen. 
If I have run strips of insulating tape down the outside to prevent the glue marking the bottom, this should work. 
In fact, while there is wet PVA on the inside of the planking I could lay down strips of fleece to bond it all together
 
Any better advice, please?

MOTOR MOUNT
The plan method is vertical formers with semicircular cutouts for the motor - which is held in place by a metal strap tensioned by self-tappers into some blocks on the base
The base is designed to fit exactly beween two of the bulkheads, more or less level
I will be folllowing this generally, but I prefer rubber bands to hold the motor down (or tywraps) and I like to prevent the motor spinning with some form of rubber friction mount.

So its out to the garage to try the hole saw on some of the same ply as used for the formers.  The nearest hole was about 3mm in diameter bigger than a 540 motor - perfect



a length of silicone fuel tubing slit along one side makes a great packer-and-friction device



This will work well - I need to make a bit of liteply to fit between the relevant two formers, (I would sit it on a couple of 1/4 square bearers glued to the face of the bulkhead) - I could even just screw it down to the bearers so that it could be changed out for the brushless ratmotor later in life - or the twin zenoahs if AndyN proves persuasive

andrew (unnumbered but genuine)


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amdaylight

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Re: Higgins PT boat, 1/32
« Reply #24 on: September 26, 2008, 04:44:16 pm »

I think that I would use an epoxy, does two things for you, first it glues all of the planks back together O0, second it will water proof the inside of the hull  O0 O0. You won't need to add and glass cloth, just epoxy will be strong enough. I usually thin the epoxy about a third with denatured alcohol so it penetrates better and I apply it with what we in the states call an "acid brush". They usually have a metal handle and black plastic bristles. And then I toss the little buggers in the trash because they cost me about $.12 each when I buy them by the box, 144 in a box.

Andre :)
Over here in Portland Oregon
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