Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: 1 2 3 [4] 5   Go Down

Author Topic: Higgins PT boat, 1/32  (Read 35312 times)

amdaylight

  • Guest
Re: Higgins PT boat, 1/32
« Reply #75 on: October 23, 2008, 05:02:17 pm »

Andrew

What you do with your Popsicle sticks is soak them in hot water or water with ammonia in it (till is easily bendable, it may take a half hour or so) and then bend them on a form that is close to the curve that you need and secure them to the form and let dry, once dry they will hold their shape and you can glue them in place. I also drill a small hole all the way through the toe rail and insert a piece of wire through them into the deck to pin them in place. Once you fill the hole for the pin, sand and paint you will never know the pin is there but it will make the toe rail much stronger. I would pin all of the details that are going on the deck just for strength.

Andre :-))
over yonder in Portland Oregon
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #76 on: October 25, 2008, 02:08:19 pm »

Thanks for the popsicle hints, Andre, I use them for lots of constructional uses as well as glue mixing, etc.

 :}WELL :}
Trial run today!

Motor in place


Floating in running trim

She runs :} :}

instant assessment - Staggeringly noisy, motor,  ESC and battery cool after 20 mins running, scale-looking and very safe (and Dull)

more in a minute
andrew

Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #77 on: October 25, 2008, 02:15:54 pm »

I have under-propped the motor (35 mm) and the S600 is a huge beast, I think I will try a little 540 buggy motor I have  - much lighter and hotter



Not easy to take pics with one hand




See whaT i MEAN ABOUT THE NOISE!

andrew
Logged

The long Build

  • Guest
Re: Higgins PT boat, 1/32
« Reply #78 on: October 25, 2008, 02:18:48 pm »

Looking good.. :-))

Logged

amdaylight

  • Guest
Re: Higgins PT boat, 1/32
« Reply #79 on: October 25, 2008, 10:19:01 pm »

Looking great  :-)) O0 :-)) O0, about the noise I don't know I didn't hear a thing (no speakers on the computer %) ;)).

Andre
over yonder in Portland Oregon
Logged

Tug-Kenny RIP

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,625
  • Location: Newport. S Wales
Re: Higgins PT boat, 1/32
« Reply #80 on: October 25, 2008, 10:49:58 pm »


Could it be noisier because the hull is empty at the moment?

ken
Logged
Despite the high cost of living   .......... It remains popular

andyn

  • Guest
Re: Higgins PT boat, 1/32
« Reply #81 on: October 27, 2008, 12:44:07 pm »

That noise is the drive system vibrating, could do with an oiler on the shaft and some grease in the coupling.
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #82 on: October 27, 2008, 04:09:59 pm »

Thanks for your noise observations - I'm sure that they are all true
I will trace and fix the worst of the noise before long - probably when the boat is hauled ashore for painting.

A few more observations from the first test (6cell nicad pack):
  • Boat very "dry"
    Prop appears to be cavitating at all speeds above half throttle
    Prop CERTAINLY cavitating when the rudder is put over  - even a small amount
    Safe to use full throttle and rudder at the same time
    Goes astern, but steering not wonderful.
    Radio range pathetic!  Some idiot  had not connected the Rx aerial, not taken any wire to the test area.  I had to poke the 3inch stub of the aerial vertically up thru the hatch and this gave me about 35 yards
    Balance appeared fine
    Bow wave thrown out "sideways" like a pair of wings
    Not exciting :((

HOWEVER
This morning at dawn I slipped in a 7cell pack of 2000SCs and gave her another test run:

Fast , not entirely safe handling
wet - water splashing over the deck
Turning, even a little at full speed led to digging in the inside chine, the bow dipping and getting very wet
(I will fit the spray rails next!)
Motor, ESC and batteries still very cool after 20 min running - I am still radically underpropped
The pack is very heavy - also the motor so the boat weight is considerable - I'm sure the right answer is 2S Lipos and a lighter motor

So this is the way to go: and if a little is good, more is better and too much is just enough :} - I will try 8 cells and see what happens!

Another trial, weather permitting, at dawn tomorrow
andrew o/c PT boat
[/list]
Logged

dreadnought72

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,893
  • Wood butcher with ten thumbs
  • Location: Airdrie, Scotland
Re: Higgins PT boat, 1/32
« Reply #83 on: October 27, 2008, 04:44:57 pm »

Would it be an insane suggestion to move the batteries depending on the motor speed? That is: all stop - waterline perfect. Full speed - batteries head transomwards?

Andy #1963#
Logged
Enjoying every minute sailing W9465 Mertensia

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #84 on: October 27, 2008, 05:01:49 pm »

Andy - thats direct thinking!  It seems that Higginses more or less do this automatically - they lift the bows as the throttle increases. 
This one - probably because of the absence of spray rails (today) did all the characteristic bows-out-of-the-water stuff, but tucked in a "shoulder" as she rolled into the turns"

It was with a big, heavy pack, so I will try 7 cells and a lighter pack, also 9.6 V and see what happens! 
As the current is very low (must be around 5A) I can try 8- pencell packs, of which I have lots from kids toys.  Might also solder up a heavy-duty Li-ion pack or use a laptop battery as is (3S, 2P) and see how that goes!
andrew
Logged

Shipmate60

  • Global Moderator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 5,611
  • You bark - I will bite!!!
  • Location: Fareham
Re: Higgins PT boat, 1/32
« Reply #85 on: October 27, 2008, 06:26:59 pm »

Andrew,
The noise sounds like driveline vibration.
In your pics there is a lot of unsupported weight revolving.
Is it possible to move the motor aft but shortening the inner propshaft.
If the outer prop tube is well supported at both ends this cant vibrate.
But with the length of the inner prop shaft and the unbalanced coupling there is a good possibility that the vibration is comming from here.
If it isn't possible to move the motor would it be possible to fit a small outer shaft epoxied into the hull.
This would only leave the coupling unsupported.
One last point, check the coupling ends as I have had some of these bored off centre!!

Bob
Logged
Officially a GOG.

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #86 on: October 28, 2008, 12:23:03 pm »

Bob,
Thanks for your reply - it certainly is driveline vibration.  I may have mentioned earlier that my local supplier of boat parts has supplied me coupling fittings which essentially do not fit the propshaft.  So the coupling is not running true.   

 :}Holy grigoli! :}
had a session in the ice this morning (6.30am at Blaby wharf) tried 9.6V (8 pencells) and this is the dog's appendages. Got about 10 minutes running, good fun and some poor pictures!
However they do show how she looks at speed - the front  is well lifted!

 
Blurry - but see what I mean about the "wings" - the bowwave is rolled out sideways



Not great pictures - I plead shortage of fingers and eyes

Steering habits - I'm getting used to her now - even with a the light battery pack she dips a shoulder and nearly stops in turns at full speed - next step is to add spray rails which should reduce this a bit. 
Turns left much tighter than right - might be prop torque or my lousy rigging of the rudder linkage
Full power in reverse gives impressive speed, marginal steering and a fast stop

OK, so this motor needs at least 9V to be interesting, and the current draw is not excessive.  The pencell nicad pack is probable rated about 1AH, so if it lasted 10 minutes it was drawing 6A approx - this seems close to other estimates. So a Nimh pack of pencells should nearly double the duration - and Li-ions will increase it a lot more

Still to try - an Overlander buggy motor - I willl return to 6cells to begin with
Outrunner bell motor - need to rig up a reverse (nother servo with microswitches)  and find a coupling for it

andrew
a little euphorious




Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #87 on: October 28, 2008, 12:32:36 pm »

Whenever I see models or full-size boats in a posture like this I am sure that they would go faster on the same power if we could get the bow down!

I am thinking strongly of fitting a (non-scale) adjustable planing tab at the stern to:
Get the bow lower
Lift the stern
reduce cavitation by preventing air entering from the stern
I'm thinking of something about 30mm wide, the full width of the bottom of the transom
I could either make it in perspex or similar plastic (so its not very visible) or include it in the Zebra camelflage so that you wouldn't know what your eyes were seeing

Could any speedboat experts tell me (a)  if this is a worthwhile idea
and (b) if  speedboats use flexidrive to get the prop drive axis more parallel to the  water?

TIA
andrew
 
Logged

andyn

  • Guest
Re: Higgins PT boat, 1/32
« Reply #88 on: October 29, 2008, 05:05:07 pm »

A flexi has to be slung out at the back of the boat to have meaningful effect, which would mean having strut / stinger, rudder at the back etc, so wouldn't be feasible, trim tabs should be fine, but should be of metal construction, as perspex would need hinges and bolts to angle them, best off for a boat this size with a couple of strips of soft ally sheet epoxied to the underside or transom, because the stress is minimal, and you would be able to angle them with your fingers. You could paint them in matching hull colours and the bits sticking out water colour for camouflage.
Logged

amdaylight

  • Guest
Re: Higgins PT boat, 1/32
« Reply #89 on: October 29, 2008, 08:43:45 pm »

Andrew,

Before you get too worried about how she runs see if you can't find some photos of a pt boat at full throttle, you may find that she is running the same way the full size ones ran. If you look at the way the real ones were fitted out with all of their gear. The engines, torpedoes, fuel, and the largest gun were all in the rear. The only thing forward were the crew quarters, bridge, chart room and a fairly light gun. So I was thinking that they must have run with their bout of the water due to the weight in the back of the boat.

Andre
over yonder in Portland Oregon

PS I seem to remember them riding high in the front in movies but I may be mistaken. %)
Logged

andyn

  • Guest
Re: Higgins PT boat, 1/32
« Reply #90 on: October 29, 2008, 09:04:17 pm »

Higgins Pt Boats sit with the bows just clear of the water, so yours should be fine.

My Hellcat has somehow decided to be way too fast at full throttle, and sits with the waterline halfway along the hull and the tail nearly out of the water, planing and riding over waves like theyre not there, has the powerboats it lives with's blood running through it's veins. Because the powerboats it lives with have no blood left ok2

To reduce cavitation, you need to re prop, possibly a brass racing prop.
Logged

Hannu

  • Guest
Re: Higgins PT boat, 1/32
« Reply #91 on: October 29, 2008, 09:29:11 pm »

Andrew,

Agree also, by referring your photos, it sits  very nicely with scalelook attitude O0

BR,
Hannu
Logged

bigfella

  • Guest
Re: Higgins PT boat, 1/32
« Reply #92 on: October 30, 2008, 12:13:57 am »

Andre & all the Andrews

I note with the photo of PT658 that the machine gun tubs are further back from the helm than other Higgins I have seen. Is this a later design?  See the photos below.
Logged

andyn

  • Guest
Re: Higgins PT boat, 1/32
« Reply #93 on: October 30, 2008, 03:07:20 pm »

Forgive me for my ignorance, but which PT is it you are building Andy number 1?
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #94 on: October 30, 2008, 03:56:12 pm »

AndyN,

Forgiveness is granted you :}
Believe me , if I knew I would tell you - Peter Miller is non-exact about the type or specific number, and I am too.  It has roll-over the sied torpedoes, but a whole slew of assorted guns.  I instinctively like the earlier boats like 235 pictured  (or retouched) but don't want the highly-angled tube launchers.

I'll let you know the moment I do - I have all the pics on 658, but still want the zebra scheme

Hannu, thanks for the comment - this was some trial outings to see what I could learn  - and I have liked what I saw.

I would, of course like to get some weight out of the boat - I have a 540 buggy motor which should do the trick without drawing more than 30 Amps :}, and I will make up some 2S;2P li-ion packs.

But mainly fit the spray rails, gunwale rubbing strip and stern bumper as well as the basic deck clobber then get lots of pale grey paint on her.

I am wortking on the theory that the Zebra camelflage measure would have been black on white, but I will use dark grey on light grey with tiny additions of "other"
andrew
(been sidetracked to finish my submersible Footy racing yacht - as you do)

Pic of ZBF on the right next to my Razor on the left
 
Logged

bigfella

  • Guest
Re: Higgins PT boat, 1/32
« Reply #95 on: October 30, 2008, 07:57:10 pm »

Hi Andrew

I have more photos of Higgins like the 235 if you would like me to post them. Myself I prefer the torpedo tubes and I have seen them in line as apposed to them being on the angle. The tubes have a system when ready to launch of being manoeuvred outwards so as to clear the sides of the boat and then be retracted.

Regards David
Logged

andyn

  • Guest
Re: Higgins PT boat, 1/32
« Reply #96 on: October 30, 2008, 09:35:23 pm »

The problems with the tipping topedo launchers always was that the sea corroded them and they stopped working, so crew members literally had to kick the torpedos off the sides of the boat.
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #97 on: November 03, 2008, 03:14:27 pm »

Andy, I can well imagine this happening! 
There is nothing quite like kicking a primed Torpedo with a pair of contra-props which can spring to life any time :}

Well its been a Good news, Bad News weekend (PT boat wise)

Good news:  The coupling I have fits the shaft exactly - and always did!.  The Graupner shaft is stepped down from 3mm to about 2mm for the last 20mm of length - I was trying to fit the coupling to the 2mm portion of the shaft - shows how much I know about boat hardware :} 
That explains all the thrashing, vibration and noise when running.

Bad news - I had unkind thoughts about the supplier of the parts

More good news:  I have fitted the spray rails and rubbing strakes, and got them dope-sealed, made good progress with the deck house.  I am taking the layout and detail of this from PT568.  The gun tubs have been cut from a length of plastic tube I have of the right diiameter with the top flanges from styrene sheet cut with a circle cutter. 
I aim to get most of the fixed deck fittings in place before diving in with the paint primer/undercoat

I will do a post on the spray rails later just in case it helps anyone getting close to that task :}
andrew
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,069
  • Location: Melbourne, Australia
Re: Higgins PT boat, 1/32
« Reply #98 on: November 05, 2008, 01:08:17 pm »

Spray rails etc.

Hull is covered in heavyweight tissue and doped heavily, so its time to fit spray rails, rubbing strips round the edge of the decks and a bumper across the transom (seen in restoration pics of PT658)

A quick scout through the strip wood I have available turned up some 1/16 square for the top rails and some 1/8 sq (both balsa) for the spray rails.  They are all medium hard wood - so i filled a tall thermos with boiling water and dunked them for an hour or so. 

When they were nicely "al dente" I brushed the water off with my fingers and pinned them in place round the hull - with some rubber bands at the bow



Next day they had set in a good curve so there was no bending to do while gluing them in place.
Balsa glue (well if it works for Glyn Guest, who am I to argue?) and pins got them fitted (I had  rounded the bow ends carefully before doing the glueing)
Note:  none of the rails on a Higgins actually reach the bow - the rubbing strips are tapered off in the last foot (full size) and the spray rails also terminate short of the bow - there are good pics in
http://www.savetheptboatinc.com/photos.htm

Also the spray rails do not reach the stern - the rail from the bow stops ahead of the front exhaust (where there is a tapered "chock") and continues between exhausts 2 and 3 where it stops completely - there is no spray rail between exhaust 3 and the stern.

This is the morning after doing the hot bending - the first rubbing strip has a good permanent bend

So now the rails are in place, and have been sanded and doped
I will be spraying the hull, but not until I have done the exhausts, which are so much of the character of a Higgins boat that they need considerable care.  I am also mortally afraid of Andyn's eyebrow if I deviate from scale :}

Boat will probably be in the car for the warwick show - on the friday. I will be (modestly) badged if anyone is interested
andrewH





Logged

andyn

  • Guest
Re: Higgins PT boat, 1/32
« Reply #99 on: November 05, 2008, 05:40:27 pm »

Coming along nicely, the eyebrow will stay down for now ok2

Found any good diagrams of this splinter camo yet? I have one somewhere if you want it

I'm going a bit scale mad now, I'm just about to take purchase of a Revell Smit Houston tug (reserved for friday in the model shop). Build thread will follow shortly, I expect it to be the backup Andy thread :-))
Logged
Pages: 1 2 3 [4] 5   Go Up