Thames river police launch

[AssociatedParticipant @associated]

Both top and bottom chines are one and set , there is a block of balsa at the bow that needs to be carved , the instructions say to glue on then carve , what is the best way to shape the front ?

Roughly cut out with a saw but it mentions to carve 2 hollows on each side , I'm a bit clueless how to do this as only got 1 block , sanding back would be a absolute chore , any other methods ?

Cheers

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Associated on 23/04/2016 13:58:37:

Both top and bottom chines are one and set , there is a block of balsa at the bow that needs to be carved , the instructions say to glue on then carve , what is the best way to shape the front ?

Roughly cut out with a saw but it mentions to carve 2 hollows on each side , I'm a bit clueless how to do this as only got 1 block , sanding back would be a absolute chore , any other methods ?

Cheers

Many people use a thing called a 'David Plane'. Here is a picture of the first one from the list I googled – any model shop should have one…

**LINK**

[AssociatedParticipant @associated]

Ahhhh I have got one of those and a subform block too . Il get a picture up of the plans .

[AssociatedParticipant @associated]

This is what the drawing shows on the plans …

[Dodgy Geezer 1Participant @dodgygeezer1]

I'm a bit clueless how to do this as only got 1 block , sanding back would be a absolute chore , any other methods ?

Mark the chine lines in plan and elevation on the block and cut approximately to them using a David plane or carving with a Stanley knife.

Then finish the shape, including carving hollows if you want, with a half-round rasp or sandpaper, moving from coarse to fine. You can use a template switched between two sides to check symmetry. A little filler or re-gluing balsa you have cut off lets you cure mistakes.

Sanding can be a VERY rapid way of cutting balsa. The cutting capability depends entirely on the grade of the sandpaper. Coarse grade can go through balsa as fast as a knife, while fine sandpaper can take ages to remove a slight bump. Get a selection of sandpapers, wrap them around an appropriate former like a section of broom handle if you want a curve, and get rubbing….

[AssociatedParticipant @associated]

Thanks ! Have got a David plane and a surform block plenty of sanding paper and a small detail sander like the b&d mouse with the pointed front . Need to get a half round course rasp really

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Associated on 24/04/2016 14:55:37:

…. Need to get a half round course rasp really

Anything round will do if you wrap sandpaper around it. Look in the kitchen for some tins…

[Charles OatesParticipant @charlesoates31738]

This is one of those jobs that sounds harder than it is. I work outside, it's very messy. Mark the bock as described and sand away, it only takes a few mins. Line it up using your Mk one eyeball, it's surprisingly accurate. I usually slap a bit of paint on at this point, when dry sand again and you can see any high spots. Use the same paint type as you will be finishing with so you don't get a reaction.

My last model, Cynette took less than 2 hours start to finish, including waiting for the acrylic paint to dry.

Chas

[AssociatedParticipant @associated]

Thanks all taking a while as a lot of pinning and waiting for glue to set before moving on to next stage , the keel goes over the carved block so have a nice guide for the shape

Thanks

[AssociatedParticipant @associated]

Been doing a bit more to the boat excuse the rough edges .

[AssociatedParticipant @associated]

Been mocking up the propshaft location and estimated 40mm prop with a slight gap above , my problem is that the rudder would come behind the box what should I do ? Mount in the lower laminated sections and drill a hole in the rear of the box for the servo push rod to go through ? Thinking what's best to do …

[Ray Wood 3Participant @raywood3]

Hi Associated

I think you need to put some filler back on your bow block the chine line should continue to the stem without the sharp change of direction, my current MTB project although different type of diagonal planked construction it shows the line to be produced, hope this helps your build in some way.

Regards Ray

[AssociatedParticipant @associated]

Yes I did realise I took a little too much away after , but there is a sculpted part of the bow block . Easy to get carried away though ! Just pondering about rudder mounting

[Ray Wood 3Participant @raywood3]

Hi the open cockpit of these launches are such a feature it would be good to keep the rudder servo under the rear deck if there's room ? on the fullsize the engine case sits in the middle of the cockpit you could use a long wire pushrod or a closed loop system from the cabin ?. If you look on the National Maritime Museum website for Service/Police Launches the collections model is superb in every respect of detail. I will build one at some time in the future.

Regards Ray

[AssociatedParticipant @associated]

That detail is superb! I did notice that my kit is slightly different to that one … The bow is not shaped with undercut/ hollowed out section … What's the advantage of doing this ? I'm going to try and mount the servo in the stern but if anything went wrong would mean to get to it would have to make a hole in the rear top deck … Any ideas as the deck is curved .

[AssociatedParticipant @associated]

What size servo would be recommended? Standard or mini servo ? Have got a spare mini one kicking about … Or wouldn't it be man enough ?

[Tony HadleyParticipant @tonyhadley]

Matt, the attached was featured in Model Boats magazine a few years ago. The rear of the launch has been extended with a false box, which the builder has probably used to house the rudder servo, I don't think it looks out of place. An alternative would be to fit seating as the NMM model (posted in the earlier link) and disguise the servo under the seats, which was what I had planned for on mine.

The original was obviously a free running model and there isn't much room under the rear section of the deck.

[AssociatedParticipant @associated]

Great idea ! Never thought of that ! How do you lads make covers and boxes that stay on but easy lift off ? Was thinking best way to get the servo wires Upto the reciver was before put the last lower skin on was to get a servo extension cable and run it under the box and come out in the area of the motor/ esc area through a hole , I'm just wondering where best place to mount the battery , esc etc directly in front of the motor and cover up with a lift off box ? Just thinking about weight distribution also .

[Paul TParticipant @pault84577]

Hi Matt

In the good old days some model builders used elastic bands to keep covers and boxes tight to the deck, fit a small hook inside the hull below the cover and put another small hook inside the cover lid then just use an elastic band looped over the hooks. The elastic band pulls the cover tight down to the deck but is flexible enough to allow the cover to lift off for access.

Given your background you could use springs like those fitted to automatic carburettors on Tecumseh and Aspera engines.

A fairly easy and more modern method is to use magnetic cupboard catches

Magnet cupboard catch………just the thing for magnetic cupboards

Paul

Edited By Paul T on 27/04/2016 15:50:17

[AssociatedParticipant @associated]

Thanks Paul I'm afraid don't work on those engines mainly Stihl … But i can use magnet idea but buy small disc magnets and with some strips of steel bonded to the hull il be able to make something work

But I think the center cover with prop, motor , esc and battery will be quite a biggish box . I'm just thinking will there be too much weight up front ?

Edited By Associated on 27/04/2016 22:29:19

[Paul TParticipant @pault84577]

Hi Matt

Easy way to check if there is to much weight in the wrong place …just stick the model in the bath and put all the bits in…if it floats lopsided then you will know its wrong.

Paul

[AssociatedParticipant @associated]

That what I was planning to do Paul , just seems a lot of weight up front and not anywhere can move it to … Unless add balast around the boat .

Matt

[Ray Wood 3Participant @raywood3]

Hi Matt

How's the launch going ? I thought smaller battery packs under the side decks would keep the weight nearer the stern, but you would need to cut & form some openings in the sides your basic box.

Regards Ray

[Daniel Cardona 1Participant @danielcardona1]

Hello To all

After I discovered this nice looking Police Patrol Launch I immediately made a search on the Internet for some plans and I found a good set on E-Bay. the plans arrived Today and after a quick look it doesn't look a too complicated model. Although one thing that I'm worried about is the side planks, I guess that they are thin Ply about 1mm or 2mm But ply it's not cheap here in my country and to buy it at a certain length it's not cheap at all. So I've been thinking if it's Ok to make the side's from 2 or 3mm Balsa instead.

I was tinkering also about the formers and keel if it's ok to make them with 3mm Poplar liteply. I was also considering the top deck to be build in liteply but 3mm is all what i can puts hands on. the Balsa skinning should then be covered with epoxy and very light glass sheet.

any suggestions?

oh ..and I forgot, a motor cover should also be build to avoid water spray on the motor and possibly esc maybe. unfortunately I have to use it on salt water….Yes salt Water!..I'm not giving up on the hobby, if I build one my wish is to see it functional on the water.

Regards

Daniel

[Tony HadleyParticipant @tonyhadley]

Daniel,

No problems with balsa for the sides and bottom, just lay the balsa with the grain vertical. 2mm, 2.5mm or 3mm would be fine. A solid balsa block is needed at the bow. To avoid the use of ply for the deck, 1.5mm balsa would be fine.

Attached are a few photographs of mine, which show the balsa was covered with one leg from a lady's nylon tight (fine denier) and the weave was filled with varnish + paint. Balsa is fine providing you are willing to spend the time finishing the wood. I've also attached a couple of old B & W photocopies from a magazine which show further the balsa laid vertical on the sides.

Good Luck with the build.

[Author]

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