Dumas Shelley Foss 36" tug build

[Frank v B]

I know this will not fly but.......

Bought* this kit on RcCanada last year.  It is both a project during my recovery from knee replacement surgery a month ago and...no RPAS needed.

This is the way it arrived.  Poorly built but very salvageable.  A good thing they did not go further.  All glue joints can be checked, fixed and the complete inside waterproofed. First time I have seen a wooden model built with hot melt glue.

Plans:
- was going to go twin shaft but Mike Brodey was kind enough to give me a Decaperm- a very powerful geared 6 volt boat motor so will go single shaft/prop.
- will probably add the Kort Nozzle- a round tube around the prop that turns to steer the boat.  It does not use a rudder.  Akin to thrust vectoring in an RC leaf blower (jet).
- waterproof the inside
- fibreglass the outside
- colours will be traditional black hull, red below the waterline, white water line stripe and white doghouse (wheel house).

Purpose
Someone needs to tow Guy's broken down sailboats and fishing boat at TooGood pond.
May as well be me.  Modelling's equivalent of RansomWare. 

There will be several progress posts but not too many because we are a flying club.

Note: I had one of these tugs before and was given to me.  It was finished but no prop shaft installed.  I painted it, added a Kort Nozzle, added a prop shaft and an Astro Geared 25 on 6 volts.  Very powerful.  It could plane in our back yard pool.  Not quite scale.  Sold it to Piker because he said "I ways wanted an RC model tug".

Frank


*thank you Oscar, my enabler.

[Frank v B]

Here is what a Kort Nozzle looks like on full size tugs.

F.

[GuyOReilly]

Purpose
Someone needs to tow Guy's broken down sailboats and fishing boat at TooGood pond.
May as well be me.  Modelling's equivalent of RansomWare. 

Well @Frank v B you definitely will need a tug to pull that sub of yours after the depth charges have hit!!

PS: Looks like we should trademark the TEMAC subsidiary (i.e., the Toronto Electric Model Aquatic Club).

[Frank v B]

quick update:
- epoxied the inside- thinned it with alcohol, then hit it with a heat gun to make it flow into crevices.
- installed the shaft, rudder and motor.  It was hard to get the angle right.  Motor donated by Mike Brodey...to a good cause.
- installed the deck and built the first level of the cabin.
- getting to the frustrating parts... pieces are missing and the drawings do not allow parts to be drawn by measurement.  Will have to fake it.

Note: the gap visible between the hull and the deck will be covered by the bulwarks (solid railing above the deck).

Frank

[Frank v B]

Bare bones of the wheelhouse and removable deckhouse taking shape.
The smoke stack is in place.

Next- filling and fibreglassing the hull.

[Frank v B]

Fibreglassed half the hull following the video instructions*.  That was easy!
Equal parts of epoxy resin (20 min.), hardner and alcohol.  The consistency was of water and it brushed out beautifully.
Note the excess cloth sticking out below the upside down hull.  Once the epoxy is hard it will be cut off with an X-Acto knife.

Letting it harden for a few hours then will do the other half.

UPDATE- just did the second half of the hull.  Total elapsed time including prep, glassing and clean-up was 20 minutes.

Frank

ps: the epoxy was the stuff I bought from the Eric Adams estate.  Thank you Eric!

*Video on a separate post https://temac.ca/smf/index.php?topic=8898.0

[sihinch]

Hey Frank,

This is super helpful, thank you! Question for you, should you install the motor and prop tube (not sure of the terminology yet!) before glassing?

Thanks!
S

[Frank v B]

Simon,

re: motor and prop tube sequence:

I would install the prop shaft and motor before glassing for 3 reasons
i) Lining up the shaft angle:  most frame-built hulls use a keel.  This tug had one about 1/4" thick (first photo).  It is tough to line it up properly so the shaft is as much in line with the motor as possible.  In this case I made the hole much larger than the diameter of the shaft so there was no binding.  I installed the shaft so it floated in the hole, then back-filled it.  Note the angle corrections on the keel outside the hole in the 2nd photo (white triangle- balsa filler).
2) Collateral damage:  using drills and making holes larger than the shaft can cause a lot of damage.
3) Separate "building" from "finishing": fixing damage during the building phase is easy.  It gets progressively more involved as you get closer to the finishing stage.

If the boat does not use a keel (few do) you can do it any time. This is usually only in completely moulded fibreglass hulls.

It's personal. I never like going backwards or fixing things twice.

Frank

[sihinch]

Hey Frank, how heavy/thick was the fiberglass that you used?  2oz cloth?

[Frank v B]

Simon,

.68 oz cloth.  Can be bought at Plastic World (Just west of A&J Hobbies https://plasticworld.ca/product/fiberglass-cloth-regualr-e-glass/).  Mark Satin bought some last week at some ridiculously low price ($6.00 per meter).
For your PT109, like my Shelly Foss, the hull is planked with plywood so the fibreglass is used as a smooth waterproof finish.  It would be different if it were sheeted with balsa where strength would have to be added via heavier cloth.

Frank

[sihinch]

Thanks Frank!

Now show us more building! 

[Frank v B]

Simon,

The update:

- installed the bulwarks (railings above the deck).  A mess!
- painted the deck, installed the windows, roof, painted the inside of the wheel house black, painted the entire superstructure.
- made the deck winch- put tow line onto the reel by attaching it to a drill and winding it up.  About 20' of tow line.

Simon, I included the photos of the Dremel Multi- Max tool for sanding the fibreglass.  Absolutely brilliant.  The rubber pad contours it enough not to sand flat spots and never sanded through the cloth.  Borrow mine when you go to glass your PT boat.  It took less than an hour to do the entire hull (twice the area of your boat).  Drips come right off and it is easy to see low and high spots because of the sheen (dull is high, shiny is low).  Because of the triangular shape you can get into corners and tight spots.

Frank

ps:  the weight of paint is not an issue because it is a boat.  Used Benjamin Moore semi-gloss white trim house paint for the superstructure.  Used Tremclad Grey rust paint for the decks... because I had them.  A good latex paint becomes scrubbable after 30 days so it will be waterproof once the water gets soft in the spring.
Will spray the fibreglass hull (black and red) when it is a lot closer to the finish line.

[GordPayne]

Hi Frank. Your boat looks beautiful!

Any concerns about water migrating through microscopic voids in the latex and sitting between the latex and glass and possibly migrating into the wood through possible small holes in the glass?

[Frank v B]

No. 

Frank

ps: Half ounce cloth (woven like this or mat-type Angel Veil with random fibre orientation) was used as a first layer in a mould by full size yacht builders as a barrier to moisture migration (osmosis) into the heavier cloth with greater chance for voids.   The latex house paint is used above the waterline.

[Frank v B]

Next Challenge (self-inflicted):

Add a bow thruster...without buying one.

Problem- to leave a dock:
- the bow needs to be pushed away from the dock before the rudder can take hold.  You cannot leave a dock just by adding forward thrust and deflecting the rudder.  The stern will hit the dock.  Unavoidable.
- A boat with a single screw will kick the stern over when reversing/slowing down.  It helps when docking with the dock on the left side but not the right.

Am cobbling a bow thruster together using:
- a small $5.00 surplus 5 volt DC pump from Princess Auto.  Bought it 4 years ago in anticipation.  Sure.
- a standard servo (got lots)
- a brushed motor ESC (got lots)
- flexible fuel tubing.

Will show photos...if it works. 

Frank

ps: There is a factory-made bow thruster from Graupner.  A proper thruster has a tube across the hull near the bow that goes through both sides of the hull.  There is an impeller inside the tube.  It was about $50.00, the price of a new airplane.  This approach uses a stream of water to push the bow over.  The ESC gives it variable thrust and the servo determines which side of the bow is pushed over.... in theory.