Good after noon all respected Modelers.. Friends.. Colleagues..
many of us thinks scratch building is making a model in to 1:200, 1:144, 1:72, 1:48, 1:35, or O (zero), HO (half the zero) and on.. but, all these scales are established scales, mostly by kit manufactures.. as a professional modeler, i never sticks on these scales, but always on my needed size and scales.. for an example, all we know, a 1:48th scale P47 D thunder bolt aircraft spans with it's wing in to 17 cms aprox, so, if a client asks me to build a P47 D with a span of 30 inches, what can i do..? simply say i cant..? why..? here came the importance of scratch building.. we can build our models in our own scale and sizes as we follows the three views and photographs of the machine.. years before, the redrawing scale was a little job, as we have to redraw all specs with our hands.. but today, we have computers and appropriate software helps us a lots and can make a needed 3 views in seconds.. and can also take a printouts within matter of minutes.. the softwares gives us an option of altering a colour photographs in to sketch.. i was making models from my child hood.. so, i clearly know thers no any written or unwritten definitions for scratch building.. we can use a wooden twig to golden rod if our financial state allows.. and a scratch built model may not be simple, as we can go to any extreme in complexity, that if we are capable of carrying it out.. but here my aim is making models from handy things around me.. and i always success.. i am adding a link from Wikipedia, regarding the scratch building.. it tells us that, about the need, material and ideas of scratch building.. i am so proud of myself, because i was using some mainly considered methods around the globe.. is paper and scaling from photographs.. a great flexibility.. so, no time to waste.. this effort is to complete my heavy duty harbor tug, in to a 4 feet long scale..  
http://en.wikipedia.org/wiki/Scratch_building

Roopesh sir, those are some very motivating words, the spirit and art of scratch building is not scaling but to start from nothing and going on to have that something in your hands.

so this tug was not from a plan.. but the dimensions were taken from a real harbor tug, from Rotterdam.. and yes added lots of my personal touches, in total shape and super structures.. because this one is realized to operate from anywhere, from lake to river, river to real harbor.. so, a low profile is a must, to keep the CG low.. because of it's two stage super structure.. the craft spans in to 4 feet.. and heavy, in its nature, because of the fully displacement type hull.. so, i added an immensely powerful motor for this.. while keeping all experiences to avoid high speed, but great torque to deliver..  
i told you all that the thermocol,( expanded polystyrene )  is the ever best material to make crafts.. when formed this can simply outclass any type of hull with it's light weight, high stiffness, reliability.. ease of repair.. ease of rework.. and gives us an excellent finish with nominal materials..so, this material is first in my list.. but, thermocol takes a little time to dry up.. as we have to treat it nicely.. but still no hard works.. even a child can do.. so, here i starts with laminated thermocol.. one sheet costs about 18/Rs.. here..

Thank you Girish..
here i havent any related materials.. no lathe works.. no expensive items.. still none of you think that i am not a capable one to get all these needed ones from outlets... from around the globe.. but still we need nothing as expensive or traditional.. here, the drive shaft and bearings from bicycle parts, and tube is a body of a pen..

can simply see the simple bearing layouts..
the craft is heavy and enormous.. so have to add a good powerful motor.. i got this motor from a fellow modeler, as fully damaged.. were no bearings.. so, instead of adding two bearings i added a full length self lube bush, that helped to cool the motor so well.. and all you know one of the most powerful motor is in it's class.. added water cooling helped a lots, keeping the motor at room temp at all speeds continuous..

very true roopeshji, I will be following this thread, I've always admired your usage of ball point pen casings for the tubes, I'm also trying to use the same technique for making tailwheels

the prop is made of aluminum sheet.. from a vessel lid.. the pitch of the blade is kept just below the stall angle.. with highly valance petals..
to keep the rpm low, while generates a high torque..
adding a kort nozzle is a must, as the tug need more directional thrust.. it also helps to add a strainer for safety, as this one is intended to operate in rivers and harbors..

Girish.. use a 2mm bicycle spoke as strut, and a toy wheel as tail wheel.. works fine.. 
here i am thanking to Mr Vinodh Madhavan, (my brother Vinoettan), for the gift of a bunch of Futaba servos, motors and radios.. ample of servos.. so added a standard servo here as the tugboat is heavy.. no any complicated layouts are chosen, but simple straight forward method.. the link is made of zink sheet, and a wire terminal is soldered to the link to from the tiller arm.. 

and added an inbound 25/75 rudder panel, to get an easy turn, in all speeds.. this elimitaed the need of adding a thrust pump, as i can control the speed of the motor from 0 to high in both directions.. result.. easy turns despite her's size.. 
can also see the intake water scoop to cool the motor..

photograph shows the fixation of the motor.. the foam board is placed in such a way to absorb any vibrations at high speeds..
and can clearly see the cooling line arrangements.. so simple and effective.. anyone can do..

once again in detail.. nothing is complicated here.. motor is fixed by two M3 screws, for easy maintenance..
the exhaust is placed at the side of the craft..

after thorough check outs for hours, time to add super structures.. the panel works are by 2 mm foam board, to keep weigh low as possible..
the bollards came from aluminum rivets.. to avoid rust, as i have to operate her from real sea harbor..

work progress.. we have to keep an eye, in working parts as the boat is not realized for keeping over bookshelf, in a glass case.. instead this one is purely made for gruesome RCying.. so, some design considerations is must..
before going to the final work, some sketch is a must, to retain scale.. a dry run helps us always.. with a paper cut..

work progress.. structure are with 2mm foam boards to reduce weights.. with added reinforcements inside..  nice progress..

super structure cabin is fully paper.. nothing can gives us the rate of finishing of the paper when completed.. feel flimsy..? not at all.. stronger than wood when finished.. gives neat cut and shut lines.. lives for centuries.. water proofed..

funnels.. funnels are made of same foam boards.. while keeping the aspect to add a smoke generator inside.. the peculiar shape is my imagination here..

the mast is my imagination, while keeping the weight low.. the original one is a bird cage like.. not much interesting to look..
here i have a plan to add powerful L E Ds just under the wings of the mast..

the pushing abosrbers are made of thick foam boards.. later planned to fix with real rubber panels..
now priming starts.. waterproofing..

time to paint.. the color scheme is taken from the real Rotter dam tugs.. industrial yellow with black belly..

careful but simple masking with masking tapes need for the painting of funnels..
water line.. oxide orange.. to get oxide orange, we can simply add a little metallic silver, a little black to orange paint.. gives us oxide orange..

the winch...
the winch is entirely made of foam board and paper...
paper roll served here as drum..

finished and painted.. the cable is fishing twine, painted with brush in aluminum paint.. finished in dull green..

the fire monitor..(water gun)..
the fire monitor is made of a rubber O ring.. and some additional handy materials..

the spray tube  is from ball point pen.. refill..
and primed..

stirring a little enamel paint in to signal red.. sure.. nothing can beat the finishing of the enamel paints.. these paints play an important role in mural paintings and dioramas..
painted.. and waiting to dry..