put a watt meter on your shopping list please. They are not expensive and will give you an informed idea of the current drawn etc. Remember LIPO batteries should not be discharged below around 3.3V per cell else they DIE.
As an afterthought when you have rubbed down with wet and dry used wet wash the paintwork off well allow to dry and then use a lint free cloth to make sure all the old paint dust is gone. Make sure you work over a surface you do not mind being marked since the drips from rubbing down make an excellent paint on an absorbent surface!! ( yes I made the mistake so I KNOW). Its a very messy process but well worth the effort.
no argument here about airbrushing BUT if your prepared to spend the time and effort rubbing down I defy you to tell a brush finish from a sprayed one. On a model a high gloss finish looks wrong anyhow ( IMHO).
At least one idiot ( sorry politician ) has tried to say the model rocket guys could produce a guided missile! Getting hold of the higher powered rocket engines in UK is difficult. With some thinking and a bit of fiddling quite effective pyrotechnic effects can be manufactured HOWEVER its your eyes and hands that are at risk if you try it.
use 600 wet and dry wet for first few coats then 1200 wet then after last coat wait a few weeks and use something like "T" cut ( used to restore car paint). The wet and dry is better used wet ( with a dash of washing up liquid in the water) since it cuts down on the clogging of the paper.
leaving aside the fact that nitromethane is not nice stuff to have around in an undiluted form I cannot see adding it to glycerine making anything like an explosive in fact the nitromethane is an explosive ( potentially) all on its own.
Meths is ethyl NOT methyl that's why you can buy it from supermarkets etc. without a whole load of safety warnings! Methyl alcohol is VERY VERY toxic and the safety equipment required ( by the book) includes face shields rubber aprons and respirators! The meths you can buy easily is not anything like as toxic and can be used with little risk ( just keep clear of naked flames and DO NOT DRINK IT)
get a watt meter they are cheap and you can read the current drawn at full revs ( although its not moving) this will give you an idea as to the run time of your battery and the capability of your ESC to handle the load. I think every one who uses electric motors and especially lipo batteries should have one!
I presume its a single cylinder single acting engine in which case have you tried an exhaust throttle? A simple lever pivoted at one end which can partially cover the exhaust port. It may seem a bit strange but if steam cannot get out there is less room for fresh to get in while keeping the full boiler pressure to move the piston. If your engine has an exhaust stub then a butterfly or slide valve across that .
if your using electric power its a case of matching rpm to watts. It is quite normal to use 3 bladed prop of the same diameter and pitch as a 2 bladed prop on the same model. The increase of blade area results in increased thrust with an obvious increase in current used. So for any given system its a case of matching motor revs/current/battery life to the motor parameters.
I am left on awe of your work. However your water engine does have exhaust its water! that's why it fills up. Every time you draw in the oxygen hydrogen mix then result of the explosion is water and if you do not figure out how to get rid of it ( feeding back to the reservoir?) your cylinder will eventually fill and you will shudder to a halt.
first take a deep breath and calm down its not rocket science. Question does your ESC have a battery eliminator ? if so take away the dry batteries to use in something else. Now your nicads connect to the POWER side of the esc. make sure you have the correct polarity. The servo plug from the ESC plugs into your receiver whichever is your throttle channel. If you have a modern set then you can put it on the wrong way round with no worries since positive is the centre post. The output of the ESC connect to your motor. If its a brushed motor no need to worry about polarity for now. With your ESC there should be some setup instructions if there are none ...... Usually its connect and switch on receiver then switch transmitter on with throttle full listen for beeps then go to low throttle. Switch receiver off. When you switch on in future make sure transmitter is switched on FIRST ok having gotten this far it only remains to check the direction of rotation of the motor. Take off the prop ( saves fingers) and put a piece of masking tale around end of prop shaft. Switch on transmitter switch on receiver and try the throttle. If the motor spins in correct direction fine if not Brushed motor swap the motor leads over Brushless motor swap any 2 of the 3 motor leads over. Job done have a cuppa then decide to sort out the rudder.
So long as the new antenna length is the same as the old no problem. You can cut the wire and replace with a length of piano ( music ) wire if you wish ( glue a bead on the end eye protection). The big no no is to coil the length up.
A quick check on the specs of your motor /esc combo states its good up to 5s LiPo. So step 1 get a watt meter ( cheaper than burned out motors ) Step 2 check with your bank manager ( or wife) for available funds Step 3 buy the biggest 4s or 5s LiPo you can fit in the available space. you will also need a LiPo charger do not attempt to skimp on that step LiPo batteries need special handling and can be spectacular if you do it wrong. You have not mentioned the prop your using if you use the watt meter you can play around with different props so the current used by your setup heads towards the point you pick twixt performance / running time. If you do go LiPo you will also need a battery monitor part of the careful handing includes not discharging them below around 3.3 Volts per cell. 3s =3cells 4s=4cells etc. So if you go 4s then you should not discharge below 13.2V. http://www.rchelicopterfun.com/rc-lipo-batteries.htmlhttp://www.4-max.co.uk/pdf/prolong-life-lipo.pdf some text on the care and feeding of LiPo batteries. The reason for your problem is a simple case of battery chemistry a lead acid accumulator cannot deliver a high current for extended periods gasses on the plates prevent the electrolyte coming in contact so the battery loses power. After a while the gasses are re dissolved and the battery can then go on providing power. Nothing wrong with the battery its just a case of wrong tool for the job.
I have used them and still do on occasions in my experience I would never trust a joint made with one that has to stand any stress. If you just want to stick something decorative down its ok. If on the other hand you need to be sure the joint will hold use something else. The more porous the item to be glued the better hot glue will hold it. Yes the glue joint is waterproof BUT its perfectly possible for water to get under ( capillary action) a joint on a smooth surface and cause a joint to fail. By now you have probably gathered I am not a fan. Oh and if you do use one watch out the glue is hot enough to cause a burn and it sticks to skin fine.
if your going to play with props get a watt meter that way you can use your test tank ( bath) to get some idea of the current draw. Way cheaper than a new motor. If you can get inside the boat consider change of motor and esc. ( and go lipo)