Puffer advice

[Colin BishopModerator @colinbishop34627]

Agreed, Len, that last little bit of fine tuning makes a big difference to efficiency. If using a wooden mount then tightening down or easing off while the motor is running can hit the sweet spot.

On the other hand, my favourite solution of round belt drive is also very easy to adjust by moving the motor slightly sideways in a slotted mount to achieve the same effect with the benefit that you can effectively make the motor even more efficient by gearing it down at the same time.

Colin

[Alasdair AllanParticipant @alasdairallan37423]

thanks for the advice everyone – yes I saw the article in this month’s magazine and will study carefully !

 

[Alasdair AllanParticipant @alasdairallan37423]

So, I am thinking along the following lines: A 400 12 v motor ; a universal coupling (poss  with inserts, as prop shaft bigger diameter than shaft on motor); a Raboesch watertight propshaft with ball bearing mounts, lock nuts and a brass propelllor to replace the white metal one in the kit.

Let me know if that sounds wrong – I am more used to paddles than propellors. not sure if motor should be geared or not, and have yet to work out bores and diameters.

[Alasdair AllanParticipant @alasdairallan37423]

At last getting a chance about how to set about the Northlight model. Looks good but first thing that jumps out is that there is something wrong with the rubbing strakes along the bow. These should be fewer and they should run parallel to line of top rail I think?

[Alasdair AllanParticipant @alasdairallan37423]

<p style=”text-align: center;”><p style=”text-align: left;”>Also, i think the for’d bulkhead will have to altered to allow some kind of access through it to focsle, where ballast may be needed, as fore deck doesn’t remove. On subject of decks, is the deck round the hatch steel (rather than planked, like it is fore and aft)?</p>

[Alasdair AllanParticipant @alasdairallan37423]

Finally, for this evening, I some posts questioning the wisdom of using the white metal parts supplied for the rudder post and structure underneath it at aft end of keel. If that is the consensus, will try to make replica in brass.

[Colin BishopModerator @colinbishop34627]

Yes, definitely make replicas in brass. I did that for all my Caldercraft kits and still have the original rudders to prove it as ballast for future models.

Colin

[Richard SimpsonParticipant @richardsimpson88330]

Interesting question.  I decided after a lot of head scratching to use the supplied rudder and stern frame for my Mountfleet Ben Ain.  One aspect was the weight, but I thought there is a large reserve of buoyancy in this model so that wasn’t a challenge, then there was the strength.  I argued to myself that, if I dropped the model on the stern frame, which is always the most likely cause of damage, then a brass stern frame is not going to be any more capable of resisting damage than a white metal casting.  I eventually decided to use the kit supplied parts because I couldn’t see any great advantage in making new ones.  Since I replaced just about every other part of the kit with scratch built items that may seem a bit odd!

I did have to make modifications though as the pintle bearings were not in line and after a lengthy argument with the proprietor I decided to apply my own version of ship construction design rather than his!

 

It did the job and looked the part

 

[Colin BishopModerator @colinbishop34627]

Imara’s rudder weighed 150 grams. I felt the weight and water resistance would put a strain on a standard servo. It was also a bit crude really.

Colin

[Alasdair AllanParticipant @alasdairallan37423]

Finally getting started on my puffer. Apologies for regularly soliciting advice, but if I get a 385 motor, I take it I need the geared down variety (more used to paddles than propellors!)?

[Colin BishopModerator @colinbishop34627]

Probably better to go with a low drain 540 such as this one:

https://www.componentshop.co.uk/540-standard-dc-motor.html.html

A 385 would need 2:1 gear reduction and is a lot more expensive plus the output shaft is 6mm instead of the usual 3.17mm. (also the gears will absorb power).

What size is the propeller?

Colin

[Alasdair AllanParticipant @alasdairallan37423]

Many thanks Colin – will go down that line. The kit is actually supplied with a better prop shaft and propellor than I was expecting.  The propellor is 40mm diameter.  However, as far as I can guage, it is a slightly unusual M3 size fitting whereas most propellors and shafts (or at least the more watertight Rabosch varieties that tempt me) all seem to come in M4.  Mulling over on whether to splash out on a Raboesch propo shaft and new prop! As discussed before, the ones with ball bearing fittings do look safer for a model like this where the inboard end is under the waterline.

[ashley needhamParticipant @ashleyneedham69188]

A low drain 540 my choice if you have room, but a 385 will turn a 40mm prop ok on 7.2v. This may be Against accepted wisdom but the motors are low drain anyway and do not take much more if “overloaded”. I must have 6 or more models using 385/40mm no probs.

Personally would bother with the expense of a fancy propshaft. Bog standard ones good enough and if adjusted correctly and with nylon washers, watertight enough.

Ashley

[Richard SimpsonParticipant @richardsimpson88330]

Just a personal choice and in no way disagreeing with Colin but, if the inboard end of the shaft was below the water line, I would prefer to fit a ball bearing tube and shaft arrangement.  This is probably driven by my 39 years at sea and the considerable number of hours during that time monitoring, and sometimes repairing, inboard shaft seals!

There won’t be many around who have changed an inboard shaft seal while the ship remains in service, there’s a story!

[Richard SimpsonParticipant @richardsimpson88330]

There you go, that is a forward shaft seal with the seal removed.  The seal is held in a clamp to ensure perfect alignment while the glue is cured with heat over around an hour.  When it is cleaned up afterwards you cannot see the joint.  The seal is temporarily maintained by a collar filled with compressed air.  Understandably everyone watches the pressure gauge very very closely during the operation!

The chap on the right is the maker’s man and the chap on the left is Roy, Chief Mechanic, and probably the most skilled machinist I ever had the pleasure of sailing with.

[Colin BishopModerator @colinbishop34627]

I didn’t mention shafts and tubes, just the motor! The Raboesch waterproof and ball raced shafts are very nice but at up to 5 times or more the cost of a conventional tube and shaft a bit over engineered for a small puffer. A properly set up conventional arrangement with a thrust washer on the end of the tube and using motor oil for lubrication should not admit more than a few drops of water during a sailing session and if the tube is short then you could get away with using something like Triflow low viscosity engineering grease which would create only minimal drag at relatively low revs and be effectively waterproof.

https://www.scmodels.co.uk/shop/triflow-pronatur-grease-50g/

Colin

[Alasdair AllanParticipant @alasdairallan37423]

Hi Colin- apologies for confusing posts there! Yes i think i will go for the supplied prop shaft and take the advice. The tube as supplied is 20cm long so hopefully either light grease or oil will do the trick. As for the white metal horizontal  piece supplied to join rudder stock to keel I am coming to view this is  unusable, as wrong shape and v soft. Will try to create something with brass.

[Alasdair AllanParticipant @alasdairallan37423]

[Alasdair AllanParticipant @alasdairallan37423]

Hi grateful for novice advice again! Motor has a 3mm shaft (unthreaded). Prop shaft is (I think) also M3, but threaded. A 3.2mm universal coupling fits onto the motor, but not onto the prop shaft.  What sort of adaptor / coupling should I be using in addition to / instead of the universal coupling here to overcome this problem? Thanks!

[Alasdair AllanParticipant @alasdairallan37423]

Also – mindful of Richard Simpson’s advice in model boats this August – I am not convined that the type of universal coupling here actually insulates the motor shaft from the effect of thrust as the splines do not allow for any give and take.

[David Marks 2Participant @davidmarks2]

I use Huco couplings which are similar to the one shown but the body is usually RED in colour. The brass inserts are interchangeable so you just buy the body and the correct inserts which have a plain hole (for the motor) and a threaded hole (for the prop shaft). See SHG Model Supplies eBay Store.

[Alasdair AllanParticipant @alasdairallan37423]

thanks-will look for in shg

 

[Alasdair AllanParticipant @alasdairallan37423]

[Alasdair AllanParticipant @alasdairallan37423]

Hi my inner pedant is taking over a bit at moment – the puffer kit needs to be adapted a wee bit to look like the puffer I have in mind. I don’t want to mess about with the detail too much, but there are a couple of rubbing strakes that need changed. If I am “rubbing out” a strake, or part of one, what is the neatest tool to fo that with? Possibly just a narrow square dowel with sandpaper on it, but maybe there is something more sophisticated than that?

 

 

 

[Stephen GarradParticipant @stephengarrad28964]

Yes, small dowel and sandpaper held on with double sided tape works well.

Stephen

[Author]

Posts