Todays Boating

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by harry smith 1 on 29/12/2017 10:18:19:

Hi Noel

I did read that tapering the jet pipe increases the thrust from the unit.

Harry

The actual volume of air shoved out the back will remain the same, but is passing through a smaller outlet, so must be travelling faster. Since the boat cannot go faster forwards than the exiting air going backwards, this limits the top speed.

[NoelParticipant @noel26080]

I'd read a few things about optimal inlet and outlet dimension ratios for EDFs, but it seemed to boil down to a minimal difference on something my size and the main job of the jet pipe for mine is to make it look like an engine and hold the EDF ring in place! So I went for a shortish parallel pipe.

Might experiment though before I make it look nice.

[ashley needhamParticipant @ashleyneedham69188]

I spoke to a man in the know on this and it seems that smoothness of exit airflow is the thing, and as unobstructed inlet as poss.

​Given the location of your edf unit, you seem to have met both criteria. Whether narrowing down the jet efflux will actually improve performance??? well I think that this can only be experimented on.

​Ashley

[ashley needhamParticipant @ashleyneedham69188]

Not sure I will be boating tomorrow as still sniffing and coughing from before xmas. Its gradually going mind you but standing in the cold may not do it any favours.

​Proj2 coming along nicely. Servo in and rudder connected. Propulsion tidied up with the small bandsaw. Bridge looks good and after a bit of head scratching I have managed to make a detachable spring-loaded mast for it.

​Fore and aft jack sockets are drying behind me as I type (waiting for the epoxy to go off.. Last bits to be made are the funnels. Always tricky…I need them to be hollow as they are "of a size" unlike the Titanic ones which are solid. I am thinking of using card wrapped round either a former, to be released after , or using a short stubby former which will stay in the bottom of the funnel, unseen. For tomorrow.

​I have loads of lead flashing to use as ballast but its a bit grubby and has "an amount" of tar on it, so that may be a job for tomorrow as well, cleaning and trimming almost 2Kg of lead sheet.

​Ashley

[ashley needhamParticipant @ashleyneedham69188]

After fiddling about with card, plasticard and contemplating solid funnels, have successfully bent some funnels out of sheet aluminium for proj 2.

​Its funny….these are the last things to be constructed and deliberately so as I was unsure how to make them, but at the end of the day, we came back from Mums (lunch) and within 40 mins I had bent up a nice even and matched pair of funnels. Just trimming them now with plastistrut styrene rod, and they will be ready to be stuck on.

​Two flag poles have been made to fit in the sockets either end, and as I was casting about for flags I was reminded that Trevor had bagged a few metres of union flag ribbon from the haberdashers in Kingston when it closed, and like the good chap he is, donated a couple of feet of same for my "come in handy" box. Well, it HAS just come in handy and the resultant flags look great, and in keeping with the style of the boat.

​Unfortunateley as a project this will be about 3th on the list to out and so you all wont see it for a couple of years, perhaps 18 months min assuming it is deemed to be of interest for the mag. As usual anyone who would like to see it (finished) I am more than happy to send pictures by mail.

Ashley

[Trevor HollowayParticipant @trevorholloway99134]

Ashley,

Looking forward to seeing on the water or in the boot at "show & tell" on Sunday.

[ashley needhamParticipant @ashleyneedham69188]

Trevor. It MAY be on the water….not finished (actually more or less just needs painting now) but ready for a trail zoom. Ashley

[ashley needhamParticipant @ashleyneedham69188]

Just tested proj S in the home test tank and with 1.8Kg of nicely scraped and flattened roof flashing in it and a 9.6V battery (and a little block at the rear to one side) all seems to be ok. Water stirred up nicely, rudder twiddled successfully, boat amazingly dead upright (judging by the mast), so its all systems go for Sunday. Did not mark the waterline and it is difficult to see exactly where the water comes to in the bath as its all white and bright, and you can only look down on it, but I am anticipating some trim change under power on the open water so I may mark a waterline in pencil so that we can judge the merits of the theoretical against the actual line requirement.

​The final topcoat of paint will be a few months down the line unless we have a really warm spell, as car spray blooms horribly in the cold/damp.

​Ashley

[Colin BishopModerator @colinbishop34627]

Ashley,

To check the waterline in the bath just borrow the missus' makeup mirror and plonk it in the water. You can then examine the model from 'sea level' by angling it.

Do ensure it is dry before you put it back though – some mirrors have hollow frames which aren't watertight…..

Colin

[ashley needhamParticipant @ashleyneedham69188]

Good idea Colin I must say.

​In theory I will paint the waterline and ballast up to it, but in practice sometimes you want a bit more freeboard or whatever and a pond test is the way to see what`s what.

Ashley

[Byron Rees…(Ron)Participant @byronrees-ron]

Hi Ashley and all.

There is a very easy and foolproof way to mark the waterline on your unpainted model boat once you are happy with the trim of your model whilst floating in the bath.

It helps if the hull is in primer, ideally white or grey as this is an absorbent medium although this stuff works, even on ceramics and glass.

You'll need a bottle of 'Marbling' paint or ink, available in a host of colours from Hobbycraft or art shops for under £5 for six small assorted bottles.. This ink is formulated to float on the surface of water.

With an ear dropper (sometimes supplied with ink set) drop a few small dots of ink near the hull and then as it spreads on the surface blow it with straw up against the hull all round. Carefully lift the model out straight and put it on some tissues to dry. It will have formed a line all around the model where it sat in the water.This may take a half hour to dry and can be washed off if you don't like it.

When wet the ink wipes away easily with a wet cloth but if any dries on the bath a normal bath cleaning wipe or cream removes it easily…………Amazing stuff.

Take the time to watch some Marbling videos on You Tube. I wonder who will be the first to build a fully marble painted model boat.

Hope this is a useful tip……………Happy New Year.

Ron.

I sometimes wonder how I know so much 'twaddle' Teaching kids craftwork probably.

[ashley needhamParticipant @ashleyneedham69188]

Ron. Like that idea, easy and foolproof, and happy new year.

​In theory the measured waterline is 45mm below the main deck, and so I will religiously mark this with a pencil line before going to the pond. I think there will probably be some discrepancy with the horizontal line and the attitude of the boat when moving, as its relatively short/fat, so there MAY be a bit of wriggle room needed to either raise (or lower) one end by a few mm , but I would sooner just mark and paint.

​The next craft you might/maybe/possibly see in the mag has a moderate list to one side when at rest, and this is due to massive torque effect and light weight, leading to counter-ballast having to be placed to counter the list at speed, however it has no set waterline so this is not so much of an issue.

​Ashley

[harry smith 1Participant @harrysmith1]

Hi Ashley

Torque effect can be decrease with the ESC, receiver and servo mounted on the port side also a 2 blade prop decreases the problem.

I use the battery for get the boat balance for the CG and offsetting it to the port side for the torque.

Decreasing the power is not on the table !!!

Yes I got you flu and SATURADAY IT'S GOING TO BE 33 DEGREES !!!!!!

Harry

[ashley needhamParticipant @ashleyneedham69188]

Harry. Sorry you have the flu….33 degrees….its about 10 here!!

​As you say having the bits over one side helps, but the constraint I am always under is making the finished product look like something it is modelled on. This means multiblade props and other difficulties.

Ashley

[Dave MilbournParticipant @davemilbourn48782]

also a 2 blade prop decreases the problem.

This must be an Australian phenomenon, like the bathwater going anticlockwise down the plughole.
In the northern hemisphere – at least in these parts of it – a 2-bade prop causes more torque reaction than a 3-blade one. I speak with experience from the performance of one of my H31's and from correspondence with my prop guru, Simon Higgins. The reason is likely because the 3-blade props I use have a finer pitch than the 2-blade props.
The drawback with using weight to counterbalance torque roll is that it only works at one speed; slow down and the model lists in the opposite direction.

I think the best approach is empirical i.e. suck it and see.

Dave M

[ashley needhamParticipant @ashleyneedham69188]

Sorry, as I was as usual "speaking in tongues" regarding projects, I was talking about AIR props, in which case Harry is right. NOT sure if Harry was talking about air props…but as he knows what I have been building, he may have been. DM is of course correct for a water prop, as usual. All my boats use the empirical method, as its unusual for any of them to work properly first time!!

​Have built a temporary corrugated card storage box for project S, and if nothing this else has shown me that a permanent ply box needs to be perhaps 1 1/2 inches WIDER than this one so I can get my hands round the hull to lift it out, as its fairly heavy for the size.

Ashley

[ashley needhamParticipant @ashleyneedham69188]

Batts charged….projects S and H and of course a lander.

​Rethinking on the width of box as there is sufficient room to get both mitts on bow/stern as the boat is sitting on 10 or 12mm of foam (in the middle) thus allowing fingers to be wrapped under the hull.

​Project S will ABSOLUTELY NOT have any torque reaction, I can guarantee this even though the propulsion is something new for me.

​Having made my position clear on driverless boats, this on has no driver (visible) as it is a warship, BUT the open bridge is begging for a figure, or two. The original, on which S is based, did not have any figures, and the large funnels did not have any smoke issuing from them…but I have discovered a large cache of fluffy white soft-toy stuffing which would make great smoke…..hmmmm. I will canvas views at the pond tomorrow. Obviously the original did NOT come with smoke, but..

Ashley

[Trevor HollowayParticipant @trevorholloway99134]

Battery on charge now, plus modification to try out on one boat before complete hull rebuild and newest watercraft build for "show and tell".

Anyone who turns up at Bushey Park will get the full low down.

[ashley needhamParticipant @ashleyneedham69188]

Todays boating marred by excessive wind and waves. Unusually the waves were a decentish height, normally a cause for joy as I bring down something to play with that likes the big seas but not good for testing new small Victorian battleships.

​Substituted the Devastation instead of project H and a good job too, however this looked like a sub as the deck was continually awash. After an hour or so I did try project S and it went ok, although it was difficult to tell HOW well it was going in the wind. I did take out a sheet of lead and this helped matters a bit, but there was no way to judge the waterline at all. I think I will just paint it on and that will be that.

​Trevor did not sail any boats, but did have plans and test mouldings for his (third) new project. These were tubes made from J cloths and epoxy resin and were very impressive for their light weight, stiffness, good smooth finish and natty blue and white patterning. He is going to mould the centre portion of the craft using a natty pink and white pattern next time, to make it pretty (before painting). he had some impressive small EDF units with which to power this beast, and we spent some time umming and arring over the best place to mount them, and provide them with air, There were several candidates for position, and as far as I could see they all had merit….which one will he go for??

We were also ARRR-ing over Richard who bought down a really really big square-rig pirate ship. Awesome, but somewhat defeated by the excessive wind. Its third time out apparently and this time with more lead in the enlarged keel. The extra lead worked a treat as we were in "worse case scenario" conditions and although it had a big heel on it, it was no where near the brown trouser angle.

Ashley

Edited By ashley needham on 07/01/2018 13:18:15

[ashley needhamParticipant @ashleyneedham69188]

sPent last few days making a plywood box for Project S. The temporary card box was defeated by the amount of water off the boat after sailing and developed a sag in the middle (and as such was pretty useless) however it provided some protection so that was ok.

​The new box interior will be painted with waterproof paint (Grey undercoat oddly enough) as there does seem to be a lot of water left on the boat even after a good shake.

​The outside will be plain old emulsion, which is actually moderately waterproof, but not for long periods. After boating I usually let the boats and boxes dry out separately in the garden, but with the cold weather and rain its best to put them in the shed, where they take a long while to dry.

​The bottom of the boat is flat and the sides vertical so it will sit on two layers of closed cell foam (total 10mm thick, cut from a camping ground warmer/damp sheet thingy) and there will be strips of 5mm foam down the sides holding it upright, the box being a reasonable fit. I did think I would make the box wider after trialling the card version but I can get my hands around the bow/stern and under the boat due to the thickness of the foam.

​Probably half my boats sit on foam rather than having a felt lined shaped base, as its easy and provides shock protection.

Ashley

[ashley needhamParticipant @ashleyneedham69188]

Batts charged (from last week) and three boats…. Project S, The Sans P and a lander all mustered on the table ready for stuffing in the car tomorrow. Chances are with the cold that only proj S will sail, but you never know.

Box made, two coats of white emulsion on the outside (dried inside the house) and foam stuck in with evo-stick. Lettered on the outside and looks quite smart…but its only a box.

​I did think something would be in Feb issue but it looks like it may be the March issue….

​Ashley

[ashley needhamParticipant @ashleyneedham69188]

 

Cold, but no wind, and a nice calm sea. Sans P all ok. Project S also ok this time and some time was spent fiddling with ballast to sort out the waterline and trim fore/aft. One sheet of lead was removed and another smaller bit added at the front and this seemed to be the best. Unfortunately the propulsion is heavy and the boat has a slightly tail-heavy attitude made worse when power is applied. Again despite a good soaking on deck the interior remained remarkably dry (not completely dry, but not swimming wet.

​Removing ballast also made the boat more wobbly, but drier up front and I will have to think on this.

Richard had the piurate shap out again, this time there was not much wind, but it did sail and stayed nicely upright.

​Trevor had the tug down, and further work on the latest project. I think something you would recognise if you had been asleep for a long time. Finally Noel and the boys were down with an assortment of boats. Amongst them, Noels light go-fast with the EDF strapped to it. We were all well impressed I must say with the performance, very brisk….the best I have seen an EDF boat go so far….as yet of course.

Ashley

​Addendum:  The turret on the SansP is already showing signs of delaminating despite several layers of paint and several thinned coats of sanding sealer to waterproof it. I have some Silicone rubber and resin left so I think I will make a mould (as I have the master already) and cast one in resin. The deck was varnished with two layers of matt varnish once the fittings had been applied, as I could see long term issues with all that water coming on the boat.

​One 6 inch gun barrel was broken off and one side gun/hatch assembly as well (fortunately is was hanging on by a thread), all due to allowing the boat to come alongside the jetty. Must try harder to keep it off the side.

 

Edited By ashley needham on 14/01/2018 17:37:26

[NoelParticipant @noel26080]

It was a nice morning at Bushey yes.

The children did not crash their speedboats into anything that was not either each other, or my craft – and they sorted out a stranding with a big stick.

The only negative was the weird steering on the destroyer, and that was explained when the rudder blade dropped off as soon as I touched it back at home. solder failure!

Now, as the EDF boat went so well again, I thought about this:

Terrible idea, wrong shape? too big? or worth a try?
The foil shown would be supported with some sort out outrigger at each end, and also there'd be a foil on the bottom of the rudder too. I spent a lot of time filing the edges during "The Voice (UK)" on Saturday night……

[Dave MilbournParticipant @davemilbourn48782]

I did think something would be in Feb issue but it looks like it may be the March issue….

It is indeed. Just had my subs copy of Feb's this morning.
DM

[ashley needhamParticipant @ashleyneedham69188]

Noel. Wont know until you get it in the water. An aluminium foil is unlikely to stick that well to the thin rudder. Make a new temporary rudder from ply, well varnished. If the dangly bits are foil shaped then they could be bent up at the end to form a "V". You don't want them to be too deep or the thing might take off. I wouldn't have thought any more support would be needed (depending on the gauge of ally used).

Cheers DM….look forward to seeing it!!

Ashley

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