Hi Ron, have you tried this? With the boat out of the water, turn the TX an RX on and watch the rudder as you walk away to see if it twitches (try operating the rudder a few times and wait). If nothing happens try running the motor and doing the same thing, if it twitches then you have a problem with electrical interference, (might be your antenna going over the motor, - assuming your motor is properly suppressed) If it twitches without the motor going and you get a fair distance away, it could be a dodgy Xtal, REC, or maybe servo (wouldn't have to be any distance away for the servo.)
Another thought is - was anyone else on the same frequency as you or standing near you with a more powerful radio swamping your signal, (had that happen to me with FM in a plane - different freq but my cheaper Acoms 4 ch radio was swamped by a Futaba 10 ch - guy got between me and the plane almost causing a crash)

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Hi Red, I had the same problems with the ST I'm building at the moment. I used the plan and elevation sketches and bulkhead/frame shapes and positions from the 1975 Model Boats articles on RAF rescue boats, but found that the chine up-sweep forward was wrong and had to be brought down.
I also had to fit an extra bulkhead between 2 and 3 (and move 2 forward) to bring the hull curve out to the correct line. Could have done with a half frame between 4 and the transom to support the stringers (found I had to prop them to hold the shape till f/glass had set) I've left them in to run hoses and wires behind so they turned out to be handy.
There are so many variations of Miamis that you have to just pick the one you like best and go for it. The one I built (very roughly) was modeled off the dwg and pic compared to the SA one which has totally different coamings (there are also a number of RAF boats similar to the SA one). I forgot to add the nice little 'barrel back'stern on mine which I was intending to.
The RNZAF 64ft 100 series HSL I built from the same mag dwgs had similar problems, (not to mention dozens of RNZAF mods while in service) so I just blended most of them into one boat. There is no one left to argue, so who will know if something is not 100% accurate, (applies to most wartime modelling subjects)
John B

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Hi Martin, That guy better brush up on his English, (hardly no cavitation - does he mean there is or there isn't any !???) I don't know why we went to school. The standard of English in some of the ads and papers here is pathetic (TV and billboard ads). Nobody seems to proof read any more
I don't know if you remember back to the 60s where Hornby came up with a 'ring field motor' which was a very thin, large diameter motor for their engines. It could run on DC for high speed and AC for low speed, and even though not the same as the motor in the vid it had a similar profile. Reminded me of it immediately.

hängt davon ab, auf welcher Seite der Spiegel beschichtet ist. Make any sense Doug? whether you glue left or right.

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Nicely hidden!

Hi Martin, I've filled it up to the top with a syringe but the small bubbles are good for an indicator as you can't see any movement otherwise. I could just make a small header tank, (or even a bit of the large silicon tube mounted vertically on a T and it would bleed itself. I'll see if it gets hot, and if so I'll probably make a small tank for expansion so it doesn't pop the hoses off.
There is good circulation all round so hopefully it won't be an issue, I certainly won't be racing it, (it's getting heavier by the minute - coming up on 6lbs and with paint and batteries probably a shade over.) It will need the weight to make it sit properly as the hull was only about 1 3/4 lbs . It will be interesting to see how these motors perform, these are 6v 45T but I can always go to 60T or 12v for more grunt. The combinations are endless!

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Nah Doug its a perestaltic / dosing pump (like an R/C plane refueler - 2 rollers on a silicone tube u bend, crude but effective but also noisy, the main pump is a diaphragm pump which I also have in my HSL and is very quiet. I'm only running the main pump on 6v because it would be a jet boat on 12v.

You're catching that German humour Doug !😊 You have to use a mirror and apply it over your shoulder!

I also have been using Orange FASST Futaba RECs since they first came out and have never had an issue with range( far as you can see). Also the Corona R6FA, R8FA and the FRSky TFR6 7ch have been faultless as well. I've been using a Futaba 6EX with all of these since 2010 with no problems. Also been using a few FHSS radios for ground use (boats) with no problems either. There don't seem to be many 3CH FASST receivers but a 4 or 6CH FASST should work ok.
A 6CH will work on 3,4,5,6,7,8CH RECs (you only run out of switches if you use a bigger one) Corona makes a R4FA but HK doesn't sell them now. plenty of Corona 6s and 8s around for about $ 25 US. I notice that the Futaba 3PK is discontinued so samc may want to look at a newer radio.

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Trying out the heat exchanger and raw water pumps. Vid is a bit boring as you can't see much going on other than the water coming out the exhausts. I left a bit of air in the closed cooling system so I could see if the water was circulating (you can see a few bubbles travelling around,-not in the vid unfortunately) Everything works well but the circulation pump is a bit noisy (running on 8v) but the main pump is quiet (running half speed on 6v - through a UBEC ) Both pumps are powered from a 2200Mah 2s LiPo at the stern, under the cockpit floor and operated by a remote switch. Main pump draws water from a pickup near the stern.

R/C 40" Seaplane tender. Heat exchanger for brushed motors.

▶️

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Hi Nerys. DG mentioned a clamp and I thought one of these would be just the ticket. The only thing might be a twist tie over the end of the clamp and around the tube ends to stop it slipping off. You should be able to get a bit of leverage with this.
John B

You'd love our Chinese $2 shops here Colin. I recently bought about 10 x 33ml tubes of genuine German UHU for $2 each (Hobby shop $10), plus I buy 90% of my superglue and epoxies from them as well. The epoxies are $4 but cheaper than big hardware stores (which sell the same Chinese stuff probably with different labels) Superglues work as well as more expensive ones such as Loctite which can be 5x the price.

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Yeah, tis a bit annoying Doug, people use sisters, brothers, friends accounts to buy things and it gets quite confusing as you are not sure who you are dealing with unless they offer the info. Same with email accounts, 'talking'to a guy up north recently using his girlfriends email acct but at least he told me. Nothing like the old face to face I reckon.
I saw a TV article where media techies can come up with virtually undetectable fake people such a actors to make totally fake news etc, which is pretty scary stuff. All they need is one pic of the person and they can place them in any scenario (not just stills either). Once they perfect it you won't be able to trust any media! (not that you can now even without this new stuff!)

Seen those, looks like heaps of fun, don't think you're allowed armour plating though, just wouldn't be cricket wot!?

Apologies Nerys, my mistake, used to people using other peoples accounts/names on our local 'Trade Me' site. You never Know who you are talking to, so it's a bit of a lottery on the internet. Not expecting a lady model boat enthusiast I suppose, and didn't even cross my mind to check the profile. Great that you're interested!
John B

The big one's just silly, it ain't got no rod holders or bait board, or rowlocks for that matter. how's he going to escape when she's scuttled, in a mini tug? Better watch out for the Kiwis in their mini Archilles with her NZ SS1 fire control radar and foils, could be deadly on foam and plywood!

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You're a lucky man, good handy women are few and far between these days!
John B

When Sir Peter Blake and crew won the Americas Cup they all had the lucky red socks on, as did half of NZ. They obviously weren't confused by having 2 port socks !⛵

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Nice collection, I'm sure Martin could be commissioned to come up with an unusual center piece!

Trial fitting all the plumbing for the heat exchanger to make sure coamings will still fit. Small pump behind port motor is the circulation pump and the other is the raw water pump. Also fitted the ESCs and made the battery holders. would have liked the batteries and pumps nearer the stern, but not enough room under the floors. May have to put a few sinkers in the stern to get the WL correct. That can come at the end once everything else is done, (paint etc)
Rudder system is also temporarily hooked up and works fine. Will remove and test water system shortly. Using 6mm silicone hose for the raw water pump for better flow. As can be seen, everything tucks away quite nicely out of sight, (was sort of like death by a thousand cuts,- fitted by a thousand slots!) some pretty close fits here and there. could have done without the heat exchanger but I don't do things the easy way.
Got to try fitting a smoke machine in somewhere so I can have smoke coming out the exhausts with the water (more tubes, more bits!) and a sound unit! Might be pushing it, but I managed to fit twin units on the HSL and that's a lot narrower. Might be a rack system yet, plenty of room upwards in the cabin. Don't really want to put anything in the wheel house, just wheel, instruments etc.

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I haven't run nitro boats for a number of years now Doug, same with the planes, everything has been converted to electric long ago, (all the nitro planes included.) No more mess and smell of burnt fuel in the house, no having to take a roll of paper towels and soap sprayer and wash your plane or boat before putting it in the car, and no more having to put a plastic 'nose bag' on the planes to hang them up so you don't get oil dripping on your carpet!
Re- Graupner 'Premium Line', certainly sounds like their quality has dropped, you couldn't fault them in the 70s, gone the way of all the others due to competition from the home of Oolong tea by the sound of it.

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No worries mate.

Nice to see you're an equal opportunity employer Nerys, no discrimination there.! 😂 she's got to be a keeper! (have you bought her a tool kit yet??)

The powerboat guys in our club years ago, used to use the same method but with a small sinker wrapped with foam, cast it out into the pond and well over the boat and slowly reel it in. Sometimes took a few casts but they always got them in, (was quite a wide pond - around 80m.) Saved a lot of swimming in nasty water. There was a guy in the club who did scuba diving who would rescue sunken boats occasionally if he had the gear with him, (good washdown afterwards required just to be safe !-Ex sewage ponds and later storm-water drainage control pond) It had a sluice gate to an estuary branch so could be drained at low tide and refilled at high, (still had a lot of nasty stuff coming in though!
John B

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Brilliant job, really looks like it's been out working!.

I'm sure you still have a lot of great creations to produce yet Martin. I was going to have a look through my bits and pieces to see if there is anything which might be useful to send you, (props etc,) think I've even got a vintage rheostatic ? speed control some where, which is operated by a servo, (fwd, rev speed, operated by a disc on top of the servo with a wiper system ,- like a potentiometer) came with the 'Fairacre' launch. Probably from the 60s. Doug will know where it's from, he's good with old stuff.
I'll see what I can find if you would like, and we can sort details. Will be gratis of course but will have to make sure you won't be whacked for tax for stuff that's really worth nothing,- except to modelers!!.
John B

Agree completely Doug, but I didn't want to muck about trying to make strut bearings etc. This way if the bearings clap out there are only 2 to replace and if all else fails, a pair of vice grips on the end of the tube gets the whole thing out real easy, chuck a new one in and you're away. Trying to replace a bush/bearing in a fragile strut (unless removable) without damaging something, would be a tricky operation I would imagine.
Most nitro boats in the past were made like this until cable drives came along (before cables, the only thing close to an open shaft on a fast model was a 'zip strut' which involved an underwater universal (see Seafury). The reason was mainly a torque issue, as if you just had a 'T' strut and open shaft, the torque from something like a hot .60 powered boat jumping out of the water was enough to bend the strut on landing, so you needed quite a substantial 'T' or better, a 'V' strut, (I even had heavy struts as well as the tube, -see pic,early 70s - strut was about 4mm thick on a .40 boat). Check out the cable drive strut size on a big model hydro or mono for eg.
A lot of kit manufacturers like Dumas,(see pic) used full length stern tubes for a number of their models, - probably more for ease of building rather than going for the full 'scale' bit. The term I've always known the 'outer tube by is a stern tube but there are probably a number of variations.

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I use SAE 90 mixed with some additives to help it stick which seems to work ok Martin. I can't get grease into the shafts through the oiler tubes (Maiami and MTB) as I have to remove the rudders to take the shafts out which is a pain ( I could try and inject grease but it would take forever to get through and would probably just come out the top end anyhow). Grease is fine for plain bearing shafts but with the new shafts I have ( for the ST) with double seal ball bearings each end, they will need filling with oil so it seeps through the bearings, (grease will just sit on the outside and not lubricate) Also, unless you use marine grade waterproof grease/oil with anti corrosion additives the shafts (and bearings) can still rust unless they are stainless or brass.
I used to run my nitro boats in the salt water and even though I greased the shafts (steel) thoroughly every time, if I left them for a few months they would be quite rusty when I checked them (using std GP grease, -I always thought grease was grease). I've found it's a good idea to remove the shafts periodically to make sure they aren't 'growing' in the middle as if any rust gets too bad you may not get the shafts out.

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Thanks Martin, it does run surprisingly well with all that weight up top. Used to have a 28mm brushless 2200kv out-runner in it but the scream was super annoying and ruined videos. It was twice as fast but no use for filming. It's still a bit noisy, especially when the shaft runs out of oil, but quietens down once oiled again, - it's only home made 5mm brass tube (with oiling tube), with a thin brass tube bush at either end and a 3mm brass shaft (same in the MTB x 2) but they have worked ok for years. If I had a lathe I'd make teflon bushes which are a lot quieter. I did the same with the MTB to look more scale like, as nothing looks worse than huge shaft tubes hanging out of a boat (in saying that, the shafts in my ST are too big, but who could turn down $7 for a 10mm D (outer) x 250mm stainless shaft with ball bearings, (cheaper than making one)! You have to love Banggood and Ali Express!
John B

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Hi R.S, Things haven't changed a lot with planing hulls in all this time. They have a bit more width in the stern these days with the planing area a bit further aft, which I think is because of the aft coaming designs and stern drives etc which need more support . These old hulls still have lovely lines and worked very well in the conditions they were designed for. The pic is of the second reincarnation of the ex RNZAF BPB 64ft HSL here in Auckland. You would not guess the hull was 80 years old (and still in good nic)

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