Hi Dave and Colin, Yes I wonder if the prop was the reason this well made boat was stuck so long in the loft. I had her well ballasted so cavitation isn't the problem.

I agree the hull shape does block a lot of the propeller but I'm going to replace it with a nice brass one I have knocking about .

Hi Bryan
I did tell you the supplied prop was useless. The shape of the hull shields most of the prop so you will need a good coarse pitch brass prop to make any headway.
Back in the day I could not afford such a prop and resorted to cutting a slot above the propeller and fitting a bigger prop. This required a 2.5:1 reduction to the shaft from the motor as the Battery (wet cell motorcycle lead acid) was being flattened too quickly. When I restore my model I think I will rework the hull to allow a better flow to the prop. It was my first model and I could have misread the plan and certainly did not have the knowledge or help at the time.
Happy days and hope you find a solution - there are decent props about at reasonable prices.
Cheers
Dave

Bryan, what power were you using, and did you have enough ballast to keep the prop well down or were you getting cavitation.
A picture or 2 would help.
Cheers Colin.

Well I took the vessel to the canal today and all systems worked but as suggested earlier the propeller is awful and wind powered the boat as much as the propeller did.

ok that's two inches wide not deep lol

tests in my white dry dock facility (the bath) have confirmed the repair was effective. directly connecting the battery to the motor has confirmed that the motor works too.

just got to try the old speed controller add a servo if it works and the receiver and she should be ready for sea trials

WOW! Gonna take you a while to sand away two inches of epoxy Bryan😮
😁😂
Sounds like a fix though 👍
Cheers, Doug 😎

Bryan, sounds like your on the right track, is there any way that you could pour resin into your Hull and tilt it around to coat the whole of the inside.
That would ensure that you are water tight.
Happy New year shipmate, cheers Colin.

Good news the leak is a single separation between planks approx 10 inches long but the only one. I mixed a batch of epoxy and ran it into the gap. covering it to an inch each side. I've just done it and leaving it to dry.

I'm waiting a few days to ensure the wood is dry before doing the repair

Good advise on the multi-meter👍

G.R.P. Resin maybe ?

Hi Bryan
Your single line crack may just be the tip of the iceberg. The paint on your hull will have hidden what is underneath and you may find that there are many more that have not appeared.
I suggest you carefully run a finger over the outside of the hull paying attention to the plank joints. If you can feel a ridge it is possible there is a crack underneath. I thought my hull just had a few cracks and sealed as you propose but found over a few sailings that there were many more.
I now intend to strip the hull and cover in fine glass cloth and laminating resin. Will take some time and effort but will last for years. Your model may not be the same and there is only one crack.
ColinH has provided a good sound solution which will work well on that crack.
Be good to hear how you progress as others will benefit from your experience.
Cheers
dave976

Thankyou for that Colin I will use your solution

Bryan, the only problem with your solution is that most superglue aren't waterproof.
When you say that the control gear is in the way, could you post a picture, you could syringe into the split with an epoxy glue thinned down with thinners.
I have done this in the past using fibre glass resin mixed and thinned using cellulose thinner and it hasn't let me down.
Hope you find this useful, cheers Colin.

its a single line crack, I'm thinking of allowing superglue to run into it to provide a seal once the boat is dry again. .the crack is only accessible from the bottom as there's the control gear above it

Hi Bryan glad you have discovered this leak. Far easier to sort out now. Merry Christmas
Dave 976

ah The bad news t has sprung a seam under the forward hatch area. Ship is now in dry dock awaiting repair

You can use the meter switched to amps in series with the motor and battery. you can have the Bob's board connected as well. Only use your meter if it has a 10 amp position.

Do not use the meter on amps with an electronic esc as they don't seem to get on!
Roy

If you are curious as to what capacity battery to use then work out the voltage and current required and if using NiMh or LiPo or Nicads then multiply the running current by 5 and this is the ideal capacity for most efficient use of the battery.
If you use a SLA (lead acid) battery then you need to multiply by 20.

This is not always practical and if you take more current the battery becomes less efficient, if you have over done it the battery will get hot. You also get a reduced effective capacity.

When buying new batteries check the maximum discharge rate, this gives you an idea of current availability.

A word of warning do not buy 'cheap' batteries from China most of the time the written capacity on the battery is a work of fiction.

The sellers do not seem to realise they give themselves away when they print the specification of the battery. A simple check is to look at the weight in grams of the battery or cell.

Then check Components Shop where you will find an honest set of numbers and see if they match. To illustrate, a sub-C cell of 1800mAh is lighter in weight than a similar looking cell of 2600mAh capacity. They are both the same physical size but weight matters most.
If in doubt get the scales out and check the weight.

Just remember that the first successful small rechargeable cells were the disc Deac cells and then the sub-C cells and the were specifically designed for powering model aircraft, as you can see the spin-off almost runs the world now!
regards
Roy

I have a standard multimeter so happy to measure voltage but no idea about amperage measurements. I'll rely on the heat test

Hi Bryan you can judge if a motor is under stress as it will get hot, warm is OK. You can also make the same judgement about batteries. If you are able to check or find out from literature what the stall current is, then running the motor at 20% of that figure is about the most efficient current for that motor.
So keeping the current down you can easily apply 50% more volts. It works the other way as well. If you have a 20 - 24 volt motor usually these are commercial ones, then you can run quite a large propellor but only using 3 - 6 volts. I do this in another boat I have.

The stall test is a good way of checking an unknown motor do not hold the motor stationary for more than a second or two as otherwise the permanent magnet will be be affected. Measure that current and divide by 5 for optimum performance.

So geared down motors have a better chance of running efficiently but there are always some losses in the gearbox.
regards
Roy

Good news it floats, I'm going to leave it there for a few hours, fingers crossed its still floating when I finish shopping

Thank you Dave for your advice, I haven't even float tested the boat yet but will stick it in the bath today

Thank you Roy. I have a few 7.2 nimh packs so could use one, I wasn't sure it wouldn't be too much for the motor

Hello Bryan, I would suggest you buy a 7.2 volt Nimh or perhaps LiPo battery as an SLA battery unless around 7 Ah 6 volts will just not last long.
My Decaperm is marked 6 volts max 7 amps. If you got to this much power the boat would be planing! As it is the motor has far more power than needed but the current taken will be determined by the size of the propeller.
If you are able to measure the current under load 2 - 3 amps will be more than enough. I have a similar sized merchant ship which runs nicely on a monoperm super and takes about one and a half amps on 7.2 volts. Don't worry about using a 7 volt battery on a labelled 6 volt motor, it is not a problem.
regards
Roy.

https://www.ebay-kleinanzeigen.de/s-anzeige/graupner-getriebe-motor-decaperm-6-volt/1504109036-249-4425

This is the motor fitted to the boat

Looking good Bryan.
The motor is clearly a Decaperm and I can send you a pic of an advert from that period showing your motor if you are interested.
It looks like Cascamite was used on your model as I can see blobs of it on the inside of the hull.
I suggest you float the model in water for a couple of hours to see if there are any leaks in the hull - be easier to fix now before you spend time finishing.
Cheers
Dave976

Thanks for that Advert it really evokes the period.

A little progress today, A big clean up of the decks to remove years of dust. The deck on the right is clean and it's getting there.

Hi Bryan
I am listing my clubs old mag collection and by chance the Model Boats 1967 mag carried an advert with pic for the Mercantic. I have enclosed a photocopy FYI
Cheers
Dave

Hi Bryan
If you look closely at my model you can just see a searchlight on the cabin so the railings dip to allow the beam unlimited throw.
I still have the original plans- rather tatty but can scan them for you if it would help.
The kit supplied a Graupner 3 blade plastic prop which was pretty useless forward and hopeless in reverse, so I suggest you replace with a nice 3 blade brass version.
Cheers
Dave 976

Dave Thanks for that photo it will really help when I do the re-rigging.

One question about the railing above the wheelhouse. Why is there a deliberate droop on one side? Please see photo

Thank you all for your guidance I will try 6v. There is a fuse inline with a 3A fuse in it. I am tempted to keep it old school as all I need is the servos and receiver (27 mhz of course). I can just use a modern esc but I've never had the old style scraper before so am tempted to try it first.

The hull seems good and needs a good clean and some re-rigging to hold the deck cranes upright. Minor wood damage will be replaced using the cut a bit of lolly stick to shape, glue and try and match paint.

I've not got a SLA 6v battery but sure the bay of e will solve that one

I'll try the old motor first but will replace if it doesn't work.

My first boat and I still have it but need restoration. 6v motorcycle batteries were the norm and usually paired with a 6v motor I agree with ColinH and roycv regarding the type but you will need to provide a better pic to correctly identify. My plank on frame was built using Cascamite and over the years the wood supplied and used in many of the Billing kits has cracked along the glue lines so needs stripping and covering with fine fibreglass cloth to seal.
Bobs Boards were the norm and worked OK but a modern ESC will work better. The motor may be OK but the magnets and wiring may have deteriorated over the years and may not be as when new. A nice 555 would work well with a new ESC. Many would decry not keeping the original equipment but it will help you sail safely.
I attach a pic of my Mercantic at New Brighton during the 1960's.
Looking forward to seeing this restoration
Dave976

Hi, that is an old 'Bobs' board. More concerned with current than voltage, I think it would be safe to guess at 5 amps and probably 6 volts for the the motor.

They sit on top of a servo and the contact arms fit on the servo and the voltage to the motor is from wires on the moving arms.
They work OK as long as the arms maintain contact on the resistive pcb.
Closer looking at the motor I can see a bit of a curve to the base and I think it is a Marx Monoperm or monoperm super motor.

Might be easier to ditch it and use a cheap esc.
regards
Roy

With an sla battery,it would be fine, I have a few setups from the late 60's early 70's like that of yours. Try with a 6v 4ah battery. Or an adjustable power supply to test.
Cheers Colin.

Hi Brian, that looks to be a decaperm geared motor, normally run on 6 volts.
If you let us have the physical size I could confirm.
Cheers Colin.

I will use a modern speed controller though I'm tempted to try the old one