Looks strong and smooth running. Great work.

Lew
Florida 😎🚤, USA

Well done Les. You will have learnt such a lot building this boat and should be very proud of the finished result. I hope it sails well.
If you need a double jointed coupling for your next project they are available in various disguises from Deans Marine. www.deansmarine.co.uk
Good luck. 😉

Well done Les, you got a great result.

Hello Les
Looks a really neat installation to me, well done and when you put the lid on the boat the moderate noise will lessen.
Regards ChrisG

Hello LesW
I'm glad we could help you. I am also very satisfied with the shaft connection. I got the tip myself from a very good friend who unfortunately has already passed away.👍

I said I would update on this problem and the motor mount is done. took me longer due to having to wait for the new coupling.
The mounting is a bit chunky in build as I used what I had in my workshop/garage. The alignment was made using a ridged substitute coupler I made. The new coupling follows forum member 'Wolle' and was bought from a CNC parts supplier I use (3d printers and similar). Its a very nice item with very good flexibility for about 5 deg each side of its axis and has 2x grub screws each side of the part for clamping, it cost £3.95. I could not find the dumas dog bone coupler in the UK. (USA has plenty) As for the sound deadening erasers, I have little room underneath the motor so had to pass on that this time and opted for a Hybrid Polymer Sealant Adhesive to provide a shallow bed of silicone under the motor mount plates. I have experience of using Hybrid Polymers on my Campervan build and they provide excellent bonding with a slightly flexible joint. So its in place and I think it is the best I can do on this build. If I build another boat next winter I will tackle the whole build differently as I have made plenty of mistakes on this first one. Thanks to all for their comments and advice and I will do the boating lake test probably next week if the weather improves. Video is shown at full motor speed and reverse.

Hello Alessandro
The connections I used are not completely rigid, they allow for a slight, non-optimal position and compensate for it.

Here is a link.

https://www.ebay.de/itm/332909225030?mkcid=16&mkevt=1&mkrid=707-127634-2357-0&ss

Hi LesW.

Very well, now you have a lot of information available and it seems to me that they are all quite in agreement or at least not in antithesis. You simply have more solutions available.

Let's recap to get things in order.

The noise is loud but not excessive, there is worse. But it's a symptom.
It is a symptom of vibrations.
Better to reduce them as much as possible. I agree with you on this.

You have narrowed down and identified the problem very well.
It is possible to act simultaneously on two directions of attack.
1. The axle and the joint.
2. The absorption on the motor block.
The potential problem with the motor brushes and any other internal problems within the motor itself, we have already ruled out.
It's excluded, the engine runs well.

1. For the axle and the joint you have two options for the solution.

1A. Finding the precise alignment (I would say perfect, even if perfection does not exist in this world) is the first choice in my opinion.
If you line everything up perfectly any joint should be fine.
But, as Wolle advised you, in a perfect alignment I would put a fixed joint and save the cardanic joint for other situations.
I like it as a solution because, generally speaking, I opt for misalignment only if I have this need.
If there are no other priorities, it is always better to align perfectly, but there are actually situations in which one is forced to make different choices.
It is the cheapest solution and you don't have to make many changes to the state of the work you are in now.

1B. As you already know, the cardan joint (in Italian we call it a "cardanic" joint or simply "cardan" after the Italian mathematician Gerolamo Cardano (1501-1576) even though it was already known to the ancient Greeks) creates vibrations at high speeds because it is not homokinetic.
At this point, if you maintain the misalignment (but I don't see the need or reason), to reduce vibrations you have two solutions to reduce vibrations:
1BA. Either you use a "homokinetic" joint (there should be "homokinetic" joints on the market also for modeling but I have never done specific research on this),
1BB. Or you use two cardan joints in series which, as they have already explained to you, create a cardan shaft that is very close to a "homokinetic" condition (instantaneous angular velocity of the driven shaft constant during a complete rotation), as long as they have the same angle of misalignment of the driven shaft axis with respect to the drive shaft axis.
To avoid confusion, I tell you that what I saw in your photo in Italian we call a "cardan" joint (it is not homokinetic). Instead, we call the double "cardanic" joint a "universal joint" (it is homokinetic).
Sorry but Google Translate is driving me crazy and always replaces words.

2. As I had already suggested to you in the twelfth message: "These supports must not "choke" the engine and it would be better to insert some rubbery material between the engine casings and the supports to dampen vibrations", it seems that this possibility is shared by many naval modelers who have adopted it successfully.
I am very pleased that it is such a shared solution even though I would have used materials other than erasers and I was sending you a hypothetical drawing of what the support with rubberized edges could look like.
However, I have a lot of respect for successful solutions dictated by experience so I won't add anything else.


For the other macro area, consisting of buoyancy in the water, we await your tests and further news.

Lew I also use dog bones in addition to using u-joints. The newest dog bones I have gotten have 4 nibs instead of 2. I don't remember were I got the new ones from. Len

I like the dog bones coupler as well, will also look at that