Also regarding the Eze-kote I purchased some sanding sealer last year is this the same type of stuff Doug???

Cheers for the photos guys I'll have a look when online with computer later on. Regarding the original hole in the hull do I just drill it or file it to achieve a more acute angle as now I've removed the old engine mount there's no way I can achieve alignment with the new motor position. I think I'll stay with my old motor as opposed to expense on a brushless as been looking and I don't think 'She that must be obeyed' would wear an 80quid spend lol, considering it's taken another year to get going again.

Hi Neil, here's my 'twopenn'orth' on this subject w.r.t. the brushless upgrade in my 24" Sea Scout. I'm happy with the relationship between prop and rudder so am concentrating on the motor mount and coupling now.
Pics show the motor removed and the new one, old and new mounts and new coupling. Alignment will be done with the help of an ammeter as usual. Minimum current draw = best alignment 😊
Insides have been cleaned up and sealed with Eze-Kote 1 part polyester resin. Lovely stuff, just wash out the brushes with hot water and you can use 'em again! When all is correct the 'engine compartment' will be painted with white gloss Hammerite. 2nd last pic shows old plastic prop (50mm) and new brass one (30mm) matched to the brushless.
Have fun, Greetings Doug 😎

Hi Neilmc
Looking at the pics it would appear you have the larger model.
I am attaching photos of the internals of my model but don't have any better of the prop shaft.
I also have a Sea Queen which is from the same stable (Les Rowell) and at 48" nearer to you model, so am attaching pics which do show what you want a bit better.
If you need more detail please let me know.
Cheers
Dave

DaveM is there any chance of some close ups of your boats prop shaft to give me some further ideas on positioning. internal pictures would be good also if not considered to cheeky 😁

Well after another pointer from DaveM to remove the old engine mount I actually managed it with some effort bit after bit was removed and the four screws shown obviously explain why previous attempt failed and it was so difficult to budge. 😤😤
With the mount removed I can now see the angle of the prop shaft is to great so some more work in this area. I'm presuming that the platform left behind would be OK to try mounting my 600 can motor?
Any tips on the best angle needed and also how this would achieved? Also thinking the prop shaft A frame support needs to go as well or could I adapt it as surely these are needed??

BTW; how did the convention go?
Let me know in good time when the next one is please. I'll try to arrange a trip to 'the old country' 😉
Doug 😎

Agreed.
But don't we also want efficiency?
Good manoeuvrability, minimum drag and longest running time from the battery! Some basic principles and guidelines are always useful, especially as you say to restorers; as this blog started.
Cheers Doug 😎

I agree Les Rowell did know his stuff and all his models sailed well.
I do believe he designed and built from personal experience so there would have been much testing and modification before the final kits were released.
I can appreciate the tests were undertaken in test tanks but for commercial ships the aim was to make them efficient for their designed purpose. Any help is always welcome if you are building from scratch but for a model I suspect the best way is to make some assumptions and then try out in the water.
Most modern kits and plans have already done this so it is not normally a problem except for restorers and scratch builders.
Dave

Hi Dave, forgot to mention that Marin tested the calculations and computer simulations with scale models in their 250m test tank, with good agreement. Later full size measurements in sea states 5 and 6, with variable winds and drift angles also gave good agreement.

One important point though; I misread a paragraph🤔
The actual distance prop tips to rudder leading edge was 1 prop radius!!
So for my Sea Scout with a 30 or 35mm prop my 17mm spacing is about right 😊 Most of the tests were actually to determine the rudder's lateral position relative to the prop shaft on multi-shaft designs and vertical position relative to hull and prop diameter.
Vertical position was determined as; if possible close to the hull, in the lamina flow region and 'covering the upper 47% of the prop diameter'.
In this position the effects of the drift angle in a fast turn (e.g. caused by wind at an angle to the bow and the turning of the ship itself, 'skidding') are reduced to practically zero.
If the rudder covers the lower half of the prop diameter it is affected by transverse water flow across the stern, reducing manoeuvrability and increasing rudder torque and stock loading!
So again Sea Scout is about right 😊 The Aerokits designers knew their stuff, or were just plain lucky!

For the shaft alignment I use the balsa wedges for fine adjustments then epoxy everything in place when the ammeter tells me all is OK.
Filler and cosmetic to finish off.
Cheers Doug 😎

Hi Doug and Neil
Fascinating details about full size props and distances. Our scaled models sail in water which is not scaled so I am not convinced the maths helps.
There are many examples of Fireboats on this site and as has often been mentioned the original Aerokits were designed when IC engines were the fashion and as a result the prop shafts were at a very acute angle to accommodate the fitting of the engine.
If you have an original kit model the easiest solution is to remove all the engine mounts and any oil soaked wood from the hull together with the prop shaft and tube.
You can then buy a suitable motor and prop and work out the best alignment. Buy a prop shaft and tube to suit the distance and adjust the slot in the keel to allow fitment. I usually make the slot big enough to allow for alignment, you can repair any gaps later. I usually tack mine in place with small dabs of superglue to hold in place, not too much as you may need to reposition. Once all aligned you can fill the gaps as Doug says with balsa. I just use Plastic Padding car body filler, but either will work. Once all is set hard you can fettle to the keel / hull shape and make good inside the hull.
Not sure which model size you have but am attaching pics of my 34" Crash tender which may help.
Happy restoration
Dave

Now there's a blast from my past career in the Navy I can remember froude numbers and other calculations during a damage control course. Blew my mind all I wanted was to play in the wave tanks 😂
I suppose you're not far off and it it's been working fine till now 🤣
I 've also found some end seals for my shaft that seem to be the same type as the ones fitted to Raboesch shafts but a little cheaper may give one a go at 8.00 from eBay. Will let you known how I get on
Cheers Neil

Hi Neil, (Old (Sea) Dogs can learn😉).
My pleasure, happy to help.
Today (quite coincidentally!) I ran across a mathematical dissertation on the relationships between prop, rudder and hull (Yawn!) done by Marin Corp. for a symposium on 'Fast Mono-hulls'. Primarily naval.
Full of Froude numbers and Lord knows what. But the upshot was that the optimum distance between prop and rudder should be 0.47 x radius of prop.
So with my 30mm prop and 17mm distance I'm a 'bit' off🤔 15x0.47=7.05.
Shucks; where are my thrust washers? Need a couple more 😉
Never mind, I wanted to make a new shaft anyway, to fit the brushless upgrade mounting. Ho hum! Whatever - Have fun, Doug 😎

Hi Doug, I've been called worse as you may imagine lol. Thanks for taking the time to post photo which has made things so much clearer as to position and distance from the rudder. Also found some photos in robbobs build blog which when you put the two together I should be able to get it right. I like the idea of packing out with balsa as I should be able to temp fix it to alignment right this time.

Hi Neil (where the heck did I get Steve from!? Sorry😲)
I don't know any hard and fast rule or formula, sure there is one that the marine architects use though.
As a guide the rudder on my 24" Sea Scout is min 1.7cm from the prop tips. See pic.
Now you've drawn my attention to it I think I'll extend the rudder shaft to bring more of it down to the prop level!!! 😉 Might be easier than lifting the prop shaft 😡
Cheers Doug 😎

Hi Doug, thanks for the reply quick question is there any recommended distance that the prop has to be from the rudder and similiar when the outer casing comes into through the hull for the shaft to attach to the motor?
Cheers Neil

Hi Steve, When I repositioned the shafts in my destroyer I wedged them in with slivers of balsa until the alignment was right, then soaked the breakthroughs in keel and bulkheads in epoxy. When all was properly cured I did the usual cosmetic filling, sanding and repainting. Has been working a treat for over 20 years. 😊
Again re Raboesch; I am gradually replacing all my plastic and no name props with Raboesch. The quality and, above all, balancing is superior.
Cheers Doug 😎

Re "new shaft through an old hole"- 😉
Answers on a sealed postcard to ......"

Seriously though folks; Yep, can thoroughly recommend Raboesch props and shafts. Expensive but D... good. Worth it! 👍
Cheers Doug 😎

Just been looking over google about my problem of how to position my prop and came across Raboesch maintenance free props. The one I have is just a tube with the shaft running it. is it worth investing in one of these Rabeosch props?