Darnell Type XX1 - Graham's Dad's boat for refurbishment

Just had a quick look at the vid, now I do think that the two ships lifting the 21 are the same two that lifted the Truculent, as they were captured from the German Navy at the end of the war, Some years back I meet up with the Senior Captain for the Truculent life and he had a scrap book of photos of all the lifts that he was in charge off, he is a great guy with lot's of story's about the lift.

Fred

Some progress with the WTBs. The two different sealing methods shown - both working well so far.

Both drive motors installed with 3:1 timing belt reduction gear and Simrit shaft seals. Both push rod glands installed - bellows not fitted yet.





David

That's coming along nicely now, David...and well done on posting the photos!

Servos, ESCs and receiver now in and working. I plan to use the ESC's BEC ,this time, to keep it simple.

Now working on the forward compartment for the USE steam engine. (The original Darnell box seals fine but I may use a smaller cylindrical forward WTC. (I'm trying to keep the weight of the model down - advancing old age!) and I also want to use a lead acid battery "in the wet" so I don't need such a large forward compartment.

I plan to hold both compartments in with Velcro - thanks for the idea Richard!

David

I understand the 'advancing old age', David...even merely lifting a smallish boat like the X craft or the Skipjack presents me with problems at the moment, hence the building of the Mk4 JellyBean. Maybe when I've been into hospital, and hopefully been refitted, I can go back to them, but for the time being...small is beautiful!

I'm planning on using Velcro to secure the box in the JellyBean as well, two long strips running the full length of the box should secure it nicely, I hope. They don't call me the Velcro Kid for nothing, you know!

First test of the original USE steam engine in the in the new forward WTC - not very promising.

Connecting up bag and original air vessel - bag empties nicely but a high - ish air pressure develops in the WTC - enough to blow the end cap off!

A pressure gauge shows a pressure which is a only fraction of an atmosphere but I need to do some more tests to see if I can reduce leaks in the USE. I can try nipping-up the spring on the cylinder but if the leak is result of wear on the piston itself it may be the end of my attempts to recommission the Darnell air pump! (And there is not much original equipment left standing!)

David

Oh dear...that doesn't sound good, David. I'm surprised that the little USE engine can build up that amount of pressure. Back to the drawing board with you!

For the record, I have confirmed that my original USE steam engine is too leaky. I can empty the bag but after a minute or so the pressure builds up too much in the WTC. Shame! The only original thing about the Darnell Type XXI is now the hull.

On to rather less time honoured methods such as the piston tank and AMS software or the pumped water pressure tank. (Both of which I have available.)

David

I'm pretty sure that USE steam engines are still available, David...maybe the steam section on Mayhem could help?



Richard

I think the leakage will be an inherent problem with the Darnell system. Speaking with Nigel it would seem that it would only work reliably in the long term with a float valve which will bring the internal pressure back to atmospheric when the boat surfaces. (That was the method that Dave Wright used.)

Also I think I will be dropping the use of the Darnell flat hatch motor box! It will be so much easier to put a full length WTC in. The hardware is all made up and I already have an end cap.

It is shame that so little of the original Darnell system will remain but it is a nicely finished hull! Without using the original air pump there seemed little point in adopting the rest of the system.

David

You traitor, sir!! There we all were, looking forward to a masterclass in restoring an original John Darnell system to it's former glory, and you're installing a...a cylinder?

How could you, David..I'm shocked and stunned. A cylinder...? Good grief...the world is coming to an end.


Richard

Yes Richard.

I am also going to burn my 1970's flared jeans and shave off my sideburns and my "Viva Zapata" moustache. I suppose things have to move on!

(The wig is going on the bonfire too!)

David

No..not the Irish? How will you keep the top of your head warm in the coming winter?

On a more serious note though, the boat is a beautifully built model, and well worth saving.After all, it's the outside that shows when it's on display...beauty is truly skin deep!


Richard

New approach, actually using the original WTC from my R class.

Inside the forward tray has the electronics and the dive system (piston or pressure tank). The rear tray is the newly made end cap with the newly installed twin 777 motors.

Altogether simpler, quicker to build and with much more reliability (a lot fewer holes!)

I'm sure that if John Darnell had access to sewer pipe he would have done it this way!

David

Sorry this is the picture for the text above.

David

Ok, I'll give you that...it looks much better than the original twin box layout. A nice, neat and tidy installation...my compliments, David..

Just an update on this.
The Darnell with my own WTC (with proportional piston tank used also in my R class.) went in very quickly and easily.
It splits into 2 parts very neatly. I can carry the Darnell hull (without the WTC) under my arm.
Fair zooms around the lake and had her diving  (first time) yesterday. Rear hydroplanes very responsive. Rudder response c**p even with a non-scale extension. But she turns nicely using the props.

I am rather pleased and my decision to drop the original Darnell diving gear was the right one. Technology moves on for a reason.

Now to get a decent paint job before summer!

David

Some photos of the Barrow Regatta (Targets + me!) taken yesterday.  An excellent day for all. The renovated Darnell Type XXI is almost finished now and she is still in undercoat but I think that grey is about right for the XXI. I will post some more photos + videos shortly.















David

Some more photos of the Type XXI and some videos taken last Sunday,including some static dives (Using the single piston tank.)






https://youtu.be/mPpItPK_ShI
https://www.youtube.com/watch?v=D4S3xeIt6oII
https://www.youtube.com/watch?v=PnwjDKGKeJY

David

Just an update on this and the Type XXI turning problems:

This version worked quite well but is not awfully scale and the "Yachties" in my club the Furness MBC pointed out that it was a "brake."



This version met the "Yachties" approval and turns her quite well. Also easy to remove.



A useful discussion on this on Model Boat Mayhem:

http://www.modelboatmayhem.co.uk/forum/index.php/topic,39951.0.html

An update on this following the fitting of twin brushless motors:



And some videos taken last Sunday in a rather flooded Barrow lake (you can hear my welly boots splashing!)  but a beautiful sunny day:

The 3rd one shows a complete static dive cycle (single home made piston tank (proportional control from openLRS system))

Flat out drawing about 3.5 amps:

https://youtu.be/M6ig24kj5BM

https://youtu.be/SKtJYzQWV8c

This shows a complete static dive cycle (single home made piston tank (proportional control from openLRS system)) One or two lost packet beeps.

https://youtu.be/eJctgegvn5U

Brillant work :)