Topic: R.T.T.L. 2751 (Read 15971 times)

cdsc123 · « **Reply #35 on:** November 23, 2009, 09:05:00 PM »

Yep, spot on

bluebird · « **Reply #36 on:** November 23, 2009, 09:16:18 PM »

bluebird · « **Reply #37 on:** November 23, 2009, 09:17:47 PM »

Now the next question Christian

both props were left hand and the rudders had trim tabs fitted to them to help steerage as thay were prone to pull to the starboard so thay say do you have any pics of the rudders fitted with the trim tabs ? pleas

john e

cdsc123 · « **Reply #38 on:** November 23, 2009, 09:51:05 PM »

Sorry, no. I'm not convinced the RTTLs had these though, I think the Brave Class which were a larger and faster version of the same hull design had them though. The RTTLs were famous for needing an experienced helm to prevent slamming onto one chine on re-entry after wave jumping, due as you say to the torque effect of having same handed props. The trick was to apply helm on take-off to counter the torque effect.
They did however have transom wedges retrofitted to bring the nose down, a comparison photo showing one boat with and another without can be seen here, close to the bottom of the page;
http://www.bmpt.org.uk/boat%20histories/brave%20class/page_two.htm
BTW I have seen a rear view of 2751 which shows the external transom planking to be horizontal.

perkasaman · « **Reply #39 on:** November 23, 2009, 11:21:41 PM »

Some great info here - it seems that a third (additional) diagonal layer was retro added to their 'bottoms' to resist the stress of prop torque slap/pounding mentioned by cdsc123.
My winter build plan of a 1:16 RTTL finished in Medit. colours (white) might kickstart earlier. These craft make fine looking models - keep up the fine work John. (I'm making a lot of notes.)

bluebird · « **Reply #40 on:** November 24, 2009, 09:36:06 AM »

http://www.bmpt.org.uk/News/Brian%20Mutton%20Memories%20of%20RAF%20Marine%20craft.pdf

some good stuff hear to have look at regarding trim flaps

john

bluebird · « **Reply #41 on:** November 24, 2009, 07:22:22 PM »

hi all

just a quick update, started on the exterior planking there are 30 mahogany planks on there - and its taken me the best part of the day to do this much....but both sides are done - I have calculated there may be 360 odd more planks to go on.....the steel tubing that you see in the foreground is what I am using to roll the planks over - to get the bend in the planks. Also, when I have put the glue on the back of the planks I use the tube similar to a rolling pin - this removes all the air bubbles from underneath - it also beds the plank in.

so here goes....planking away

oh - and I have added a front view to show the flares of the bow.

aye
john

bluebird · « **Reply #42 on:** November 25, 2009, 06:30:32 PM »

Some great info here - it seems that a third (additional) diagonal layer was retro added to their 'bottoms' to resist the stress of prop torque slap/pounding mentioned by cdsc123.
notes.

Hi ya Brian this is interesting, I havent managed to find any facts to back this up yet. The only thing I can find on the web and in a few books which I have is where it mentions strengthening the starboard side chine and adding extra supports to the affected areas - logically thinking I cannot see them adding an extra layer of diagonal planking over the bottom of the hull as this would increase the weight of the vessel and dratrically decrease its performance.

I would have thought that if they were that concerned, they would have just reduced the govenor settings on the engines. I did, however, find reference to strengthening the hull at the chine on the experimental boats which had aluminium bottoms on the hull and they were prone to cracking around the chine where stress was caused, but, this was later rectified where they stripped off all of the aluminium and fibre glass and replaced it with double diagonal planking.

aye
john e
bluebird

perkasaman · « **Reply #43 on:** November 25, 2009, 09:37:25 PM »

Stengthening/adding frames after skinning x2 and final fitout would be a nightmare/uber expensive exercise (Vosper liability - design unfit for purpose i.e. 40knots?????) After the inexpensive final trim wedge solution (a la' E or S BOOTE fashion) adding a third 'stiffening' bottom layer of 15/16" must have been a hugely cheaper/getout for Vosper. The waterline on the mk11 rttl's is very interesting/revealing. Don't forget that these structural issues ocurred in only certain sea states and general governing of the throttles would have been inappropriate/unnecessary in all other sea conditions where the full monty ok.
You are not seriously intending to add an extra skin if you verify the fact

cdsc123 · « **Reply #44 on:** November 26, 2009, 09:20:26 PM »

Hi John

This is a superb treasure trove of RTTL photos, the 2751 gallery has a few good views;

http://www.asrmcs-club.com/BoatsWebsite/rttl1ab2.html

I took this photo of 2753 when she was being broken up, you can clearly see there are 2 layers of planking despite what I have read on the subject.

The really interesting thing is the cross section of the trim wedges;

HS93 · « **Reply #45 on:** November 26, 2009, 09:23:10 PM »

is that one of the wedges and if it is how far across does it go and have you any other pictures of the wedges

thanks

peter

cdsc123 · « **Reply #46 on:** November 26, 2009, 09:28:33 PM »

Hi Peter

Yes, all the way, and no, not in cross section.

HS93 · « **Reply #47 on:** November 26, 2009, 09:41:50 PM »

Thanks anyway.

peter

bluebird · « **Reply #48 on:** November 26, 2009, 11:35:26 PM »

Hi Christian thanks very much for putting that link on

so can we say that no boats of this class had three layers of bottom planking ?

john

cdsc123 · « **Reply #49 on:** November 27, 2009, 06:37:54 PM »

Hi John

I suppose some must have, as lead historian T Holtham says they did in his published work (RAF Marine Craft Directory).

Perhaps 2753 slipped through that net. The thing to look for is the direction of the outer layer on the bottom, as a 3rd layer would surely have gone in a different direction to the 2nd layer. I note from recent photos that 2751's outer layer of bottom planks runs parallel to the stem, i.e. "leaning forwards", whereas 2753 had the opposite. This could mean 2753 never got the 3rd layer but 2751 was one of the boats that did (this assumption is made safer as they both came from the same builder).

Pure conjecture, but a theory nontheless.

bluebird · « **Reply #50 on:** November 27, 2009, 06:42:03 PM »

hi ya there Christian

put this into the pot for the theory.....I did a quick calculation of the weight of an extra skin made of mahogany 1/2 inch thick - using the model to scale the area required and it comes just under 1/4 of a ton in weight

now you stick that 1/4 ton on top of the total weight of the hull already and to maintain the average of 39-40 knots the power requirements - you would have to find another approx 10 horse-power per engine

...... does this make sense

ah but to be on the safe side I might put a 3rd layer of skin on .....

what really surprised me were the actual trim wedges - I was visualising a lot larger wedge in depth - just goes to show it doesnt take much to trim a boat.

aye
john

perkasaman · « **Reply #51 on:** November 30, 2009, 12:26:07 AM »

The film 'Hell Boats' features two disguised RTTL's - sadly, footage of these handsome craft seems very scarce.

bluebird · « **Reply #52 on:** December 04, 2009, 09:46:50 PM »

hi all just a little progress report

side planking is finished and progressing the bottom planking

johne

riggers24 · « **Reply #53 on:** December 04, 2009, 09:50:57 PM »

Bluebird,

What preparation do you do to the inner layer before you start the outer layer of planking

Riggers

DickyD · « **Reply #54 on:** December 04, 2009, 10:04:55 PM »

Where would you be without Perkasaman John ?

Lonely

perkasaman · « **Reply #55 on:** December 05, 2009, 01:58:41 AM »

Divvent fret Dicky!

bluebird · « **Reply #56 on:** December 05, 2009, 09:41:51 AM »

Quote from: DickyD on December 04, 2009, 10:04:55 PM

Where would you be without Perkasaman John ?

Lonely

the same as you you would be knackered without your very best mate GOOGLE

bluebird · « **Reply #57 on:** December 08, 2009, 02:28:38 PM »

Hi All

All the outside planking is now finished and it has been sanded down. This has now been given one coat of finishing epoxy and will now be left to dry for twenty-four hours then it will be sanded down and re-coated with two more coats of Zepoxy finishing resin.

Aye
John e
bluebird

steve pickstock · « **Reply #58 on:** December 08, 2009, 03:21:48 PM »

That is a thing of beauty.

Flying Sparks · « **Reply #59 on:** December 08, 2009, 10:14:53 PM »

Looks too good to paint

Keep up the good work.

Phil

bluebird · « **Reply #60 on:** December 18, 2009, 07:18:49 PM »

Hi there all

Just a quick update. I have finished rubbing down the outside of the hull; and removed it from the building board. As you can see, I have installed the prop shafts and the motors. The motors at the moment are only in temporarily and so I can see how they perform - they are an MTronik Vision Motor - originally I was going to use a Graupener 600E motor - and I still may go down that route.

Also, I have added the rudders and the rudder tiller arms. As yet I havent fitted up the linkage between them.

Here's a couple of pics....
aye
john e
bluebird bloobs

DickyD · « **Reply #61 on:** December 18, 2009, 09:12:19 PM »

I bet you change those motors John, I have two in my workroom.

Came out of my gunboat and PT boat because they were so noisy I could not hear the sound units.

Looking good though.

bluebird · « **Reply #62 on:** December 19, 2009, 05:44:20 PM »

Dicky hi ya there

The motors run nice n sweet and quiet. The problems, which I have sorted now were the:

Cheap - Ebay prop shafts

which I have managed to re-bush in situ with smaller bushes which fit the propeller tube properly rather than being a rattling good fit.

Couplings - I removed the red insert and replaced it with a bit of silicon tubing and the motor can hardly be heard, whilst its running at full belt. But, as soon as the red couplings are put back - its like a bag of hammers - so that is the next job to sort out.

I have tested the model in the bath - and it empties the bath quite nicely!

Drawing all of 12 amps per motor.

So, I think I am going to have Mr ACTion's heavy duty P94.

aye
john e
bluebird

DickyD · « **Reply #63 on:** December 19, 2009, 06:44:34 PM »

Aye John roll on Christmas.

bluebird · « **Reply #64 on:** December 24, 2009, 10:50:48 AM »

Hi all
just a quick update, started fitting the deck planking

aye john e

bluebird

ONE DAY TO GO

Dicky

FullLeatherJacket · « **Reply #65 on:** December 24, 2009, 11:04:03 AM »

Don't forget to leave room for a 4" speaker, Bloobs

FLJ

bluebird · « **Reply #66 on:** December 24, 2009, 11:06:44 AM »

Quote from: FullLeatherJacket on December 24, 2009, 11:04:03 AM

Don't forget to leave room for a 4" speaker, Bloobs
FLJ

Its all in the plan

davidm1945 · « **Reply #67 on:** December 24, 2009, 02:47:43 PM »

Quote from: FullLeatherJacket on December 24, 2009, 11:04:03 AM

Don't forget to leave room for a 4" speaker, Bloobs
FLJ

Does anyone make a sound unit that sounds like 2 RR Griffons?

Dave.

bluebird · « **Reply #68 on:** December 27, 2009, 12:22:18 PM »

aye aye there

Through the grapevine I have heard there is a sound unit on a test bed ... it has had a brief outing ... but stilll in test. This unit, so I believe, reproduces digital sound recordings and which may be downloaded from the computer.

One of the main sounds, if required, can be a multiple Griffen engine.

Also, one may record other sounds onto this unit - but - we will have to wait and see.

I believe the code name of it may be the P100.

aye
john e
bluebird

davidm1945 · « **Reply #69 on:** December 27, 2009, 05:25:20 PM »

Somebody mentioned to me that Tamiya do a sound unit for their tanks. Yeah, I know it's probably some big German diesel but it may sound better than the little 4 cylinder petrol jobbies on offer at the moment. Does anyone have any more info on this? I can't seem to find anything on the net.

Dave.

Modified for spelling

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Author Topic: R.T.T.L. 2751 (Read 15971 times)

steve pickstock

Flying Sparks

FullLeatherJacket

davidm1945

davidm1945