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Author Topic: Delta 28, another LONG term project...  (Read 1483 times)

KitS

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Delta 28, another LONG term project...
« on: March 22, 2009, 11:04:24 PM »

I've been a plastic modeller since before I did any other sort of modelling, but very few boats came my way, I modelled mostly aircraft and a few cars. Years ago, mid 70s, I bought an Otaki plastic kit of dubious parentage that purported to be a racing speed boat, but I never did anything with it as it was just too toy-like. (see the first pic below)

Backing up some years I've always been a fan of Sony Levi's 'Delta' shape boats, having seen 'Surfury', 'Delta 28', 'Merry-Go-Round' and others racing in the Cowes-Torquay races in the 60s, and of these 'Delta 28' has always been my favourite. It was just SO over-the-top, vastly overpowered and stupidly unstable! From Durlston Head I saw it almost loop once, luckily the driver did a splendid job and just averted total disaster. Needless to say a model of 'Delta 28' has always been in my mental short-list since I got back into model boating recently, but I was sure it was above my capabilities. A few months ago things took a radical turn for the better when I managed to get hold of a copy of Sony Levi's book 'Milestomes of my Designs'. I'd had 'Dhows to Deltas' for some years, but I knew 'Milestones' had much more detail than the other book, now at last I had both of them.

Looking at the plans in 'Dhows' it occured to me I'd seen that shape before........ (see pic 2)

I was almost sure it was the Otaki model so I dug the kit out of the loft and compared the two. It was difficult to be sure so I scanned and enlarged the plans to the model scale, around 1/20th, and there it was! The Otaki kit was an almost EXACT model of the 'Delta 28' hull even if the rest was imaginary. (see pic 3)

After trying a huge transom mounted fin in the '68 season, which worked about as well as lead manhole cover, the Gardner brothers fitted a long 'ran bow' to 'Delta 28', extended the aft hull surfaces and mounted the prop and rudder on a stinger, and some of these can be seen in the fourth pic below. This is how I wanted to model 'Delta 28' and Sony kindly provides excellent drawings of this modification, even down to the full size material specs! (see 5 below)

I scanned and re-scaled the ram bow drawings to the same 1/20 scale and compared it to the Otaki hull (pic 6 below) and I think it's possible. OK, so it won't be all that strong or as fast in scale as the real thing, but I think it will look good anyway! I'm working on installing a thick keel to make the ram bow profile and then add a couple of formers before skinning it in some fairly thick styrene. i've got a few 540-550 motors about and the hull is deep enough to take a beefy battery pack as well as the radio gear. The prop-shaft exit fairing will need moving aft and I'll have to do something about the stinger, but maybe a few words to Astec will solve that.

Plastic cutting starts tomorrow!  :-)
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Kit

KitS

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Re: Delta 28, another LONG term project...
« Reply #1 on: March 28, 2009, 12:11:56 AM »

'Cutting Plastic' turns out to be a trifle understated.......

The styrene that this hull is made from seems to be related to re-inforced concrete as it gets through scalpel blades like a knife through butter.

Because the ram bow version of 'Delta 28' had her propshaft exit point moved right aft, only inches forward of the transom, I had to do the same on the model hull, so I cut out a rectangular section along the keel from the transom to forward of the shaft exit fairing, as shown in pic 07 below. This took 3 blades and a nicked thumb, so tough was the styrene even though it's only 1.5 mm thick.

Then I cut the rectangular section in half and replaced the halves the other way round, with the fairing right aft and the plain section forward. To ensure they stayed in place and to strengthen the joint I glued some 40 thou styrene strips inside the hull to locate the cut-out sections against.  A gash propshaft was fitted after cutting away surplus plastic in the fairing and a trial motor fit showed I need a much shorter shaft if the motor isn't be up inside the cockpit! See pic 08.

I'd already made a cutting diagram for the spine of the ram bow and cut out the shape in some 50 thou with the aid of some French curves (and a few more scalpel blades......) and I intented it to be inset into the bow to give it more strength than just glueing onto the hull. Therefore I drilled a row of holes through the hull keel and bow in the area where the ram would fit, and then formed the slot by filing, a process that took AGES! See pic 09.

Then came gluing the ram in position, which went surprisingly well, using copious amounts of Revell Contacta and then some Mek afterward to flood the joint. The ram was lined up using the plans I'd scanned and printed and left to dry. Some of the pre-drilled holes were still visible due to misalignment but I intend to use P38 along the length of the ram anyway so it's not so much of a problem. See pic 10

Now to make the hull extensions aft, which will need some thinking to give them a strong mechanical bond to the hull.

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Kit

KitS

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Re: Delta 28, another LONG term project...
« Reply #2 on: October 08, 2018, 05:16:56 PM »

I asked this elsewhere but didn't get an answer......

How can I edit older posts to re-link the missing pics please?

On other 'Simple Machines' Forums that I inhabit there's a 'modify' tab above each post, but it's missing on here.
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Kit
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