Brutus

[ashley needhamParticipant @ashleyneedham69188]

Yup, so right. Should have reread a bit! Ashley

[Bob Abell 2Participant @bobabell2]

Yes, Ash and Dave…..The keel is concave by about 15mm……..I wonder why?

Can`t imagine how Paul conceived this design?

The final bows skin is extra tricky……..The ply grain has a mind of it`s own!

Could do with a few more breasthooks to tie it down…….Or solid balsa?

Paul….Are the bows concave?

Bob

PS……By having the grain at 45 degrees, it seems a possibility

Edited By Bob Abell on 25/01/2014 09:57:41

[Dave MilbournParticipant @davemilbourn48782]

Bob

Try running the grain of the ply from keel to chine rather than along the length of the model. It will bend a lot easier that way.

Dave

[Paul TParticipant @pault84577]

Hello Captain Bob

Firstly don't worry about the build as it is going exactly as envisaged.

To answer your questions

I never intended this hull to have an external keel and I fully expect the hull to be skittish when making high speed turns but this will simply separate the men from the boys.

Our discussion about sponsons related to a warship derivative of this design, which is still kicking around in the back of my mind, and are not needed on this particular model. The whole point of the Brutus design from an atheistic point of view is that it has a single long hull.

The keel is this curved shape in order to keep the bow in the water whilst the rest of the hull rises onto the plane (or semi plane) as shown below

The curved design of the lower hull is quite a complicated shape and took some time to achieve, this is due to the changing water contact point (the contact point moves toward the stern as the boat accelerates)

And lastly, but still very importantly, the bow is exactly 90deg vertical to the foredeck and knife sharp.

Paul

[Bob Abell 2Participant @bobabell2]

Paul,

This is how the Bows skin is turning out

Do we like it?…..Got the makings of a slight protruding bulge

The diagonal bend could be a straight joint line?………I`ll try it tomorrow

Bob

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Hello Bob.

Now, that is gruesome! One of the traditional full size methods of planking that bow shape was to use over thick, narrow vertical staves, which were then dubbed down, inside and out to the required thickness. It would produce a much nicer bow shape

regards

Aj

[Bob Abell 2Participant @bobabell2]

That`s gruesome?

You ain`t seen nothing yet!

New X Rated pix coming shortly!………Get behind the sofa and peep over the top!

In fact……..It`s lovely……In a funny sort of way?

Frankinstein……..OOOOooooooooooooooo!!!!!!!!!!!

[Paul TParticipant @pault84577]

Bob

The photo angle doesn't show the true extent of the 'bulge' so before you change anything could you please take a few more photos of the area.

Sorry to mess you about Bob but the shape of the bow is very important.

Paul

[Bob Abell 2Participant @bobabell2]

OK, Paul

But the die is cast!………Once more into the breach, dear friends!

Only larking about

You may be intrigued by this lateral suggestion?……….

What do you think of this then?

Bob

[Paul TParticipant @pault84577]

Hi Bob

I am sorry but the diagonal cut is too abrupt a change of angle as it is very important that the shape of the hull is formed by curves. It might be better to carve this section from a solid block .

For the benefit of the readers. The lower skin panels of the hull change profile from vertical to horizontal very quickly and because so much of the forward hull is visible it is critical that this change in profile be done with smooth, graceful curves.

Its a very difficult shape to achieve even with 1mm ply and it is going to be a challenge.  

Paul

Edited By Paul T on 26/01/2014 07:22:16

[Bob Abell 2Participant @bobabell2]

It's all your fault!…..lol

You've stipulated a sharp corner!…..Are the full size ships like this?

Please reconsider, your adverse thoughts and comments…..

On the photos, the keel and hull sides are smooth and inline with the rest of the hull!

Only the straight joint line looks aggressive…….If this was rounded off, would that meet the design requirement?

On the other hand……….II could make this from sheet Aluminium?

Bob

[Bob Abell 2Participant @bobabell2]

It's all your fault!…..lol

You've stipulated a sharp corner!…..Are the full size ships like this?

Please reconsider, your adverse thoughts and comments…..

On the photos, the keel and hull sides are smooth and inline with the rest of the hull!

Only the straight joint line looks aggressive…….If this was rounded off, would that meet the design requirement?

On the other hand……….II could make this from sheet Aluminium?

Bob

 

 

 

Edited By Bob Abell on 26/01/2014 07:25:25

[Paul TParticipant @pault84577]

Captain Bob

Yes I know its 'my fault' but Brutus was always going to be a complex build.

I will take your photo of the diagonal cut and overlay the correct construction lines but the best way to explain the concept is to maintain a straight line between the keel and chine.

Paul

Who is Lol

[Bob Abell 2Participant @bobabell2]

Imagine the shape in the photos was a solid block of Balsa

Try and round the joint line off!

You could round off the middle, but at each end, you couldn't do it!…..How strange?

Bob

[Bob Abell 2Participant @bobabell2]

In that case, to maintain a straight line from the chine to the keel, is what Amy Jane has suggested…

We can plank it!……Thanks Amy J

Bob

[Paul TParticipant @pault84577]

This area could be planked but in order to maintain the shapes of the subtle curves each plank could only be 5mm wide and even then you run the risk of creating holes when sanding into shape.

It would be difficult to increase the thickness of the planks from the present skin thickness without creating rebates at each end of the planks.

Although we have already established the need for straight lines I thought it best to demonstrate, for the benefit of the readers, the principal that I am trying to explain.

Taking a view of Bobs photo each of the black lines represents points of contact on the keel and chine similar to what would happen if a straight edge was placed between these two points.

[Amy jane SeptemberParticipant @amyjaneseptember49770]

…..You're welcome Bob.

If you do go with the planking, each vertical stave was made over thick because the angle where the plank meets the chine is different to the angle where the same plank meets the keel. To save having to put considerable twist in the plank, the twist was craved into the over thick plank. In practice this meant beveling the top and bottom of the plank, just where it sat on the chine and keel. once all the planks where on,it looked like a row of twisted steps! This was then faired down smooth. On the model I would just suggest two layers of very thin ply staves twisted in, with the top layer covering the joins in the lower layer, a la Ashscroft.

Aj

[Bob Abell 2Participant @bobabell2]

Thanks for that, Amy J……….That's a good idea

We might go for thick Balsa planking and a good dollop of P38?

All I need now are a few contour lines from the Drawing Office and I'll get cracking!

Bob

[Amy jane SeptemberParticipant @amyjaneseptember49770]

If it comes out the right shape and keeps the water out, what ever does, will do nicely!

[Colin BishopModerator @colinbishop34627]

Bob, it is usually best to use filler which dries to approximately the same hardness as the material being filled. If it is harder then you tend to get high spots when sanding.

I have found P38 to be OK for plywood but prefer to using something a bit softer such as Ronseal High Performance Wood Filler. You mix it in the same way as P38 but it is softer and easier to sand. Or you could even go for one of the tube fine surface type fillers like Polyfilla which also work well with balsa.

Colin

[Bob Abell 2Participant @bobabell2]

Thank you, Colin

Just ordered a large tin of P38 too!

I should imagine it is tricky stuff when used with soft Balsa

I'll look into the other stuff as well now

Bob

[Bob Abell 2Participant @bobabell2]

Hello Paul

I've only just spotted your post with the marked up planks section

We may have an unavoidable problem looming!

The skin from Former 2 to Former 3 has a distinct twist and this has created a concave surface!

We need to modify our aim for the perfect theoretical surface?

Is this acceptable?

Bob

[LARRY WHETTONParticipant @larrywhetton68737]

Good Morning Bob/ PAUL,

build is getting a little complex ,

what if the lower bow area in solid block sand to a nice flair bow …

i did this on DM swordsman , made the hull come on plane quicker and it turned on a tanner,

just a idea ,…….hope sketch shows what i am about,…

Paul , got mail ok thank you ……..cheers Larry…

[Bob Abell 2Participant @bobabell2]

Thank you, Larry

Planking with chunky balsa will have the same sffect

Bob

[Paul TParticipant @pault84577]

Bob

A quick fix to the concave panel is to glue in two 6×6 rib stiffeners behind it.

Paul

[Author]

Posts