Calling all "41 for Freedom" SSBN fans

[Maarten Sch�nfeld]

I just picked up my MikroMir 640 Ben Franklin kit from Hannants at the Telford show. First thing I looked for were the endplates at the horizontal dive planes - they weren't there! In fact the kit looks like a plain copy of the Lafayette kit, only with new decals.

Did all the 640 boats have the endplates, or was Ben Franklin an exception?

Knowledgeable answers, please!
Maarten

[Tom Dougherty]

They all had them. Here's a link to a photo of the launch of the Mariano Vallejo; you can see the end plates:
http://navsource.org/archives/08/0865831.jpg

[Maarten Sch�nfeld]

Tom,

thanks for your confirmation. I'm afraid MikroMir got it wrong this time, by cutting corners to get a kit onto the market.

So, then I will scratch those endplates myself, documentation on the Franklin class was passed in this thread earlier on.

Cheers!

[krgf15]

You guys know a lot more about this than me, but on the 688 sub forum there is a link to a propeller site that shows several Ethan Allen and beyond FBMs that dont have the vertical plates. If that is what you guys are talking about....

[Maarten Sch�nfeld]

Hi krgf15,

Only the 640 Benjamin Franklin boats had the endplates, the Ethan Allens and Lafayettes hadn't.

[krgf15]

copy thanks

[Maarten Sch�nfeld]

So, then I will scratch those endplates myself, documentation on the Franklin class was passed in this thread earlier on.

Here some pics in the raw form, so you can see well what I did. Still some sanding to be done when all cement is dry.

It was necessary to modify the aft diving planes to a great extend, as these appeared incorrect in the first place. Also for any of the 609 or 616 boats that is. The only difference is the wider section where the endplates are based on. Some homework to do on my Lafayette and Ethan Allen models!

[krgf15]

It would be nice if there was an Ethan Allen.... Im not sure where to cut he hull on the Lafayette to make one, or if it is even possible to modify one to make Ethan Allen.

[Maarten Sch�nfeld]

Here's the math: there are eight missiles lengthwise, each Poseidon missile adds 22", so that makes 176" in total. The difference between the Allans and the Lafayettes is 180", so only 4 inches not accounted for, or less than .3mm on 350 scale...

Most authoritative sources quote the length of the Ethan Allens as 410 feet 4 inches, so the difference with the Lafayettes is only 14 feet 8 inches, or 176 inches. This equals therefore exactly the added increase of the diameter of eight missiles.

I was convinced, so I bit the bullet. Here's my Ethan Allen, in company with a George Washington and a Lafayette model, with the missile compartments aligned:

SSBN 1.jpg

SSBN 2.jpg

I'm only somewhat uncertain about the location of the hydrophone stump on the bow, it seems somewhat closer to the sail than on the subsequent Lafayettes. Can someone shed some light on this maybe?

Hi kgrf15,
Starting from here you can find everything you need to convert a Lafayette into an Ethan Allen. Beware, my assumption on the size of the tubes was not correct, but then you have to read through the entire thread. Good luck!

[Maarten Sch�nfeld]

While getting more intimate with the Franklin class I started wondering: looking at the pictures of the rudders it seems that the top draft mark is 38 (feet), meaning that the total rudder height is around 40 feet total.

It seems to me that the Lafayettes and Allens had a much taller rudder, the top standing around 47 feet: the draft marks over 40 are not applied. Picture of SSBN 611 John Marshall (Ethan Allen class) below.

Did the Franklins have a less tall rudder, and was this maybe related to the endplate fins taking part of the side forces? In this case I touched on another error in the MikroMir kit, the rudder being of the same height as the Lafayettes. It needs to be reduced then by about 6mm.

[Maarten Sch�nfeld]

David, many thanks for spotting the error in the assumptions, and Jacob & John for providing the documents to get it right! Good teamwork I would say.

Maarten

Hi gentlemen,
I'm getting more and more doubts how correct MikroMir's Lafayette and Franklin kits actually are. With your help I got the Ethan Allen more or less right, but now these others seem to require more scrutiny.

To come to the point: does anyone has plans of one of these 616 plus boats, giving the same frame position details as we had for the 608 class? That would really help cracking this puzzle!

Thanks in advance!

[aptivaboy]

The Floating Drydock has plans of the Lafayette in their TFW range. No idea of quality. If they're like their Ohio-class plans, which I have, they're likely more basic. The Ohio plans did have frame callouts but were nothing like the long defunct and missed Deep Sea Design plans of the Ohio and various SSNs.

Bob

[Maarten Sch�nfeld]

Thanks, Bob!

Here a picture of my Boomer family as it stands now, with all the required mods.

[Tom Dougherty]

Nice work on the modifications.

[aptivaboy]

Are there any reviews of the Micro-Mir Lafayette/Franklin/Kamehameha class SSBNs? I'm thinking I'd like to get one, but would appreciate any pointers on their accuracy. I'm more interested in the basic shapes and dimensions being correct. A lot of sins can be covered up with some putty and sanding, but the basic shapes and dimensions need to be correct.

Many thanks,

Bob

[Maarten Sch�nfeld]

but the basic shapes and dimensions need to be correct.

Hello Bob,

Length and width of the hull of these kits are correct within a mm or so, the tapered shape of the forward and rear of the hull seems close enough to the naked eye when compared to the official drawings. Same is true for the sails and the upper hull casing with the missile tube hatches. Only quite some putty is required to blend the forward upper casing with the hull.

The errors with these kit lie in the horizontal and vertical tail surfaces, both in shape and dimensions. I need to make some more detailed sketches to explain the errors maybe, but the drawings published earlier in this thread provide clear reference. Basically, the width over the horizontal surfaces should be 40 feet.

Also the fairwater planes need refinement, their rounded corners should be square. Finally, the PE metal propeller provided in the kit is a very poor representation in my opinion, but I can provide you with a much better example.

Is this a good review for a start?

[aptivaboy]

Thank you, yes, that's perfect! I can probably CAD up and 3D print some control surface replacements when time allows.

Bob

[Maarten Sch�nfeld]

Hi Bob,

Then I like to add a few more characteristics I noted: the horizontal surfaces (dive planes) of all the USN nuclear subs, beginning with the Permits and through to the Los Angeles class, and also including the '41 for freedom' boomers all had the same basic size and shape: 40 feet width (or 'span' if you are more into aircraft), straight rear edge and 30 degrees backward angled front edge.

In case of the MikroMir Lafayettes and Franklins the forward edge is angled too sharply and needs correcting. Also, the dive rudder hinges are 2 mm too far forward: I solved this by adding a .080 x .080 Evergreen square rod insert after the fixed portion, and removing a similar amount from the dive rudder.

The Franklins have end plates attached to the top and bottom, these are markedly different from those in the Sturgeon class: these are single endplates added to the outside of the dive planes. For the Franklin class you need to study how the 'horn' of the dive plane is arranged, as it needs to provide sufficient room for the end plates.

In the MikroMir kit of the Franklin the end plates are missing, and studying the dive planes will reveal that there is no room at all for them. This triggered me to restructure the dive planes, and in retrospect I had to do that also to the Lafayette and my own Ethan Allen class conversion. These look much better now too.

As for the vertical rudders, the kit provides rudders that are more or less right for the Lafayette (and Ethan Allen) class, but watch that the rear edges of the upper and lower rudders are not exactly lined up. For the Franklin class the upper rudder needs to be reduced in height, but that was described above in the thread.

[Vepr157]

Good detective work there Maarten!

A while ago I did a comparison between piping TAB drawings, photos, and the kit, and found that the sail was very out of shape. I 3D printed a significantly larger sail with a flatter top designed by using the drawings, and it seemed to match photos very well.

[Maarten Sch�nfeld]

Detail of the dive planes of my MikroMir Franklin. The Lafayette and Ethan Allen planes are similar, but lacking the end plates.