Project 945 - Sierra I (1/60 scale)

[cstranc]

Hey now we are getting

Hey now we are getting to the exciting stuff (I was born a mechanical engineer and took a wrong turn into software development).

It was time to start thinking about how to control the rear dive planes and rudders. As with any single screw submarine you need some ingenuity to get the pairs of control surfaces behaving as one. And you have to do this down where the hull is tapering away to nothing.

Originally I was planning on using belts and pulleys to actuate the control surfaces. Then I found that a "in-expensive" pulley would cost $20USD. And I would need 8+ the belts. Ha. Time for a re-design.

I really wanted to maximize the range of motion for the control surfaces. Let's face it, compared to the model they are pretty small, and I will need to manouver in a space smaller than the Atlantic ocean.

In the end I decided to use something like...


In the picture above you can see the taper of the hull (screw would be at the left). and the control rod arriving through the hull pointing directly at the stuffing box. Using a pair of control arms and a push rod I connect the primary control rod to a secondary control rod that is offset from the propeller shaft. The same idea for the other control suface. Now both control surfaces are connected to a secondary shaft, and that secondary shaft is out and easy to access...

Looks like this when installed in the test hull.


Hmm, maybe a little hard to see everything that's going on.
There is a block of resin, the stuffing box / shaft goes through it's center. This allows me to stabalise the shaft, reducing any vibration. It will be fixed to the real hull with a screw.

To the right of the propeller stuffing box is a vertical shaft. This is the secondary control rod for the two rudders. On the top of this secondary control rod you can see the linkage to the top rudder. Similary there is a linkage to the bottom rudder at the bottom. The pushrod from the servo will also connect to the bottom of the secondary control rod.

Similarly the left and right dive planes are connected to a control shaft that is offset below the propeller shaft.

If you look end on you will see that all the control arms point in the counter clockwise direction. They have to do this or else they start bumping in to each other.

When constructing this I thought it was critical to get all the control arms to the same length. So I made a little jig to get the holes drilled perfectly.

After installing it I was happy to find that there is almost 60deg motion to either side for each control surface. Almost 120 degrees in total.

This made my little engineering heart happy. But what is a linkage without something to actuate! It's time to build those control surfaces.

[cstranc]

The control surfaces have been

The control surfaces have been another learning experience. How not to do things... I really could have carved them out of balsa, made a mold and then poured them getting the right shape. But I did not.

I traced the outline of each surface onto some 3/4" ply, then used a bandsaw to remove the center and create a form (actually my Dad did this for me. Thanks Dad). Then I sealed the playwood and stared pouring in the resin. I added 6 pre-cut fiberglass outlines just to add a little strength...

This gave me 3/4" resign blanks that I had to sand down to the correct shape. The correct shape was also a bit nebulous. I did not trust the taper that was drawn on my scale plans. So I went to my trusty "Guardians of the Motherland" (thanks Wayne) and looked at pictures of the Akula. I know, it's cheating, but I could find no better reference.

Here you can see them partially sanded. Note the foam they are sitting on. I did most of my work on that foam. There are a couple of edges that might possibly get damaged if you did something silly. Working on that foam was a little saftey factor for the parts.


Then I looked at Wayne's book and found they had to be much thinner. So it was back to shop vac & belt sander followed by that Ryobi corner cat. Sure beat hand sanding, but there was a part of me that was thinking "this would be faster if it was balsa wood..."

The area of the fin where it joins the hull also had to be sanded to get the right curvature to match the hull. I used a file for this work.

Then it was time to compare to the drawings and plan what was ahead...


Those were the official plans. If you look closely you can see where I marked in the control rod. I actually had to move the control rod forward a touch to allow space for the control arms so they did not hit the resin bulkhead. I should have planned that a little better / earlier.

It's tough to see but on the drawings the hull right under the rudders has a slight concave. I did not duplicate this. It was very subtle on the plans and at this point I was not going to make the adjustment.

Next I drew everything out on grid paper.


It was just easier to work this way. While drawing this on paper there was some logic that had to be worked out. At this point the control rod holes had been drilled into the hull. Each control surface required 3 cuts to be marked. The two cuts parallel to the axis of the sub (these came off the plans) and the one that is parallel to the control rod. The location of this last cut must harmonize with the thickness of the control flap. Ideally it should be located about 1/2 the thickness of the flap forward of the control rod. This will allow it to rotate without binding.

While marking things I used blue foam to get the pieces to lie flat.

I would stick painters tape on the parts so the pencil could give me a good line.


At this stage my primary concern was ensuring the alignment of the control rod and the flap. I am using a 1/8" brass rod as the control rod. To ensure the alignment I will drillout and then insert a 5/32" tube.

I marked each end of the fin where the 5/32" tube would be...


Then I created a jig to align the fin properly.


and then I drilled out the 5/32" holes...

If I did it again I would modify the jig to have 4 adjustment screws. The two allowed me to adjust one angle, but I was slightly off on a couple of the peices.

I would also drill half way through from each side. I think there will always be a minimal mis-alignment on these holes. If you push the drill all the way through then your exit hole will be off. That is harder to fix then filing the center of the hole where they don't quite align. The location of the two exit holes is critical, so drill from both sides...

As you may guess, only one of my four was "perfect" the other three needed a little adjustment with a 1/8" rat file. But eventually the 5/32" tubes fit, even though some of the exit holes were a little larger than planned...



Those were the brass tubes, after a light sanding, ready to be glued into place.

Speaking of glue. I know how we are meant to share our favorite tools and materials. This is mine.



That little 89cent CA dispenser is a god send. You can suck up a quantity of the thin CA and then dispense it with great accuracy. The nozzle never get blocked. The CA can stay in the bulk for a long time. I never use the CA from the bottle any more.

You can never check anything too much. After all the work adjusting and gluing in the tubes the handling had faded the lines I was planning to use for cutting out the control surfaces. So I drew them again to make them darker. Then a final test...



With the 5/32" tubes in place I could put a 1/8" rod through each set of fins. This ensures the alignment between them. Then I used a ruler to compare all the lines and found a little misalignment on the top left peice.

To ensure that all peices were identical I created a little jig.


It's just two peices of wood with carefully drilled 1/8" holes. But this allowed me to perfectly align my ruler to the control rod so my cut would be exactly where it should be...

And with that it was time to cut the control flap from the rest of the fin...



As you can see I mounted each fin on a peice of foam. While mounting I cut the foam so that the fin was perfectly flat to the table. Don't want any weird angles creeping in now.

You can also see a 5/32" hole in the front left corner of the flap. My plan was to cut up the right side, then cut up the left side, then use that hole to turn the piece and cut the final side that is parallel to the control arm.

It seemed like a good plan and it worked well on all four pieces.


You can see the flap free of the fin. The brass tube running though both peices gives me my alignment.

If you look closely you can actually see the fiberglass cloth inside the resin. As a little side note. Only one Sierra I was built, the Tula. One day it was out doing the things that submarines do when it bumped into USS Baton Rouge (SSN 689). Both subs sustained damage, but no human casualties. But the Tula was brought to dry dock and has remained there ever since Various components on my model have been re-inforced to prevent this fate from occuring again...

All I need is a way to lock the flap onto the control rod...



And there it is. On the outside end of the flap I drilled down just deep enough to embed a collet. I plan to glue the collet into this location. I will have acces to the set screw when the flap is rotated off normal.

It was time to start sanding again. I had to round the leading edge of the flap so that it would not interfere with the trailing edge of the fin. Also I had to create a groove in the trailing edge of the fin to accept the flap as it rotated.

This was mostly done with a dremmel tool.



You can see the three dremmel bits that I used for the job.

On the assembled fin you can see some masking tape. I put this on both sides of the flap right over the centerline of the control rod. I used it as a visual guide "sand / round the corner up to the tape and no further".

You can see the rounding of the fins on the fins that are lying down. The brass rod is also clearly visible within them.

It's much harder to see the concave on the trailing edge of the fin. Believe me it's there.

For each fin I would first round the edges on the flap, then start grinding away the concave on the fin. I would stop regularly and assemble the two together and see where they were binding, then adjust...

Most of the time I used the finer rounded dremmel bit. A lot of the work was at the top and bottom of the groove. The big rounded bit could not get in there. After everything moved nicely I ran the large round bit over the concave to smooth it out.

Those with sharp eyes may note that the brass tube on the fin on the right is not quite centered. Sigh. Not enough coffee as I started working. When I found this I was horrified. I have been working on these for the last three weekends. There was no simple way to remove and re-align the tube...

I resigned to building a new one. But then as I practiced cuttin the concave in the back of the fin I found that I could get the motion I needed and the misalignment was not an issue. Maybe it's ok. I shall watch it carefully as I dry assemble to the hull.





It's starting to look more like a sub now...

Ha, funny side note. As I mentioned I have been working on this for the last three weekends. At first my attitude was "3/4 inch cast resin, indestructable" then it became "if I goof I shall just build another". By the end of tonight I would only carry one at a time. I made sure they were always well away from any table edge. I would only work on them above foam, ...

[jeffrey j]

....

The fin jig is a very neat idea... OK, this guy just moved to the head of the class.... very very nice work ! Jeff Jones

[mylo]

Chris,

Fantastic build thread. I

Chris,

Fantastic build thread. I picked up a few pointers and ideas.

Glad to see you made good use of your original "test" hull. When I read the part of you having to start over with your foam, I had INSTANT recall, kind of a "Yeah, been there, done that" type of thing. You had the sense to bail on that original plug, learn, and move forward. .....I'll bet when you did that you confirmed in your own mind that making one of these things miiiiight take a little longer than you first thought. Kudos big time on continuing and coming up with what is shaping up to be a great looking boat.


...........it just dawned on me, between you, Kevin McLeod, and myself, Canada has a pretty reasonable showing of recent scratch builders. I guess, what else is a guy going to do during 6 months of winter ? Does Canada have their own tent at the Sub Regattas ? If so, we'll need room to squeeze all these boats in there. That'll be more subs than our actual Navy. .....probably more sea worthy too.

Keep up the great work. I love seeing another's perspective/approach to a build.

Mylo

[jeffrey j]

,,,

Does Canada have a Navy ? ,,, LOL,, If they don't, I know a few great Canadian engineers!!! They could end up with the first real flying sub............... Can't wait for this Regatta, got side tracked with a new baby last summer that kept us home.. Jeff Jones

[mylo]

Jeff,

We've got some targets.

.....and

Jeff,

We've got some targets.

.....and I think one or two leaky subs that the Brits were smart enough to unload on us. I wonder if the Canadian Gov. put those on E-Bay yet ?

...but this is an entirely different topic of discussion, or lack thereof as it were.

Mylo

[cstranc]

Canadain Navy. I bet there

Canadain Navy. I bet there are some fine people in it, but sadly lacking in equiptment. As for Canadian winters, what else could a modeller want. 6 months where there's no pressure to put a hull in the water. Unless you are buildng an ice breaker...

I look forward to seeing everyone, and especially the Canadian contingent, at the regatta this year. I have my room booked. Now there's that small matter of finishing the boat...

Jeff,
That jig was so simple, but it was born out of desperation. I had layed out those line as carefully as I could. To see them off like that, brrr. It's weird sometimes you plan things out, then mark everything up, and by the time you are half way through some steps become totally redundant. Still overplanning is seldom as bad as that feeling you get when you fail to plan...

Those boats look amazing. You make this hobby into an art form. I am determined to build a fleet boat next. I thought a scratch built fleet boat was too far ahead of my skills. I have to do a lot more reading (thanks Mylo, Kevin, and everyone else for the great build threads) before I try.

I must be one of those cautious Canadian engineers

Not like Mylo. Wow

I have been scanning the Message Board, but please feel free to point me at any "classic" build threads. I'm sure there is excellent info out there I have not found yet.

I'm going to take a little break from this thread for tonight. I want to start the other thread on putting pitch control into a model.

But before I go a question. Has anyone had any experience with LePage 5 minute epoxy going "soft" after water immersion? I did a model last year and two joint in the boat went loose. The rest seemed to hold fine. The epoxy itself seemed to go a little milk colored and then switch from hard to a rubber texture. It had cured well over 24 hours.

[silent runner]

Excellent work here.

There are no

Excellent work here.

There are no 5 minute epoxies that are waterproof, Always use a slow cure epoxy. Myself, I use 2 hour.

[cstranc]

Many thanks for the info.

Many thanks for the info. I shall add slow cure epoxy and patience to my workbench.

Chris

[mylo]

Chris,

ANYBODY who takes on

Chris,

ANYBODY who takes on a scratch build has patience......period. You turfed a whole ton (grams....whatever) of foam to start over again, and you don't think that's patient ? Got new for ya, you've got it. ....sorry to be the bearer of bad news. I think you can get a shot at the clinic to clear it up though.

I took quite a bite when I decided to tackle my 1:25 VIIc/41, but I saw no use in building a boat that wasn't just what I wanted because it might be "easier". I'll build a nuke boat some day, and when I do, I'll have to learn a whole bunch of other techniques for that style of boat, just as you'll have to when you take on your Fleet Boat, but I'll enjoy it because it'll be what I want to do. Bottom line....build that which turns your crank as it will help keep you motivated and to heck what anybody might say.....including your own self. I'm very reluctant to listen to "nay sayers" anyway, I find them........negative and unimaginative. Can't say I've run into any here at Subcommittee. As for your comment, I'm not an engineer at all, never mind a cautious one. Shucks....I'ze aint got da smarts da be no engineer no how....hyuk hyuk.

Keep pushing forward with your build. I am constantly reading and learning new things about subs here at Subcommittee and your thread is more of the same. Whatever kind of boat, I like them all. I look forward to attending your online engineering classes. Great boat, great build. Me....well.....just hangin around....waitin' for supplies. *whistles tune*.

Ya'll be cool now....hear ?

Mylo

[jeffrey j]

....

hey Chris,
Thats right , 2hr epoxy only. But if your "gluing" inside the wet area of the hull, I always use polyester resin with baking soda mixed in to glue the items down! But my hulls are also ploy. Also, 2 part "JB Weld" will work on about everything and is bullet and water proof. Really great work, Scratch built subs are always my favorite. Jeff Jones

[cstranc]

Mylo,
You are right you

Mylo,
You are right you have to build the boat that works for you. I really like the shape of the nukes. Especially the Russian Alpha, Akula & Sierras. But the fleet boat. What a challenge, and there is something about the bow cutting through the water that is so cool.

Then there was the "5 minute epoxy question"...

Ohh darn. You know I just kinda threw that one in at the end of the post. It was time to go to bed, but something was nagging me... Could it be that I had just glued my four tail fins in place on the hull using 5 minute epoxy? Maybe my mind was catching the anguish waves as they travelled back in time from when I read Silent Runners reply....

The lesson from this (besides using the right materials, doh). Start your build thread when you start the model. Don't do the catch up game I have been doing over the last few weeks. I bet I have missed a lot of great tips & ideas because I was too busy in the workshop. I know I have forgotten some of the stuff that did not get a picture, or written down in my log book.

Time to upload some pictures.

[cstranc]

So yesterday after 3 weeks

So yesterday after 3 weeks elapsed time working on the fins I was ready to mount them on the hull. Yippee. First step to put them on the hull, lightly mark their outline, and then sand the hull so the adhesive (sigh) can get a grip. (unlike me).



I glued the fins on one at a time using LePage 5 minute epoxy.

Sigh. It's not as crazy as it sounds. Earlier in the week I tested both 5 minute epoxy and 30 minute epoxy. I glued up some scrap fiberglass / resin sheet, let it set for 24 hours, and then left it in water for days. Before gluing the fins up I went and double checked and both test peices are still perfect.... Of course I check them every two hours now, waiting for the moment when the bond will break, or they will spontaneously ignite, or maybe the dog will be attracked to the smell of the glue and take them away and eat them (I hope not, I like our dog). Anyway, you get the idea I am deeply worried about using 5 minute epoxy...



This is the first fin (top one) being glued into place. Note that I still put a 1/8" brass rod from the top to the bottom to ensure alignment. I actually rounded the edges on the brass rod so I did not have to fiddle with it while gluing the parts. It slides easily from top to the bottom engaging the opposite fin. I would apply the glue (which I now don't like) to the underside of the fin, then drop the fin into place. Tape and clamp and finally check and recheck the alighment (from both ends of the hull).

Repeat this procedure 4 times and you get.



At this point I learned that 5 minute epoxy and water don't work. It's funny the toughts that run through your head at a time like this.
- Can I seperate the fins from the hull? Not a chance they are solidly bonded. (my son suggested dropping the whole thing in water, he's grounded now)
- Should I tell the folks on the build thread? Of course. It's all about the mistakes we make (as well as our triumphs), so this is great
- Maybe I should just walk off into the distance and build a "desert submarine" it's like a real submarine, but it never sees water.

So in the end my plan was simple enough. If 5 minute epoxy does not like water, and I cannot undo what I have done, then this epoxy will never touch water. All I need to do is make sure there is no epoxy exposed. Water will not get at it through the polyester resin. All I need to do is seal where the edge of the fin touches the hull. And that needs to be filled anyway to give a nice radius. (I will also be carefull to seal where the brass rod goes through the hull). Then this 5 minute epoxy can remain sealed safely inside the hull / fin space.

So here I am sanding away all the exposed epoxy.



I was using one of those black nail files you can get at a drug store. Sanding the epoxy would load the file up pretty quickly, so I kept trimming the end off to get fresh grit to work with. I would trim the end of the file into a V shape because it was nice and versatile.

After doing the sanding I also took one of those sharp dental picks and carefully cleaned out the corner where the fin and hull met one more time.

That gave me something like:



Now you may notice the leading edge of the fin does not taper down smoothly to the hull. I thought that would be too fragile, so it would be added now after the fin is assembled to the hull.

As I kept turning the hull I found the front edge of the fins were not all perfectly aligned. Hard to tell how far off they are, so it's time to measure it. I'm sure all of you know that marking lines on a curved hull is a pain. To get an accurate reading on my fins I first put a ruler along the midway mark between the fins and made a tick 6" from the end of the hull.



I did this four times, then I used a ruler aligned to the mark on either side of each fin to get a consistent location on the axis of each fin.



Note that the mark is just a little under 6" due to the curvature of the hull, but it should be consistent for all fins.

Then I measured the distance from each fin to their datum and ran to the plans. Sure enough the horizontal fins actually do start a little further up the hull then the verticle fins. All is good.

While I was at the plans I traced the outline of the front edge of a fin and taped it to MDF board. This would become my jig to ensure I get the correct taper into the hull.



I cut this on the bandsaw then finished it off on a 1" belt sander. This is it showing me how much bondo I need to get the right taper.



At this point my camera broke, or I became ashamed, because I think I put the bondo on a little too thick. I think I would have been far better off applying multiple thin coats of bondo.

And there we are. With the bondo quitely drying in the basement.

[cstranc]

Not sure how I almost

Not sure how I almost forgot this.

Is is safe to use "Hot Stuff" CA glue in the wet areas of the hull.

I sure hope so...

Chris

[cstranc]

Well a post is great

Well a post is great to keep you honest with yourself. I was not happy with the thickness of Bondo, so I went down and scraped it off. That's the good thing about too much bondo: It takes forever to set, so you can remove it...

This time round I applied the bondo in a thinner layer.


I used a plastic card to apply the bondo. Even being carefull on the thickness I found that it did not give me good control and I ended up applying the bondo to a larger area then I had planned.

So it was on to sanding.


The sanding removed all that excess bondo nicely. I used one of those sanding paper on a foam backing pads. It's nice and gentle.

When I looked carefully I found that I was not getting a constant radius where the fins connected to the hull. Well that was not good enough. Let the bondo fly again....



I hope you can see the bondo went on much more smoothly this time. This time I would use the plastic card to scoop the bondo out of it's container, but then use my finger to apply the bondo to the hull. I had much better feel / control over what is going on. I think it's the only way to go in tight radius locations or on complex shapes.



So this time when sanding I used a block that had a radius on the corner. I would use this block exclusively for the fin / hull joint area. This time I got my nice consistent radius.

Here is a run down of the tools used to sand...


Left to right:
- Wooden sanding block with rounded edge. Good for the fin/hull joint.
- 1.5" from a drywall sanding block. I used this the most. I found that it gave me the best ability to shape the bondo into smooth curves.
- Fine sand paper on a soft foam pad. This was great for blending / tapering the edge of the bondo where it came down to the hull. I did not like using it for shaping the curves in the hull.