Moebius SeaView RC Conversion Build

[junglelord]

So although the manta fins increase pitch control...as well they would...the fixed vanes will do a good job, not perfect, but a good job of countering the manta fins downward pitch...

The fix was to install permanent vanes within each propulsion nozzle, their job to direct the exhausted water upward, countering the pitching moment at the bow. In water tests verified that the fixed vanes countered the bow induced pitching problem throughout the SEAVIEW's speed regime, net angle change as a consequence of submerged speed was zero. Mission accomplished!

After installation of the fixed vanes in the nozzles depth control of the SEAVIEW became no more difficult than driving a 'traditional' type r/c submarine.

If I want better control then the manta fins are a must, but it seems to me that the fixed vanes will do a fairly good job according to the quotes above.

Mr Merriman, were you using the fixed vanes when you made your pool side video with the SeaView?

I ask because its not listed on the fittings kit and you mentioned that they are being produced. What if anything made you add them in?

As of last week I started making the two fixed vanes a standard item included in the SEAVIEW fittings kit -- if you purchased a fittings kit without them, send me your mailing address and I'll get a pair of them off to you.

As they are designed, they assume the correct angle in the propulsion tube when you set them in there -- just glue them in with RTV adhesive and you're good to go.

David,

I guess because the front bow fins were not enough control of the downward pitch created....buts thats only a guess.

Actually after some research I am surprised that they were left out of the original concept.

I look forward to your R&D reply.
Thanks so much.

[He Who Shall Not Be Named]

Okay, If I understand this correctly there are 3 modifictions that can be made to get better pitch control, being discussed?
1. Add Bow planes
2. modify aft fins into dive-planes
3. Add fixed fins inside exhaust nozzles

If they all work equally, it seems that fixed internal fins would be the easiest, Correct?

Correct.


At the conclusion of the article Junglelord quoted above -- which appears at the SubCommittee site, http://www.culttvman.com/david_merri...__seaview.html -- I pointed out that the model would be easier to handle if I made the bow planes practical and linked them to work in concert with the stern planes. Which is exactly what I did on the Moebius SEAVIEW conversion.

David,

[toppack]

Okay, If I understand this correctly there are 3 modifictions that can be made to get better pitch control, being discussed?
1. Add Bow planes
2. modify aft fins into dive-planes
3. Add fixed fins inside exhaust nozzles

If they all work equally, it seems that fixed internal fins would be the easiest, Correct?

[junglelord]

No I am showing that Mr Merriman said that the SeaView would work fine with fixed vanes inside the tubes. The outer control surfaces at the aft end of the propulsion tubes I had seen done on a Rick Teskey model. They are just something I saw as I surfed the web for this build. Mr Merriman was clear that fixed vanes were the answer and so I think I would rather not cut the manta fins and just go with the fixed vanes that will come with the revised fittings kit according to Mr. Merriman.

In profile the bow of the SEAVIEW is in the shape of a wedge which assured that water passing over it has to produce a downward force at the bow. The faster the boat goes, the more pronounced this pitch-down moment. As I demonstrated at the lake, the sailplanes and stern planes did not have the authority to overcome the designs inherent tendency to pitch down when advancing submerged.

The fix was to install permanent vanes within each propulsion nozzle, their job to direct the exhausted water upward, countering the pitching moment at the bow. In water tests verified that the fixed vanes countered the bow induced pitching problem throughout the SEAVIEW's speed regime, net angle change as a consequence of submerged speed was zero. Mission accomplished!

After installation of the fixed vanes in the nozzles depth control of the SEAVIEW became no more difficult than driving a 'traditional' type r/c submarine.

But, keep in mind that the two pitching forces (shape of the hull forward, the fixed vanes in the nozzles aft) are directed down; the net force on the vehicle is a downward one. However, this downward force acting on the submerged submarine is of low magnitude and is easily countered by operating the boat at a slight up-angle or simply by cranking in a bit of 'rise' on the sailplanes.

So, here's the straight poop: In fact, the manta-fins produce a counter torque (outboard rolling moment, counter of the vehicles turn) that works to negate the de-stabilizing inboard torque produced by the SEAVIEW's sail and 'V' shaped 'Cadillac' fins at the stern. The manta-fins contribute to the dynamic roll stability of the SEAVIEW in a tight turn. As the submarines angle of attack about the yaw (turning) axis increases, and starts to 'skid' into a turn, a situation occurs at the manta-fin tips (those tips well below the vehicles longitudinal center of rotation) where the inboard manta-fin tip begins to generate an upward moment (force) and the outboard manta-fin tip produces a downward moment. These two forces induce a torsional moment that works to right the boat in the turn; the manta-fins improve the boats roll stability dynamically in a turn.

The only vice I can lay at the feet (fins) of the manta-fins is that they work to de-stabilize the boat in the pitch plane and contribute a great deal of flow and wave-making drag.

The SEAVIEW, as an r/c submarine, can be made to be dynamically stable in pitch and yaw as it travels submerged - without need of non-scale 'stabilizing' fins or control surfaces.

The DeBoer SEAVIEW cruising along at 'periscope depth'.


I've already installed the pitch vanes in the nozzles to correct for the boats natural tendency to 'dive' while moving ahead submerged. Now, when the ballast tank is flooded and the boat settles into submerged cruising, it does so with little operator input from the transmitter.

The submarine is surprisingly responsive to sailplane deflection as I work at the transmitter to change or hold depth, the SEAVIEW holds pitch angle well, and it does that near the surface too, where other submarines become a bit more temperamental.

Unless he has since changed his mind on the performance of a SeaView structure, then fixed vanes will be enough to counter the manta fins. Especially with the Caswell Pitch Control. Correct me if thats not true.

[toppack]

In the sea-trials account he didn't say if he had Bow-planes or not did he? Maybe that was the problem?
Or are you saying that aft dive-plane will fix the problem without the extra trouble of adding the bow-planes?
Sorry I can't be more help, I've not built the Seaview yet. This is all very interesting tho since I may someday.

[junglelord]

There is a reason David added them since the Debor.

True and if you read the following report you will see that the answer was fixed vanes.
At least on the Debor it was and are now being sent out as part of the fittings kit as standard items for the Moebius.
So it seems that fixed vanes are, at least on the Debor enough to provide adequate balance to the manta fins.

Practical Design Shortcomings of the SeaView Design
As I mentioned the SEAVIEW revealed nasty inherent design flaws that evidence themselves when the model operates beneath the surface of the water.

The two big 'V' arranged Cadillac fins overhanging the stern work to over stabilize the boat about the yaw axis while submerged … even the three big rudders, two of them benefiting from the high velocity flow from the propulsion nozzles, were not enough to adequately overcome the stabilizers 'weather cocking' effect underwater.

Turning radius above the surface (with the fins sticking in the air) is good. Turning radius submerged (with the fins in the water flow) is awful!

Additionally, those huge 'V' arranged Cadillac fins contribute to another stability problem: In a submerged high-rate turn they produce a torsional moment that rolls the boat into the turn – that torque, when coupled with that of the sails torsional force, is enough to roll the boat so far over that rudder deflection begins to contributes a 'down pitch' component; as the boat rolls nearly on its side the rudders act to pull the stern up and the boat heads to the bottom, out of control.

As pointed out above, the manta-fins induce a stabilizing force about the roll axis, negating a good portion of the 'V' shaped Cadillac fin/sail inboard torsion/rolling force. Without the manta-fins the SEAVIEW would be an impractical, almost impossible to control r/c submarine.

On the maiden dive of the SEAVIEW model, after a few circles and figure-of-eight turns on the surface to check out the running gear, I commanded an 'all-stop' and waited for the big model to coast to a stop. I then commanded a vent of the ballast tank and took the SEAVIEW to submerged trim. With only an inch of the sail projecting above the water (the boat is trimmed a tad light in submerged trim) I was ready to run the model submerged for the first time … little did I know! I slowly advanced the throttle and noted a slight pitch-down of the model, so I threw both transmitter sticks full over to command full rise on the sailplanes and full rise on the stern planes. No change! Even with a low throttle setting the SEAVIEW, both sets of horizontal planes on 'rise', continued to pitch down to a dangerously high angle. It was headed to the bottom! Only full astern and ballast blow commands arrested the dive and got the boat back to the surface, in a flurry of foaming water and swirling thick gas vapor – I just managed to keep the SEAVIEW's bow out of the lake mud. An embarrassing performance to say the least. What went wrong?!

After a reflective pause, I repeated the maneuver. Same thing! Again and again, each time I tried it, the boat dove to the bottom at a severe down angle. Obviously there was something intrinsically wrong with the design – it was not a problem of static trim or improper control surface response to commands, I checked all that. No matter how much 'up' I cranked into the stern planes and sailplanes, the SEAVIEW model, once the ballast tank was full and the throttle advanced and the boat got some way on, it would pitch down.

Back at the shop and a good hard look at the SEAVIEW bow in profile. OK, I see … how could I miss that! It became obvious then what was going on: In profile the bow of the SEAVIEW is in the shape of a wedge which assured that water passing over it has to produce a downward force at the bow. The faster the boat goes, the more pronounced this pitch-down moment. As I demonstrated at the lake, the sailplanes and stern planes did not have the authority to overcome the designs inherent tendency to pitch down when advancing submerged.

The fix was to install permanent vanes within each propulsion nozzle, their job to direct the exhausted water upward, countering the pitching moment at the bow. In water tests verified that the fixed vanes countered the bow induced pitching problem throughout the SEAVIEW's speed regime, net angle change as a consequence of submerged speed was zero. Mission accomplished!

After installation of the fixed vanes in the nozzles depth control of the SEAVIEW became no more difficult than driving a 'traditional' type r/c submarine.

But, keep in mind that the two pitching forces (shape of the hull forward, the fixed vanes in the nozzles aft) are directed down; the net force on the vehicle is a downward one. However, this downward force acting on the submerged submarine is of low magnitude and is easily countered by operating the boat at a slight up-angle or simply by cranking in a bit of 'rise' on the sailplanes.

So, here's the straight poop: In fact, the manta-fins produce a counter torque (outboard rolling moment, counter of the vehicles turn) that works to negate the de-stabilizing inboard torque produced by the SEAVIEW's sail and 'V' shaped 'Cadillac' fins at the stern. The manta-fins contribute to the dynamic roll stability of the SEAVIEW in a tight turn. As the submarines angle of attack about the yaw (turning) axis increases, and starts to 'skid' into a turn, a situation occurs at the manta-fin tips (those tips well below the vehicles longitudinal center of rotation) where the inboard manta-fin tip begins to generate an upward moment (force) and the outboard manta-fin tip produces a downward moment. These two forces induce a torsional moment that works to right the boat in the turn; the manta-fins improve the boats roll stability dynamically in a turn.

The only vice I can lay at the feet (fins) of the manta-fins is that they work to de-stabilize the boat in the pitch plane and contribute a great deal of flow and wave-making drag.

The SEAVIEW, as an r/c submarine, can be made to be dynamically stable in pitch and yaw as it travels submerged - without need of non-scale 'stabilizing' fins or control surfaces.

The DeBoer SEAVIEW cruising along at 'periscope depth'.


I've already installed the pitch vanes in the nozzles to correct for the boats natural tendency to 'dive' while moving ahead submerged. Now, when the ballast tank is flooded and the boat settles into submerged cruising, it does so with little operator input from the transmitter. The submarine is surprisingly responsive to sailplane deflection as I work at the transmitter to change or hold depth. ven at a 'flank' bell the SEAVIEW holds pitch angle well, and it does that near the surface too, where other submarines become a bit more temperamental.

The significant maneuverability problems with this boat occur as a consequence of a turn while submerged. Sea-trails taught me to 'ease' the SEAVIEW into high speed submerged turns. To put the rudder hard over while running at any significant speed rolls the boat into an uncontrollable dive to the bottom. (American LOS ANGELES class attack submarines have the same problem). Other than that, and the SEAVIEW's woefully poor backing down ability, it handles pretty much like any other r/c submarine.

I still fail to see how the fixed vanes that are being completed and are part of the fittings kit, will not correct the problem as it did on the Debor unit. I am sorry for being so hesitent to try just the fixed vanes. I am not trying to be anal...please no voodoo dolls...LOL. I want this to sink and swim, not just sink.

For the record I will not be making my purchase till March 09.
I will have both models by then in my hands as well.
I am just trying to gather all the possible alternatives that have been tried, and maybe succeed.

I know that Dave Merriman is the King of Subs and of the SeaView in particular. I hope its not seen as insolence to ask newbie questions out of just plain old newbieness.

Hey I made up a new word...probably just polite for insolence.
:p

[junglelord]

Whoa ... whoa, horsey!

Removing the superstructure off the SEAVIEW involves no Dermal tool cutting. It's all hand scribing and work with a #11 blade.

Buy and watch the frig'n DVD set!

You're confusing the GATO conversion with the SEAVIEW conversion.

You people! ....

David,

I will be buying the DVD for sure.
Sorry I ask questions that the DVD will answer...
I am just excited....
Blah

I'm not familiar with Merriman's Dremel Jig. Where can I find out about that? My free hand cutting skills are very poor. I try to use jigs whenever possible, but I don't recall seeing one to cut the manta fins.

Do you have the DVD? How far along are you in your build and could you give pictures please.
Thanks.

I am looking forward to my Caswell/Merriman Snort SeaView as my first project this year and sailing my Robbe SeaWolf Dynamic Diver with my SeaView Snort Diver.

Here is an excellent thread by Stingfly on a Merriman/Caswell Conversion and good pics of the Manta Fins conversion.

http://s181686668.onlinehome.us/phpBB2/viewtopic.php5?t=7847&highlight=seaview

It looks like you could create dive fins from the outer nicelle fins, might be a good idea...watch Dave blast me...LOL>

[toppack]

Yes, one is talking about cutting Manta fins and another is talking about the hull. I guess we need to specify which we're refering to. :)
I think the Dremal was for the fins? What's wrong with using a Dremal for the fins?
I used a Dremal-saw for free-hand hull separation cuts on my Gato with no problems as long as I went very slowly, so not to Melt it.

[mickelsen]

I'm not familiar with Merriman's Dremel Jig. Where can I find out about that? My free hand cutting skills are very poor. I try to use jigs whenever possible, but I don't recall seeing one to cut the manta fins.

[He Who Shall Not Be Named]

I have a Dremel but it is not variable speed. Will this matter?
Thanks.

Whoa ... whoa, horsey!

Removing the superstructure off the SEAVIEW involves no Dermal tool cutting. It's all hand scribing and work with a #11 blade.

Buy and watch the frig'n DVD set!

You're confusing the GATO conversion with the SEAVIEW conversion.

You people! ....

David,

[toppack]

I have a Dremel but it is not variable speed. Will this matter?
Thanks.

When cutting styrene-plastic the saw blade needs to go as slow as possible, or it will Melt it more than cut it.
And at high speed it's much more difficult to hold steady also.
So I suggest getting one with varible speed.
So you won't make Mistakes so Quickly. :D LOL :D

[Nuke Power]

As long as it cuts the hull it works. The jig is important aswell so dont rush.

[junglelord]

I am confident in Dave's conversion.
I have some doubts about my cutting skills.
:rolleyes:

That's easy, just set it up with Merrimans Dremel Jig and practice once on a 4" plastic pipe.

I have a Dremel but it is not variable speed. Will this matter?
Thanks.

[junglelord]

There is a reason David added them since the Debor. Did you see half way through the video when it took a nose dive. If you watch SC Regatta 08 video there are some nice underwater shots of the 2 boats driving in the same pond and you can see what a diff they make.

That I have not watched. Do you have a link?

I am a newbie....so my hobby cutting skills are newbie too.
:(

I have never even taken out my Robbe SeaWolf yet.
I let it sit all summer long due to my older Robbe Plans and a new V2 version.
I had cemented the front hull together, which was the old plan.
Censored

I did however sit down in Janurary and did figure out how to complete the unit. So this is going to be a big summer for me and my granddaughter. After some consideration I am confident I can cut those manta fins.
I'll drink to THAT!

[junglelord]

I am sure that I will be able to cut them properly and "professionally" with the help of the Dave Merriman 5 DVD set.

Thanks everyone for all the time to "steer" me in the right direction.
I'll drink to THAT!