Berkeley Sea Cat
 

I'm looking for a Berkeley Sea Cat 1959/60's version? Anyone got a kit out there they haven't built?
Appreciate an answer by Email to:
[email protected]

RE: Berkeley Sea Cat
 

I think you would be better off looking for plans rather than a kit. I have an old Berkly Ercoupe of about the same vintage and the wood has totally dried out and is very brittle. (The first $100 takes it). It would not build well and I feel the Sea Cat would be the same. It was one of my favorites when I was a kid. Nice lines but probably too much dihedral to make into a good R/C. It's been done though.
Good Luck.
Peter

RE: Berkeley Sea Cat
 

Peter-- why not just reduce the diahederal to what you think is enough and get busy cutting balsa. also its easy to make new balsa parts- cut out the parts from the old balsa and use them as templates on new balsa. beleive me there isn't a set of plans tooo old to use with new balsa. I do it all of the time. dick

RE: Berkeley Sea Cat
 

Fred Mulholland used to fly one of those. He ia an AMA assoc VP (Dist V) so his contact info is in MA.
He could prpbably arrange for copies of the plans. Fred's plane flew quite well. It LOOKED like an old-timer, but with a modern engine it would rip holes in the sky.

RE: Berkeley Sea Cat
 

Before Berkeley kitted it, Struck's Sea Cat was published as a construction article in August, 1954, Model Airplane News, starting on p. 20. Two pages are the plans, at 1/4 size, and include all the ribs & formers, which the kit plans probably didn't include. Check with MAN to see if they have the plans available.

Berkeley's kits were considered by many to be very expensive plans because, while the plans were great, the wood quality was poor and the die-crunching inaccurate. Even if you traced the kit's parts on good wood, they probably wouldn't fit. If I were to build the Sea Cat, I'd do it from the MAN plans. Besides, a Berkeley kit is a token of a great period in modeling and I'd hate to see one lost when there's no need.

Just my opinion.
-Dave

RE: Berkeley Sea Cat
 

Back almost ten years ago I did laser cut flat parts to the Sea Cat for a customer. Only sale I had on it, and was only request. There are a number of common big balsa blocks which need to be sanded to shape, now making the reproduction a bit costly.

I think the plans and the parts are still in the computer, and another set of replicas can be made up.


Wn.

RE: Berkeley Sea Cat
 

MODOC,

I don't have a sea cat but I do have a Berkeley Privateer Super 15 R/C kit. I purchased this in the early 60's and have kept it safe ever since. The kit is un-touched with the plans, and the box is very good some storage wear only. If interested let me know. It's not a SEA Cat but it is a looker.

Gerry (sledge_78

RE: Berkeley Sea Cat
 

Gerry, Could you please tell me some more about your Privateer?

RE: Berkeley Sea Cat
 

whats the wing span? also- whats the cost of a copy of the plans. do not need balsa. dick

RE: Berkeley Sea Cat
 

I have one that is about 80% built. Let me know if you are still interested

RE: Berkeley Sea Cat
 

Plans for the Sea Cat are included in the John Pond collection made available through the AMA. Both the Berkeley and the magazine plans are offered. See page 16 of this .pdf for the listing and prices.


http://www.modelaircraft.org/pondplansPDF/NOS_all.pdf

regards, John

RE: Berkeley Sea Cat
 

And here you can find, online, a reproduction of the magazine plan, and the first page of the article that accompanied it. Lots of other seaplane plans and photos on this page too, I notice. Scroll down to Sea Cat.

http://skystone.biz/pictures/sport%20rc/

RE: Berkeley Sea Cat
 

Learning a little more about the hull. In the MAN article, Henry Struck says he was impressed with post war NACA studies of a then-new type of flying boat hull, characterized by the long, narrow hull and a planing tail. If you google on "planing tail," you can find quite a bit of material on these new long hulls. Here for example is a NASA precis on the new hull form, as applied in the Martin P5M:

"No large, multiengine propeller-driven flying boat has been developed in the United States since the Martin P5M Martin first flew in 1948. (The jet-powered Martin P6M Seamaster flying boat is described in part II.) With a gull wing of the same size as that used on the earlier PBM Mariner, the P5M was, however, a much heavier aircraft equipped with more powerful engines.

Although bearing many configuration similarities to the PBM, the P5M had an entirely new, high length-beam ratio hull with a planing-tail afterbody.

This new and greatly improved hull form had been extensively studied in both the towing tank and wind tunnels at the NACA Langley laboratory (refs. 36, 37, and 124, for example) and offered the possibility of reducing the unfavorable drag differences between flying boats and landplanes. It was found that by maintaining the product bl2 constant and increasing the value of the length-beam ratio l/b, the water drag and spray characteristics of the hull were little altered and the aerodynamic drag was significantly reduced (l and b are the length and beam of the hull, respectively).

The planing-tail afterbody ameliorated the stability problems of porpoising and skipping. As compared with more usual values of 5 to 6, the hull length-beam ratio of the P5M was 8.5, while some of the experimental data in reference 124 are for hulls of length-beam ratio as high as 15."

So this is the novel type of hull design Henry Struck was working to capture in the Sea Cat. Long, narrow, pointed step, planing tail.

RE: Berkeley Sea Cat
 

One of the problems associated with long planing hulls is their inability to rotate into a take off attitude. Many poorly designed hulls and/or floats have this problem and the solution is that the wing must be set into the take-off position while the hull or floats are relatively level. Many models can overcome the problem with lots of power but lightly powered planes must be more scientific inthe way they are rigged. The Martin Mars, which I watch fly every summer is like this. At rest the wing is in a fairly positive angle of attack. As the plane accelerates the nose rises and the plane accelerates until the aft end of the fuselage is clear of the water and the fuselage is back to a fairly level attitude at which point it continues to accelerate until it reaches flying speed at which point it flys off with minimal rotation. The Mars has been described by others as a giant powered glider. Watching it fly it is easy to see why it is described so because it flys so slowly. It has thousands of horsepower but it also has tons of wing area which must give it a very light wing loading. When water bombing it initially takes off empty of water and then scoops up tons of water on a pick up pass. I don't know if the Mars qualifies as a long planing hull since I have never actually analyzed it's length-beam ratio but it must be close. Every sea plane enthusiast should make an effort to watch that beauty in action.
Peter

RE: Berkeley Sea Cat
 

A propos, could one use flaps to help? Wonderful lake ... are you in BC?

Here are some pictures of the model. It appears to be long, narrow, and deep, per the NACA prescriptions.

RE: Berkeley Sea Cat
 

The photo was taken at Sproat Lake on Vancouver Island which is in British Columbia Canada and yes, it is a beautiful lake with lots of recreational boating and camping and many very upper end summer residences and some really great model seaplane flying as it is rarely windy there.
One of the most memorable moments for me with respect to the Mars was one evening we were sitting on the pier enjoying some refreshment and the Mars flew directly overhead at about 200' altitude. About 30 seconds later we were given a brief shower from the moisture condensation from the plane passing overhead. The plane has to be seen to be believed. If anyone is in the area tours can be arranged of the facilities and the plane(s).
Peter

RE: Berkeley Sea Cat
 

Wow. One of the beautiful places in the world, Peter.

My thought for the Sea Cat is to consider scaling it down to about 1/2 size, or 34". According to Coos Bay (above) the cutfile already exists.

RE: Berkeley Sea Cat
 

I just got started building 1 after buying it . Actually , I started to look for information , after I bought it , and viola , here I am.
I have an original 1954 full sized plan and kit. Berkeley distributed the kit that was designed and drawn by Henry Struck. The kit was
engineered by Bill Effinger , this is printed on the plan. This is the same kit that Henry Struck used to fly air mail across the Detroit
River by radio control , into Windsor , Ontario when he was working for the Plymouth Motor Corporation and doing military experimentation.

These plans are not simple , as the age could suggest , as there are alot of intracate lines drawn through each other that make it
harder than usual , I noticed , to concentrate on what line you are tracing with your eye , let alone figure out what goes where.
The plan does come with some detailed instructions along the bottom of the 38"x49" drawing , taking up what amounts to mostly general
descriptions of how to progress through the assembly. There are also some step by step listings laid out through the drawing.

The kit came with a strip sheet of engine installation and operating instructions which were to be used on the finished model and are
obviously not new , they are for a .024 sized engine. Right out of the gate I tried to locate a logical place to begin building , and came
up with the wing , as a logical start. Low and behold , even then , there were mistakes in the drawing to placement or construction
characteristics of trying to match what is written or suggested together. The plan suggests building the fuselage first.

For example : The side view of the wing clearly shows subframe stringers , bonded to both ends of the ribs , before the actual
tapered edges are bonded onto them. Suggesting that there are no flaps or ailerons needed. Yet , the half wing drawing shows
that there is absolutely nothing bonded between the tapered trailing edge and the rib trailing edge. Also suggesting that there are no
flaps or ailerons necessary. I took that as a sign of the times that the model was designed in and have decided to work ailerons into both the wing and the tail ( elevator ). Which the tail also shows as being solid with no allowance for an elevator in it's construction.

Eventually I realized that there was some sort of elevator in the tail wing , but it appears to be the type of elevator that allows for the
entire tail wing to go up and down. There is a rubber band and servo apparatus that loops over the tail from front to back , and it
attaches complicatedly with the rudder itself by a wire mechanism extending from both. It would have to pivot somehow through the
vertical tail structure ahead of the rudder itself. It is still not quite clear to me how this would work , but that's the challenge of building
such a flying model.

The plane itself has a 68" wingspan , and surprisingly the tail is almost 30". That also suggested to me that the design for steerage
was going to come from the rudder and tail alone. But I couldn't see the plane flying properly that way in any wind as it is also a
polyhedral design with a 5 & 1/2" rise to the wingtip from the bottom of the cowl. That incident got me thinking that the plane would
naturally swing back and forth from side to side when held stationary , which would greatly benefit from a little aileron for control.

Basically , the major part of the drawing is that of an oversized baseball bat for a fuselage , extending sharply and contoured to the
substantial tail and rudder. The fuselage section looks like a drawing of a submarine with a conning tower for the wing to sit on. The
box reads "The First All Purpose Gas Model" and the parts sheets are thick and rough. The die cuts are sharp and clean enough to be
able to trace through but are in fact , so sharp that they are harder than normal to trace along when cutting. Alot of care must be
taken to ensure that you are cutting where you need to.

This plan includes every angle of every section , as you would get from any model these days . Surprisingly , the plan doesn't show
it's age or suggest that it is from the 1950's at all. Absolutely not a general drawing , I have decided to build this plane special , in that
I will be changing alot of the suggested or required assemblies to suit my theory of design efficiency. After all the width of the wing is
over 9 & 1/2" while the 2 sponsons or wing stabilizers are just as long. Pictures do not do justice to this model , as it is a large craft
in that there is a top view picture of the completed model , clearly showing that it has a wing construction that resembles that of one of
the era's bomber wings. Heavy , to say the least. I will also be increasing the size of the engine to ensure that weight is not a factor.

I guess you could say , all things considered , that this plane was a glider , with it's silkskin covering , in the minds of the designers at
the time. It was supposed to be like a glider , not a aerobatic performer. The plans mention that it typically takes 50' to take off.
This model surprised me the more I looked at it , as it is much bulkier than I had originally anticipated. I guess I paid alot of attention
to the fact that it has a thining style fuselage , which led me to believe that it was a completely thin design , it is not , as the nose is
5 & 1/8" at the widest point. Not exactly the few inches the pictures suggest. The actual plans have the fuselage from nose to tail
across them and don't allow the tail to be added to the end in 49" , so the tail section is drawn above , which is also another 9 & 1/2" ,
making the total dimensions 68" x 58 & 1/2".

If anyone is interested in having a true copy of the plans or any information or ideas about building this plane , please feel free to
contact me by email : [email protected]

This plane will be built with the US Air Force "Star & Bar" pasted right under the wing , across the wing supports on both sides , in
memory of those who have lost their lives since 911 , and the City Of New York , USA.

RE: Berkeley Sea Cat
 

Subsequent to posting my opinions and rather lengthy comments about the building of my Berkeley Seacat , the email box I listed for
any communication on the subject has changed to : <[email protected]> cuzz , Goowy is gone. It was only used for convienience anyways - so I wasn't able to view any mail I may have received - Sorry.

As suggested here and in many other places , the building of the kit has become somewhat of a mysterious pleasure. I am finding that
as I build , it is like adding weight to a balance beam , one that had alot of thought put into it's design. Not that all models are not like that , but this one , seems to have a mind of it's own and keeps tilting towards the ceiling no matter where weight is added. In other words , Struck paid attention to the lifting characteristics first , and built on to that theory of design.

I have the fuse and center section of the wing built , now I am moving on to the tail , since I am a little stuck where the drawing
seems to suggest a skid plate type trailing edge to the boat bottom , in the fuse drawing , but then contradicts that by having another
angle shot on the drawing , which clearly shows the trailing edge of the boat bottom to be like that of the end of a canoe. I am hedging towards building the trailing edge as a skid plate type which will give the plane alot more stability in the water at all times.
Also taking pressure and reliance off of the sponsons and wings. I think balance is needed since the bottom of the boat section which
starts like a destroyer hull , coming to a complete "V" at the front , tapering to the trailing edge , has no balance characteristics.
For example : trying to stand a complete "V" hull in water will only end up having the boat on it's side without a considerable bottom
or weight applied to it. I am thinking this is another mistake , or very well , just a sign of a work in progress itself.

Most of the pictures I have seen of the Seacat show the trailing edge of the boat bottom to be like that of a canoe , leaving what I feel
is a back and forth rocking motion in the water that can be cut down by using the skid plate design instead of the canoe.

Looking again at the 2 fuselage drawings , they also don't coincide very well with any attention being paid to whether or not the plane
will sit properly in the water. The length of the bottom seems a bit short , especially in the canoe style trailing edge design. It seems as if , if this were your own design , you would expect the tail to always be dipping into the water due to having too short of a base for
the entire plane to sit upon. I think the skid plate type bottom would allow the tail to skid just slightly over the water line , also very
characteristic of being nose up. It's almost as if Henry Struck had been thinking the same things when he drew the drawings himself
and drew both ideas on the 2 separate drawings as a result. It also seems to me that the entire weight of the plane is resting on this
very small area , depending on it's balancing point to be a major factor , with the wing and engine directly overhead.

Even though the difference will only be a small amount , as I will be using the same peices to build the framework of the trailing edge ,
I think the benefits will be a substantial improvement for both landing and take off stabililty , disallowing the sponsons to dig in quite so
much into the water . Instead of building the trailing edge from left to right , it will be built from top to bottom , as the full sized drawing of the fuselage suggests , but plane at the same angle. At any rate , I am working on incorporating both ideas into 1 trailing
edge , in the space that the downward curve will produce , using the skid plate design.

I am wondering if anybody can give me any information about this area of balancing , as this situation creates with respect to sponsons
and alike.

:D[>:][X(]

RE: Berkeley Sea Cat
 

I don't think the V shape of the hull is any problem. After all, that is what the tip floats are for. The shape of the step also should not be a problem as long as the line of the bottom of the hull does not reflex back upward and it ends with a sharp cut off. The Sea Cat was primarily a free flight design with a simple radio, usually rudder only put into it. I would go with your best interpretation of the plans. As for ailerons, the plane was designed when ailerons were a hopeful wish among modellers and also, as I said, primarily a free flight design so it was meant to fly in calm conditions so cross winds would be of no concern.
You could update the design by using knowledge which we have accumulated over 50 years of modelling but then, it wouldn't be a Sea Cat.
Just my thoughts,
Peter

RE: Berkeley Sea Cat
 

I have made up a few sets of laser cut ribs for the Sea Cat now. No one has tried to install any ailerons on the wings, for the dihedral angle is just too great.

Was mention in a few older M.A.N. magazines that the actual model will not R.O.W. no matter how much it is tried. Untill it gets overpowered, it then lifts off, and then immediately zooms up into the ionosphere. (Like I found) That water is like a magnet for it. It lands and floats just fine though.

One magazine in the 1960's mentioned an Itallian firm was making the same kit, but calling it a Sea Tiger. That one had R.E.M. (no ailerons) and, would R.O.W. properly. I haven't seen one of these ever, so know little about it, other than it was popular in the 1960's and popular to obtain plans and modify Berkeley Sea Cat's into them.

The Sea Cat? Well, it has a lot of basic blocks of balsa in the kit box.

Wm.

RE: Berkeley Sea Cat
 

Thanks for your input CoosBayLumber & Peter C . I don't think I am going to have any problems incorporating ailerons into the center section of the wing only . I will simply have to add a piece for the aileron to hinge on , where the dyhedral wingtip sections begin , and split it behind the engine cowling section that drapes over the wing , for left and right application. This type of aileron is on many planes , including PBY's like the Catalina , and sailplanes with dyhedral wings. So , I am not reinventing the wheel. LOL

These types of modifications may seem like having to add alot of blocks to the design in the minds of some RC modelers , as they also seem to think that there are alot of blocks in the SeaCat kit , which there are not. The only "BLOCKS" , in the SeaCat kit are for the
familiar nosecone block that are in most kits , and the sponsons , which are also familiar in Seaplanes.

I have decided to decrease the dyhedral angle measurement by 50% , as a direct result of adding the ailerons. I have been giving the SeaCat alot of thought , thinking about that in 1954 , this plane had the rudimentary full tail lever and rudder design only as "steering". That would be the reason that the dyhedral angle was increased to a wopping 5" or so , where any more than that would almost be creating "fins" on the wings. This is what is involved in building such an old kit , it requires "thought" mostly , not extra parts that are not normally found on any RC airplane.

As Peter C suggested , the SeaCat was built during a time when model airplanes were primarily "freeflight" designs , or gliders. That was because there were no radios or servos to adjust them while in flight. So , if we understand that the SeaCat and other gliders of the time , would have been launched earlier without any controls , we should understand that dyhedral was the first construction adjustment made to attempt to control the area of flight that the plane would follow. Humerously , I have found some information that suggested that Bill Effinger and Henry Struck had these very problems at early competitions where the SeaCat had flown uncontrolled , but won the distance awards. Specifically , they had experienced that the gliders could fly into the next state , and they would not know where they would be able to retrieve the plane. Humerous , but it makes sense that with no dyhedral angle on the wings , your park flyer would become a county flyer in a matter of minutes , even though you had control over the tailwing and 1&1/2" rudder assembly. Needless to say "maximum dyhedral" had to be incorporated into the design.

This is what was happening in model RC airplanes at the time. A very humerous event , which makes me wonder about the boat bottom to sponson control area that I am modifying to incorporate the skid plate I referred to. It will be very small but what I am going to do is match the sponson bottoms to the skidplate. We are only talking about adding a 3-4" straight line across the back of the tapered trailing edge of the bottom , under the fuselage. In fact , the Catalina and others have that type of design , I feel that if I leave it out , I may find it difficult to steer at the point of initial water contact , possibly landing on the friction of a sponson and turning left or right , while trying to adjust with the ailerons at the same time. Bouncing back and forth on the sponsons is not something I want to do while landing , as soon as the skidplate touches the water , ( sponsons will make contact too ) , forcing the nose down steadily making the landing in a straight line.

I have to bear in mind that this plane was designed in 1954 when there were no options available to them at all. The more I look at the full sized drawing , I come to realize that the SeaCat is a compilation of designs , all honed into 1 plane.
For example we have as follows : A wide rowboat bottom , shaved at the front like a destroyer or battleship into a "V" for cutting
A submarine conning tower shape to provide good support for a large wing
A modern characteristic , center mounted , (single) above wing propulsion source
A narrowing helicopter style fuselage ( a result of the rear only controls )
A bomber wing and tail to create maximum lifting characteristics
Seaplane sponsons to aid the landing requirements
A cockpit designed forward of any engine water spray
The characteristics and size specifications of a sailplane or glider

This is not a simple water aircraft , it is an incorporation of designs , but the picture of the boat also makes it look like some sort of futuristic Orson Wells spacecraft. The box it came in is long , not square or rectangular as some pictures in magazines suggest. The box had probably been part of a shipping and packing design as well , packed like a cube.

Since I am also working on a sailplane ( GP Spirit Elite ) of the same size , I can make a close comparison as far as gliders go. In the future I am looking at building a ( Boeing 314 Pan American Clipper Seaplane ) , I see some plastic models , but nothing in wood. The Clipper is the plane with the adjustable lower water wing , that may also , be some sort of skidplate to assist in braking while near or on the water. Any suggestions or help finding a kit or plans to build a kit would be very much appreciated.

Thanks for the feedback .[8D]

RE: Berkeley Sea Cat
 

Concerning long planing hulls: does anyone have a specific NACA paper reference? I have most of them, probably, filed away, but if there's a specific paper that gives the basics, I've not found it. So far, all I have is specific to one design. I was wondering whether the idea would work well for an airboat.
Thanks.

RE: Berkeley Sea Cat
 

Peter C.
Thanks for the suggestion about trying to find plans rather than a kit. I need to edit my request on the ad forum to reflect that.
Modoc...

RE: Berkeley Sea Cat
 

Coos Bay,
I would like to get a set of plans if you have some available. If so, are they ligible and fairly easy to read and most importantly, understand?

I'm not a total novice having built several wheel types, but in reading comments by some of the builders here about the Sea Cat, I'd be a bit concerned about the plans readability.
Modoc...