Catamaran beams

sorry Ad Hoc,
my mistake.

let me clarify,
the advice i really want is the specks for a single truss.
single line is what i'm after.
you're going to far too much trouble just for me, when all i want is a single line.



(why? see the specs above? done by me! so imagine betting your little bum on that baby a thousand miles from shore.

so if you can,
please improve my specs. is my math correct? i wouldn't put a single dollar on it.)






thanks rick,
you've helped me heaps.

definitely talked me into a normal mast section for the front beam, so this is half a victory for reality Vs me at any rate.





after i have a enjineer say "Great Work Mal!, but, you're truss calculations are OUT! (Shocked! tone), you need 4mm T6 to get 0.3% deflection with 1200Kg right in the middle."

then i'll try improve the twisting.

i think all the guys here should be able to come up with a good solution, but in the end it may be like the front beam, and just be more sensible to fit a big round tube, say 150mm round 4mm walls? then attach the 50Kg outboard with bolts in the middle of it.


right now i'm thinking maybe another truss the same say 7ft in. great! idea hey?




thanks all,
mal

 

mal

Your first post was asking which type of beam, now your saying the spec's; as in the scantling or the material or what? Single liners don't do it. If all you wnat is a quick one liner, you'll get plenty here.

For me, without knowing the application, the loads service life, method of attachment etc etc somewhat pointless, as i noted above, how long is a piece of string...or in your case no idea if your maths are correct because insufficient information.

But that's my tuppenc penny worth...

 

Mal
To comment as you suggest requires a designer to do a design check, which involves work on their part. Most people seek payment for work.

If you pay them there is an obligation and the result has value. If you do not pay them there is no obligation and the result is just an opinion that you may or may not value. It was free after all.

There are examples on the forum where the opinion changes in subsequent posts from the same individual once the opinion is challenged.

I take any opinion offered in this forum with skepticism. Unless you have the means to validate it it is worthless. After all you did not pay for it. If payment is involved you seek references and look at past results.

Most opinions are given in good faith but often from limited experience or a myopic view of things because that is the way it has always been done. Hard for people trained a certain way to untrain themselves and be open minded enough to accept improved methods and new ideas from what they were taught.

I have learnt that no one knows what they don't know AND the more you know the more you know you don't know. So learning is an ever expanding horizon.

Given all of the above, I accept that anyone can build a boat. If the design is poor the launching will mark the start of a lengthy, frustrating and possibly expensive development process. If the design is good then expectations are met. You have to work out how much you need to know to achieve your ends.

This thread might give a better idea of my point:
http://www.boatdesign.net/forums/open-discussion/build-yourself-boat-do-lap-crazy-not-21058.html

Rick W

 

thanks adhoc,

try this then. pretend this is a real engineering exam question;

a ***** built a truss, with 70 x 100 x 5mm T6 aluminium tube top and bottom, 60cm apart, the same material was used for the 45 degree webbing, and got a 4m beam on which he placed 1200Kg in the middle. how many mm's deflection occurred?

really looking forward to hearing from you this time,
and
thanks for all your time as well.

cheers,
mal.


also,

didn't "decline" (!),
just didn't understand.

i thought that;
you and rick were engineers,
that had known each other for years,
and were having some sort of philosophical re the mathematical mapping problems of deciding on the universe of discourse for translating your then agreed on logic into practical engineering math, all for my benefit, and how ricks empiricism (while precisely communicating to me in terms i appreciated) violated your far more expansive, though less pragmatic philosophical tenents.

all i was after was pragmatics.
i was hungry, an you gave me zen.

which i didn't decline,
just didn't understand.

But! Thank you for your time.

and stay passionate fellas!







(these forums are fun! )

(also; how honest should i be on these forums?
i've often seen australians abused elsewhere by americans for speaking perfectly normally.
cause what i really thought was you n rick were old mates havin a ****, and wished you'd done it elsewhere)

my position is
i'm far more focused than all of you guys out there in cyber space, cause i wanna start welding these beams now, whereas you guys can sit back an ponder the universe, have a scratch, adjust the fruitbowl, n say mal!, you've not considered the extra super powerful way! which is only gunna take you 5 years of study to understand, you lazy bugger. n then have another scratch,

i'm looking to start planking soonas.

so can i speak normal here (like the above) or do i have to dumb it down and speak american? (the long winded philosophical version of the above)

who thinks what?

am i in trouble yet? have i drunk too much coffee?

ps, i've just started smoking again 4 days ago after a year of no coffee and cigarettes.

thanks all,
mal.

 

rick,

i don't wish to appear light hearted, but i'm used to flippantly juggling abstracts all the way in one direction, and then all the way in the opposite.

so, although i'm a nerd and my verbiage is torrential and light, i have lived on a yacht before, and realise hard facts do exist.

it's not that big a deal to me, to ponder one way, then change to a more traditional method. i haven't looked at your other posts here on this forum, but from your tone, i would guess you do serious boat stuff for work. ie you have to take other peoples engineering seriously.

"To comment as you suggest requires a designer to do a design check"
no it doesn't. a design check implies hours of work.
a simple beam or truss inertia is a matter of a minute at the outside.
some people do formulas everyday, and might take some person here 10 seconds in a truss program to check my calculations. that is what i was after, all the rest is gravy.


you have to start somewhere. i started all by me little lonesome, after YEARS of reading and making other designs, seen lots of plans, and in my mind, think i can build much better than a foam cat. (professionals and food) http://www.boatdesign.net/forums/multihulls/good-reasons-not-design-13162-6.html

been on expensive foam cats recently, and refuse to even listen to these people anymore. won't let them put their biased info into my mind. walking on jellyfish. felt professional boat builders work after 20 years.

payment! absolutely not. all you get is one persons opinion. an i much prefer a gift like what you gave me. you had nothing to gain, and so spoke freely.

i prefer a menu, like what's happening here. a smorgas board of different opinions from all over the world. brilliant. and then choose the one that appeals.


my brother used to build drag racings cars. he's not an engineer. he would typically buy parts from engineers and then put them together. he didn't want a plain vanilla honda.

i talked to you and now i'm doing a plain vanilla beam on the front, MUCH better and easier.

i'm very happy. now to continue the refining process.

sure, i won't end up with a shiny! General Motors car, and that makes me very happy.

i just repaired a mazda e2000 van 9! years old. the paint fell off the roof, and there were rust holes big as your hand all through the roof.

professionals. all yours mate.

 

Mal
I have owned a few boats and boats are a lifetime hobby. I currently play with design concepts and have built some reasonable models that are large enough to pedal. I started this thread to catalog my recent efforts and hopefully encourage others:
http://www.boatdesign.net/forums/boat-design/pedal-powered-boats-23345-20.html
I have learnt about doing more with less in boats from these experiences.

My aim is to learn and have a nice retirement project for a boat I can get built and cruise the Australian coast and rivers economically and safely.

I am an electrical engineer and have managed multi-disciplined engineering teams for many years so I have reasonably wide knowledge across a number of engineering and business disciplines. I am currently paid by an insurance company to be the devil's advocate and work out how things might fail. I am in a position where I can have others do the detail engineering for my paid work.

Similar for boats. If I want design detail on a boat I pay a trusted Naval Architect to do the work as he is forced to know detail on crap that bores me to death. I can play with concepts and have acquired or developed some very good tools for preliminary design. I was suggesting you also find a good NA to bounce ideas off. A good one, like I use, does not bother charging for a casual minute here and there.

I give my opinions on boats in good faith and am glad you appreciated my input here.

I am not sure if you read much of that thread on Tin Can but one of the reviewers offered this:
Yet as Theodore Roosevelt said, …"credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly, who errs and comes short again and again, who knows the great enthusiasms, the great devotions, and spends himself in a worthy cause, who at best knows achievement and who at the worst if he fails at least fails while daring greatly."

There is nothing like getting the hands dirty. It is rewarding in itself and I find therapeutic. At present I build about 2 boats a year for myself and am helping about 10 others with various concepts they are developing. All input at no cost because it is all interesting and helps me learn. It rapidly amplifies my experience base on novel concepts.

I hope you take the time to post the progress on you boat and how you overcome the various challenges. Most here try to help and offer encouragement.

Rick W

 

mal

sorry, but without a picture how can i tell if it is "stable" or statically indeterminate or how many connections or how the connections are made, how the load is applied and where etc etc etc.

 

can i suggest downloading beamboy v2.2 or a truss program then?

good for you in your professional life to be able to answer the simplest beam question known.

 

no offense

 

Mal

In my professional life, the simplest questions are the hardest to answer.

No offense taken.

Those who are not naval architects or structural engineers always ask a simple question and wonder why the answer or reply is anything but. Or those who are not naval architects or structural engineers like to pop up with one line answers or wonder why "we" do not and constantly question their 'claim's. Because there is always much more involved. Which is why, one assumes, you seek advice. Since if it were that simple, you would download the "simple" program yourself and not require any validation from any posts here!

 

Bob, on a small cat like yours im curious why you dont want to use the simple round aluminum tube approach, its well proven and cheap. As a reference i used to own a Macgregor 36 and all three beams were stock off the shelf round tubes between 16 and 17 ft long and 6 5/8 inch diameter, the mid and aft beams were 1/4 inch wall thickness and the fwd beam 1/8 inch. The mast beam had a substantal dolphin striker and the forestay used a bridle and no seagull striker.
Steve.

 

the front bridge deck lent itself naturally to an enclosed triangular space 3' x 2', so o thought, why not have a ply or aluminium box beam, since the outsides of the box beam are going to be present anyway. thus saving on weight.

there's open deck at the back with open hulls. a truss style transom would suit perfectly.

i've got oodles of other round aluminium beams specs suitable to do the job, and plain vanilla engineering is the default option.

i may well use both a truss and beam together in the end.
the truss to weld on wing seats outside the cat, cut and weld outboard fitting on, bolt on to the thick ply hull bulkheads, weld pole holders on, weld sampson post on etc etc etc.

the utility and ease of attaching fittings is astounding compared to the delicacy of the round beam, which some people don't even drill for the main bolt holes.

 

Mal
Incorporating a box beam in the bridge deck is a good solution that I have seen others use. It is the ideal moment resisting member being near the centre of the hulls and with large enclosed space. Ideally the ends are enclosed and able to transmit the stress smoothly into the hulls.

Remember that any hole in this beam will see stress concentrations at the corners. If you can avoid holes all the better but generally such space needs to serve more than one purpose.

Rick W

 

Chris

“…I wish I could accept that position, Ad, but unfortunately, some of your posts do take on that... "Hey, Look At Me" sort of tone…”

Well that is a perception of your own making, I cannot control that.

“…I see a consistent process where you take others to task, without offering-up anything of your own work to drive the argument…”

That’s where you don’t understand what a technical debate is all about. It is not about the person, it is about the posting. The comments/claims made. Whether I am a newbie or a professor or whatever, doesn’t alter the comments, only your perspective of them. That in itself speaks volumes about how you understand technical debates and critiquing.

“..Nobody here knows who you are because you operate behind a nom de plume of a smoke screen…”

As noted above, what difference does it make who I am?...unless of course you’re more interested in the person than the comments made. Again, you’re missing the point of a debate/forum. How many boats I have designed doesn’t alter my posting, only your perception of me, not the comment.

If it were about how many boats etc and qualifications etc…this website would have a “validation” process to review those that wish to join to establish their “status/credibility” within the marine world and provide “levels of status” to know whether postings from said person are genuine or not. Trouble with that is, those that posture and rant and rave on this website of which there are many, would turn from the majority to the extreme minority in terms of “status”. That would diminish their raison d’etre!

As noted here, you fail to answer a simple question about a post you made. You like others question the questioner, rather than answer the claims being made by you, not by them.
http://www.boatdesign.net/forums/multihulls/solo16-sport-trimaran-26541.html

..you ignore the posts seeking clarification to your statements and twist in another direction, rather than answering your claims that you have made.

“..What is it about your posture that keeps you from being a regular guy among other, "regular guys"?..”

What is it about guys like you that have chips on their shoulders and have an inferiority complex when someone can speak in a manner different to yours? I have a friend who is very small, he is constantly aggressive and when we were young always trying to pick fights,…why?...because he felt inferior owing to his size. It is all in his mind, just as the statement above, it is in your mind and others.

“..You wish to conduct this substantiation of your credentials in private, yet you seek to castigate those on this Forum in public…”

Under what obligation am I or others to provide their personal details?....how many pseudonyms are there here and how many real names???

“..Act this way too often and the other guys like me will quickly find other sources of the same information, which you seem to think, is so exclusively precious…”

Please do, that is the point, if I’m wrong prove it, and we learn. But that means taking away the debate from me, which is your only focus, not the question at hand.

“…There’s nothing special about your knowledge…”

Never said there is, again that is your own personal perception. However your posts are contrary to this as you do not feel the need to answer direct questions about your postings. See above link again.

“…Of course, you can come out from behind your Wizard of Oz curtain and join the gang here,..”

Ahh..i see now. It is a clique!.....sorry I was under the impression this was an open forum, not a “come join our club, if you don’t you can’t play”...oh how pathetic and childish…that is school play ground mentality!

As Woody Allen put it, I don’t want to be a member of a club that wants me to join!

“…My email address is easy to find and I welcome your contribution to that which you seek;..”

See again, you do not comprehend.
1) It is you that wishes to know more, not me. So the onus is on you contacting me, but you choose not too.
2) I seek nothing. Many like you use this forum as some sort of acceptance or redemption or validation from others on this website. I seek none. I just offer advice, which can be taken or not. This forum is not where I conduct my business for business. I don’t need this forum to obtain some recognition, clearly you do. As such you view all comments in that vein.

“…Each and every Naval Architect, or Marine Engineer that I know, is so fully occupied in the business of their trade that they have absolutely no time at all to dick around on Forums of this type, even if they were so inclined…”

Ahh, so you have tarred everyone with the brush that…if they can reply on this forum more regularly than you they must be wasters, great conclusion!

You are like the many others on this website who are not formally trained nor professional, yet feel the need to act as so. You do not like being questioned, you attact the questioner, rather than the question. When asked for references, to try and deflect the question, like others below:
http://www.boatdesign.net/forums/multihulls/load-paths-catamaran-26229-5.html

Clearly, because you are not a naval architect or professional engineer, you feel intimidated by the stance taken by me, er…how is that my problem?

Obviously knowing who or what I am will therefore make no difference if one cannot even acknowledge sound references, or just twist away from justifying claims made on ones own design, what is one more of who I am going to make to your MO, none. It just points again to some inferiority complex, why I have no idea.

The fact you selected not to contact me directly just suggests that you have no concept of the professional integrity. If a client or person wishes to reveal themselves, to you personally but remain anonymous, you have selected to ignore that. That is grossly unprofessional.

There are several on this site who know who I am, some I have worked with over the years. Some even have had others contact me to try and see if I am real, as if I didn’t know!...but they have respected my anonymity.

In addition, comments that suggest “..Hardly any of the guys here are mechanical engineers, yet you hold this information over their heads as if you, and you alone, are capable of sorting these commonly phrased issues…”, again totally miss the point. To allow information that is clearly misguided and incorrect to be let loose on those that come on this site seeking advice, is unprofessional. It gives this site a bad name, as well as “professionals”. So I speak it as it is. This at least offers the poster an opportunity to see that there maybe another avenue to explore, rather than accepting one persons comment, simply because he/she is part of the “lets sit around a camp fire and sign songs and join hands” club.

“…Until that time, you have acquired the ignominious position of being a wannabe poser,..”

If that is yours, and others opinion, so what? The fact you cannot add or counter any technical argument put forward remains. Personal feelings are not part of the equation, only solutions. But you elect to probe who I am not what claims have been cited. When money is at stake, as it is for many seeking advice on here, time=money, not time=feelings.

 

he also can't answer the most basic engineering 101 question about a simple beam.


there is a band in australia called TISM.

one of their biggest hits (music charts, top 40 song, HUGE airplay) was called "What Are Ya?"

they hypothesised, basically, that guys could be divided into two distinct categories, yobs and *******.

basically they were alluding to a person being driven hard all their life with adrenalin so as to achieve good marks in school, as performance increases dramatically with adrenalin. the so called fight, flight, or f_ck system of brain stimulus, the most basic ON! ALERT! RUN! burn the candle faster.

or a person not driven, and akin to an analog device, speaks slow like a farmer, lazy, and has far less polished verbiage.

a yob or a ******, make your f_in choice.



(
as a personal aside
i find it interesting, who has the most powerful brain? the farmer, and his insight? or the person driven all his life to spin his little wheels faster and faster, into ever smaller finer points?
)


(
as a personal aside
i find it interesting, who would actually feed you if you were hungry? is one so removed from reality they would just blankly stare at you while feeling nice and snug and secure?

who would actually give you a piece of fruit, rather than just ****?