basic engineering help/input needed please

[aviro]

hi folks,
looking at the drawing the dimension looks like it is for a walkerbay tender.
if it is that, check you need 36 inches for the walkerbay with the tube kit.
the tube kit is the accesories that you by afther the first time you see yourself and more problematic, the admiral with
the head in the wather and the dingty upside down above you.http://www.macgregorsailors.com/forum/p ... =8&t=22920#
curious that apen in a fraction off second and you ear about it for years afther thathttp://www.macgregorsailors.com/forum/posting. ... =8&t=22920#
at the same time you discover that the groceries make a good fish meal to
J F

[aviro]

by the way did somebudy can tell me the good size for a stainless tubing going 36 inches out the boat with a load of 125 pounds per arm.
i am probably going to make one this summer.
i am considering stainles 316 11/2 in or 2 in diameter.
witch is the best wall?
for the walkerbay i have one with the tubing and i love it
thanks
J F

[Wayne nicol]

thats just too funny mon ami!
i have quite the visual image in my head

yes sir you are correct, it is for a walker bay 8
do you really find the walker bays that tender- without the tube

[aviro]

hi,
yes and worst than that, it is like a canoe or a kayak
afther you are seated it is ok.
the boat is so light it move to easily
with the tubes (if you find some foam you can make it yourself ) it is a great boat.
for me a lot beter than an inflable due to the fact that you dont need a motor
it go easily on the wather
definitively need some flotation on the side and rear
see you
J F

[RobertB]

by the way did somebudy can tell me the good size for a stainless tubing going 36 inches out the boat with a load of 125 pounds per arm.
i am probably going to make one this summer.
i am considering stainles 316 11/2 in or 2 in diameter.
witch is the best wall?
for the walkerbay i have one with the tubing and i love it
thanks
J F

Do you mean 125 pounds working load or after a factor of safety (a 5x SF means 25 pound working load, 3x SF is 42 pound working load)? If 125 pounds is your working load, I would recommend designing to a 625 pound load.

Have you calculated how much weight you are adding to the stern of your boat - worse yet, suspended high past the stern? I see easily in the neighborhood of 350 pounds with a CG 4 to 5 feet above the waterline. How do you intend to offset/accommodate this?

[aviro]

hi
that is the result of my bad English
the davit is for a walkerbay breze 89 pounds total
i am calculating 100 or 125 pounds total some time a little bit of wather in it
i dont use a motor
yes i am concern about the moment of maybe 125 pounds thats hight and on the stern
i have a lot of weight down fuel tank water tanks
i dont no if somebudy instaled that before in a M
thanks for your observation
J F

[RobertB]

BTW, I do not want to seem too critical - it is just the engineer in me.

Now you have me thinking. How about replacing the rear stations with a taller and very stout pole each side with a block at the top and braced well like the stern seat mod. Then, mount on the stern two swivel points that connect to a rigid frame that bows aft. Small tender attaches to the frame and then frame and boat is pulled up and against the modified stations. Advantage is that when lowered, the tender is held fairly rigid behind the boat for entering/exiting. Also, to deal with overloading the structure, size the line used to raise the frame/boat to be just a bit weaker than the max strength of the support structure. This is essentially a davit system.