Calculate the Resultant Force Between 4 Points

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Discussion Overview

The discussion revolves around calculating the resultant force between four anchor points for suspending two kayaks using ropes. Participants explore the implications of weight distribution and the dynamics involved in the setup.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the method for calculating the resultant force between four anchor points, suggesting a possible approach of distributing the weight evenly between pairs of points.
  • Another participant agrees with the initial inquiry, noting that while the calculation may seem straightforward, practical considerations such as pulling and tugging could introduce higher forces.
  • A later reply reiterates the agreement but emphasizes the need for caution regarding the forces involved when handling the kayaks.
  • Another participant challenges the assumption of even weight distribution, stating that the kayaks must be positioned correctly for the weight to be evenly divided, and warns that one rope could bear the entire load if not positioned properly.

Areas of Agreement / Disagreement

Participants express differing views on the weight distribution among the ropes, with some suggesting it can be evenly divided while others argue that it depends on the positioning of the kayaks.

Contextual Notes

The discussion highlights the importance of the kayaks' center of gravity and the potential for uneven weight distribution, which remains unresolved in terms of specific calculations or methods.

AmateurHour
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I am trying to figure out how to calculate the resultant force between 4 anchor points. Basically I want to hang two kayaks on two ropes suspended across a room. Below I have some crudely drawn images of the set up:
upload_2018-5-14_10-39-19.png


upload_2018-5-14_10-39-39.png

I found how to calculate the vector forces between two points as pictured below below but am wondering how it would work with four points. Is it as easy as calculating each set of two points with half the weight distributed to each set? Both kayaks should have a combined mass of less than 32kg.

vector-math-1.jpg

vector-formular.jpg

F is the resultant force exerted to each anchorage.
W is the weight of the load.
α is the internal angle between the two slings.
 

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AmateurHour said:
Is it as easy as calculating each set of two points with half the weight distributed to each set?

Yes, it is. Just be aware that getting the kayaks in and out of there will involve higher forces while you are pulling and tugging, and maybe jerking.
 
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jrmichler said:
Yes, it is. Just be aware that getting the kayaks in and out of there will involve higher forces while you are pulling and tugging, and maybe jerking.
Thanks!
 
AmateurHour said:
Is it as easy as calculating each set of two points with half the weight distributed to each set?
The weight generally will not be evenly divided between the two ropes; you'd have to get the kayaks positioned with their centers of gravity exactly between the two ropes for an even division of the weight. Worst cas, all the weight will be on one rope while the other is doing nothing.
 

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