November 26, 2012 AWS
(This document will be updated frequently with new question and answer postings)
November 26, 2012 1. Q: What effects will towing the barge have on the design of the boat? A: In a most general sense Towing an object behind the hull as described in the guidelines will affect the overall speed, maneuverability, and trim of the design. The exact impacts cannot be determined due to the variety of possible design configurations, but as a general guideline, the effects of towing will result in: 1) Reduced vessel speed 2) Increased vessel turning radius / decreased maneuverability 3) Trim at the stern will decrease during towing* * It is difficult to determine the impact to vessel trim. The design/engineering team suggests designing the vessel to trim by the bow by at least one inch which will cause a near level trim during towing. Please be aware that the impact to trim is highly dependent upon the hull form and a best practice for designing to accommodate towing is to design additional volume at the stern. This can be accomplished by increasing the beam at the stern or by increasing the height from baseline to deck edge at the stern. 2. Q: Is it possible to have our team name cut out of the battery box? A: We cannot cut the team name into the battery box. This would require extra time and effort to the lofting of the parts, a process that historically has been challenging to complete on schedule. 3. Q: Guidelines state COG (Center of Gravity) for new steering assembly will be provided on or before Nov 16th. When will they be available? A: The CGs will be provided no later than COB Friday, 11/30/12. Continue to use the geometric center as a placeholder until this data is provided. We apologize for the delay.
1
4. Q: We cannot find any information about the freeboard of the barge in the Guidelines. Also, what material is the barge made of and how much does it weigh? A: The barge details have been confirmed and are as follows:
Total Barge Weight (unloaded) = 25.3 lb Total Barge Weight (loaded) = 93.3 lb Design Draft = 7 inches Freeboard = 7 inches Constructed of ½ inch Plywood, secured by an inner framework of 2x4’s and sealed.
December 3, 2012 1. All, There has been an important change to the Competition Guidelines. Because of some technical difficulties, we were unable to incorporate the new steering assembly box. The steering assembly mechanics inside the box have not changed and remain the same as what was used last year. The Guidelines (sheet 15, Steering, Steering Assembly) section has been updated showing the new steering assembly data. Also, (sheet 16, Steering Box Template) has been changed. The competition website Guideline files have been updated to reflect these changes. Please update your designs and calculations to suit this change. We are sorry for any inconvenience this may bring. 2. Q: Are you still using the windshield wiper motor for the steering assembly? A: Yes, there are no changes to the steering box internals. 3. Q: Is there any sort of penalty/point deduction if the barge touches the boat at any point? A: No penalty/point deduction for barge touching boat.
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4. Q: On page 16, the steering template sketch, there are two dimensions at the top of the diagram…one says 6.5” from edge to CL of rudder stock…the other says its 11.125” from CL to edge…which is correct? A: We understand your confusion after looking at the dimensions on the sketch. The 11.125 dimension is for the mounting hole location. Notice how the dimension for the top mounting hole (13.125 from the bottom) when added to 11.125 equals the total length of the box (24.25). The 6.5 dimension is for the location of the rudder shaft; dimensionally not in the same location as the mounting hole. The location of the dimension is confusing visually and can be misinterpreted.
December 10, 2012 1
Q: The Guidelines state “ALL THREE MOUNTING HOLES FROM THE PROVIDED TEMPLATE MUST BE USED.” I was assuming that the third hole is for the rudder stock. So, is the rudder stock actually a fourth hole? A: Yes, three mounting holes and a fourth hole used for the rudder stock. You need to incorporate for the 3 mounting holes and the rudder stock when designing the steering assembly structural platform.
2
Q: We are running into issues regarding the half-breath calculations of our boat. Towards the stern the boat is a W-shaped hull and as you travel toward the bow the center rises to the top of the boat, creating a catamaran-like bow. How do we calculate the half-breadths considering at certain hull stations and waterlines the hull is not present for part of the distance to the outside of the hull? Would we just subtract the distance that the hull is not present from the half-breadth? A: To account for the W-shaped hull in question:
From the calculations spreadsheet, select the Catamaran hull form from the drop down list.
Add two reference center lines for the W-portion of the hull. These lines will be the reference point from which you will take your half-breadth measurements.
Enter the offsets for the waterplane(s) that resemble a catamaran (your sketch looks like only two waterlines) following the directions for a catamaran design and using the reference centerlines.
3
For the remaining waterplanes, the outer half-breaths should be measured from the reference centerline and the inner half-breadths MUST be the distance from the reference centerline to the (true) centerline of the boat.
4
November 26, 2012 1. Q: What effects will towing the barge have on the design of the boat? A: In a most general sense Towing an object behind the hull as described in the guidelines will affect the overall speed, maneuverability, and trim of the design. The exact impacts cannot be determined due to the variety of possible design configurations, but as a general guideline, the effects of towing will result in: 1) Reduced vessel speed 2) Increased vessel turning radius / decreased maneuverability 3) Trim at the stern will decrease during towing* * It is difficult to determine the impact to vessel trim. The design/engineering team suggests designing the vessel to trim by the bow by at least one inch which will cause a near level trim during towing. Please be aware that the impact to trim is highly dependent upon the hull form and a best practice for designing to accommodate towing is to design additional volume at the stern. This can be accomplished by increasing the beam at the stern or by increasing the height from baseline to deck edge at the stern. 2. Q: Is it possible to have our team name cut out of the battery box? A: We cannot cut the team name into the battery box. This would require extra time and effort to the lofting of the parts, a process that historically has been challenging to complete on schedule. 3. Q: Guidelines state COG (Center of Gravity) for new steering assembly will be provided on or before Nov 16th. When will they be available? A: The CGs will be provided no later than COB Friday, 11/30/12. Continue to use the geometric center as a placeholder until this data is provided. We apologize for the delay.
1
4. Q: We cannot find any information about the freeboard of the barge in the Guidelines. Also, what material is the barge made of and how much does it weigh? A: The barge details have been confirmed and are as follows:
Total Barge Weight (unloaded) = 25.3 lb Total Barge Weight (loaded) = 93.3 lb Design Draft = 7 inches Freeboard = 7 inches Constructed of ½ inch Plywood, secured by an inner framework of 2x4’s and sealed.
December 3, 2012 1. All, There has been an important change to the Competition Guidelines. Because of some technical difficulties, we were unable to incorporate the new steering assembly box. The steering assembly mechanics inside the box have not changed and remain the same as what was used last year. The Guidelines (sheet 15, Steering, Steering Assembly) section has been updated showing the new steering assembly data. Also, (sheet 16, Steering Box Template) has been changed. The competition website Guideline files have been updated to reflect these changes. Please update your designs and calculations to suit this change. We are sorry for any inconvenience this may bring. 2. Q: Are you still using the windshield wiper motor for the steering assembly? A: Yes, there are no changes to the steering box internals. 3. Q: Is there any sort of penalty/point deduction if the barge touches the boat at any point? A: No penalty/point deduction for barge touching boat.
2
4. Q: On page 16, the steering template sketch, there are two dimensions at the top of the diagram…one says 6.5” from edge to CL of rudder stock…the other says its 11.125” from CL to edge…which is correct? A: We understand your confusion after looking at the dimensions on the sketch. The 11.125 dimension is for the mounting hole location. Notice how the dimension for the top mounting hole (13.125 from the bottom) when added to 11.125 equals the total length of the box (24.25). The 6.5 dimension is for the location of the rudder shaft; dimensionally not in the same location as the mounting hole. The location of the dimension is confusing visually and can be misinterpreted.
December 10, 2012 1
Q: The Guidelines state “ALL THREE MOUNTING HOLES FROM THE PROVIDED TEMPLATE MUST BE USED.” I was assuming that the third hole is for the rudder stock. So, is the rudder stock actually a fourth hole? A: Yes, three mounting holes and a fourth hole used for the rudder stock. You need to incorporate for the 3 mounting holes and the rudder stock when designing the steering assembly structural platform.
2
Q: We are running into issues regarding the half-breath calculations of our boat. Towards the stern the boat is a W-shaped hull and as you travel toward the bow the center rises to the top of the boat, creating a catamaran-like bow. How do we calculate the half-breadths considering at certain hull stations and waterlines the hull is not present for part of the distance to the outside of the hull? Would we just subtract the distance that the hull is not present from the half-breadth? A: To account for the W-shaped hull in question:
From the calculations spreadsheet, select the Catamaran hull form from the drop down list.
Add two reference center lines for the W-portion of the hull. These lines will be the reference point from which you will take your half-breadth measurements.
Enter the offsets for the waterplane(s) that resemble a catamaran (your sketch looks like only two waterlines) following the directions for a catamaran design and using the reference centerlines.
3
For the remaining waterplanes, the outer half-breaths should be measured from the reference centerline and the inner half-breadths MUST be the distance from the reference centerline to the (true) centerline of the boat.
4
