| MudmotorTalk.com https://www.mudmotortalk.com/mmt_v2/ |
|
| Boat draft calculation/ light vs heavy? https://www.mudmotortalk.com/mmt_v2/viewtopic.php?f=4&t=71807 |
Page 1 of 1 |
| Author: | 50fps [ Fri Dec 29, 2017 4:21 pm ] |
| Post subject: | Boat draft calculation/ light vs heavy? |
Ok I keep seeing some talking about light hulls vs heavy hulls. I am wondering how much of a difference it can really be. So you have two hulls 1848 with identical rakes and 12' of flat surface. One weighs 500lbs, the other 300lbs. Both are square chine. How deep does each one draft? |
|
| Author: | Will C [ Fri Dec 29, 2017 5:28 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Not sure on actual measurements but its very noticeable exspecially on 48 wides. The deeper that ass runs the slower she be. Who's gonna make us a calculator? |
|
| Author: | Russ [ Fri Dec 29, 2017 8:08 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Can of worms. A 500lb boat drafts 2 inches of water with those bottom measurements. A 300lb boat will draft 1.2". Not the whole story, but those are taken with expectation of a level float. I know this is all part of the ultimate discussion and not really the point of this thread, but I dont want any newbies to read those draft numbers and set theur expectations as such. Hang a motor on it, you are no longer getting an apples to apples comparison. Weight of water displaced is the same with a pair of 500lb boats, but if one has a motor on the rear, and one is just that weight balanced, then boat A drafts more water. It's ultimately just changing the actual bottom shape in relation to the water. Simple concept, but can make a huge difference. Motor trim angle, thrust angle, prop rake, etc all changes that too once underway, even at slow speeds (which is actually where draft matters more to most of us since it directly affects our ability to build enough speed to get on plane). Lift created at specific speeds, and draft depth at that moment in time is the REAL headscratcher that would answer it all. Even if we could calculate it at a specific speed for one boat, it would be a good baseline. The math and instruments needed for that are a tad past my pay grade lol. #CFFITR #TheGhostBoat #whoneedsphysicsihaveamudmotor |
|
| Author: | Russ [ Fri Dec 29, 2017 8:47 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Btw, 50, read my last hashtag. You've broken the cardinal rule LOL #CFFITR #TheGhostBoat #whoneedsphysicsihaveamudmotor |
|
| Author: | CypressCritter [ Sat Dec 30, 2017 9:20 am ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Lighter load == planning hull Heavier load or too heavy == plowing hull One reason why with all that horse power a tug boat is very slow in comparison to another type of hull. Also why a good designed bass boat will "walk on water" planes out and also very little hull in contact with water at high speeds. |
|
| Author: | 50fps [ Sat Dec 30, 2017 10:43 am ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
| Author: | MNGunner [ Sat Dec 30, 2017 11:34 am ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
The 500 lbs boat needs to displace 1.67 (i.e. 500/300) as much volume of water to float. You can make that volume calculation (LxWxDraft) depending on your approximations . If you approximate it's a rectangular solid then the calculation is easy. You can get a better approximation, assuming the length changes because more and more of the rake gets submerged as you increase weight (but requires knowing the rake angle). If you're taking about a boat that is moving it becomes more complicated... |
|
| Author: | kirk [ Sat Dec 30, 2017 9:31 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
| Author: | Will C [ Sun Dec 31, 2017 12:22 am ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Comparing 48 wides light vs heavy |
|
| Author: | MNGunner [ Sun Dec 31, 2017 2:37 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
BTW the formula for buoyancy is BoatWeight = (62.4 lbs/cubic foot) * (Volume of water displaced) solve for the volume (the draft is the hieight) |
|
| Author: | kirk [ Mon Jan 01, 2018 5:54 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Always found this topic pretty interesting. But what I would really like to see is actual boats that differ in size with identical loads, on let’s say a 10mi straight run, deep water. And see what size comes out on top. Does the boat that displaces The most weight always come out on top? Or is there a point to when The boat can be too big/heavy and causing a decrease in speed. Mainly comparing larger boats like 17x54, 18x48-54, 20x48.. etc Sent from my iPad using Tapatalk |
|
| Author: | DENNYEDWARDS [ Tue Jan 02, 2018 9:11 am ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
Here is our comparison. Excel 1851 F4 MB 7000. Bare boat weight 750 #, with motor, 12 gal. fuel, battery and Misc. equipment, 250# operator, 1460#s. Other boat 1648 Alumacraft MB 45 BD bare boat 300# with motor, 12gal fuel, battery, and 250# operator 1010#s. Side by side comparison, Alumacraft up on plane faster. At WOT 4550RPM with Hammer prop on both rigs Alumacraft runs Side by side with Excel. Excell rated for 4 people, Alumacraft for 5. With rated person load in Excel and Alumacraft, Alumacraft will still run side by side wth Excel, even with added weight of extra person. |
|
| Author: | 50fps [ Tue Jan 02, 2018 1:48 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
| Author: | BlueShamu [ Tue Jan 02, 2018 2:21 pm ] |
| Post subject: | Re: Boat draft calculation/ light vs heavy? |
http://blueheronwings.com/bh/comps/bdesign.html This should help answer all physics questions related to mudboats. Sent from my iPhone using Tapatalk |
|
| Page 1 of 1 | All times are UTC - 6 hours |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|