Nate and his boat

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Son brag moment

When I picked him up from after school care, he was surrounded by a few older kids and a teacher while listening to him explain his ideas about how to create a remote control boat using certain materials. The detail he provided was incredible.

I guess he was talking for about 35 minutes before I arrived. When I arrived, he started from the beginning telling me ways to make the plastic boat heavy enough to hold a motor. I honestly couldn't follow that part. He then was very specific about the type of motor and rudder that his boat needed. He was even showing me with his hands what the specific parts in the motor needs to look like and how it is supposed to function. He got all of his ideas from three plastic cups - incredible. Tonight, we looked up motors to see if we can find one that fits his description. We found two that closely resemble what he was describing. I think we should start with building a model. Dad will help him as I am seriously spatially challenged!

Two days ago he explained why trees have trunks and went into great detail. He first explained for about ten minutes how trees need the roots for stability. He then described how the roots provide nourishment to the entire tree which took another five minutes.

His expressive language skills are significantly increasing. In the past two weeks, he has rarely stuttered. His overall fluency is improving. The speech/language therapist expressed that he has made huge gains this past few weeks.

I learn something new from him everyday!

Wow....that sure is inspiring. Its so great when you see the hard work paying off.

What was lovely too was, not just the ability to express himself so beautifully, but that he was dead interested to tell you all about it, to share his knowledge with you. I love those moments.

My son is only just 4yrs, and his language is only really starting to kick in now!! I look forward to moments like those, when he can talk to me, and tell me all about boats/dinasours/train timetables or whatever might interest him!! !

Thanks for giving us hope xx

Happy dance for you!! !

yea!! !! !! !!

Do you think he will be able to understand the concept of torque, specifically starting torque? Torque is basically the movement of force. A motor, axel and wheels basically can convert angular movement (rotating) into linear movement.

You can say that heavier objects need more force to get them moving, but once you get them moving they have a "momentum". So if you turned off the motor once it is started moving then without resistance to oppose it, then it would continue on its path. Of course there is always some resistance like friction, but breaks, etc offer more resistance and can stop it quicker.

Back on torque. If you have can have two motors that are as powerful. One with the lower starting torque might not get the heavy object going, and will probably will stall. It can not create enough in order to push/pull the object into motion, even though if the motor is going at full plenty it has plenty of power. The second motor has a high starting torque. You could say it "shunts" or "shoves" the object into motion.

So if wanted to design a motor that would move a train he would need to make one that would shunt the train into motion. The weight of the train is a downward force, which causes resistance, which is why it is difficult to get it moving. Rails are designed to help aid the moment. If you have two materials like the steel used on the wheels and than steel used on the tracks the have a specific "coefficient of friction". He doesn’t need to understand this yet, but just giving a flavour. You need some resistance "traction" otherwise the wheel would just spin and the train would not go forward. This is related to ->rolling resistance<-.

When you are talking about a boat. There is less resistance in water. You can paddle with your hands and the boat will move. The motor of the boat is causing forward motion by screwing the water. The starting torque doesn't need to be a height as that need for a train, but it does need some starting torque in order to get the water moving.

If you make the boat too heavy, and it will be heavier with the motor in it may well sink. Buoyancy is the upward force that keeps things a float. It is related to the density of the object (boat) and the density of the water.

The way boats work is through hull design they displace enough water to keep the boat buoyant for the weight. This is because the weight of the fluid displaced is proportional to the volume of that water. density equals the mass per unit volume. So if the boat hull is mostly made of thinner surfaces and voids, but design to displace more water it will stay buoyant.

However it is a compromise you want the boat to be able to cut thought he water when it is going forward. There is some complex fluid dynamics going on there. But I think your son would agree if he has a large square piece of wood and held it out in front of him underwater and tries to push it forward under water. It would be difficult. I if he has a wedge shaped like the front to a boat it "cut" through the water more easily.

It occurs that your son may be talking about ballast. Balast is strategically placed weight primarily to make sure the boat sit correctly in the water, and is submerged enough so it is stable, to prevent it rolling onto its side and sinking that way. This applies less to hydrofoils as they already have other ways of stabilising. The canoes from pacific islanders, and trimarangs have out-board stabilisers. However you can stabilise a boat with just a single hull. Also large ships have ballast tanks in order to change the ballast depending on what cargo they are carrying.

Ballast has another use. Different engines and different propellers are designed to sit differently in the water. Some are fully submerged, others are fully submerged. There are many different designs. Ballast could be used in the back of a power boat to make sure the engine and prop is in the correct position. However engine can already weight a great deal. Often as the engine accelerates the front of the boat goes up. The boat can start to "aquaplane". Some weight at the front may be needed so it starts take off and start flipping backward, which is what can happen at high speeds such as water speed record attempts.

The technical side I have no clue on but I LOVE that your son is getting his own version of groupies. That will help insulate him from bullying. SO very useful. I've seen it with my son.

And the special skills are pretty cool, too.

If you make the boat too heavy, and it will be heavier with the motor in it may well sink. Buoyancy is the upward force that keeps things a float. It is related to the density of the object (boat) and the density of the water.

If this is just a model boat then you should be able to just increase the size to compensate for engine weight. Its mostly empty space after all. Of course if the plastic is to heavy to float then your stuffed.

Wow. Thank you for all of the advice. I will look that information up with him tonight and see if he was talking about the things some of you have mentioned.

This stuff is way over my head but at least I can learn!

Groupies - I love it!

Actually, the ballast is usually used in the keel of a sail boat(because the high sails, especially with winds, will cause it to tip). A lot of other boats are often built lighter.

Generally, a boat will carry as much weight as the water it displaces. The lighter the boat is, the more weight it can carry. Of course, you probably want to make sure that the bulk of the hull rarely comes near the water line, as a pound of water will reduce its ability to carry a pound of something else, etc.....

I seriously am out of my league. I give Nate wrong information. I told him that his boat wouldn't be able to carry certain motors because they seem too heavy (just from a website) for his light boat. He then said something like - just make the boat a little more flat and larger on the bottom as that will carry the motor.

Interesting stuff.

That would work, an alternative to a flat keel is to make the boat wider. Boats sink or float based on the ratio between surface area (in contact with the water, not total) and weight.