Help me lighten a boat

[mistel]

I am going to build a small Dumas boat as a winter project, probably the Deep Vee

http://www.dumasestore.com/catalog/product_info.php?cPath=47_58&products_id=421

It will be electric. So the idea is, this boat was originally made to be gas, so it is built very sturdy (heavy). To make it perform better I want to lighten it a bit. I will paint it, so I am not worried about having nice wood grain showing.

I was thinking I could replace some of the plywood hull pieces with thinner plywood. I could maybe make some holes in some of the bulkheads?

Any good ideas?

Thanks

Peter

[pusar]

Taking a "heavy" wood boat and making it lighter by using thinner pieces may make the boat weaker. If you want to gain speed and performance look into motors props and batteries to achieve that. Changing the design of the wood hull to lighten it will only give you minimal results.

What do you plan to do with the boat?

Marty

[mistel]

I'm going to put a Graupner z-drive in it

http://www.offshoreelectrics.com/proddetail.php?prod=grp-1985

Just ordered it. I want to try and make a scale looking boat. Maybe I won't try and change any of the wood parts, but I would like to make it as light as possible. Any techniques?

Thanks

Peter

[toesup]

...but I would like to make it as light as possible. Any techniques?

Use a thin ply / balsa / thin ply sandwich for the bulkheads.. still keeping the original thickness.. and then put some 'air' in the solid parts of the bulkheads... ;)
http://www.rcgroups.com/forums/attachment.php?attachmentid=1198709

.. though, be warned, you may have to add lead to ballast the model back to the waterline...

[Shaun Hendricks]

You can also switch materials.

Carbon Fiber or Fiberglass plate bulkheads.
Solid Foam Hull with fiberglass covering - you can remove as much foam as you like once FG'd.
-or- use substitute planking like Sintra and overcoat with ¾oz FG cloth.

You'll have a model that will weigh much less, but since the plans are for wood, your performance may vary wildly from the original.

I have 2 ABS Electro-Vee hulls, they weigh very little, far less than a wood boat of the same size. I don't know if they will perform better or worse than wood. No bulkheads, no internal framing... this is another way to go for a light deep vee design. I got mine from Hobby Lobby. $35 for both on sale... :D

[Ghost 2501]

you dont want it too light otherwise handling may be adversly affected, best thing is a big motor!

[retoabcr]

Belive it or not, use thin ca on balsa wood makes it stronger. I picked this up on the RED forum 7 years ago that Ernie Lanzberry of U.K.. I used thin balsa with 1/64 ply on both sides and was strong yet had very little flex. The hulls Shaun is referring to cannot be bought any more but was a very good value. There is another deep vee called UFO made of .060 abs and wears like iron but is 22" long from Fine Design which weighs 10 oz. and a real good value for 6 or 8 cells and a 632 prop. Forgot, Des mentioned add support under motor. Just ca 1/32 ply at least 2 1/2" all around where motor mount will be and be home free. Your Dumas probably has parts you can trace like inner supports, just use balsa and thin ply like Toesup mentioned for those supports. I wouldn't drill holes in supports ( new ones-balsa and ply ). Now before you put motors and etc in ; put a finger on both sides and lift and find balance. Place motor near that point and batteries and rx batteries, rx, servo and work around that balance point. Just lay these parts in and you may have to juggle things around especially getting parts in and out for possible repair later if needed.. I have several 22" monos and me with long and BIG fingers can sometimes talk French ( means break time ). I found Gorilla glue to answer questionable areas over ca and paid off.

[mfr02]

Hulls for electric propulsion need strength in different areas to IC hulls. With electric, you dont put any strain on anything starting it. The power unit should not vibrate. Both of these considerations mean that a lot of the internal woodwork is redundant. On the other hand, you need to accomodate the battery, which will likely be a large heavy lump of a thing.

[Deestingray]

Having been through a similar excercise recently with my Wild Thing, I will agree with retoabcr in that balsa combined with a very thin sheet of ply is as strong as anything you need. I was going to run into the same problem with too much weight if using 2mm ply all over so instead, I have used 2mm ply on the vee, the bulkheads are 3mm ply(probably a bit heavy) but the sides and deck are 3mm balsa with .5mm timber planking over the top of that, which provides both an aesthetic effect and some good strength whilst keeping the weight down. One thing to consider if you are running a reasonably powerful motor is to strengthen the bottom of the vee with epoxy and some cloth, I found that the torque of the motor cracks the keel there right under the motor. Other than that, the strength is great, I have had a few good hits into the bouys with no ill effects.