tried to build a light weight tub... and failed :(

[TomMoorehouse]

I tried to build a light weight jae tub and failed. Here is what I did:

tub sides are 1/4" light ply with big holes cut in them to make them lighter. Then I skinned it with 1/64" plywood

radio box front bulkhead is 1/8" 3 ply

Transom is 1/16" plywood (was going to double this but have not yet)

front is just foam, no bulkhead.

tub top is 1/64" plywood

tub bottom is 1/32 plywood

No tub nose has been attached yet. It was going to be just balsa.

weight is 225 grams

How can this be improved?

Ideas?

 

[Richard Dahlheimer]

Hello Tom, i dont think your tub is to heavy. Just my opinion though. Just select the rest of the components to finish your boat carefully. One example is the motor mount. A motor mount that is bolted to the tub sides, using delrin rails, 4 nylon bolts, and 4 rubber gromets will only weigh 1oz. I would go with the 1/8th transom like you mentioned. Have fun, Tom. Richard D

 

[Tim_Duggan]

Tom,

What was the weight of the 1/4 ply with the holes in them prior to laminating them with 1/64"? (1/4 seems overkill to me) How did you bond the sheeting - epoxy?

Tim

 

[TomMoorehouse]

Tom,

What was the weight of the 1/4 ply with the holes in them prior to laminating them with 1/64"? (1/4 seems overkill to me) How did you bond the sheeting - epoxy?

Tim

I just got my scale today so I don't know what the 1/4 alone was. I do believe the 1/4" light ply was the reason it came out heavier than I would have liked. I used almost all CA glue for building the tub. Only used epoxy with the foam.

for comparison. I built another .21 tub (different design) with my regular methods 1/8" 3ply tub sides 1/16 tub bottom, and 1/32 tub top and it came in at 215grams

only thing i can think of would be to use 1/8" 3ply or 1/8" light ply skinned? but that would be like I always do so no weight savings.

 

[Tim_Duggan]

I'd be willing to bet the 1/4" tub sides are the issue. Overkill.

 

[anthony_marquart]

I build them with 1/8 doubler and 1/32 skins.

 

[dwilfong]

Tom, Try Okoume marine plywood 1/4" it is liter than 1/8" plywood. Good stuff. It is a little pricey and hard to find in small pieces. If you need some I have some you can try.

David

 

[TomMoorehouse]

ive been looking at Okoume but it is expensive! anybody know a good source? ill i ever find is entire 4 X 8 sheets with expensive shipping.

 

[dwilfong]

ive been looking at Okoume but it is expensive! anybody know a good source? ill i ever find is entire 4 X 8 sheets with expensive shipping.

I got a 4x4 piece cut down to 2x4 and had it shipped . The price was not to bad. I think it was about $60 with shipping. let me look and see where I got it from.

David

 

[dwilfong]

ive been looking at Okoume but it is expensive! anybody know a good source? ill i ever find is entire 4 X 8 sheets with expensive shipping.

I got a 4x4 piece cut down to 2x4 and had it shipped . The price was not to bad. I think it was about $60 with shipping. let me look and see where I got it from.

David

this is the place http://www.noahsmarine.com/United_States/Plywoods-us/plywoods-us.html

 

[TomMoorehouse]

ugh.... need to find a way to make more money!

 

[Glenn Quarles]

Tom, if I may suggest...

Use 1/8 balsa with either 1/64 or 1/32 skins for the sides (I use the 1/64!). the 1/32 bottom and 1/64 top are good. Make the front radio box bulkhead out of the same. I use either 1/8 or 3/32 ply for the transom (in-between the sides) and a 1/32 or 1/16 transom doubler all the way across. The front of the engine compartment probably needs something beside foam...I would use 1/8 balsa with 1/64 ply on the inside (the side towards the engine). Yes CA is the way to go for all of the joints (with a THIN coat of epoxy over the joints on the insides). Radio box lid rails should be 1/32 ply, the radio box lid should be 1/64 if the pipe is not going to mount to it or 1/32 if the pipe mount is going on it. You may want to add SMALL pieces of either balsa or 1/32 ply where the mount goes. The cowling (if used) should be 1/32 and 1/64.

The big thing is to stay away from the epoxy! Think about where the forces/stresses are and add strength only in those places...EVERYTHING ELSE IS JUST ALONG FOR THE RIDE!

And then there are all of the other parts....

Glenn

 

[TomMoorehouse]

I've been trying to talk a buddy of mine in to making me a CF balsa panel without success. He keeps saying I need to make the whole thing out of carbon. I just don't have the tools. He might help me out yet!

How should the ply be attached to the balsa? Medium ca?

Have you tried the okume plywood Glenn?

How about the wire drive for .21's got that figured out?

 

[Tim_Duggan]

I've been trying to talk a buddy of mine in to making me a CF balsa panel without success. He keeps saying I need to make the whole thing out of carbon. I just don't have the tools. He might help me out yet!

Food for thought Tom. My link

 

[TomMoorehouse]

I'd love to try that..... but it's too much$$$

 

[Ron Jefferson]

I tried to build a light weight jae tub and failed. Here is what I did:

tub sides are 1/4" light ply with big holes cut in them to make them lighter. Then I skinned it with 1/64" plywood

radio box front bulkhead is 1/8" 3 ply

Transom is 1/16" plywood (was going to double this but have not yet)

front is just foam, no bulkhead.

tub top is 1/64" plywood

tub bottom is 1/32 plywood

No tub nose has been attached yet. It was going to be just balsa.

weight is 225 grams

How can this be improved?

Ideas?

Tom,

Is 225 grams actually all that heavy? I just built my own tub using balsa with 1/32 ply and westsystem everywhere. I was able to keep the hull just under that weight with added gussets and dowl disks where ever holes go through the hull. I was looking for a fairly light hull but with good strength as well. I'm not sure what weight you're looking for but I was hoping to come in around 3 1/2 lbs.

Ron

 

[Marty Davis]

Tom, if I may suggest...

Use 1/8 balsa with either 1/64 or 1/32 skins for the sides (I use the 1/64!). the 1/32 bottom and 1/64 top are good. Make the front radio box bulkhead out of the same. I use either 1/8 or 3/32 ply for the transom (in-between the sides) and a 1/32 or 1/16 transom doubler all the way across. The front of the engine compartment probably needs something beside foam...I would use 1/8 balsa with 1/64 ply on the inside (the side towards the engine). Yes CA is the way to go for all of the joints (with a THIN coat of epoxy over the joints on the insides). Radio box lid rails should be 1/32 ply, the radio box lid should be 1/64 if the pipe is not going to mount to it or 1/32 if the pipe mount is going on it. You may want to add SMALL pieces of either balsa or 1/32 ply where the mount goes. The cowling (if used) should be 1/32 and 1/64.

The big thing is to stay away from the epoxy! Think about where the forces/stresses are and add strength only in those places...EVERYTHING ELSE IS JUST ALONG FOR THE RIDE!

And then there are all of the other parts....

Glenn

Tom:

I agree 100% with Glenn. This is the way that I also build my boats.

 

[Ron Jefferson]

Tom, if I may suggest...

Use 1/8 balsa with either 1/64 or 1/32 skins for the sides (I use the 1/64!). the 1/32 bottom and 1/64 top are good. Make the front radio box bulkhead out of the same. I use either 1/8 or 3/32 ply for the transom (in-between the sides) and a 1/32 or 1/16 transom doubler all the way across. The front of the engine compartment probably needs something beside foam...I would use 1/8 balsa with 1/64 ply on the inside (the side towards the engine). Yes CA is the way to go for all of the joints (with a THIN coat of epoxy over the joints on the insides). Radio box lid rails should be 1/32 ply, the radio box lid should be 1/64 if the pipe is not going to mount to it or 1/32 if the pipe mount is going on it. You may want to add SMALL pieces of either balsa or 1/32 ply where the mount goes. The cowling (if used) should be 1/32 and 1/64.

The big thing is to stay away from the epoxy! Think about where the forces/stresses are and add strength only in those places...EVERYTHING ELSE IS JUST ALONG FOR THE RIDE!

And then there are all of the other parts....

Glenn

Tom:

I agree 100% with Glenn. This is the way that I also build my boats.

Glenn and Marty,

What would your hull weigh before sealing or installing hardware?

Ron

 

[Glenn Quarles]

I've been trying to talk a buddy of mine in to making me a CF balsa panel without success. He keeps saying I need to make the whole thing out of carbon. I just don't have the tools. He might help me out yet!

How should the ply be attached to the balsa? Medium ca?

Have you tried the okume plywood Glenn?

How about the wire drive for .21's got that figured out?

Tom, I have found that carbon/balsa is WAY overkill for a .21 boat...carbon/foam or carbon/kevlar honeycomb is what I normally use.

Yes thick CA will work to put the ply on the balsa. No I have never tried the okume.

Yes my new .21 hydro has a wire drive setup that Charles Perdue built. If we can find someone to build a few of the pieces, I may start selling the entire wire drive setup that Charles has developed.

Glenn

 

[Glenn Quarles]

Tom, if I may suggest...

Use 1/8 balsa with either 1/64 or 1/32 skins for the sides (I use the 1/64!). the 1/32 bottom and 1/64 top are good. Make the front radio box bulkhead out of the same. I use either 1/8 or 3/32 ply for the transom (in-between the sides) and a 1/32 or 1/16 transom doubler all the way across. The front of the engine compartment probably needs something beside foam...I would use 1/8 balsa with 1/64 ply on the inside (the side towards the engine). Yes CA is the way to go for all of the joints (with a THIN coat of epoxy over the joints on the insides). Radio box lid rails should be 1/32 ply, the radio box lid should be 1/64 if the pipe is not going to mount to it or 1/32 if the pipe mount is going on it. You may want to add SMALL pieces of either balsa or 1/32 ply where the mount goes. The cowling (if used) should be 1/32 and 1/64.

The big thing is to stay away from the epoxy! Think about where the forces/stresses are and add strength only in those places...EVERYTHING ELSE IS JUST ALONG FOR THE RIDE!

And then there are all of the other parts....

Glenn

Tom:

I agree 100% with Glenn. This is the way that I also build my boats.

Glenn and Marty,

What would your hull weigh before sealing or installing hardware?

Ron

Ron, I don't remember...my latest .21 hydro heat racing boat weights 2-14 RTR. The one I'm building now is going to be a little more (on purpose).

GQ