TX18 Foam core stringers, ribs and sole. Strakes.

[Vundu]

I am glad to hear that you like your TX18 but can we have a performance report and some pictures?

Some of your questions are easy to answer, others not.
Let's start with the easy ones.

Scale by 7%: no problem at all.

Raise the sides 4 to 6" easy, you can do that.
BTW, we can talk metric, 10 to 15 cm is fine.

Raise sole for storage: yes, as long as all the framing is present and is raised the same way.

More HP: not ideal but the transom can take it. Trim at rest may not be nice but it is possible. We will have to move tank and battery for the CG.

Foam core: no problem at all if you make the bottom from plywood epoxy. All other parts can be made in foam sandwich and I can give specs.
I can give specs for the bottom too but I will consider them experimental. You may have seen the debate about the PH22 in foam. The TX18 does not slam as much as a low deadrise and with the proper foam and resin, there will be less risk of shear failure than with the PH22.
Your problem is one of supplies: how easy is it to get supplies in Zambia? BBC can ship in a container, we have done it a few times.

Strakes: I don't like that idea. You know that the boat hull shape is based on the Hickman's sled. Hickman and others designed many hulls in that style and in some cases, there was a problem with chine tripping. For that reason, the last Hickman's design and my own have those small slanted chines. Strakes could be dangerous and I don't think that they would reduce blowouts. Blowouts may happen in turns with the TX18 and with tunnel hulls. In a straight line, the flow to the prop is steady, regular but in turns, you will always have turbulences and the only way to avoid blowouts is to take wide turns.
Did you try different height settings?

Hi Jacques. I have lofted the boat +10% all round. I have also found mycell 40, 60 and 80 in South Africa as well as Corelite 450. If you have the time could you please help me with advice on the type of core to use and laminating schedule for the sole. Could you give me your thoughts on using the Corelite 450 for the transom? If its useable do you ahve a laminating schedule for it? Thanks very much!

[fallguy1000]

Corelite 450 is fine for a transom. Two pieces with a 1mm pb epoxy bond done at about 2-4psi bond pressure. Wet both sides with thickened epoxy using a 1/16" or 1/2mm vee trowel. The schedule is up to JM. Something in the neighborhood of 5 or 6 layers of db 1700 each side with wraps over the top. First piece would be 12" overlaps all sides. So inside wraps bottom and sides and top 12". Next 10", etc. The fillets and radiuses need to be good sized like 3/8" to allow for all the wraps. It might be nice to get some uni into the layup as well as the short strands would be vertical...up to JM.

The top of the transom should get wrapped by both the inside pieces and the outside pieces. In order to do this well, you must also fair the landing zone for the outside or the inside with pb epoxy. This will be 10-12 layers of glass along the top. Each side takes a day of work. Be careful to mix the epoxy here. I made the mistake of putting my epoxy for the transom into a roller pan and forgot to mix one batch... luckily it was the last piece..

After the wraps; you will want to square off the bottom edge for performance. The top can be squared off, but that is just for looks.

The pieces of glass should be dry fit first, with some sharpie writing on them so you remember any special overlap wishes.

[Vundu]

Corelite 450 is fine for a transom. Two pieces with a 1mm pb epoxy bond done at about 2-4psi bond pressure. Wet both sides with thickened epoxy using a 1/16" or 1/2mm vee trowel. The schedule is up to JM. Something in the neighborhood of 5 or 6 layers of db 1700 each side with wraps over the top. First piece would be 12" overlaps all sides. So inside wraps bottom and sides and top 12". Next 10", etc. The fillets and radiuses need to be good sized like 3/8" to allow for all the wraps. It might be nice to get some uni into the layup as well as the short strands would be vertical...up to JM.

The top of the transom should get wrapped by both the inside pieces and the outside pieces. In order to do this well, you must also fair the landing zone for the outside or the inside with pb epoxy. This will be 10-12 layers of glass along the top. Each side takes a day of work. Be careful to mix the epoxy here. I made the mistake of putting my epoxy for the transom into a roller pan and forgot to mix one batch... luckily it was the last piece..

After the wraps; you will want to square off the bottom edge for performance. The top can be squared off, but that is just for looks.

The pieces of glass should be dry fit first, with some sharpie writing on them so you remember any special overlap wishes.

Thanks very much Fallguy. I really appreciate your help!

[fallguy1000]

What is the sole core in this boat?

[Vundu]

What is the sole core in this boat?

Hi Fallguy, I a looking at Mycell80 PVC foam core I can buy 10, 15 and 20mm thick.

[fallguy1000]

You want the sole to be thick in foam and spans to be 20" or less. Longer spans require making supports. I made some foam core i beams..

[Vundu]

You want the sole to be thick in foam and spans to be 20" or less. Longer spans require making supports. I made some foam core i beams..

Thanks again Fallguy. I have been holding off for a few weeks before ordering, appreciate your input, I can get started now!! Are there pics of your I beams on your build thread?

[Vundu]

Hi Jaques, Please can I take you up on the offer to help me with the foam core choices and glass schedule for my build (TX18+10%).
I would like to build the stringers, ribs, sole and transom out of foam core. The hull from BS1088 ply. I have access to:
Mycell 80 in 10, 15 and 20mm.
Corelite 450 in 16mm.
I will be using a 170kg motor, 115hp.

[jacquesmm]

Yes, we started that discussion in another thread but I don't know the products you mention.
Can you give me link to the specs or ask your vendor to supply those specs or better, have him compare them to Corecell 500A?

[Vundu]

Yes, we started that discussion in another thread but I don't know the products you mention.
Can you give me link to the specs or ask your vendor to supply those specs or better, have him compare them to Corecell 500A?

Hi Jaques. Thanks for getting back to me. I'll start a new thread in the same forum.