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Mycell 80 and Corelite 450 for TX18 build

Posted: Wed Oct 20, 2021 12:24 pm
by Vundu
I have started a new thread with more technical info as advised by Jaques. Thanks very much for the advice in the last thread, I really do appreciate it.

Brief history;
I'm building my second TX18, but increasing the dimensions by 10% all round. Also lifting the gunnels by 10cm. I will not be increasing the depth (height) of the ribs and stringers. She'll be be powered by a motor weighing 180kg +-. I would like to carry approximately 70 litres of fuel and possibly a livewell also 70 Litres.

I would like to keep the hull core BS1088 6mm ply and convert the Transom, stringers, ribs and sole / front deck to Foam core.

I have access to:
Mycell 80 in 10, 15 and 20mm thickness (data sheet below) which I was hoping to use for the stringers, ribs sole and deck.
Corelite 450 in 16mm thickness (data sheet for the transom. I don't have access to Gurit products or Coosa, and my supplier has no data on the Gurit cores or coosa to be able to assist with comparisons.

I do plan to add an additional set of ribs, which should bring the spacing to slightly less than that designed, to aid sole support and the hulls larger dimensions.

Based on the data sheets below I would be extremely grateful for help with what to use and where, and a proposed laminating schedule. Thanks in advance.
MYCELL_M080_Scheda.pdf
(183.53 KiB) Downloaded 9 times
CoreLite Board Data Sheet.pdf
(142.57 KiB) Downloaded 8 times

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Wed Oct 20, 2021 6:59 pm
by jacquesmm
Thanks for starting this new thread.
About materials substitutions, I can not do much until early November.
I never heard of those core materials. Your suppliers should be able to give you specs.
It's impossible to guess shear strength from those specs, I will have to search for boat builders opinions.
Does the seller have some references?
Fortunately, you are doing the right thing and using plywood for the skin.

Some of you know that I am retired and like to travel. Right now, I am camping (in a motorhome) on some beach along the Gulf of Mexico. I travel with all my plans in my laptop and can answer most questions about my designs but not much more. Internet is either spotty or inexistent where I camp but I'll try to do some searches.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Wed Oct 20, 2021 7:24 pm
by jonnymac
here is a link to some of the same specs for coosa. some names are different, but the same test is listed

https://www.merrittsupply.com/wp-conten ... t-Data.pdf

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Wed Oct 20, 2021 8:12 pm
by fallguy1000
Corelite 450 is a substitution for coosa. To me, it is not as good as coosa BW, but I used it on my two small transoms for 90hp engine.

Mycell 80 is 1.06 nominal vs Gurit M80 of 1.09 MPa nominal shear. So, they are nearly comparable. I see the Mycell shows stronger compressive strength, and a cursory review shows no deficiencies.

Anyhow, I see no issue with either choice, but I would still prefer coosa.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Wed Oct 20, 2021 11:31 pm
by jacquesmm
Thanks Fallguy. Since he does not plan to use any of those for the hull skin, it will probably work.
I will look for more details about the use of those for transom foam but the TX18 is not going to suffer from extreme transom stress.
Thanks again.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Thu Oct 21, 2021 6:04 am
by fallguy1000
The only comment I will make is the Mycell 80 used as a stringer offers very little structurally. It will really only be operating as a former for a solid glass stringer. For this reason, the only tangible benefit is that it won't rot. But it doesn't do much structurally. I would prefer to see the stringer structure made with a stronger core and less glass and epoxy. The coosa could or even a coosa 20 or the corelite 450 which is more up front core cost, but less glass, less epoxy, and less time to build. On the other hand, if you are building/specifying solid glass stringers, the core/former could be xps as it is not a concern for shear.

He refers to ribs, which I assume are transverse floors or bulkheads. The Mycell 80 will work nicely for that with proper tabbing to the hull and proper skins. Something on the order of db1700 or 1708 each side.

The sole in my boat is made of two different products. One is Gurit M80 12mm with triaxial glass 850g each side. I can't recall if I doubled it on the bottom; probably not. The other is plascore 25mm with one layer of 850g triaxial each side. The plascore is a far stiffer floor which makes sense based on the cube rule. The sole for the sled should be made fairly durable and db1700 is a bit light, so the obvious choice here is also 1708. For wear, the top layer could be laid with the mat out for a little unnotable tradeoff in flex. The bottom should be mat in, or a better layup could be db1200 times two for both or at least the bottom.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Thu Oct 21, 2021 7:37 am
by Vundu
jacquesmm wrote: Wed Oct 20, 2021 6:59 pm Thanks for starting this new thread.
About materials substitutions, I can not do much until early November.
I never heard of those core materials. Your suppliers should be able to give you specs.
It's impossible to guess shear strength from those specs, I will have to search for boat builders opinions.
Does the seller have some references?
Fortunately, you are doing the right thing and using plywood for the skin.

Some of you know that I am retired and like to travel. Right now, I am camping (in a motorhome) on some beach along the Gulf of Mexico. I travel with all my plans in my laptop and can answer most questions about my designs but not much more. Internet is either spotty or inexistent where I camp but I'll try to do some searches.

Hi Jaques, Firstly thanks very much for taking time away from your break to help out, I am very grateful. I can wait till early November for indepth answers. I took a chance and ordered some cores with my ply already, so will likely just have to add as needed. I attach the core materials Data sheets to my first post, at the bottom. Please let me know if they are accessable.
Corelite450
Compressive Strength ASTM D1621 psi 847
Compressive Modulus ASTM D1621-B psi 423
Tensile Strength ASTM C297 psi 481
Shear Strength ASTM C273 psi 445
Shear Modulus ASTM C273 psi 5519
Shear Elongation at Break ISO 1922 % 1.404
Flexural Strength ASTM D790 psi 1799

Mycell 80:
Compressive strength ASTM D1621-10 MPa average min-ave, min-min 1,43; 1,22; 1,03
Compressive modulus ASTM D1621-10 MPa average min-ave, min-min: 68: 53: 44
Tensile strength ASTM D1623 MPa average min-ave, min-min: 2,60: 1,82: 1,63
Tensile modulus ASTM D1623 MPa average min-ave, min-min: 137: 107: 94
Shear strength ASTM C273 MPa average min-ave, min-min: 1,13: 1,06: 0,92
Shear modulus ASTM C273 MPa average min-ave, min-min: 29: 25: 22
Shear elongation at break ASTM C273 % average 20

To give a general response to the other comments.

I am buying out of South Africa and have been unable to find any coosa products.

I wanted to use the Mycell80 in the stringers and ribs to save weight and rot resistance. I would be happy to use the corelite 450, it would be fractionally heavier if at all as they say 27% ligther than plywood.... so may be the same or lighter, but wider (16mm corelite450 vs 2 x 6mm ply + epoxy), which suits me. I can only buy 16mm corelite450.

The sole, front deck and transom I would like in synthetic core, but only the transom is a real must have. I have access to 20, 15 and 10mm Mycell80 and was hoping to use that on the sole and decks.

Once again, thanks to you all for your comments and advice.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Thu Oct 21, 2021 7:48 am
by Vundu
fallguy1000 wrote: Thu Oct 21, 2021 6:04 am The only comment I will make is the Mycell 80 used as a stringer offers very little structurally. It will really only be operating as a former for a solid glass stringer. For this reason, the only tangible benefit is that it won't rot. But it doesn't do much structurally. I would prefer to see the stringer structure made with a stronger core and less glass and epoxy. The coosa could or even a coosa 20 or the corelite 450 which is more up front core cost, but less glass, less epoxy, and less time to build. On the other hand, if you are building/specifying solid glass stringers, the core/former could be xps as it is not a concern for shear.

He refers to ribs, which I assume are transverse floors or bulkheads. The Mycell 80 will work nicely for that with proper tabbing to the hull and proper skins. Something on the order of db1700 or 1708 each side.

The sole in my boat is made of two different products. One is Gurit M80 12mm with triaxial glass 850g each side. I can't recall if I doubled it on the bottom; probably not. The other is plascore 25mm with one layer of 850g triaxial each side. The plascore is a far stiffer floor which makes sense based on the cube rule. The sole for the sled should be made fairly durable and db1700 is a bit light, so the obvious choice here is also 1708. For wear, the top layer could be laid with the mat out for a little unnotable tradeoff in flex. The bottom should be mat in, or a better layup could be db1200 times two for both or at least the bottom.
Hi Fallguy, Thanks for the thoughts. Less glass and no wood, is ideal, so Corelite450 may be the way to go for the stringers, hopefully Jacques will also have some thoughts when he sees the specs. I mention ribs meaning the crossbracing/bulkheads below the sole. From your other post I recall the advice on keeing the supports close together so will be adding an extra set of ribs, or 2, depending on advice.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Thu Oct 21, 2021 10:42 am
by fallguy1000
There is a fallacy present in boat construction these days. And that is the wood stringers are bad.

The reason for this fallacy or falsehood is for the following reasons:

1. Prior wood stringer boats were made with polyesters and not epoxies.

2. Wood stringers in boats where the stringers are holed, like inboards or i/o are more susceptible to failure.

It is important to understand the likelihood of a stringer covered in two layers of 1200 db glass or more and done properly has almost no chance of leaking or failure from rot.

I am planning to build a PH22, and I will be using specified materials, but will go away from wood on the transom and sole because they get penetrations.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Thu Oct 21, 2021 3:12 pm
by Vundu
fallguy1000 wrote: Thu Oct 21, 2021 10:42 am There is a fallacy present in boat construction these days. And that is the wood stringers are bad.

The reason for this fallacy or falsehood is for the following reasons:

1. Prior wood stringer boats were made with polyesters and not epoxies.

2. Wood stringers in boats where the stringers are holed, like inboards or i/o are more susceptible to failure.

It is important to understand the likelihood of a stringer covered in two layers of 1200 db glass or more and done properly has almost no chance of leaking or failure from rot.

I am planning to build a PH22, and I will be using specified materials, but will go away from wood on the transom and sole because they get penetrations.
Hi Fallguy,
We trailer on some extremely bad roads. The last TX18 I built I epoxied the sole to the stringers and ribs then added stainless screws to keep everything tight before the final layer of glass. As you said the issue is penetrations, and that is my major concern. In this build I would like to make some storage under the sole so would have hinges and latches adding to the potential ingress points for water.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Mon Nov 01, 2021 3:08 pm
by Vundu
jacquesmm wrote: Wed Oct 20, 2021 11:31 pm Thanks Fallguy. Since he does not plan to use any of those for the hull skin, it will probably work.
I will look for more details about the use of those for transom foam but the TX18 is not going to suffer from extreme transom stress.
Thanks again.

Hi JM, Not sure if you picked up the message below re the core foam values. When you ahve some time I would really appreciate your advice on lamination schedules and which cores you advise for sole, deck and transom.

Corelite450
Compressive Strength ASTM D1621 psi 847
Compressive Modulus ASTM D1621-B psi 423
Tensile Strength ASTM C297 psi 481
Shear Strength ASTM C273 psi 445
Shear Modulus ASTM C273 psi 5519
Shear Elongation at Break ISO 1922 % 1.404
Flexural Strength ASTM D790 psi 1799

Mycell 80:
Compressive strength ASTM D1621-10 MPa average min-ave, min-min 1,43; 1,22; 1,03
Compressive modulus ASTM D1621-10 MPa average min-ave, min-min: 68: 53: 44
Tensile strength ASTM D1623 MPa average min-ave, min-min: 2,60: 1,82: 1,63
Tensile modulus ASTM D1623 MPa average min-ave, min-min: 137: 107: 94
Shear strength ASTM C273 MPa average min-ave, min-min: 1,13: 1,06: 0,92
Shear modulus ASTM C273 MPa average min-ave, min-min: 29: 25: 22
Shear elongation at break ASTM C273 % average 20

To give a general response to the other comments.

I am buying out of South Africa and have been unable to find any coosa products.

I wanted to use the Mycell80 in the stringers and ribs to save weight and rot resistance. I would be happy to use the corelite 450, it would be fractionally heavier if at all as they say 27% ligther than plywood.... so may be the same or lighter, but wider (16mm corelite450 vs 2 x 6mm ply + epoxy), which suits me. I can only buy 16mm corelite450.

The sole, front deck and transom I would like in synthetic core, but only the transom is a real must have. I have access to 20, 15 and 10mm Mycell80 and was hoping to use that on the sole and decks.

Once again, thanks to you all for your comments and advice.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Mon Nov 01, 2021 4:33 pm
by jacquesmm
I just came back from a short vacation during which I had very little internet access. I will compare those core materials to Corecell and Aquaplas.
This will take a day or two: I have to find the specs of each for the same ASTM test method and also check if those ASTM methods are adequate to measure peel strength.

Can you get samples? You can apply skins to the samples and do some testing but we'll talk more once I assemble data for comparison.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Tue Nov 02, 2021 12:11 am
by Vundu
jacquesmm wrote: Mon Nov 01, 2021 4:33 pm I just came back from a short vacation during which I had very little internet access. I will compare those core materials to Corecell and Aquaplas.
This will take a day or two: I have to find the specs of each for the same ASTM test method and also check if those ASTM methods are adequate to measure peel strength.

Can you get samples? You can apply skins to the samples and do some testing but we'll talk more once I assemble data for comparison.
Hi JAcques, Thanks very much. Unfortunately I can't get samples.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Tue Nov 02, 2021 1:12 pm
by jacquesmm
Corelite 450 looks very close to Aquaplas and could be used as transom foam IF it bonds well with epoxy.
That would require a sample and some testing.
It's a PVC and some PVC's like Aquaplas III bond well but many other high density PVC foams peel easily.
Corelite agrees with me about testing. This is what their processing guide says:
All 3 CoreLite core materials are compatible with epoxy, polyester and vinylester resin systems. It is
advisable to create a test sample of the core-laminate sandwich panel with reference
to the resin suppliers recommendations, prior to initiating a full core installation.
Note that it states compatibility with polyester and epoxy, a good point.

The Maricell Mycell 80 characteristics are close to Divynicell, shear strength is good, compatible with epoxy. I would use it for all flat panels like sole, stringers, bulkheads.
I would not use it for hull panels without testing but you plan to use a plywood core there.

Assuming that there is no peel problem, and there should not be since each of them clearly mention compatibility with polyester and epoxy, I would use Corelite for the transom
and Mycell for all flat parts.

It is strange that you can get an Italian foam but no others. I suppose that you deal with the South African distributor. Can he not help you with samples? I feel good about those two core materials now that I read their brochures and data sheets but nothing beats a test.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Tue Nov 02, 2021 1:53 pm
by Vundu
jacquesmm wrote: Tue Nov 02, 2021 1:12 pm Corelite 450 looks very close to Aquaplas and could be used as transom foam IF it bonds well with epoxy.
That would require a sample and some testing.
It's a PVC and some PVC's like Aquaplas III bond well but many other high density PVC foams peel easily.
Corelite agrees with me about testing. This is what their processing guide says:
All 3 CoreLite core materials are compatible with epoxy, polyester and vinylester resin systems. It is
advisable to create a test sample of the core-laminate sandwich panel with reference
to the resin suppliers recommendations, prior to initiating a full core installation.
Note that it states compatibility with polyester and epoxy, a good point.

The Maricell Mycell 80 characteristics are close to Divynicell, shear strength is good, compatible with epoxy. I would use it for all flat panels like sole, stringers, bulkheads.
I would not use it for hull panels without testing but you plan to use a plywood core there.

Assuming that there is no peel problem, and there should not be since each of them clearly mention compatibility with polyester and epoxy, I would use Corelite for the transom
and Mycell for all flat parts.

It is strange that you can get an Italian foam but no others. I suppose that you deal with the South African distributor. Can he not help you with samples? I feel good about those two core materials now that I read their brochures and data sheets but nothing beats a test.
Hi Jacques. I have only found 2 suppliers of core materials in South Africa. The suppliers of the corelite and mycell have been extremely helpful and supportive and advised that the corelite450 is usually used for transoms. The alternative supplier has not. Coosa also seems to not be sold there at all.

As I am a few thousand miles and 2 countries away I have a few logistical issues LOL. I took a chance and ordered some corelite450 and the mycell 80 in mid October. I hope to have it in the next 2-3 weeks.

How you would like the peel tests undertaken?

Could I use the 16mm corelite 450 for the stringers too?

Thanks.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Tue Nov 02, 2021 1:59 pm
by jacquesmm
Yes, you could use Corelite for every thing.
I will try to find pictures of a simple peel test. I use the same method than Boeing: a sample with a tab of skim that extends from the core and is pushed up and won by an eccentric, a cam.
There is an ASTM method, just do a google search.

Re: Mycell 80 and Corelite 450 for TX18 build

Posted: Sun Nov 07, 2021 12:20 pm
by Vundu
jacquesmm wrote: Tue Nov 02, 2021 1:59 pm Yes, you could use Corelite for every thing.
I will try to find pictures of a simple peel test. I use the same method than Boeing: a sample with a tab of skim that extends from the core and is pushed up and won by an eccentric, a cam.
There is an ASTM method, just do a google search.
Will do, thanks, Materials arrive this week.