Honeycomb tansom core.

[Rip it up]

I have a cruise craft rogue 14 that requires a new transom and floor. And because I never want to do it again I would like to use polycore honeycomb throughout the rebuild. The honey comb panel is 80kg/m density with a compression strength of 2.2Mpa.
My layup plan is as follows.
450gsm double bias fabric. Laminated with FGI epoxy. Onto 20mm polycore.
A sandwich layer of 450gsm then another 20mm polycore.
This panel would then be bonded to the original transom fibreglass from the inside using westsystem microfiber filler mixed with epoxy.
Once cured for 48hrs, clamps off. Cove around edges and wet lay 450gsm with 3 overlapping layers.

This transom would support a 4st Yamaha 60hp engine. 126kg.

To help the compression strength of the honey I plan to use stainless crush sleeves on the engine bolts. Also hollow out the core 2" around each bolt and replace with microfiber filler.

What do the experts think? Anybody tried to use honeycomb on a transom before. I did a thorough search and did not find much on honeycomb transom.

I will work on pics as I figure out how.

 

[a1964rn]

Re: Honeycomb tansom core.

Welcome!
Honeycomb is not recommended for transoms, from what I've read anyway. Here's one article I found on honeycomb cores.

Fiberglassic Guide to: Transoms, Floors, and Stringers - fiberglassics.com

That stuff is much expensive, anyway. I would use the Arauco Plywood from Home Depot. The epoxy is totally moisture proof and will outlive you, provided it's done correctly.
Good Luck!

 

[Woodonglass]

Re: Honeycomb tansom core.

We get this all the time here on the forum. A properly glassed and maintained wood core transom will last 50 years. I seriously doubt you will own the boat that long. It will cost less than half the cost of what you are proposing an the honeycomb is not advisable for a transom. There are composites that can be use but as stated are much more expensive.

 

[Rip it up]

Re: Honeycomb tansom core.

Thanks for the replies but I need people to think outside the square. I know people go back to the same old construction plywood time and time again. However has anybody gone to effort of testing new grounds.

I have already brought the honey comb. It was cheaper than ply at AUS$40 per sheet.

The compression strength is better than most foams at 80kg density so why not use it. 2.2Mpa vrs 1.3Mpa

I have never seen a failed honeycomb laminate to understand why it can not be used. And with solid cores around the bolting points what can fail in my design? I don't mind beefing up the laminate around the bolt pattern and feathering out the spread the load.

Surely somebody has used honeycomb in a transom.

 

[sphelps]

Re: Honeycomb tansom core.

Have you thought about a pourable transom material ? Solid core with nothing to rot ..

 

[Woodonglass]

Re: Honeycomb tansom core.

Uhmm if they have why haven't you been able to find it posted anywhere on the web??? Answer...Because it's not suitable for the purpose. If you don't want to use wood, look into the Pourable Seacast, Nidabond, Arjay products or the Other Solid Core Marine composites i.e. Coosa Board, that ARE suitable for transoms. Like I said you are not the first on the forum to pose this question. However, It's your boat and you are free to do as you wish. But safety should be your main concern. Why don't you contact the manufacturer of the product and see if they would recommend it for making a transom for a boat. I'm sure they would be more than happy to discuss it with you.

 

[colbyt]

Re: Honeycomb tansom core.

I have a cruise craft rogue 14 that requires a new transom and floor. And because I never want to do it again

Please don't confuse me with an expert on transoms. I do however think of myself as an expert at common sense and fairly logical.

The goal stated above is incompatible with the following statement:

However has anybody gone to effort of testing new grounds.

The surest way to get a do over if you don't drown when the rear of your boat is ripped off is to use untested materials in the construction phase. Believe me when I say if anyone had done it with success and published those results, you would find some reference to it online.

I have 2 boats in the yard right now, both with the original transoms and they are both in sound sturdy condition. The 1973 model was built before they started using plywood so it is a real piece of wood which has been kept painted over the years. The 1994 has no exposed wood. It is covered with metal and properly capped. Fifty years seems like a good long time to me. It is about 4.5 life sentences.

Now since I have used an epoxy system to repair quite a few rotten window sills, if I were building a transom I would surely be reading the link posted by a1964m.

Advice is what you asked and it has been given by more than one person. If absolution for the sins you are about to commit is what you want you should consult a member of the clergy.

 

[Rip it up]

Re: Honeycomb tansom core.



I found out how to load photos but not great quality

I found 150kg of wet timber sloshed down the back of the boat when the floor came up.

I spoke with the supplier of my honeycomb. He was happy to recommend using it with my application.

I went with the following lay up.

Original fibreglass outer skin.
Wet laid 450 biax
15mm honeycomb
450 biax
15mm honeycomb
2" holes made in cores around bolt pattern for outboard
Fibre bog around edges and bolt pattern
4" biax taped
Pad around the bolt pattern
3" overlap 3/4 height 450 biax
6" overlap fully transom
Peel ply

 

[matt167]

Re: Honeycomb tansom core.

Sure your supplier may agree with you on the Honeycomb, but he probably does not have a clue about boats, and he's going to make the money anyway.. I had a supplier recommend BC pine interior grade plywood instead of Exterior grade for building a small boat. He didn't have Exterior in the right thickness, but still wanted to make a sale.

You asked for professional opinions, when the pro's told you it was a bad idea, you said they needed to think outside the box, and now you've went along with your original plan regardless of any advice.. Why did you ask for advice in the first place?

 

[jigngrub]

Re: Honeycomb tansom core.

I'm not an expert, just an enthusiast... but I know if you keep your boat protected from the elements when not in use wood will last a lifetime.

Abuse and neglect rots a boat, not the materials it's made of.

Let us know how the honeycomb holds up for you.

 

[Woodonglass]

Re: Honeycomb tansom core.

Well... I'm not afraid to admit I need to do more research! Having done that, I think the jury is still out on the Polycore but...it may have a future in boat restoration. You all can decide for yourselves.

This guy designed and built a very large House boat out of the stuff.

Polycore Honeycomb Lightweight Construction Material - 1750567

 

[73Chrysler105]

Re: Honeycomb tansom core.

Nice Read WOG very interesting and if he built an entire boat like that from poly core it should be sufficient for a little old transom in a fiberglass or aluminum boat like ours.

 

[F14CRAZY]

Re: Honeycomb tansom core.

Install it, mount the outboard, tilt the outboard up/out all the way, then stand on the end of the outboard and see if it flexes. If it doesn't, you're probably alright

 

[archbuilder]

Re: Honeycomb tansom core.

Interesting idea, I actually looked at using composite fiberglass sheets for my deck. I ended up using marine plywood for two reasons, cost and primarily I was concerned that I might be making the hull to rigid. I did use seacast for my stringer and transom, great product, great results. That being said, I had some concerns that I might stress the hull by making it to rigid with the composite panels and the seacast. I probably over thought that aspect, but sometimes to much of a good thing is a bad thing! I also was concerned about how to anchor things to the deck with a hollow core, but that turned out to be a non-issue later. I'll be interested to hear what your results are.

 

[Rip it up]

Re: Honeycomb tansom core.



Just an update of the progress.

Transom skin finished and knee braces coved and taped.
Rear bulkhead in position.

Basically the transom is ready for the cap to go back on and get glassed.

I will be transforming the original transom edge from a screwed edge with Aluminium capping.
To a solid cored, biax taped finish. Lapped from transom over core to the motor well.

 

[jigngrub]

Re: Honeycomb tansom core.

Your work looks good, but that material looks thin... what's the thickness of it? 3/4"?

 

[Rip it up]

Re: Honeycomb tansom core.

Thanks for the neatness observation. Working clean is easier than grinding.
I'm in Australia so all dimensions are metric.
The original transom was 40mm with external skin. New transom is 38mm.
External skin.
Biax 450gsm
15mm honeycomb
Biax
15mm honey comb
3 layer biax.

The knee braces are 20mm honeycomb. I would not call them thin. It's only a small boat.

 

[V153]

Re: Honeycomb tansom core.

We have a honeycomb product called 'plascore' that's used extensively in flooring/decking. I'd never heard of using it for a transom but what the heck why not. I used 'tuff stuff' laminated w/biax exclusively for transom, stringers & floor in my 153 resto. The result was extremely strong & light. And of course totally waterproof.

I disagree with those who say it's a waste of money. I think you recoup at least some of the cost in ease of working with the stuff. Much easier'n wood.

Not trying to say people shouldn't use wood, properly sealed of course, but it is a lot heavier.

 

[beardeddone]

Re: Honeycomb tansom core.

Thanks for the replies but I need people to think outside the square. I know people go back to the same old construction plywood time and time again. However has anybody gone to effort of testing new grounds.

I have already brought the honey comb. It was cheaper than ply at AUS$40 per sheet.

The compression strength is better than most foams at 80kg density so why not use it. 2.2Mpa vrs 1.3Mpa

I have never seen a failed honeycomb laminate to understand why it can not be used. And with solid cores around the bolting points what can fail in my design? I don't mind beefing up the laminate around the bolt pattern and feathering out the spread the load.

Surely somebody has used honeycomb in a transom.

I tend to wonder if your not correct on your thinking of using honeycomb after doing some reading on this, I guess boaters are stuck on the thinking that a boat needs to be made out of just plain wood in a fiberglass boat, there is some good reading on the use of honeycomb Honeycomb structure - Wikipedia, the free encyclopedia and the use of it in military applications..

Even 3M has use for it Nida-Core Lightweight Composite Honeycomb Core Materials and Structures
http://nida-core.com/english/nidaapp_marine.php

 

[archbuilder]

Re: Honeycomb tansom core.

I second the neat work Rip it up! You guys have me more interested in the possibilities of the honeycomb construction! Any additional info would be appreciated. Rip how about some more pics of the product you are using?