stems
IF the hull is visually unacceptable, paint. Paint the felt before attacking it.
Felt on my Rendezvous is painted white on a maroon hull. I can see damage. Painting a vehicle or parts with white functions for seeing first rust.
Kevlar doesn’t sand well. Why would a Kevlar felt sand better than a Kevlar fabric ?
I wanted Blanc’s discussion of bow/stern strips. I’ll avoid distorting what he said but suggest we may be discussing two different materials properties and approaches to stem protection.
Felt absorbs impacts stress within felt. Adding more hull skin with a laminate strengthens a hull. The dividing line is discussed as does the extra skin absorb impact or strengthen the hull that is the hull with a fabric laminate continues absorb all impact where the felted hull receives less impact.
The two concepts are not splitting hairs but widely significant design approaches in all vehicles…including helmets and body armor.
Read:
https://www.google.com/#q=wiki+materials+definitions+strength+
Good info…
and I’ve enjoyed your posts and Mike’s over at the tripping site.
I do my skid patches similarly to how Mike illustrated, I’ve always used S-cloth and epoxy resin. They’ve performed well but I plan to use Dynel on my Magic next spring when I add skid patches to it. I believe I can realize similar performance with less material build. And using peel ply will be a new technique for me, too.
I appreciate the time you’ve taken to post your tutorials. They are most useful for many of us.
Felt absorbs impact?
Maybe if you don’t soak it with resin first…
For something to absorb impact it either has to be elastic (malleable) or it has to be crushed. Resin-soaked and hardened kev felt is neither.
I have had one hard direct impact on the kev felt skid on my Prospector, high up on the stem. It did not crush and it did not deform like rubber or foam. It did leave a mark much like a rock leaves when impacting my car’s windshield. I can tell you that the only place any impact was “absorbed” was on my body when I lunged forward in the boat as it stopped instantly. No - I’m sure the boat also flexed throughout it’s length, absorbing some of the impact. But the skid plate only chipped and slightly cracked - it absorbed nothing.
With that one exception on this one canoe, all other wear and tear on my stems has been abrasion. I see no advantage to these felt skids…none, other than ease of installation - and that’s debatable.
I’m with Steve
my anectdote is when we hit the rock full speed ahead the Kevlar skid plate got a hole punched right through it. Absorbed anything… not.
My thigh absorbed energy and so did the thwart that I broke when my leg hit it and broke it off.
OTOH
OTOH - my Penobscot had been in what must have been a real doozy of an impact when it had no skid plate. Right on the blunt end of the vertical part of the nose, the stem was actually crushed in and permanently deformed in an area about two or three inches in diameter. Above the waterline, so of no consequence to me - but that blow was surely absorbed to some degree by the royalex hull at the point of impact.
yeah blame it
on the felt.
try
not to be …
‘For something to absorb impact it either has to be elastic (malleable) or it has to be crushed. Resin-soaked and hardened kev felt is neither’
steel is malleable and crushable…also HEAVY.
coefficient of restitution
resisting impact with materials largely depends on speed and weight limits.
https://goo.gl/x6eqFx
Your communication skills…
really leave a lot to be desired. Much of the time I can’t tell what in creation you are actually saying. Confident I’m not the only one who feels this way.
Ignore this guy
Remember the time I tried to explain to him that cracks in gel coat due to a hull’s impact with a solid object were caused by the gel coat’s inability to flex as much as the underlying hull material? All the while he preached that cracks in the gel coat were proof that it had “absorbed energy” and thereby significantly reduced stress on the hull. I could explain the problem with that logic (again), but you get the idea.
how do you feel ?
The resin felt question:
If there is a less than resin filled felt but still cohesive before the impact…then hypothetically this product would offer more energy absorption than a filled felt.
Refer to crunchy candy bars
How that would be approached ? I dunno.
The OP’s hull has stem protection, my subject.
I agree others feel the same way. Probably most of Maine and some of New Hampshire.
Nonetheless ! the felts are on the stems.
all rise
cracks are evidence of energy absorption. The area absorbed energy and cracked. It’s eternal.
DK loves google
Google Datakoll. aka Gene something. And grab your beverage of choice. Its an eternal evening of reading how he has wrecked other forums.
He is doing a very good job on this one but I think and hope his time has run out.
But when it’s incidental and minimal, …
... you can ignore it.
Consider an eggshell. If you could coat your boat with eggshell, it would crack when the hull flexed, no matter how slightly it flexed. Yes, the eggshell would absorb energy when it cracked, but is it enough to matter? I say it's not. Gel coat is more flexible and a little stronger than that, but its flexural strength is still miniscule in comparison to any material from which a hull would be constructed. The stress it takes to make a paper-thin layer of gel coat break when flexed is so slight that you can (and should) ignore its contribution to strengthening the hull (or protecting it via energy absorption, as you prefer to say).
Using your logic, the paint on your car helps protect the metal when that metal is stressed. After all, the paint cracks if the metal bends more than little, so it must have absorbed energy, right? Well, you are right, but is it enough of a contribution to matter? Does your car benefit from the paint when you have a minor collision?
as with
felt, gelcoat has the quality of absorbing energy then cracking or popping off and in that process protecting the laminate.
This is what happens. What you’re involved in is overstating a position in disagreement with a process that occurs and is foundational to your crit of it.
With gelcoat and felt stem protection, the facts are not negated on the VOLUME or DEGREE of the protection because the laws of physics state that the protection exists.
Try not to be dense?
Yeah - good idea. Speaking of dense, you might consider matters of degree. Put that steel on your stems and it won’t absorb any impact either - unless it’s density is such that it can be crushed (such as a “crush zone” provided by voids in the matrix ).
I can say something is malleable or not as a matter of degree (according to the force that can be reasonably expected to be appliied), and most people in the conversation will know what my point is…except for that one guy who has to divert from the point to avoid addressing the flaw in his ridiculous argument.
and that is a reason…
…to choose either over a stronger material?
That’s. …rich.
That’s true, but you can’t see my point?
Using that same logic, I can truthfully state that when I jump off the ground, the whole earth moves in the opposite direction, and rebounds to its original position during the time that I fall back to the floor. There comes a point where theory, no matter how undeniable, is useless from any practical standpoint.
Steve gets it perfectly. Just because one material fails when bonded to a material with greater durability doesn't mean that failure is a desirable or intentional outcome. In this case, the design purpose of the gel coat is to take the wear of abrasion so that the structural material beneath doesn't. The fact that the gel coat cracks when the hull is flexed beyond a certain point is incidental, not a design feature, and not a benefit.
Excellent summary. n/p
Looks as if I should…
just skip right over his posts in the future. No sense feeding it.
As an aside, I hope you are doing well these days.
abrasion is impact
abrasion is impact abrasion is impact
stems are stems and keels are keels…no turning a stem argument into a keel argument
water flows downhill not uphill