Getting Specs on Blocking A Boat...-gctid348002

[Guest]

I'm trying to find out the specifications on the proper way to block the front of a boat, under the keel. I can only find "opinions" through Google but would like to find something more exact, preferably from the manufacturer. I'm not concerned with HOW to get it on blocks, but rather the specifics of blocking itself. I've written Bayliner as to the proper location, size of block, material of block, and number of blocks, etc., but I have not heard back.

I'm asking for my particular boat.

Thanks.

[dmcb]

Mike, go to a local marina and see what their time tested method is.

There most likely are not any specs.

The keel carries the weight. The sides are just to balance.

Larger boats will have a tag showing sling. This is where the blocking should be placed. Not the only place however.

Your boat does not have these tags.

You want blocks under the heavy part (engines). There is no set place for the others. I imagine the pros have 3 keel blocks on a boat your size. Side blocks should be at the transom. On my 38' they block the transom and one other set of side blocks. Imo, you wouldn't need more than the transom blocks. Others if it makes you comfortable but you don't want much weight on them.

Doug

[2850Bounty]

Doug makes a good suggestion. See how other yards are point loading the keel area.

My thoughts are, and I've cribbed my share of hulls, that the stern cribbing is not an issue as long as you crib outside and near the transom. This is a very stout area.

This becomes two points of your triangulation. Third point being the keel load point.

As for cribbing or blocking the keel, I'd want to make sure that I did NOT point load with too small a surface, AND that I'd want to load this on a block that ran parallel with the keel, NOT perpendicular to the keel.

Then there's the distance from the stern.

The closer that you block to the stern, the more leverage advantage the hull has against the point load.... or the greater the "disadvantage" the point load has!

IOW, as you move the point load from the bow towards the stern, the effective point load becomes greater. (I.E., more hull leverage that is NOT in your favor)

I'd block the keel with an adequate length timber that is parallel to the keel, and FWD enough to reduce the hull's leverage advantage.

The truth is..... I'd not block the keel at all, I'd use crib stands AFT and FWD....., and omit the load from the keel.

That way I'd have a four point load, and none would be on the keel alone.



However, keel blocking is done all the time.... just don't block perpendicular to the keel, and make sure that you're not too far AFT....., and I think you'll be OK.

Does that make any sense?

.

[boatworkfl]

A 3870 should have at least 3 keel blocks I use 4, a 32 ft should have 3 blocks, unless you have a small trailerable boat do not block with out keel blocking.

This is a 3870 I always use 4 keel blocks. Not my boat. I repowered this boat 6 years ago with 2 300 HP saber/perkins, it fly's, 27 knots @ max rpm, then re pitched props up.

[2850Bounty]

Mike's boat is a 1986 Bayliner 28' Contessa Sunbridge.

[boatworkfl]

2850Bounty wrote:
Mike's boat is a 1986 Bayliner 28' Contessa Sunbridge.

2 - 3 keel blocks, 4 total side stands.

[Guest]

Thanks guys. Very helpful.

[boatworkfl]

Gilligan wrote:
Thanks guys. Very helpful.

Do not forget to chain the stands together, side to side so they do not slip out.

[Guest]

Gilligan wrote:
I'm trying to find out the specifications on the proper way to block the front of a boat, under the keel. I can only find "opinions" through Google but would like to find something more exact, preferably from the manufacturer. I'm not concerned with HOW to get it on blocks, but rather the specifics of blocking itself. I've written Bayliner as to the proper location, size of block, material of block, and number of blocks, etc., but I have not heard back.

The applicable standard is http://www.abycinc.org/standards/pur... /> ABYC TY-28. It is available to ABYC members or available for purchase.

boatworkfl wrote:
This is a 3870 I always use 4 keel blocks. Not my boat.

There are several improvement possible over that blocking shown.

One would be to move the keel block farther aft.

Another is to place each course of 8x8x22 keel blocks perpendicular to the one below and to spread the pair of blocks on each course about 6" apart, so the 22" wide block is supported below on the ends.

Here is an example showing how to orient keel blocks that are more than one course tall.



When I block my boat I use a 2x4 scrap as a crush member on top of the keel block, to conform to the hull.

[Guest]

Every owner's manual should show where blocks are to be placed; too bad many don't.

TY-28 doesn't give you as much detail as you might want. It talks about what the builder should provide, send you elsewhere with a mix of references, and finishes up with common sense and generalizations.

Here's the best of it.... (sorry - copy and paste stripped out all the formatting)

BLOCKING

Boat keels should be blocked as close to the ground as practical. Keel blocking should be used to support the weight of the boat,

unless otherwise specified by the boat manufacturer. Keel blocking should be distributed to prevent high local loading. The

blocking should be adequate to support the boat, taking the condition and slope of the ground, and the size, shape, weight, and

condition of the boat into account. Use a minimum of two sets of keel blocking per boat. The blocking should be as large as

practicable and appropriately sized for the boat. The minimum dimension measured fore and aft along the keel should be four

inches nominal per block. If the blocking is over two tiers high, it should be cribbed. Cribbing height should not exceed 1 1/2

times the minimum base footprint dimension. Barrels and cinder blocks should not be used for blocking. See TABLE 1 for

minimum block dimensions. 12 inch X 12 inch (30.5cm X 30.5cm) blocks are usable in all cases.

TABLE 1 - MINIMUM BLOCK DIMENSIONS

BOAT LENGTH MINIMUM BLOCK WIDTH MINIMUM BLOCK LENGTH

less than 30 feet (9m) 4 inches (10.5cm) 18 inches (46cm)

31-40 feet (9.45-12m) 6 inches (15.5cm) 18 inches (46cm)

41 feet (12.5m) or over 8 inches (20.5cm) 18 inches (46cm)

STANDS

Stands should be installed and adjusted by qualified, experienced, and authorized persons. Do not use any boat stand that is

damaged or structurally deteriorated. Maintain equipment as required by the manufacturer. Keep moving parts lubricated.

Stand Placement

As a general guideline, there should be no less than two pairs of stands, e.g., 4 stands, placed under boats. Conditions such as

hull configuration and structure, windage, weather and ground conditions, or other exposures, may require more stands to be

used.

[boatworkfl]

wingless wrote:
The applicable standard is http://www.abycinc.org/standards/pur... /> ABYC TY-28. It is available to ABYC members or available for purchase.

There are several improvement possible over that blocking shown.

One would be to move the keel block farther aft.

Another is to place each course of 8x8x22 keel blocks perpendicular to the one below and to spread the pair of blocks on each course about 6" apart, so the 22" wide block is supported below on the ends.

Here is an example showing how to orient keel blocks that are more than one course tall. I only see one stand at the bow end?



When I block my boat I use a 2x4 scrap as a crush member on top of the keel block, to conform to the hull.

I block a 3870 with 4 blocks, one as far aft as possible and spact the others, 1/2" plywood works well as a shim/crush adjustment. All 4 blocks must contact at the same time, those blocke are 12" x 12" rough cut blocks. The stands should be on 3/4" plywood unless on concrete.

The photo I provided was not my blocking.

[Guest]

Thanks for the continued help.

I've run into a problem that I'm hesitant to post pics of right now for various reasons. I'd LOVE it if someone could show me a "manufactures recommendation" on blocking. All I can find is various opinions of "professionals". I would like to find something that would be admisable (sp?) in court.

[Guest]

Gilligan wrote:
I've run into a problem that I'm hesitant to post pics of right now for various reasons. I'd LOVE it if someone could show me a "manufactures recommendation" on blocking. All I can find is various opinions of "professionals". I would like to find something that would be admisable (sp?) in court.

That sounds bad. Photographs are useful. Photographs of the before condition are better.

Here is another http://blog.boattrader.com/2011/10/b...e: <br /> link describing the proper way to block a boat.

My experience when dealing w/ boat yards and unsafe blocking is that they are self-proclaimed "experts" w/ X years (a big number) of experience and they know what they are doing. My experience is that they have no interest in improving their process to conform to standards, to block the boat so it cannot ever fall.

The issue is that a poorly blocked boat will not / cannot resist forces, like wind, pushing fore / aft or side to side and the boat will fall.

Here is a poorly blocked boat.

Good luck.

[Guest]

wingless wrote:
That sounds bad. Photographs are useful. Photographs of the before condition are better.

Here is another https://"http://blog.boattrader.com/...e: <br /> link describing the proper way to block a boat.

My experience when dealing w/ boat yards and unsafe blocking is that they are self-proclaimed "experts" w/ X years (a big number) of experience and they know what they are doing. My experience is that they have no interest in improving their process to conform to standards, to block the boat so it cannot ever fall.

The issue is that a poorly blocked boat will not / cannot resist forces, like wind, pushing fore / aft or side to side and the boat will fall.

Here is a poorly blocked boat.

Good luck.

The falling of the boat is not the only issue. The crushing of the keel is also a concern. placement of the blocking therefore is just as important.

[yachtman]

Maybe I don't need to say this but it I will. Don't use cement or cinder blocks they will crush.

Use three block for keel but make sure there isn't more pressure on the center block. It can distort the keel.