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Author Topic:   Hull Foam and Sprue Holes
jimh posted 01-09-2002 12:55 AM ET (US)   Profile for jimh   Send Email to jimh  
I am asking this question in order to elicit some discussion for inclusion in the FAQ on this general topic.

On a Whaler that I own (1976 15-Sport) there is an area in the bow locker that has no gelcoat, but instead appears to be the foam interior of the boat. This area is circular and about eight inches in diameter. I assume this the access hole into which the liquid foam is poured during construction and out of which excess foam excapes as it expands.

In molding jargon I believe such a hole is called a sprue.

The foam has been finished to a smooth surface and is faired and flat with surrounding gelcoat finish of the bow locker comparment. It shows no sign of absorbing water.

In preparing the FAQ I made the assumption that such unfinished sprue holes were fairly common. I would like to know more about them.

Has anyone else has seen such a sprue hole in their Whaler?

Is this instance (on my boat) fairly rare?


Dr T posted 01-09-2002 01:14 AM ET (US)     Profile for Dr T  Send Email to Dr T     
I have something virtually identical in my 1982 13-Sport. Same location, size, and finish.

This question also raises the issue of the completeness of the foam fill. For example, when I installed the transducer for the new sonar last summer, I mounted it to the transom by drilling two holes that were about an inch above the bottom edge. When I drilled the pilot holes, they went through about 0.25 inch of fiberglass and into an air pocket. Is this also common?

Whalerdan posted 01-09-2002 07:44 AM ET (US)     Profile for Whalerdan  Send Email to Whalerdan     
My '85 Montauk has the same thing in the anchor locker floor. One more thing I never put the anchor locker through hole plug in and, like Jim says, the foam shows no signs of absorption.
gunnelgrabber posted 01-09-2002 08:11 AM ET (US)     Profile for gunnelgrabber  Send Email to gunnelgrabber     
Drt,.. that comes up every time you drill the transom..see the hull wood location diagrams that are around here..they are very helpful..lm
JFM posted 01-09-2002 08:57 AM ET (US)     Profile for JFM  Send Email to JFM     
On both my 1969 and 1972 13' sports, the sprue hole is capped with a matching blue glass plate. The plate looks like the rest of the interior gel and glass, however it is not well finished around the rim. Regards, Jay
Tom W Clark posted 01-09-2002 11:45 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I have never seen the sprue hole left uncapped. This includes my own 1976 13-Sport, 1979 15-Striper, 1980 Montauk, and 1981 Montauk. They all have a cap like that described by JFM. This cap is usually finished very nicely to the point where it is hard to tell that it did not come out of the mold with the rest of the liner.

In the old 13's the sprue hole is in the foredeck in front of the forward locker and on some old 13's I have seen the cap look less well finished around the perimeter like JFM says.

I may be making a false assumption, but this cap must be installed after the foam has been poured and cured, for as jimh points out, the foam is smooth and flat as though it were faired out after curing. If the cap were installed after the foam cured then there would not be a bond between the foam and the under side of the cap and thus it would be more susceptible to falling out if the seal around the rim were to fail.

jameso posted 01-09-2002 12:59 PM ET (US)     Profile for jameso  Send Email to jameso     
I have no cap on my 15 and there is no cap on my friends Montauk, my boat is an 83 and the Montauk is a 85?, I wonder if Whaler stopped capping the sprue after changing to a more closed cell type foam. I am assuming, and I think it is suspected that Whaler did change the type foam used from the early whalers to later ones, does anyone know more about this?
Jim Armstrong
Bigshot posted 01-09-2002 01:12 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
i have had the same "uncapped" spot on all mine. Without seeing it I know the coloring is different but I believe it is coated with something. Reason being my anchor lays on top and it has no chunks missing. From what I understand they stand the boat on the transom and inject the foam down into the hull. Has anyone ever stuck a knife into it?
NEVER SCARED posted 01-09-2002 01:14 PM ET (US)     Profile for NEVER SCARED    
Greetings fellow Whalers and Whaleretts

On my 87 Outrage 18', theres a hole about 3/8 in. diameter with foam inside. Theres a string coming from the hole and is attached to a circular coin shaped glass/gelcoat thingy. Its a obviously a cutout from the hole. It appears to be for running wires through for a pump? I wonder why everyones "hole" is different?

Reliant posted 01-09-2002 02:01 PM ET (US)     Profile for Reliant  Send Email to Reliant     
Here is what I think is the location of at least one sprue hole on a 1983 Outrage 25 Cuddy. This photo was taken in April of 2000 when we had pulled up the floors to replace my rotten fuel fill lines. Those would be the lovely black and red striped hoses in the picture. Looking at this picture brings back to mind just what a disaster this boat was when I bought it. Good thing classic whalers clean up well.

Jimh feel free to use this photo in the reference section if you so desire. Sorry the resolution is not better. The digital camera I had at this time was rather crappy.

Hope this is helpful,


Bigshot posted 01-09-2002 02:31 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
bigz posted 01-09-2002 02:56 PM ET (US)     Profile for bigz    
Yep Pete she was a mess, you took beautiful care to strenghten that out I must say.

Now spures and foam.

The above post relayed some interesting information from a factory tour taken in August 2000 by Ed Stone.

There are a number of post from 2000 regarding foaming procedures from people who have taken the tour. Since I don't have the time to waste trying to find them and obviously JimH doesn't either since he wouldn't be asking about spures and foaming if he did. You all will just have to except the fact there is no injection per se they mix bucket batches and pour the foam into the mated hulls --- which are clamped together until the foam fills and sets up --

A few comments in this post might also enlighten some why the demise of the old 13 and why the Montauk is a poor seller at some dealers. These comments again were made in 2000!

I believe Louie Kokinis and Jim Hooper also have previously commented on the production procedures they witnessed at the plant.


PS the 27 ccc has a sealed hole right in the middle of the cuddy sole, on the 27 WA the hole is actually 4" diameter and 8" deep used for the table leg recess -- the foam surrounding the hole is not coated --- the '89 13 has the typical locker hole but this is coated with some form of hardener --- the deep V Outrage '78 had a similar locker hole though it was capped with a fiberglass or plastic top. These holes were for the bow areas which received a lot more foam than the rest of the boat.

Reliant posted 01-09-2002 03:37 PM ET (US)     Profile for Reliant  Send Email to Reliant     
Tom – Thanks for the compliment. High praise indeed and I mean that sincerely.

You are right about the foam being poured in while the molds are clamped together. Here is one of those 2000 threads where this is discussed;

I think jimh was talking about the location of these

sprue holes
which I do not think has been covered before, so I think we are covering new ground after all. I am including the above link because the foaming technique could also be a good thing to have in the reference section.


P.S. Bigshot – My sentiments exactly when we pulled up the floor. Of course the language I used at the time was a little harsher then yikes ;-)

Reliant posted 01-09-2002 03:43 PM ET (US)     Profile for Reliant  Send Email to Reliant     
Sorry about the strange looking post above. I was trying out the UBB codes and the quote one wasn’t what I thought it was. I had just meant to put SPRUE HOLES in quotation marks.

Pete “fools rush in where wise men fear to tread” Ferguson

Tsuriki BW posted 01-09-2002 04:05 PM ET (US)     Profile for Tsuriki BW  Send Email to Tsuriki BW     
"Fools rush in where wise men fear to thread.



Reliant posted 01-09-2002 04:15 PM ET (US)     Profile for Reliant  Send Email to Reliant     
Touché ;-)

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